Podcast
Questions and Answers
A novel bacterial species exhibits an unusual mechanism for circumventing phagocytosis. Instead of merely inhibiting phagocytic adsorption, the bacterium synthesizes a complex polysaccharide that remodels the surface of the phagocyte itself, diminishing the expression of key recognition receptors. Which of the following outcomes is most likely to arise due to this bacterial strategy?
A novel bacterial species exhibits an unusual mechanism for circumventing phagocytosis. Instead of merely inhibiting phagocytic adsorption, the bacterium synthesizes a complex polysaccharide that remodels the surface of the phagocyte itself, diminishing the expression of key recognition receptors. Which of the following outcomes is most likely to arise due to this bacterial strategy?
- Aberrant activation of the inflammasome within the phagocyte, leading to pyroptosis.
- Enhanced opsonization by antibodies due to increased surface antigen presentation.
- Impaired antigen presentation to T lymphocytes, resulting in a blunted adaptive immune response. (correct)
- Increased susceptibility to neutrophil extracellular traps (NETs) due to altered surface charge.
Upon exposure to sublethal concentrations of penicillin, a Staphylococcus aureus population exhibits a significant increase in the expression of peptidoglycan hydrolases, specifically targeting regions of newly synthesized cell wall material. This compensatory response, however, renders the cells more susceptible to hypotonic environments. Which of the following explains this phenomenon?
Upon exposure to sublethal concentrations of penicillin, a Staphylococcus aureus population exhibits a significant increase in the expression of peptidoglycan hydrolases, specifically targeting regions of newly synthesized cell wall material. This compensatory response, however, renders the cells more susceptible to hypotonic environments. Which of the following explains this phenomenon?
- Penicillin directly inhibits teichoic acid synthesis, reducing cell wall rigidity.
- Protoplast formation occurs, leading to irreversible cell wall collapse.
- Autolysins are activated, causing complete degradation of pre-existing peptidoglycan.
- Increased hydrolase activity disrupts existing cross-links, weakening the cell wall's structural integrity. (correct)
A bacterial strain is isolated from a patient exhibiting symptoms of Toxic Shock Syndrome. Biochemical assays reveal the production of a novel superantigen that, unlike typical superantigens, directly binds to and activates intracellular signaling cascades within macrophages, bypassing typical MHC-II presentation to T-cells. What is the most likely consequence of this unique mechanism of action?
A bacterial strain is isolated from a patient exhibiting symptoms of Toxic Shock Syndrome. Biochemical assays reveal the production of a novel superantigen that, unlike typical superantigens, directly binds to and activates intracellular signaling cascades within macrophages, bypassing typical MHC-II presentation to T-cells. What is the most likely consequence of this unique mechanism of action?
- Selective depletion of specific T-cell clones with high-affinity TCRs for the superantigen.
- Development of long-lasting, protective immunity against subsequent infections.
- Enhanced clearance of the bacterium due to hyper-activation of the adaptive immune system.
- Exacerbated inflammatory response and cytokine storm due to direct macrophage activation. (correct)
In a bacterial conjugation experiment, an F+ strain of E. coli carrying a high-copy-number plasmid encoding resistance to multiple antibiotics is mixed with an F- strain lacking antibiotic resistance. High concentrations of DNAse are added to the medium to prevent transformation. After incubation, transconjugants are selected on antibiotic-containing agar, but the frequency of transfer is significantly lower than expected. Which modification to the experimental design has the highest probability of increasing the conjugation frequency?
In a bacterial conjugation experiment, an F+ strain of E. coli carrying a high-copy-number plasmid encoding resistance to multiple antibiotics is mixed with an F- strain lacking antibiotic resistance. High concentrations of DNAse are added to the medium to prevent transformation. After incubation, transconjugants are selected on antibiotic-containing agar, but the frequency of transfer is significantly lower than expected. Which modification to the experimental design has the highest probability of increasing the conjugation frequency?
A research team is engineering a novel antimicrobial peptide (AMP) to target Gram-negative bacteria. To be effective against LPS-induced endotoxicity, the designed AMP must selectively bind to Lipid A but avoid activation of TLR4 signaling. Which of the following structural modifications would best achieve this goal?
A research team is engineering a novel antimicrobial peptide (AMP) to target Gram-negative bacteria. To be effective against LPS-induced endotoxicity, the designed AMP must selectively bind to Lipid A but avoid activation of TLR4 signaling. Which of the following structural modifications would best achieve this goal?
A remote research station in Antarctica experiences an outbreak of a previously unknown bacterial disease among its personnel. Initial analysis reveals a Gram-positive, spore-forming rod-shaped bacterium with a unique adaptation: its spores require exposure to extremely high levels of UV radiation for germination, achievable only during brief periods of peak solar activity in the Antarctic summer. What evolutionary pressure most likely drove the development of this germination requirement?
A remote research station in Antarctica experiences an outbreak of a previously unknown bacterial disease among its personnel. Initial analysis reveals a Gram-positive, spore-forming rod-shaped bacterium with a unique adaptation: its spores require exposure to extremely high levels of UV radiation for germination, achievable only during brief periods of peak solar activity in the Antarctic summer. What evolutionary pressure most likely drove the development of this germination requirement?
A newly identified bacterial species, isolated from a deep-sea hydrothermal vent, possesses a unique cell wall structure: the peptidoglycan layer is entirely replaced by a complex polymer composed of alternating archaeal-type pseudomurein and a novel sulfur-containing polysaccharide. Which of the following would be the most likely outcome when this bacterium is subjected to Gram staining?
A newly identified bacterial species, isolated from a deep-sea hydrothermal vent, possesses a unique cell wall structure: the peptidoglycan layer is entirely replaced by a complex polymer composed of alternating archaeal-type pseudomurein and a novel sulfur-containing polysaccharide. Which of the following would be the most likely outcome when this bacterium is subjected to Gram staining?
A modified Gram staining procedure is developed where the decolorization step with acetone is omitted. Instead, a competitive inhibitor of the crystal violet-iodine complex-binding site on peptidoglycan is introduced during the counterstaining step. Which of the following outcomes would be expected when staining both Gram-positive and Gram-negative bacteria with this method?
A modified Gram staining procedure is developed where the decolorization step with acetone is omitted. Instead, a competitive inhibitor of the crystal violet-iodine complex-binding site on peptidoglycan is introduced during the counterstaining step. Which of the following outcomes would be expected when staining both Gram-positive and Gram-negative bacteria with this method?
Several newly discovered bacterial species isolated from hypersaline environments have a cell wall structure fundamentally different from both Gram-positive and Gram-negative bacteria. The S-layer proteins are modified with unique sulfated polysaccharides that directly bind divalent cations ($Ca^{2+}$, $Mg^{2+}$), effectively crosslinking the entire cell wall into a dense, impermeable lattice. Which of the following would be the most likely consequence of this adaptation?
Several newly discovered bacterial species isolated from hypersaline environments have a cell wall structure fundamentally different from both Gram-positive and Gram-negative bacteria. The S-layer proteins are modified with unique sulfated polysaccharides that directly bind divalent cations ($Ca^{2+}$, $Mg^{2+}$), effectively crosslinking the entire cell wall into a dense, impermeable lattice. Which of the following would be the most likely consequence of this adaptation?
A research team aims to develop a novel broad-spectrum antibiotic that selectively targets bacterial cell division. They identify a protein essential for Z-ring formation that is highly conserved across diverse bacterial species but has no eukaryotic homologues. However, the protein's active site exhibits significant structural plasticity, adapting to different ligand conformations. What experimental strategy would most likely lead to the identification of an effective inhibitor?
A research team aims to develop a novel broad-spectrum antibiotic that selectively targets bacterial cell division. They identify a protein essential for Z-ring formation that is highly conserved across diverse bacterial species but has no eukaryotic homologues. However, the protein's active site exhibits significant structural plasticity, adapting to different ligand conformations. What experimental strategy would most likely lead to the identification of an effective inhibitor?
A graduate student, after several failed attempts, finally develops a Gram stain protocol that consistently stains archaea. His procedure involves a modified mordant composed of tannic acid and aluminum potassium sulfate. Under the microscope, the archaeal cells appear intensely purple. Which of the following inferences is most accurate about the cell wall structure of these archaea?
A graduate student, after several failed attempts, finally develops a Gram stain protocol that consistently stains archaea. His procedure involves a modified mordant composed of tannic acid and aluminum potassium sulfate. Under the microscope, the archaeal cells appear intensely purple. Which of the following inferences is most accurate about the cell wall structure of these archaea?
In a remote field study, researchers discover a novel species of anaerobic bacteria thriving in an extremely acidic hot spring (pH 2.0, 90°C). Genomic analysis reveals an absence of typical peptidoglycan synthesis genes. Instead, the genome encodes a highly divergent set of glycosyltransferases predicted to synthesize a unique heteropolysaccharide that is heavily modified with sulfated monosaccharides and unusual polyamines. What is the evolutionary significance of this unique cell wall composition?
In a remote field study, researchers discover a novel species of anaerobic bacteria thriving in an extremely acidic hot spring (pH 2.0, 90°C). Genomic analysis reveals an absence of typical peptidoglycan synthesis genes. Instead, the genome encodes a highly divergent set of glycosyltransferases predicted to synthesize a unique heteropolysaccharide that is heavily modified with sulfated monosaccharides and unusual polyamines. What is the evolutionary significance of this unique cell wall composition?
A team of scientists studying the spread of methicillin-resistant Staphylococcus aureus (MRSA) in a hospital environment discovers a previously unknown mechanism of antibiotic resistance. The MRSA strains produce a cell-surface exopolysaccharide that selectively binds and inactivates methicillin, but only at temperatures above 39°C. What is the most plausible explanation for this temperature-dependent inactivation?
A team of scientists studying the spread of methicillin-resistant Staphylococcus aureus (MRSA) in a hospital environment discovers a previously unknown mechanism of antibiotic resistance. The MRSA strains produce a cell-surface exopolysaccharide that selectively binds and inactivates methicillin, but only at temperatures above 39°C. What is the most plausible explanation for this temperature-dependent inactivation?
Researchers engineer a strain of Bacillus anthracis lacking the ability to synthesize its capsule. In vitro, the mutant strain exhibits significantly reduced virulence in macrophage infection assays. To restore virulence, the researchers attempt to complement the mutation by introducing a plasmid expressing the missing capsule synthesis genes. However, even with capsule production restored to wild-type levels, the complemented strain remains avirulent in vivo. Which of the following most accurately explains this result?
Researchers engineer a strain of Bacillus anthracis lacking the ability to synthesize its capsule. In vitro, the mutant strain exhibits significantly reduced virulence in macrophage infection assays. To restore virulence, the researchers attempt to complement the mutation by introducing a plasmid expressing the missing capsule synthesis genes. However, even with capsule production restored to wild-type levels, the complemented strain remains avirulent in vivo. Which of the following most accurately explains this result?
A newly identified species of Corynebacterium is isolated from a patient with a chronic skin infection. Unlike C. diphtheriae, this species does not produce diphtheria toxin. However, it synthesizes a novel cell-surface polysaccharide with remarkable adhesive properties. Genetic analysis reveals that the genes encoding this polysaccharide are located within a mobile genetic element that also carries genes conferring resistance to multiple antibiotics. What is the clinical implication of this finding?
A newly identified species of Corynebacterium is isolated from a patient with a chronic skin infection. Unlike C. diphtheriae, this species does not produce diphtheria toxin. However, it synthesizes a novel cell-surface polysaccharide with remarkable adhesive properties. Genetic analysis reveals that the genes encoding this polysaccharide are located within a mobile genetic element that also carries genes conferring resistance to multiple antibiotics. What is the clinical implication of this finding?
A research team studies a strain of Yersinia pestis that exhibits reduced virulence compared to historical isolates. Transcriptomic analysis reveals a significant down-regulation of genes involved in the synthesis of the plasminogen activator Pla. Further investigation reveals that this reduced expression is due to a single point mutation within the ribosome-binding site (Shine-Dalgarno sequence) of the pla mRNA. Which compensatory mutation(s) would most likely restore Pla production and virulence?
A research team studies a strain of Yersinia pestis that exhibits reduced virulence compared to historical isolates. Transcriptomic analysis reveals a significant down-regulation of genes involved in the synthesis of the plasminogen activator Pla. Further investigation reveals that this reduced expression is due to a single point mutation within the ribosome-binding site (Shine-Dalgarno sequence) of the pla mRNA. Which compensatory mutation(s) would most likely restore Pla production and virulence?
A remote village experiences an outbreak of a severe diarrheal disease. Public health officials identify the causative agent as a novel strain of Vibrio cholerae. Unlike classical V. cholerae, this strain lacks the cholera toxin gene (ctxAB) entirely. Further investigation reveals that the strain produces a novel toxin that directly disrupts the function of intestinal tight junction proteins, increasing paracellular permeability. What mechanism is most likely responsible for the severe diarrhea?
A remote village experiences an outbreak of a severe diarrheal disease. Public health officials identify the causative agent as a novel strain of Vibrio cholerae. Unlike classical V. cholerae, this strain lacks the cholera toxin gene (ctxAB) entirely. Further investigation reveals that the strain produces a novel toxin that directly disrupts the function of intestinal tight junction proteins, increasing paracellular permeability. What mechanism is most likely responsible for the severe diarrhea?
A researcher discovers an exceptional strain of Pseudomonas aeruginosa capable of thriving in environments with extremely limited iron availability. This strain produces a novel siderophore analogue that, along with a high affinity for ferric iron ($Fe^{3+}$), also exhibits an unusual ability to disrupt the biofilm matrix produced by other bacterial species. Predict the most likely mechanism behind the disruption of the biofilm matrix by this siderophore analogue.
A researcher discovers an exceptional strain of Pseudomonas aeruginosa capable of thriving in environments with extremely limited iron availability. This strain produces a novel siderophore analogue that, along with a high affinity for ferric iron ($Fe^{3+}$), also exhibits an unusual ability to disrupt the biofilm matrix produced by other bacterial species. Predict the most likely mechanism behind the disruption of the biofilm matrix by this siderophore analogue.
A patient diagnosed with a serious Bacillus anthracis infection is treated with a novel antibiotic that inhibits mycolic acid synthesis. Although Bacillus species do not typically produce mycolic acids, the antibiotic surprisingly proves highly effective in clearing the infection. What explains this?
A patient diagnosed with a serious Bacillus anthracis infection is treated with a novel antibiotic that inhibits mycolic acid synthesis. Although Bacillus species do not typically produce mycolic acids, the antibiotic surprisingly proves highly effective in clearing the infection. What explains this?
A researcher aims to eradicate a persistent Clostridium difficile infection in a patient using a highly targeted, modified bacteriophage. This modified phage expresses a protein-disulfide isomerase (PDI) on its surface. This PDI is known to cleave specific disulfide bonds of proteins that stabilize the C. difficile spore coat. Which action is most likely to occur when using this intervention?
A researcher aims to eradicate a persistent Clostridium difficile infection in a patient using a highly targeted, modified bacteriophage. This modified phage expresses a protein-disulfide isomerase (PDI) on its surface. This PDI is known to cleave specific disulfide bonds of proteins that stabilize the C. difficile spore coat. Which action is most likely to occur when using this intervention?
A research team is investigating a novel species of Treponema isolated from a patient with atypical syphilis-like symptoms. Microscopic analysis reveals that these bacteria lack flagella and the periplasmic flagella typically associated with Treponema pallidum, but demonstrates rapid motility in highly viscous environments. What mechanism is most likely driving the motility of this novel Treponema species?
A research team is investigating a novel species of Treponema isolated from a patient with atypical syphilis-like symptoms. Microscopic analysis reveals that these bacteria lack flagella and the periplasmic flagella typically associated with Treponema pallidum, but demonstrates rapid motility in highly viscous environments. What mechanism is most likely driving the motility of this novel Treponema species?
A novel approach to preventing Neisseria gonorrhoeae infections involves the development of a synthetic glycan that mimics the structure of human glycosphingolipids found on the surface of epithelial cells. This glycan is administered as a topical microbicide before sexual contact. Through what mechanisms might this strategy function?
A novel approach to preventing Neisseria gonorrhoeae infections involves the development of a synthetic glycan that mimics the structure of human glycosphingolipids found on the surface of epithelial cells. This glycan is administered as a topical microbicide before sexual contact. Through what mechanisms might this strategy function?
A researcher is investigating the genetic basis of erythromycin resistance in a clinical isolate of Streptococcus pyogenes. Sequencing reveals a point mutation in the 23S rRNA gene, altering a single nucleotide within the peptidyl transferase center. To understand the evolutionary origin of this mutation, the researcher attempts to recreate it in vitro using site-directed mutagenesis. Introduction of mutated 23s rRNA into a wild-type strain results in erythromycin which does not confer the same degree of resistance observed in the clinical isolate. How would you enhance erythromycin resistance?
A researcher is investigating the genetic basis of erythromycin resistance in a clinical isolate of Streptococcus pyogenes. Sequencing reveals a point mutation in the 23S rRNA gene, altering a single nucleotide within the peptidyl transferase center. To understand the evolutionary origin of this mutation, the researcher attempts to recreate it in vitro using site-directed mutagenesis. Introduction of mutated 23s rRNA into a wild-type strain results in erythromycin which does not confer the same degree of resistance observed in the clinical isolate. How would you enhance erythromycin resistance?
The most effective treatment for diptheria is what?
The most effective treatment for diptheria is what?
A research team engineer a novel bacteriophage with an altered tropism, enabling it to selectively infect cells of Staphylococcus epidermidis that colonize implanted medical devices. The phage is further modified to express a human defensin. What outcome would most likely occur with this bioengineered therapy?
A research team engineer a novel bacteriophage with an altered tropism, enabling it to selectively infect cells of Staphylococcus epidermidis that colonize implanted medical devices. The phage is further modified to express a human defensin. What outcome would most likely occur with this bioengineered therapy?
A woman with a history of recurrent UTIs presents with symptoms suggestive of pyelonephritis. Culture of her urine reveals a Gram-negative bacterium identified as Escherichia coli. Antimicrobial susceptibility testing reveals resistance to multiple antibiotics, including fluoroquinolones and trimethoprim-sulfamethoxazole. Further investigation reveals that the E. coli strain possesses a novel plasmid encoding an enzyme that modifies lipopolysaccharide (LPS). Which aspect of the E. coli could be most greatly affected?
A woman with a history of recurrent UTIs presents with symptoms suggestive of pyelonephritis. Culture of her urine reveals a Gram-negative bacterium identified as Escherichia coli. Antimicrobial susceptibility testing reveals resistance to multiple antibiotics, including fluoroquinolones and trimethoprim-sulfamethoxazole. Further investigation reveals that the E. coli strain possesses a novel plasmid encoding an enzyme that modifies lipopolysaccharide (LPS). Which aspect of the E. coli could be most greatly affected?
What is the outcome for a newly identified bacterial strain that possesses exotoxins?
What is the outcome for a newly identified bacterial strain that possesses exotoxins?
A public health emergency arises due to the deliberate release of aerosolized Bacillus anthracis spores in a major city. Compounding the crisis, it is discovered that the released spores carry a genetically engineered modification making them resistant to the standard antibiotic prophylaxis (e.g., ciprofloxacin). What measure would be most effective?
A public health emergency arises due to the deliberate release of aerosolized Bacillus anthracis spores in a major city. Compounding the crisis, it is discovered that the released spores carry a genetically engineered modification making them resistant to the standard antibiotic prophylaxis (e.g., ciprofloxacin). What measure would be most effective?
A researcher is studying a novel method to combat biofilms formed by Staphylococcus aureus. They discover that a specific quorum-sensing molecule (QSM) produced by the bacteria also facilitates the transport of iron ions across bacterial membranes. Which of the following strategies would be most effective in disrupting the biofilm?
A researcher is studying a novel method to combat biofilms formed by Staphylococcus aureus. They discover that a specific quorum-sensing molecule (QSM) produced by the bacteria also facilitates the transport of iron ions across bacterial membranes. Which of the following strategies would be most effective in disrupting the biofilm?
Several patients undergoing routine colonoscopies develop severe Bacteroides fragilis infections, despite standard sterilization procedures. A thorough epidemiological investigation reveals that the source of the infections is a specific lot of endoscopes used in the procedures. Further analysis suggests that the endoscopes have microscopic defects promoting the persistence of B. fragilis. What changes would you implement?
Several patients undergoing routine colonoscopies develop severe Bacteroides fragilis infections, despite standard sterilization procedures. A thorough epidemiological investigation reveals that the source of the infections is a specific lot of endoscopes used in the procedures. Further analysis suggests that the endoscopes have microscopic defects promoting the persistence of B. fragilis. What changes would you implement?
Patients are coming down with E. coli. Upon a study of E. coli that has O157:H7, produces bloody diarrhoea, and kidney failure, what has most likely occurred?
Patients are coming down with E. coli. Upon a study of E. coli that has O157:H7, produces bloody diarrhoea, and kidney failure, what has most likely occurred?
What is the best way to prevent the start and spread of Haemophilus influenza?
What is the best way to prevent the start and spread of Haemophilus influenza?
An unusual infectious outbreak has occurred stemming from Yersinia. What do we know based on the material provided?
An unusual infectious outbreak has occurred stemming from Yersinia. What do we know based on the material provided?
A researcher is testing vibrio and its properties in a lab. If we already know that it is in water, what is the next question that could be answered?
A researcher is testing vibrio and its properties in a lab. If we already know that it is in water, what is the next question that could be answered?
A researcher finds Corynebacterium on a patient, what is important to note? (Select all that apply).
A researcher finds Corynebacterium on a patient, what is important to note? (Select all that apply).
Considering the complex interplay between bacterial surface structures and host defenses, what would be the most likely consequence of a mutation in Staphylococcus aureus that disrupts the d-alanylation of teichoic acids?
Considering the complex interplay between bacterial surface structures and host defenses, what would be the most likely consequence of a mutation in Staphylococcus aureus that disrupts the d-alanylation of teichoic acids?
A novel bacterium employs a unique strategy to evade the host immune response. It synthesizes a cell-surface molecule that mimics a key human complement regulatory protein, Factor H. Which of the following mechanisms would most likely contribute to immune evasion by this bacterium?
A novel bacterium employs a unique strategy to evade the host immune response. It synthesizes a cell-surface molecule that mimics a key human complement regulatory protein, Factor H. Which of the following mechanisms would most likely contribute to immune evasion by this bacterium?
A research team is investigating a novel Pseudomonas aeruginosa strain resistant to multiple antibiotics and capable of forming exceptionally robust biofilms. Transcriptomic analysis reveals overexpression of a previously uncharacterized efflux pump and a novel exopolysaccharide. What experimental approach would give the MOST comprehensive understanding of the synergistic contribution of these two factors to antibiotic resistance?
A research team is investigating a novel Pseudomonas aeruginosa strain resistant to multiple antibiotics and capable of forming exceptionally robust biofilms. Transcriptomic analysis reveals overexpression of a previously uncharacterized efflux pump and a novel exopolysaccharide. What experimental approach would give the MOST comprehensive understanding of the synergistic contribution of these two factors to antibiotic resistance?
A novel bacterial pathogen is discovered in a population of immunocompromised patients. This bacterium expresses a surface protein with a high affinity for the PD-1 receptor on T cells. What is the most likely mechanism by which this interaction contributes to bacterial pathogenesis?
A novel bacterial pathogen is discovered in a population of immunocompromised patients. This bacterium expresses a surface protein with a high affinity for the PD-1 receptor on T cells. What is the most likely mechanism by which this interaction contributes to bacterial pathogenesis?
A researcher is investigating the mechanism of action of a newly discovered antibacterial compound that selectively inhibits peptidoglycan synthesis. Biochemical assays reveal that the compound does not directly inhibit any of the known enzymes involved in peptidoglycan precursor synthesis or polymerization. However, further analysis demonstrates that the compound binds specifically to the undecaprenyl pyrophosphate (UPP) recycling phosphatase. What is the MOST likely mechanism by which this binding disrupts peptidoglycan synthesis?
A researcher is investigating the mechanism of action of a newly discovered antibacterial compound that selectively inhibits peptidoglycan synthesis. Biochemical assays reveal that the compound does not directly inhibit any of the known enzymes involved in peptidoglycan precursor synthesis or polymerization. However, further analysis demonstrates that the compound binds specifically to the undecaprenyl pyrophosphate (UPP) recycling phosphatase. What is the MOST likely mechanism by which this binding disrupts peptidoglycan synthesis?
A novel species of Mycobacterium isolated from a patient with disseminated infection exhibits an unusual cell wall structure lacking mycolic acids. Instead, the cell wall is composed of a unique arabinogalactan modified with sulfated glycolipids. What compensatory adaptation is most likely present in this bacterium to maintain cell wall integrity and prevent lysis?
A novel species of Mycobacterium isolated from a patient with disseminated infection exhibits an unusual cell wall structure lacking mycolic acids. Instead, the cell wall is composed of a unique arabinogalactan modified with sulfated glycolipids. What compensatory adaptation is most likely present in this bacterium to maintain cell wall integrity and prevent lysis?
A researcher is studying a novel mechanism of bacterial persistence in Escherichia coli during antibiotic treatment. They discover that a subpopulation of cells enters a dormant state characterized by drastically reduced metabolic activity and ribosome silencing. Further investigation reveals that this dormancy is triggered by the accumulation of ppGpp, a bacterial alarmone, but unexpectedly, these persistent cells lack the canonical ppGpp synthetases RelA and SpoT. What is the most plausible explanation for ppGpp accumulation in these cells?
A researcher is studying a novel mechanism of bacterial persistence in Escherichia coli during antibiotic treatment. They discover that a subpopulation of cells enters a dormant state characterized by drastically reduced metabolic activity and ribosome silencing. Further investigation reveals that this dormancy is triggered by the accumulation of ppGpp, a bacterial alarmone, but unexpectedly, these persistent cells lack the canonical ppGpp synthetases RelA and SpoT. What is the most plausible explanation for ppGpp accumulation in these cells?
A research team is investigating the molecular basis of biofilm formation in a newly isolated species of Vibrio. They identify a gene encoding a novel protein with significant homology to bacterial cupins, a diverse superfamily of proteins with varied enzymatic activities. Deletion of this gene results in a dramatic reduction in biofilm formation. What experimental approach would be MOST effective in determining the specific role of this cupin-like protein in biofilm development?
A research team is investigating the molecular basis of biofilm formation in a newly isolated species of Vibrio. They identify a gene encoding a novel protein with significant homology to bacterial cupins, a diverse superfamily of proteins with varied enzymatic activities. Deletion of this gene results in a dramatic reduction in biofilm formation. What experimental approach would be MOST effective in determining the specific role of this cupin-like protein in biofilm development?
A novel bacterial species is isolated from the gut microbiome of individuals with inflammatory bowel disease (IBD). This bacterium produces a unique polysaccharide that potently activates the NLRP3 inflammasome in macrophages, leading to the release of IL-1β and exacerbation of intestinal inflammation. What strategy is most likely to prevent this?
A novel bacterial species is isolated from the gut microbiome of individuals with inflammatory bowel disease (IBD). This bacterium produces a unique polysaccharide that potently activates the NLRP3 inflammasome in macrophages, leading to the release of IL-1β and exacerbation of intestinal inflammation. What strategy is most likely to prevent this?
A team of researchers discovers a new species of archaea living in extremely acidic conditions. Unlike other known archaea, this species lacks a cell wall composed of pseudomurein. Instead, microscopic analyses reveal a complex outer layer composed primarily of highly glycosylated S-layer proteins cross-linked by disulfide bonds. Genetic analysis reveals the presence of genes encoding a novel family of glycosyltransferases and a unique disulfide bond forming enzyme. Which of the following experimental approaches would be MOST effective in determining the specific roles of these glycosyltransferases and the disulfide bond forming enzyme in maintaining cell integrity and acid resistance?
A team of researchers discovers a new species of archaea living in extremely acidic conditions. Unlike other known archaea, this species lacks a cell wall composed of pseudomurein. Instead, microscopic analyses reveal a complex outer layer composed primarily of highly glycosylated S-layer proteins cross-linked by disulfide bonds. Genetic analysis reveals the presence of genes encoding a novel family of glycosyltransferases and a unique disulfide bond forming enzyme. Which of the following experimental approaches would be MOST effective in determining the specific roles of these glycosyltransferases and the disulfide bond forming enzyme in maintaining cell integrity and acid resistance?
A newly identified bacterial pathogen possesses a Type VI secretion system (T6SS) with a unique effector protein. This effector, upon delivery into a eukaryotic host cell, directly binds to and ubiquitinates host cell ribosomes. What is the most likely consequence of this activity?
A newly identified bacterial pathogen possesses a Type VI secretion system (T6SS) with a unique effector protein. This effector, upon delivery into a eukaryotic host cell, directly binds to and ubiquitinates host cell ribosomes. What is the most likely consequence of this activity?
A genetic screen in Bacillus subtilis identifies a mutation that results in a complete absence of spore formation under conditions of nutrient deprivation. Further analysis reveals that the mutation lies in a gene encoding a novel RNA methyltransferase. Which of the following substrates of this methyltransferase would most likely be involved in the regulation of sporulation?
A genetic screen in Bacillus subtilis identifies a mutation that results in a complete absence of spore formation under conditions of nutrient deprivation. Further analysis reveals that the mutation lies in a gene encoding a novel RNA methyltransferase. Which of the following substrates of this methyltransferase would most likely be involved in the regulation of sporulation?
During an investigation into the spread of antibiotic resistance genes, a mobile genetic element is discovered in a clinical isolate of E. coli. This element contains a cluster of genes encoding enzymes that modify lipopolysaccharide (LPS), specifically adding unique sugar residues to the Lipid A region. What is the most likely consequence of this modification?
During an investigation into the spread of antibiotic resistance genes, a mobile genetic element is discovered in a clinical isolate of E. coli. This element contains a cluster of genes encoding enzymes that modify lipopolysaccharide (LPS), specifically adding unique sugar residues to the Lipid A region. What is the most likely consequence of this modification?
A newly discovered bacterial pathogen specifically targets and destroys Paneth cells in the small intestine. Paneth cells are critical for maintaining the gut microbiome balance by producing antimicrobial peptides (AMPs). What is the most likely downstream consequence of Paneth cell depletion caused by this pathogen?
A newly discovered bacterial pathogen specifically targets and destroys Paneth cells in the small intestine. Paneth cells are critical for maintaining the gut microbiome balance by producing antimicrobial peptides (AMPs). What is the most likely downstream consequence of Paneth cell depletion caused by this pathogen?
In a laboratory experiment, Streptococcus pneumoniae cells are grown in a chemically defined medium containing a limiting concentration of choline. The resulting cells exhibit a significant reduction in the amount of teichoic acid incorporated into their cell walls. What alterations to the cell could be expected?
In a laboratory experiment, Streptococcus pneumoniae cells are grown in a chemically defined medium containing a limiting concentration of choline. The resulting cells exhibit a significant reduction in the amount of teichoic acid incorporated into their cell walls. What alterations to the cell could be expected?
A research team is studying a quorum-sensing system in a novel Gram-negative bacterium. They identify a unique autoinducer molecule that, unlike typical acyl-homoserine lactones (AHLs), contains a complex cyclopeptide structure. This autoinducer binds to a LuxR homologue, but, instead of directly activating transcription, the complex recruits a histone deacetylase (HDAC) to specific promoter regions. What is the most likely consequence of this quorum-sensing mechanism?
A research team is studying a quorum-sensing system in a novel Gram-negative bacterium. They identify a unique autoinducer molecule that, unlike typical acyl-homoserine lactones (AHLs), contains a complex cyclopeptide structure. This autoinducer binds to a LuxR homologue, but, instead of directly activating transcription, the complex recruits a histone deacetylase (HDAC) to specific promoter regions. What is the most likely consequence of this quorum-sensing mechanism?
A researcher discovers a new bacterial species that exhibits an unusual mechanism for iron acquisition. Instead of producing siderophores, this bacterium synthesizes and secretes a small molecule that directly reduces $Fe^{3+}$ to $Fe^{2+}$ in the extracellular environment. The $Fe^{2+}$ is then transported into the cell via a specific ferrous iron transporter. What is the principal challenge?
A researcher discovers a new bacterial species that exhibits an unusual mechanism for iron acquisition. Instead of producing siderophores, this bacterium synthesizes and secretes a small molecule that directly reduces $Fe^{3+}$ to $Fe^{2+}$ in the extracellular environment. The $Fe^{2+}$ is then transported into the cell via a specific ferrous iron transporter. What is the principal challenge?
A novel antimicrobial peptide (AMP) is designed to target Gram-negative bacteria by disrupting the outer membrane. This AMP is highly cationic and amphipathic, but, unexpectedly, it exhibits very low activity against bacteria grown in high-salt conditions. What is the most likely explanation for this observation?
A novel antimicrobial peptide (AMP) is designed to target Gram-negative bacteria by disrupting the outer membrane. This AMP is highly cationic and amphipathic, but, unexpectedly, it exhibits very low activity against bacteria grown in high-salt conditions. What is the most likely explanation for this observation?
A researcher is studying the impact of horizontal gene transfer on the evolution of virulence in Vibrio cholerae. They discover a previously unknown genomic island integrated into the V. cholerae chromosome. This island encodes a novel ADP-ribosylating toxin that targets a specific component of the host cell cytoskeleton. However, the expression of the toxin gene is tightly repressed by a small regulatory RNA (sRNA) also encoded within the genomic island. What condition could activate the toxin?
A researcher is studying the impact of horizontal gene transfer on the evolution of virulence in Vibrio cholerae. They discover a previously unknown genomic island integrated into the V. cholerae chromosome. This island encodes a novel ADP-ribosylating toxin that targets a specific component of the host cell cytoskeleton. However, the expression of the toxin gene is tightly repressed by a small regulatory RNA (sRNA) also encoded within the genomic island. What condition could activate the toxin?
During biofilm formation, bacterial cells transition from motile to sessile states. Which post-translational modification plays a crucial role?
During biofilm formation, bacterial cells transition from motile to sessile states. Which post-translational modification plays a crucial role?
A research team is studying a novel approach to combatting Clostridium difficile infections (CDI) using engineered bacteriophages. They construct a phage that expresses a cell wall hydrolase (CWH) targeted to cleave a specific glycosidic bond within the C. difficile peptidoglycan. However, they find that while the engineered phage effectively kills vegetative cells, it has limited impact on spore germination. What modification strategy could enhance the efficacy?
A research team is studying a novel approach to combatting Clostridium difficile infections (CDI) using engineered bacteriophages. They construct a phage that expresses a cell wall hydrolase (CWH) targeted to cleave a specific glycosidic bond within the C. difficile peptidoglycan. However, they find that while the engineered phage effectively kills vegetative cells, it has limited impact on spore germination. What modification strategy could enhance the efficacy?
What is a critical adaptation to survive and colonize the stomach?
What is a critical adaptation to survive and colonize the stomach?
In areas where plague is endemic, why is it crucial to monitor rodent populations?
In areas where plague is endemic, why is it crucial to monitor rodent populations?
A patient is diagnosed with tuberculosis (TB) but is unable to tolerate the standard first-line drug, isoniazid (INH), due to severe side effects. Which alteration to therapy is best?
A patient is diagnosed with tuberculosis (TB) but is unable to tolerate the standard first-line drug, isoniazid (INH), due to severe side effects. Which alteration to therapy is best?
An outbreak of erythrasma is observed in a long-term care facility. What regimen is best?
An outbreak of erythrasma is observed in a long-term care facility. What regimen is best?
A novel efflux pump is identified in Pseudomonas aeruginosa, which, surprisingly, exhibits highest activity in the periplasmic space rather than the inner or outer membrane. Mutation studies reveal that this pump specifically interacts with and removes misfolded outer membrane proteins (OMPs) before they can be properly inserted. Which scenario would MOST likely arise from the inactivation of this periplasmic efflux pump?
A novel efflux pump is identified in Pseudomonas aeruginosa, which, surprisingly, exhibits highest activity in the periplasmic space rather than the inner or outer membrane. Mutation studies reveal that this pump specifically interacts with and removes misfolded outer membrane proteins (OMPs) before they can be properly inserted. Which scenario would MOST likely arise from the inactivation of this periplasmic efflux pump?
A research team discovers a bacterial species capable of thriving in extremely oligotrophic (nutrient-poor) environments. Genomic analysis reveals a highly unusual modification in its ribosomes: the replacement of several universally conserved ribosomal proteins with novel paralogs containing extensive intrinsically disordered regions (IDRs). What is the MOST plausible selective advantage conferred by this ribosomal modification?
A research team discovers a bacterial species capable of thriving in extremely oligotrophic (nutrient-poor) environments. Genomic analysis reveals a highly unusual modification in its ribosomes: the replacement of several universally conserved ribosomal proteins with novel paralogs containing extensive intrinsically disordered regions (IDRs). What is the MOST plausible selective advantage conferred by this ribosomal modification?
A bacterial pathogen has evolved a unique mechanism to subvert host immunity. It synthesizes a family of secreted proteases that specifically cleave and inactivate host microRNAs (miRNAs) that regulate the expression of key inflammasome components. What is the MOST likely consequence of this activity?
A bacterial pathogen has evolved a unique mechanism to subvert host immunity. It synthesizes a family of secreted proteases that specifically cleave and inactivate host microRNAs (miRNAs) that regulate the expression of key inflammasome components. What is the MOST likely consequence of this activity?
A horizontally acquired genomic island in a bacterial pathogen encodes a novel class of restriction-modification (R-M) system. Unlike typical R-M systems that protect the bacterial genome from foreign DNA, this system exhibits 'epigenetic editing' activity: it selectively methylates specific adenine residues within the host bacterium's own tRNA genes, modulating their folding and aminoacylation efficiency according to environmental signals. Which of the following is the MOST plausible outcome of this epigenetic editing?
A horizontally acquired genomic island in a bacterial pathogen encodes a novel class of restriction-modification (R-M) system. Unlike typical R-M systems that protect the bacterial genome from foreign DNA, this system exhibits 'epigenetic editing' activity: it selectively methylates specific adenine residues within the host bacterium's own tRNA genes, modulating their folding and aminoacylation efficiency according to environmental signals. Which of the following is the MOST plausible outcome of this epigenetic editing?
During prolonged antibiotic stress, a subpopulation of E. coli cells enters a deep quiescent state characterized by the formation of intracellular crystalline structures composed of aggregated ribosomal proteins and mRNA. These structures are resistant to proteolysis and RNase activity, and cells remain non-culturable on standard media. What is the MOST plausible mechanism underlying the formation of these protective crystalline structures?
During prolonged antibiotic stress, a subpopulation of E. coli cells enters a deep quiescent state characterized by the formation of intracellular crystalline structures composed of aggregated ribosomal proteins and mRNA. These structures are resistant to proteolysis and RNase activity, and cells remain non-culturable on standard media. What is the MOST plausible mechanism underlying the formation of these protective crystalline structures?
A research team is studying a novel species of Mycobacterium isolated from a patient with disseminated infection that exhibits an unusual cell wall structure lacking mycolic acids. Instead, the cell wall is composed of a unique arabinogalactan modified with sulfated glycolipids. What compensatory adaptation is most likely present in this bacterium to maintain cell wall integrity and prevent lysis?
A research team is studying a novel species of Mycobacterium isolated from a patient with disseminated infection that exhibits an unusual cell wall structure lacking mycolic acids. Instead, the cell wall is composed of a unique arabinogalactan modified with sulfated glycolipids. What compensatory adaptation is most likely present in this bacterium to maintain cell wall integrity and prevent lysis?
A novel bacterial species is discovered in a highly alkaline environment (pH 11). Its cell envelope exhibits an exceptionally high proportion of unusual lipids containing branched isoprene chains and ether linkages. Furthermore, the cytoplasmic membrane is unusually rich in hopanoids modified with positively charged amino groups. What is the MOST plausible explanation for these unique lipid adaptations?
A novel bacterial species is discovered in a highly alkaline environment (pH 11). Its cell envelope exhibits an exceptionally high proportion of unusual lipids containing branched isoprene chains and ether linkages. Furthermore, the cytoplasmic membrane is unusually rich in hopanoids modified with positively charged amino groups. What is the MOST plausible explanation for these unique lipid adaptations?
In a bacterial stress response study, researchers discover that under prolonged exposure to oxidative stress, Bacillus subtilis cells undergo a morphological transition, forming multicellular aggregates encased in a protective matrix composed of extracellular DNA (eDNA) and amyloid fibers. Further analysis reveals that the eDNA within these aggregates is heavily modified with 5-hydroxymethylcytosine (5hmC). What is the MOST likely function of 5hmC modification in this context?
In a bacterial stress response study, researchers discover that under prolonged exposure to oxidative stress, Bacillus subtilis cells undergo a morphological transition, forming multicellular aggregates encased in a protective matrix composed of extracellular DNA (eDNA) and amyloid fibers. Further analysis reveals that the eDNA within these aggregates is heavily modified with 5-hydroxymethylcytosine (5hmC). What is the MOST likely function of 5hmC modification in this context?
A novel bacterial species displays a unique mechanism of horizontal gene transfer that involves the formation of intercellular nanotubes directly connecting the cytoplasm of adjacent cells, even across species boundaries. These nanotubes are stabilized by a novel cytoskeletal protein with homology to eukaryotic septins. Which of the following is the MOST likely evolutionary consequence of this unconventional horizontal gene transfer mechanism?
A novel bacterial species displays a unique mechanism of horizontal gene transfer that involves the formation of intercellular nanotubes directly connecting the cytoplasm of adjacent cells, even across species boundaries. These nanotubes are stabilized by a novel cytoskeletal protein with homology to eukaryotic septins. Which of the following is the MOST likely evolutionary consequence of this unconventional horizontal gene transfer mechanism?
A research team identifies a novel bacterial species that secretes vesicles containing catalytically active Cas13 enzymes. These vesicles are taken up by other bacteria, where the Cas13 enzymes degrade specific host mRNAs, leading to growth inhibition. What is the MOST plausible ecological role of this inter-bacterial CRISPR-Cas13 system?
A research team identifies a novel bacterial species that secretes vesicles containing catalytically active Cas13 enzymes. These vesicles are taken up by other bacteria, where the Cas13 enzymes degrade specific host mRNAs, leading to growth inhibition. What is the MOST plausible ecological role of this inter-bacterial CRISPR-Cas13 system?
A researcher discovers that a particular strain of Staphylococcus aureus exhibits increased resistance to vancomycin following exposure to sub-inhibitory concentrations of a cationic antimicrobial peptide (CAMP). Further investigation reveals that CAMP exposure induces the expression of a membrane-associated flippase that selectively transports phosphatidylglycerol (PG) from the inner to the outer leaflet of the cytoplasmic membrane. What is the most likely mechanism by which this phospholipid remodeling contributes to vancomycin resistance?
A researcher discovers that a particular strain of Staphylococcus aureus exhibits increased resistance to vancomycin following exposure to sub-inhibitory concentrations of a cationic antimicrobial peptide (CAMP). Further investigation reveals that CAMP exposure induces the expression of a membrane-associated flippase that selectively transports phosphatidylglycerol (PG) from the inner to the outer leaflet of the cytoplasmic membrane. What is the most likely mechanism by which this phospholipid remodeling contributes to vancomycin resistance?
A novel bacterial species, isolated from a deep-sea hydrothermal vent, possesses a unique metabolic adaptation: it utilizes a Type IV secretion system (T4SS) to inject a bacterial luciferase directly into eukaryotic host cells residing within the vent ecosystem. Once inside the host cell, the bacterial luciferase catalyzes a bioluminescent reaction, producing light that attracts other marine organisms, which subsequently become prey for the host cell. What is the MOST plausible evolutionary driver for this inter-kingdom signaling strategy?
A novel bacterial species, isolated from a deep-sea hydrothermal vent, possesses a unique metabolic adaptation: it utilizes a Type IV secretion system (T4SS) to inject a bacterial luciferase directly into eukaryotic host cells residing within the vent ecosystem. Once inside the host cell, the bacterial luciferase catalyzes a bioluminescent reaction, producing light that attracts other marine organisms, which subsequently become prey for the host cell. What is the MOST plausible evolutionary driver for this inter-kingdom signaling strategy?
A previously unknown bacterial species is discovered residing within the chloroplasts of a marine algae. The bacterium possesses a reduced genome lacking genes for peptidoglycan synthesis, but contains a complete set of genes for synthesizing a unique class of branched, non-canonical lipopolysaccharides (LPS) with unusual sugar modifications. What is the MOST plausible function of these non-canonical LPS within the unique endosymbiotic lifestyle of this bacterium?
A previously unknown bacterial species is discovered residing within the chloroplasts of a marine algae. The bacterium possesses a reduced genome lacking genes for peptidoglycan synthesis, but contains a complete set of genes for synthesizing a unique class of branched, non-canonical lipopolysaccharides (LPS) with unusual sugar modifications. What is the MOST plausible function of these non-canonical LPS within the unique endosymbiotic lifestyle of this bacterium?
A research team is investigating the spread of antibiotic resistance in a population of Streptococcus pneumoniae isolates. They discover that conjugative transposons—mobile genetic elements that can excise from and integrate into DNA—are playing a central role in disseminating resistance genes. However, the frequency of conjugative transposition is significantly higher in biofilms compared to planktonic cultures. What is the MOST plausible explanation for this observation?
A research team is investigating the spread of antibiotic resistance in a population of Streptococcus pneumoniae isolates. They discover that conjugative transposons—mobile genetic elements that can excise from and integrate into DNA—are playing a central role in disseminating resistance genes. However, the frequency of conjugative transposition is significantly higher in biofilms compared to planktonic cultures. What is the MOST plausible explanation for this observation?
A novel bacterial pathogen is discovered in immunocompromised patients. This bacterium expresses a surface protein with a high affinity for the PD-1 receptor on T cells. What is the most likely mechanism by which this interaction contributes to bacterial pathogenesis?
A novel bacterial pathogen is discovered in immunocompromised patients. This bacterium expresses a surface protein with a high affinity for the PD-1 receptor on T cells. What is the most likely mechanism by which this interaction contributes to bacterial pathogenesis?
A novel species of archaea living in extremely acidic conditions. Unlike other known archaea, this species lacks a cell wall composed of pseudomurein. Instead, microscopic analyses reveal a complex outer layer composed primarily of highly glycosylated S-layer proteins cross-linked by disulfide bonds. Genetic analysis reveals the presence of genes encoding a novel family of glycosyltransferases and a unique disulfide bond forming enzyme. Which of the following experimental approaches would be MOST effective in determining the specific roles of these glycosyltransferases and the disulfide bond forming enzyme in maintaining cell integrity and acid resistance?
A novel species of archaea living in extremely acidic conditions. Unlike other known archaea, this species lacks a cell wall composed of pseudomurein. Instead, microscopic analyses reveal a complex outer layer composed primarily of highly glycosylated S-layer proteins cross-linked by disulfide bonds. Genetic analysis reveals the presence of genes encoding a novel family of glycosyltransferases and a unique disulfide bond forming enzyme. Which of the following experimental approaches would be MOST effective in determining the specific roles of these glycosyltransferases and the disulfide bond forming enzyme in maintaining cell integrity and acid resistance?
Flashcards
Direct Transmission
Direct Transmission
Direct transmission of a disease from one infected person/animal to another.
Indirect Transmission
Indirect Transmission
Transmission of a disease from an infected person to another via an intermediate object or substance.
Vector Transmission
Vector Transmission
Transmission of a disease via another organism from person to person or animal to person.
Person-to-Person Transmission
Person-to-Person Transmission
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Droplet Transmission
Droplet Transmission
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Fecal-Oral Transmission
Fecal-Oral Transmission
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Airborne Transmission
Airborne Transmission
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Fomite
Fomite
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Insect Bite Transmission
Insect Bite Transmission
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Endogenous Sources
Endogenous Sources
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Exogenous Sources
Exogenous Sources
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Fimbriae/Pili
Fimbriae/Pili
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Bacterial Chromosome
Bacterial Chromosome
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Plasmid
Plasmid
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Cell Wall
Cell Wall
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Flagellum
Flagellum
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Endospore
Endospore
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Bacterial Conjugation
Bacterial Conjugation
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Bacterial Classification
Bacterial Classification
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Gram Staining
Gram Staining
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Gram-Positive Cell Wall
Gram-Positive Cell Wall
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Gram-Negative Cell Wall
Gram-Negative Cell Wall
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Lipopolysaccharide (LPS)
Lipopolysaccharide (LPS)
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Bacterial Cell Wall
Bacterial Cell Wall
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Pathogen
Pathogen
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Pathogenicity
Pathogenicity
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Invasiveness
Invasiveness
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Exotoxins
Exotoxins
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Endotoxins
Endotoxins
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Hyaluronidase
Hyaluronidase
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Collagenase
Collagenase
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Streptokinase/Staphylokinase
Streptokinase/Staphylokinase
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Enzymes Destroying Human Cells
Enzymes Destroying Human Cells
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Penicillin Action
Penicillin Action
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Bacterial Spores
Bacterial Spores
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MRSA
MRSA
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Staphylococcus Aureus
Staphylococcus Aureus
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S. Aureus
S. Aureus
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Streptococcus Pneumoniae
Streptococcus Pneumoniae
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Erythrasma
Erythrasma
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Neisseria
Neisseria
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Salmonella
Salmonella
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E. Coli
E. Coli
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Yersinia-pestis
Yersinia-pestis
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Vibrio Cholerae
Vibrio Cholerae
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Helicobacter Pylori
Helicobacter Pylori
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Pseudomonas Aeruginosa
Pseudomonas Aeruginosa
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Mycobacterium Tuberculosis
Mycobacterium Tuberculosis
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Study Notes
Microbiology Topics
- Spread of infectious disease
- Structure and pathogenicity of Bacteria, Viral, and Fungal organisms.
- Important diseases caused by bacteria, viruses, and fungi
- Microorganisms of the foot
Spread of Organisms
- Diseases can be transmitted from person to person in many ways
- Some can be transmitted in more than one way
- Some transmissions involve direct contact with an infected person
- Other transmissions only require being near an infected person
- Some diseases aren't even spread through contact with people at all, but through contact with animals
Methods of Disease Transmission
- Direct transmission means the disease is passed directly from one infected person or animal to another person or animal
- Indirect transmission happens when a disease is passed from an infected person to another person, even though the two people have not had direct contact
- Vector transmission requires another organism to transmit a disease from person to person, or from animal to person
- This is a type of zoonotic (animal to person) transmission, different from direct zoonosis, where a vertebrate animal contracts a disease and passes it directly to a person, as with rabies
Transmission Types
- Person-to-person transmission can happen anytime an infected person touches or exchanges body fluids with another person
- Kissing can be a method of person-to-person transmission
- A pregnant mother can pass a disease to their unborn child
- Some diseases are spread by coughing or sneezing, which can cause droplets containing the infectious agent to land on nearby people
- Fecal-oral transmission happens when feces, often microscopic amounts, are transmitted from an infected person or animal to another person by mouth.
- This can happen if food workers use the restroom but do not adequately wash their hands before preparing food for customers
- Sometimes, an infectious agent enters the air when an infected person sneezes, coughs, laughs, or even just breathes, and it can remain in the air for an extended period of time
- When another person comes into contact with the agent, it can lead to airborne transmission
- A fomite is an inanimate object that serves as a vehicle to pass an infectious disease from an infected person to a healthy person
- A water fountain can become contaminated by the saliva of an infected person and pass the disease to another person who drinks from it
- Other potential fomites include doorknobs, handrails, and shared computer keyboards
- Vector-borne diseases are most commonly transmitted by insect bites
- For example, mosquitoes acquire malaria parasites by feeding on infected humans and then transfer that infection to other people when they feed again
- The plague, which killed tens of millions of Europeans in the fourteenth century, was transmitted from rats to humans through flea bites
Sneeze Facts
- During a sneeze, millions of tiny droplets of water and mucus are expelled at about 200 miles per hour (100 meters per second)
- The droplets are initially about 10-100 micrometers in diameter, but they dry rapidly to droplet nuclei of 1-4 micrometers, containing virus particles or bacteria
- Sneezing is a major means of transmission of several human diseases
Diseases Transmitted by Inhaled Airborne Particles
- Virus diseases: Chickenpox, Flu, Measles (Rubella), German measles (Rubella), Mumps, Smallpox, Covid 19
- Bacterial diseases: Whooping cough, Meningitis, Diphtheria, Pneumonia, Tuberculosis
Sources and Reservoirs
- Endogenous sources are sites of flora or infection on a person's own body
- Exogenous sources include infected or colonized people, infected or colonized animals, and environmental sources
Exogenous Sources
- People
- Animals
- Environmental sources
How Diseases Enter the Body
- For any disease to progress, it has to enter the body
- Entry points include the mouth, conjunctiva, skin (scratch or injury), respiratory tract, alimentary canal, urogenital tract, and through arthropods
Adhesion
- Once a microbe enters the body, it must adhere to the tissues
- Microbes will us a number of methods to do this: Fimbriae, capsules, spikes, hooks or flagella
Bacterial Structure
- Bacteria are very small but show a surprising degree of structural complexity
- Bacteria can adhere to their “victim" by pili, a proteinaceous surface structure
- Many bacteria are capable of movement in their environment by flagella
- Flagella are a long, flexible, spiral-shaped structure that helps to push the microbe through solution
- As a microbe grows it has to synthesize more of itself
- Microbes are also capable of exchanging genetic information by mating
- Bacteria will create of resting structures that allow it to "sleep" during bad times and ensure their survival
- During abundant times, many microbes will store excess carbon, nitrogen, sulfur or phosphorous in inclusions in the cell
Bacterial Spores
- Many bacteria produce spores when times are hard
- Spores contain almost no water or proteins but still contain all the genes of the bacterium
- Almost all life processes are shut down
- Spores have very tough walls and can survive very harsh conditions
- Dormant bacteria are able to survive for weeks, even years, through drought, heat, and even radiation
- Bacteria will transform from spore back to cell form during favorable conditions, with more water or more food available
- Some bacterial spores may have been revived after laying underground for more than 250 million years!
E. Coli
- E. coli is a Gram-negative rod just after division with pili (fimbriae) on the cell surface
- E. coli can cause urinary tract infections, traveler's diarrhea, and nosocomial infections
Bacterial Classification
- Bacteria are classified based on their microscopic appearance
- Bacteria is classified as gram positive OR negative based upond staining characteristics
- Bacteria shape (cocci or bacilli) is dependent upon morphological characteristics.
- Bacteria can be classified by utilisation of oxygen and by spore production
The Gram Reaction
- The Gram reaction is named after the Danish physician, Christian Gram, who developed this staining technique in 1884
- Bacterial cells are dried onto a glass slide and stained with crystal violet, then washed briefly in water
- Iodine solution is added so that the iodine forms a complex with crystal violet in the cells
- Alcohol or acetone is added to solubilize the crystal violet - iodine complex
- The cells are counter-stained with safranin, then rinsed and dried for microscopy
Gram + and Gram -
- The difference in staining reflects a fundamental difference in the organization of the bacterial cell wall or "cell envelope"
- Gam positive cells have a thick peptidoglycan layer, and a cell membrane
- Gram negative cells have an outer membrane, a thin peptidoglycan layer, and a plasma membrane
Gram Reaction Summary
- The method separates bacteria into two types
- Gram-positive cells retain the crystal violet-iodine complex and thus appear purple (shown for Bacillus cereus in the left-hand image)
- Gram-negative cells are decolourised by the alcohol or acetone treatment, but are then stained with safranin so they appear pink (shown for Pseudomonas aeruginosa in the right-hand image)
- The essential difference between Gram-positive and Gram-negative cells is their ability to retain the crystal violet-iodine complex when treated with a solvent
The Bacterial Cell Wall
- The cell wall is a critical structure in bacterial cells; its absence would cause the cell to swell and burst
- Many compounds found in the bacterial cell wall are found nowhere else in nature
- Numerous antibacterial agents target the cell wall because mammals do not synthesize walls and therefore are immune to the toxic effects of these agents
- Lysozyme is an enzyme found in tears and saliva that breaks down a component of cell walls and it is a critical part of the mammalian defense against bacterial invasion
Bacterial Cell Wall Properties
- Peptidoglycan is a thick rigid layer that is found in both G+ and G- cells (but in different amounts)
- Peptidoglycan composed of overlapping lattice of two sugars that are crosslinked by amino acid bridges
- The Gram+ cell wall has a thick peptidoglycan layer
- the G+ cell wall is very sensitive to the action of lysozyme and penicillin, or its derivatives
- Penicillin is often the antibiotic of choice for infections caused by G+ organisms e.g. Streptococcus pyogenes, which causes strep throat
- Teichoic acid is bound to the peptidoglycan layer & may facilitate attachment to mucosal surfaces via binding to fibronectin e.g. Staphylococcal infection
Gram Negative Cell Wall
- G- cell walls have a more complicated structure
- There is a thin layer of peptidoglycan
- External to the peptidoglycan is an additional membrane, the outer membrane (OM)
- The OM is a lipid bilayer similar to the cell membrane, containing lipids and proteins, but also contains lipopolysaccharides
Lipopolysaccharide
- LPS is biologically very important because it has pathogenic activities in humans
- Free LPS in solution is toxic and is called endotoxin & can cause the induction of a fever, because endotoxins are 'pyrogenic'
- LPS can cause changes in white blood cell counts
- It can cause disseminated intravascular coagulation
- LPS can cause dropping blood pressure leading to vascular collapse and eventually shock
- At high enough concentrations, endotoxin can be lethal.
Bacterial Shapes
- Bacteria may be: circular, rod-shaped, curved, or other shapes (helical, club, spiral)
- Circular: Diplococci (in pairs), Streptococci (in chains), Staphylococci (clusters)
- Rod-shaped: Coccobacilli (oval), Streptobacilli, Mycobacteria
- Curved: Vibrio (curved rod), Sprilla (coil),
- Other: Helicobacter (helical), Corynebacter (club), Spirochete (spiral), Streptomyces
Aerobic Vs Anaerobic
- Aerobic bacteria require oxygen for their growth
- obligate aerobic bacteria cannot survive in absence of oxygen
- microaerophilic bacteria require lower concentration of oxygen
- Anaerobic bacteria do not require oxygen for growth
- obligate anaerobic bacteria annot survive in the presence of oxygen
- facultative anaerobic bacteria can grow without oxygen but use oxygen if it is present
- aerotolerant bacteria cannot use oxygen for their growth but are not harmed by it
Active Antibiotics for Gram + and Gram - Bacteria
- Co-amoxiclav
- Piptazobactam
- Ertapenem
- Imipenem
- Meropenem
- Cefuroxime (no anaerobic cover)
- Cefotaxime (no anaerobic cover)
- Ceftriaxone (no anaerobic cover)
Active Antibiotics Against Anaerobes
- Co-amoxiclav
- Piptazobactam
- Ertapenem
- Imipenem
- Meropenem
- Clindamycin
- Metronidazole
Bacterial Pathogenicity
- A pathogen is a microorganism that is able to cause disease in a plant, animal or insect
- Pathogenicity is the ability to produce disease in a host organism
- Microbes express their pathogenicity by means of their virulence/ the degree of pathogenicity of the microbe
- The outcome of an infection depends on the virulence of the pathogen and the relative degree of resistance or susceptibility of the host, due mainly to the effectiveness of the host defense mechanisms
Pathogenic Factors
- Pathogens have two main abilities: to invade tissues and to produce toxins
- Invasiveness the ability to bypass or overcome host defense mechanisms, and the production of extracellular substances which facilitate invasion
- Toxigenesis - exotoxins and endotoxins
- Exotoxins are released from bacterial cells and may act at tissue sites removed from the site of bacterial growth
- Endotoxins are cell-associated substances that are structural components of the cell walls of Gram-negative bacteria
- Endotoxins may be released from growing bacterial cells or from cells which are lysed as a result of effective host defense e.g. lysozyme or the activities of certain antibiotics (e.g. penicillins and cephalosporins)
- Bacterial toxins, both soluble and cell-associated, may be transported by blood and lymph and cause cytotoxic effects at tissue sites remote from the original point of invasion or growth.
Invasiveness Explained
- The invasion of a host by a pathogen may be aided by the production of bacterial extracellular substances which act against the host by breaking down primary or secondary defenses of the body
- Hyaluronidase is produced by Streptococci, Staphylococci, and Clostridia. The enzyme attacks the interstitial cement ("ground substance") of connective tissue
- Collagenase is produced by Clostridium histolyticum and Clostridium perfringens. It breaks down collagen, the framework of muscles, which facilitates gas gangrene due to these organisms
- Streptokinase and Staphylokinase are produced by Streptococci and Staphylococci, respectively
- Kinase enzymes convert inactive plasminogen to plasmin which digests fibrin and prevents clotting of the blood
- The relative absence of fibrin in spreading bacterial lesions allows more rapid diffusion of the infectious bacteria
Enzymes That Destroy Human Cells
- These enzymes insert into the cell membrane forming a pore that results in cell lysis OR by enzymatic attack on phospholipids, which destabilizes the membrane
- Haemolysins are produced by Staphylococci, Streptococci i.e. streptolysin and various Clostridia & destroy red blood cells and other cells i.e. phagocytes by lysis
- Leukocidins (Staphylococci) & streptolysin (Streptococci) specifically lyse phagocytes and their granules. These latter two enzymes are also considered to be bacterial exotoxins
- Phospholipases, produced by Clostridium perfringens hydrolyse phospholipids in cell membranes by removal of polar head groups
- Lecithinases, also produced by Clostridium perfringens, destroy lecithin (phosphatidylcholine) in cell membranes
Overcoming Host Defenses
- Bacteria can avoid the attention of phagocytes in a number of ways:
- Invade or remain confined in regions inaccessible to phagocytes (the lumen of glands & surface tissues like skin
- Avoid provoking an overwhelming inflammatory response
- Inhibit phagocyte chemotaxis
- Hide the antigenic surface of the bacterial cell
Avoiding Engulfment
- Many important pathogenic bacteria display surface substances that inhibit phagocytic adsorption or engulfment
- Resistance to phagocytic ingestion is usually due to a component of the bacterial cell wall, or fimbriae, or a capsule enclosing the bacterial wall
- Examples: Polysaccharide capsules of S. pneumoniae, Haemophilus influenzae, Treponema pallidum and Klebsiella pneumoniae, M protein and fimbriae of Group A Streptococci, Surface slime (polysaccharide) produced by Pseudomonas aeruginosa, O antigen associated with LPS of E. coli, *K antigen of E. coli or the analogous Vi antigen of Salmonella typhi, Cell-bound or soluble Protein A produced by Staphylococcus aureus
Survival Inside the Phagocyte
- Bacteria that can resist killing and survive or multiply inside of phagocytes are considered intracellular parasites
- Most intracellular parasites have special (genetically-encoded) mechanisms to get themselves into their host cell as well as special mechanisms to survive once they are inside, surviving by virtue of mechanisms which interfere with the bactericidal activities of the host cell
- Some mechanisms include: Inhibition of phagosome-lysosome fusion, survival inside the phagolysosome, and escaping from the phagosome
Exotoxins and Endotoxins
- Toxins are classified by their origins
- An exotoxin is an unbound toxin molecule secreted by a living cell
- An Endotoxin is released after the pathogen is dead
Penicillin
- The antibacterial effect of penicillin was discovered by Alexander Fleming in 1929
- He noted that a fungal colony had grown as a contaminant on an agar plate streaked with the bacterium Staphylococcus aureus, and that the bacterial colonies around the fungus were transparent, because their cells were lysing
- Fleming devoted much of his career to finding methods for treating wound infections and immediately recognised the importance of a fungal metabolite that might be used to control bacteria
- The substance penicillin, because the fungal contaminant was identified as Penicillium notatum
- Fleming found that was effective against many Gram positive bacteria in laboratory conditions, and he even used locally applied, crude preparations of this substance, from culture filtrates, to control eye infections.
- He could not purify this compound because of its instability, and it was not until the period of the Second World War (1939-1945) that two other British scientists, Florey and Chain, working in the USA, managed to produce the antibiotic on an industrial scale for widespread use
- All three scientists shared the Nobel Prize for this work, which saved literally millions of lives
- It is still a "front line" antibiotic, in common use for some bacterial infections although the development of penicillin-resistance in several pathogenic bacteria now limits its effectiveness
Penicillin Actions
- Penicillin prevents the cross-linking of small peptide chains in peptidoglycan, the main wall polymer of bacteria
- Pre-existing cells are unaffected, but all newly produced cells grow abnormally, unable to maintain their wall rigidity, and they are susceptible to osmotic lysis
Antibiotic Resistance
- Several hundreds of compounds with antibiotic activity have been isolated from microorganisms over the years, but only a few of them are clinically useful.
- The reason for this is that only compounds with selective toxicity can be used clinically - they must be highly effective against a microorganism but have minimal toxicity to humans
- The repeated or continued use of the small number of effective antibiotics creates selection pressure favouring the growth of antibiotic-resistant mutants
- The situation has now become alarming, with the emergence of pathogenic strains that show multiple resistance to a broad range of antibiotics.
MRSA
- One of the most important examples concerns multiple-resistant strains of Staphylococcus aureus in Hospitals.
- Some of these strains cause serious nosocomial (hospital-acquired) infections and are resistant to virtually all the useful antibiotics, including methicillin, cephalosporins and other beta-lactams that target peptidoglycan synthesis, the macrolide antibiotics such as erythromycin and the aminoglycoside antibiotics such as streptomycin and neomycin, all of which target the bacterial ribosome.
- The only compound that can be used effectively against these staphylococci is an older antibiotic, vancomycin, which has some undesirable effects on humans (nephrotoxic & blood disorders).
- Some clinical strains of S. aureus have developed resistance to even this compound
Bacterial Nomenclature
- Bacterial families are further divided into genera/genus and species
- Staphylococcus aureus: FAMILY=MICROCOCCACEAE
- HAS 4 GENERA: PLANOCOCCUS, STOMATOCOCCUS, MICROCOCCUS & STAPHYLOCOCCUS
- SPECIES = Staphylococcus aureus
- The genus is ALWAYS given a capital letter and the species ALWAYS a small letter
- The genus and species also are ALWAYS written in italics
- AfterStaphylococcus aureus It is acceptable having written once in full, to abbreviate to S.aureus
Major Bacterial Human Pathogens
- Aerobic: Staphylococcus, Streptococcus, Bacillus, Corynebacterium, Neisseria, Escherichia, Salmonella, Yersinia, Klebsiella, Proteus, Vibrio, Helicobacter, Pseudomonas, Haemophilus, Bordetella, Mycobacterium, Treponema
- Anaerobic: Clostridium, Bacteroides
Staphylococcus Aureus
- Rosenbach described the two pigmented colony types of Staphylococci and proposed the appropriate nomenclature: Staphylococcus aureus (yellow) and Staphylococcus albus (white) back in 1884
- The latter species mentioned by Rosenbach is now named Staphylococcus epidermidis
- S. aureus is a spherical Gram + bacterium (coccus) which on microscopic examination appears in pairs, short chains, or bunched, grape-like clusters.
Important S. Aureus Characteristics
- Gram-positive, cluster-forming coccus, nonmotile, non-spore forming facultative anaerobe, fermentation of glucose produces mainly lactic acid
- Bacteria is coagulase-positive, found with golden yellow colored colonies on agar
- Bacteria is normal flora of humans found on nasal passages, skin and mucous membranes
- Bacteria a pathogen of humans, causes a wide range of suppurative infections, as well as food poisoning and toxic shock syndrome
Staphylococcal Disease
- Superficial skin lesions such as boils, styes and furuncles
- Serious infections such as pneumonia, mastitis, phlebitis, meningitis, and urinary tract infections
- Deep-seated infections, such as osteomyelitis, septic arthritis and endocarditis.
- S. aureus is a major cause of hospital acquired (nosocomial) infection of surgical wounds and infections associated with indwelling medical devices.
- S. aureus causes food poisoning by releasing enterotoxins into food
- Also causes Toxic shock syndrome by release of pyrogenic exotoxins into the blood stream
- S.epidermidis can infect prostheses and catheters
Staphylococcal Infections
- Serious consequences of Staphylococcal infections occur when the bacteria invade the blood stream
- A resulting septicemia may be rapidly fatal
- A bacteremia may result in seeding other internal abscesses, other skin lesions, or infections in the lung, kidney, heart, skeletal muscle or meninges
Methicillin Resistant Staphylococcus Aureus (MRSA)
- Staphylococcus aureus is found in 20-30% of the noses of normal healthy people and is also commonly found on people's skin.
- Most strains of this bacterium are sensitive to many antibiotics and infections can be effectively treated.
- Staphylococcus aureus which are resistant to an antibiotic called methicillin (same as flucloxacillin) are referred to as methicillin-resistant
- Many commonly prescribed antibiotics are not effective against these bacteria e.g. erythromycin and the cephalosporins
- Staph bacteria and MRSA can spread among people having close contact with infected people
- MRSA is almost always spread by direct physical contact, and not through the air
- Spread may also occur through indirect contact by touching objects (i.e., towels, sheets, wound dressings, clothes, workout areas, sports equipment) contaminated by the infected skin of a person with MRSA
Streptococcus
- A wide variety of both pathogenic and commensal gram + bacteria
- Streptococci often colonize the mucosal surfaces of the mouth, nares and pharynx
- In certain circumstances, they may also inhabit the skin, heart or muscle tissue
- Pathogenic species - S. pyogenes, S. pneumoniae, and S. faecalis
- S. pyogenes or group A streptococci causes acute pharyngitis ("strep throat"), Impetigo, rheumatic fever, scarlet fever, glomerulonephritis, cellulitis & necrotising fasciitis
Bacillus Arthracis
- The arthrax bacillus, Bacillus anthracis, was the first bacterium shown to be the cause of a disease.
- In 1877, Robert Koch grew the organism in pure culture, demonstrated its ability to form endospores, and produced experimental anthrax by injecting it into animals.
- B. anthracis is very large, Gram-positive, and spore forming
- The bacterium can be cultivated in ordinary nutrient medium under aerobic or anaerobic conditions
- Genotypically and phenotypically it is very similar to Bacillus cereus, which is found in soil habitats around the world & is a common cause of gastroenteritis
Arthrax
- Anthrax is primarily a disease of domesticated and wild animals, particularly herbivorous animals such as cattle, sheep, and horses
- Humans become infected if contact with diseased animals, which includes their flesh, bones, hides, hair and excrement.
- Risk of human infection ~ 1/100,000
- Cutaneous anthrax - A minor scratch or abrasion is inoculated by spores from the soil or a contaminated animal or carcass
- The spores germinate & a papule forms within 12-36 hours after infection
- The papule changes rapidly to a vesicle, then a pustule (malignant pustule), and finally into a necrotic ulcer from which infection may disseminate, giving rise to septicaemia
- Lymphatic swelling also occurs within seven days
- In severe cases, where the blood stream is eventually invaded, the disease is frequently fatal.
- Inhalation anthrax (woolsorters' disease) - inhalation of spore-containing dust where animal hair or hides are being handled
- This gives way to fever, chest pain, and a systemic hemorrhagic pathology- fatal if treatment cannot stop the invasive aspect of the infection
- Gastrointestinal anthrax is analogous to cutaneus anthrax but occurs on the intestinal mucosa; the bacteria spread from the mucosal lesion to the lymphatic system
- Results from intestinal anthrax result from the ingestion of poorly cooked meat from infected animals, it is rare with high mortality rate.
Cornyebacterium
- C. diptheriae = diptheria, a Gram + cocci
- diptheria is an acute bacterial disease that usually affects the tonsils, throat, nose and/or
- Droplet transmission, usually by breathing in diptheria bacteria after an infected person has coughed, sneezed
- Can also be spread by handling used tissues or by drinking from a glass used by an infected person
- diptheria can lead to breathing problems, heart
- Vaccine for prevention: Most people receive their first dose as children in the form of a combined vaccine called DTP (diphtheria-tetanus-pertussis)
- For adults, a combination shot, called a Td booster, protects against both tetanus and diptheria - given once every 10 years after age 7 to maintain immunity
- Nearly one out of every 10 people who get diphtheria will die from it
- A recent epidemic of diphtheria in Eastern Europe and the New Independent States of the former Soviet Union resulted in over 5,000 deaths
Corynebacterium Minutissimum
- Erythrasma is a chronic superficial infection of the intertriginous areas of the skin. The organism is usually is present as a normal human skin inhabitant.
- Corynebacteria invade the upper one-third of the stratum corneum, where with heat and humidity, can proliferate
- The stratum corneum is thickened. The organisms are seen in the intercellular spaces as well as within cells, dissolving keratin fibrils
- The coral red fluorescence of scales seen under Wood light is secondary to the production of porphyrin by these diphtheroids
- Frequency: global ~ 4%
- Mortality/Morbidity: Erythrasma is usually a benign condition BUT may become widespread and invasive in immunocompromised individuals
- A 40-year-old diabetic man in study developed well-defined erythematous itchy patches in the groin and axillae (see below). Although the eruption did not improve with topical antifungal meditations, it cleared with topical and oral erythromycin
- Erythrasma characteristically involves the skin creases
Neisseria
- N.meningitidis can cause fulminant meningitis, pneumonia, arthritis, and urethritis
- Meningitis is spread by respiratory secretions and colonizes the nasopharynx and travel through blood damaging blood vessels (can cause disseminated intravascular coagulation) and meningitis
- Infants Mortality: 100% without Tx and 15% with Tx
- Neisseria gonorrhoeae is the second only to chlamydial infections and can be transmitted through gonorrhoea. (CDC):
The infection of Gonorrhoea
- Affects the skin and mucous membranes - including the mouth and genitals - involving a rash, inflammation and sometimes a purulent (pus) discharge (especially in males)
- Complications may include pelvic inflammatory disease in females & rarer complications include blood-borne infection resulting in arthralgia (joint pain) or arthritis, endocarditis, or meningitis; Tx now complicated by widespread antibiotic reistance
Enterobacteriaceae
- A Gram – ve bacillus causing:
- Urinary Tract Infections (UTI) – causing >80% of all community/hospital acquired UTIs
- Neonatal Meningitis, which is the commonest cause
- Septicaemia, which may spread from UTI or GI spread into bloodstream via perforation or infectious spread
- Intestinal diseases (gastroenteritis)
Escherichia Coli (E. Coli)
- E. coli is a well known cause of food poisoning
- Produces a powerful toxin and can cause severe illness e-g., bloody diarrhoea, and occasionally to kidney failure
- Was first recognized as a cause of illness in 1982 during an outbreak of severe bloody diarrhoea and the outbreak was traced to contaminated hamburgers
- An estimated 73,000 cases of infection and 61 deaths occur in the United States each year, most illness has been associated with eating undercooked, contaminated ground beef and Person-to-person contact in families and child care centers and contaminated water
Salmonella
- A non spore-forming, gram-negative rod that occurs through contaminated food/water or fecal-oral spread in children (typhi/other S.)
- Source = poultry, eggs(inc outside surfaces) & dairy Products
- Symptoms: : severe diarrhoea, fever, chills, abdominal discomfort, & vomiting occurs within one to three days with serious blood borne infections
- The infectious period can vary from several days to many months
- Infected handlers are advised not to act as carers/food-workers
Yersinia Pestis
- Y.pestis causes the plague or "black death" after a bite that transports the bacteria from an animal host
- Millions of people in Europe died from plague in the Middle Ages because it is inhabitated by those flea-infested rats
- Today modern antibiotics are highly effective against it, but without those in place, the infection can have high mortalities
Other Enterobacteriaceae
- K.pneumonia causes "Community acquired lobar pneumonia"
- Alcoholics/compromised pulmonary function is a increased risk.
- Also causes wound & soft tissue infections & UTIs
Vibrionaceae – Vibrio Cholerae
- Gram – ve curved bacilli primarily found in water
- Cholera binds to cells to cells in the small intestine, enters the mucosa and causes the rapid secretion of sodium, potassium & bicarbonate into the intestine causing diarrhoea & vomiting Mortality without treatment 60%
Helicobacter Pylori
- Spinal shaped gram-bacilli that is associated with the cancer •Until a few years ago nobody knew of this bacterium
- But exists in very strong hydrochloric acid and proteolytic environments
Pseudomonas Aeruginosa
- Gram-negative, aerobic rod, that inhabits soil and water
- Causes opportunistic infection
- Bactaraemia is dangerous, has a very strong resistance to a particular set of antibiotics
- Patients have infected wounds/surfaces
Pneumoniae /haemophilus
- Primarily a paediatric cough with high sputum, with a high chance of a superinfection and an ear infection.
- Most haemophilus is a simple bacterial infection
Mycobacterium
- Gram=ve and are pleomorphic, that relates to causing leprosy
- Causes pulmonary tuberculosis and white death
Leprae (Hansens)
- Is slow and very difficult to cure and very hard to get in the first time
- This is curable but takes 1 year with a long and strict regimen of multiple treatment
- Leprae is not very difficult to detect from the tissue
- This causes Mutilation and death.
Reaction to Leprae
- Mutilial form of leprosy is from the tissues and other surfaces to fight the initial infection
- Occurs after six weeks and the infections, is found to increase
Tabes Dorsalis
A condition that results from the destruction of the dorsal columns in the spinal cord, which are normally responsible for position sense and motor control.
Clostridial perfringens Causes tissue
- Toxin releases an endotoxin by spreading through direct water
- Requires a surgical wound to progress infection
Antibiotics for Clostridium perfingens
- G or pencil
Antibacteroides
Comprise major microorganisms inhabiting the digestive tract and in fact
Pathogens of skin
Staphylococcus aureus
The skin flora has the ability too
Stye infection from the foot is exposure and has a lot to do with the risk
The wound and foot
Must be treated quickly from complications may occur.
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