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Questions and Answers
Why are Mycoplasma and Archaea resistant to penicillin?
Why are Mycoplasma and Archaea resistant to penicillin?
What is one of the primary mechanisms by which bacteria can pump out antibiotics?
What is one of the primary mechanisms by which bacteria can pump out antibiotics?
Which process involves modifying an antibiotic to prevent it from binding to its target?
Which process involves modifying an antibiotic to prevent it from binding to its target?
How does a change in wall protein affect antibiotic resistance?
How does a change in wall protein affect antibiotic resistance?
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What are porins, and how do they relate to antibiotic resistance?
What are porins, and how do they relate to antibiotic resistance?
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Which characteristic of a drug makes it selectively toxic to microbial cells but not to human cells?
Which characteristic of a drug makes it selectively toxic to microbial cells but not to human cells?
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Which class of antibiotics disrupts cell wall synthesis?
Which class of antibiotics disrupts cell wall synthesis?
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What is the role of Ergosterol in fungal cells regarding drug action?
What is the role of Ergosterol in fungal cells regarding drug action?
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How do sulfonamides affect bacterial cells?
How do sulfonamides affect bacterial cells?
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Which of the following is a characteristic of bacteriocidal drugs?
Which of the following is a characteristic of bacteriocidal drugs?
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Which antibiotics are examples of bacteriostatic agents?
Which antibiotics are examples of bacteriostatic agents?
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What does the term 'spectrum of activity' refer to?
What does the term 'spectrum of activity' refer to?
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What is the main action of drugs like Metronidazole?
What is the main action of drugs like Metronidazole?
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What role do plasmids play in antibiotic resistance?
What role do plasmids play in antibiotic resistance?
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Which mechanism allows for resistance to tetracycline?
Which mechanism allows for resistance to tetracycline?
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What is the significance of selective toxicity in antimicrobial therapy?
What is the significance of selective toxicity in antimicrobial therapy?
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Which process involves the transfer of DNA from the environment to a bacterium?
Which process involves the transfer of DNA from the environment to a bacterium?
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What mechanism do bacteria often use to develop resistance against aminoglycosides?
What mechanism do bacteria often use to develop resistance against aminoglycosides?
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How can resistance genes be categorized?
How can resistance genes be categorized?
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What is the function of a bacteriophage in gene transfer?
What is the function of a bacteriophage in gene transfer?
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Which of the following is NOT a method of gene transfer between bacteria?
Which of the following is NOT a method of gene transfer between bacteria?
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What is a key characteristic that distinguishes prokaryotic cells from eukaryotic cells?
What is a key characteristic that distinguishes prokaryotic cells from eukaryotic cells?
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Which process is associated with bacterial reproduction?
Which process is associated with bacterial reproduction?
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What type of bacterial structure is commonly targeted by antibiotics?
What type of bacterial structure is commonly targeted by antibiotics?
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Which of the following correctly describes a gram-positive bacterium?
Which of the following correctly describes a gram-positive bacterium?
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What is a benefit of having normal flora in the human body?
What is a benefit of having normal flora in the human body?
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Which group of antimicrobials is primarily effective against viruses?
Which group of antimicrobials is primarily effective against viruses?
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What distinguishes eukaryotic cells from prokaryotic cells in terms of genetic material?
What distinguishes eukaryotic cells from prokaryotic cells in terms of genetic material?
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In the phylogenetic tree of life, which of the following groups is characterized as prokaryotic?
In the phylogenetic tree of life, which of the following groups is characterized as prokaryotic?
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Which bacteria are primarily targeted by Penicillin G?
Which bacteria are primarily targeted by Penicillin G?
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What is a common unwanted effect of using antibiotics?
What is a common unwanted effect of using antibiotics?
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For how long is antibiotic treatment usually recommended?
For how long is antibiotic treatment usually recommended?
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What mechanism allows some bacteria to evade antibiotics?
What mechanism allows some bacteria to evade antibiotics?
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What defines a virus as an intracellular parasite?
What defines a virus as an intracellular parasite?
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Which antiviral drug is specifically known to stop viral replication by becoming part of viral DNA?
Which antiviral drug is specifically known to stop viral replication by becoming part of viral DNA?
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What is the primary purpose of reverse transcriptase inhibitors like AZT in the treatment of HIV?
What is the primary purpose of reverse transcriptase inhibitors like AZT in the treatment of HIV?
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How are enveloped viruses distinct from non-enveloped viruses?
How are enveloped viruses distinct from non-enveloped viruses?
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Which type of bacteria cell wall primarily contains peptidoglycan?
Which type of bacteria cell wall primarily contains peptidoglycan?
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What is the predominant bacteria found in the human stomach?
What is the predominant bacteria found in the human stomach?
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Which of the following best describes the growth pattern of most bacteria?
Which of the following best describes the growth pattern of most bacteria?
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In which anatomical location would you predominantly find Staphylococci?
In which anatomical location would you predominantly find Staphylococci?
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Which species is known to cause 95% of bacterial pneumonia cases?
Which species is known to cause 95% of bacterial pneumonia cases?
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What type of bacteria can act as opportunistic pathogens in the human body?
What type of bacteria can act as opportunistic pathogens in the human body?
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What is a major component of the bacterial cell wall that is unique to bacteria?
What is a major component of the bacterial cell wall that is unique to bacteria?
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Which type of bacteria is predominantly found in the lower respiratory tract?
Which type of bacteria is predominantly found in the lower respiratory tract?
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Study Notes
Microbiology & Antibiotics
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Learning Outcomes: Students should be able to:
- Discuss differences between prokaryotes, eukaryotes, and viruses
- Discuss differences and significance between gram-positive and gram-negative bacteria
- Describe features of normal flora
- Outline reproductive and DNA transfer processes of bacteria
- Outline major groups of antimicrobials
- Discuss mechanisms of action of a range of antimicrobials and anti-viral agents
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Relevance to Courses:
- Audiology: Bacterial infections can lead to otitis (middle ear infection)
- Cardiac Physiology: Infections of the endocardium (inner lining of heart chambers and heart valves) can occur via bacteria spreading through the bloodstream.
Microbiology
- Phylogenetic Tree of Life: Based on ribosomal RNA sequencing, showing prokaryotes (Bacteria and Archaea) and eukaryotes (animals, fungi, plants) branching from a common ancestor.
Prokaryotes and Eukaryotes
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Prokaryotic Cells:
- Smaller, typically less than 2µm
- Simple internal structure
- No membrane-bound organelles
- Circular DNA (nucleoid)
- One chromosome plus plasmids
- Small ribosomes (70S)
- Reproduce via binary fission
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Eukaryotic Cells:
- Larger, typically greater than 2µm
- Complex internal structure
- Membrane-bound organelles
- DNA within a nucleus
- More than one chromosome
- Larger ribosomes (80S)
- Reproduce via mitosis and meiosis
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Prokaryotic Cell Structure:
- Diagrams depicting capsule, cell wall, cytoplasmic membrane, chromosomal region, ribosomes, pili (attachment structures), and flagella (motility)
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Bacteria Structure: (Diagram Shown)
- Illustrates the key components of a bacterial cell including the chromosome (nucleoid region) , ribosomes , food granules, flagella, cell wall, capsule/slime layer and plasmid.
Bacteria Cell Wall
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Peptidoglycan: A unique bacterial cell wall component composed of alternating sugars (NAM and NAG) cross-linked by peptides.
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Gram-Positive Bacteria: Thicker peptidoglycan layer and teichoic acids.
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Gram-Negative Bacteria: Thinner peptidoglycan layer, outer membrane with lipopolysaccharides (LPS).
Gram- and Gram+ Bacteria
- Gram Staining Procedure: The steps of the staining protocol to differentiate between gram + (purple) and gram - bacteria (pink).
Bacteria Found at Anatomical Sites
- A table listing various anatomical locations, and the prevalent bacteria commonly found there.
Normal Flora/Indigenous Microbiota
- Normal Flora: Composed typically of staphylococci and corynebacteria.
- Protection: Lactobacillus vaginalis provides protection against mucocutaneous infection.
- Opportunistic Pathogens: Some normal flora members can become opportunistic pathogens.
Growth and Reproduction
- Binary Fission: The primary method of bacterial reproduction, occurring typically when the cell reaches a critical size. It requires suitable environment, including temperature, pH, and nutrients. Growth continues exponentially until resources become scarce or growth inhibitors accumulate. This triggers sporulation.
- E. coli: Generation time of approximately 20 minutes.
Sporulation
- Spores: Dormant structures that allow bacteria to survive adverse conditions (e.g., extreme temperatures, lack of nutrients). Spores can last centuries and require specific conditions for germination to occur.
Antibiotics
- Classes: (Diagram showing examples and their mechanisms of action). Various classes of antibiotics; including beta-lactams, aminoglycosides, chloramphenicol, tetracyclines, macrolides, ansamycins, streptogramins, lipopeptides and their common mechanisms of action.
Antibiotic-Mechanisms of Action
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Cell Wall Synthesis Inhibition: Penicillins and Bacitracin target enzymes crucial for peptidoglycan cross-linking, disrupting cell wall integrity.
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Cell Membrane Function Disruption: Polymyxins target the bacterial outer membrane, causing leakage and death.
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Protein Synthesis Inhibition: Aminoglycosides and macrolides disrupt protein synthesis within bacterial ribosomes, interfering with peptide chain elongation and bacterial growth.
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Nucleic Acid Synthesis Inhibition: Quinolones target DNA gyrase in bacteria, while rifamycins target RNA polymerase, thus hindering DNA replication and reproduction.
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Action as Antimetabolites: Sulfonamides and trimethoprim interfere with bacterial metabolic processes for DNA synthesis by inhibiting folic acid synthesis.
MRSA - Methicillin-Resistant Staphylococcus Aureus
- Classification: Gram-positive, spherical (coccus), forms clusters, aerobic, coagulase-positive and producing toxins.
- Resistance mechanism: Presence of a β-lactamase enzyme degrading methicillin, and other β-lactam antibiotics.
Antibiotic Resistance
- Natural: The inability of antibiotics to penetrate or target a specific bacteria because of biochemical differences.
- Acquired: The development of resistance in bacteria owing to mechanisms, including genetic variations.
Mechanisms of Antimicrobial Resistance
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Alter/Degrade Antibiotic: Bacterial defense mechanisms that modify or destroy the antibiotic to prevent its action.
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Pump Out Antibiotic: Active efflux pumps remove the antibiotic from the cell, rendering the drug ineffective
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Decrease Permeability: Modifications in the bacterial cell wall that prevent antibiotic entry.
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Mutate Target Gene: Bacterial mutations that change the antibiotic's targeted protein or enzyme, thus reducing the antibiotic sensitivity.
Porins:
- Proteins in the outer bacterial membrane that form channels for molecules to pass through. Their presence influences antibiotic permeability and is closely linked to antibiotic resistance mechanisms.
Efflux Pumps:
- Active transporters in the bacterial cell membrane, expelling antibiotics from the cell, thus avoiding antibiotic action. RND, MATE, MFS and SMR efflux pumps are identified in the mechanisms of active expulsions of antibiotics.
Degradation:
- Bacterial enzymes such as penicillinases degrade antibiotics, rendering the drug chemically ineffective.
Mutation of target genes:
- Genetic changes to proteins or enzymes that the drug targets. These changes can render the affected protein or enzyme insensitive to antibiotics.
Origin and spread of resistance genes
- Genes can be found on the chromosome or on plasmids. Transfer of genetic material between bacteria occurs through horizontal gene transfer mechanisms, such as conjugation, transduction, or transformation.
Mechanisms of Plasmid-Encoded Antibiotic Resistance
- Various bacterial mechanisms of resistance conferred by plasmids (transferable genetic elements) are outlined, such as resistance to ẞ-lactam, Chloramphenicol, Aminoglycosides, Tetracycline, and Erythromycin.
Gene Transfer between Bacteria
- Transformation: Bacterial cells take up free DNA from their surroundings.
- Transduction: Phage (viruses) transfer bacterial DNA to other cells.
- Conjugation: A direct transfer of DNA from one cell to another usually via a conjugation pilus.
Search for New Antibiotics: Selective Toxicity
- Selective toxicity is the key concept for antimicrobial therapy, in which the drug is toxic towards microbes but not to humans.
- Exploiting differences in bacterial structures, processes, and metabolism enables targeting of microbial cells and avoiding harm to host cells .
Specific Targets
- Cell Wall: Drugs targeting bacterial cell walls inhibit peptidoglycan synthesis (penicillins, cephalosporins, and vancomycin) to avoid disruption of structural integrity.
- Cell Membrane: Targeting bacterial membranes with drugs that disrupt their function or permeability (e.g., polymyxins) or targeting sterol biosynthesis (e.g., nystatin) for antifungal activity.
- Ribosomes: Antibiotic targeting bacterial ribosomes (e.g., aminoglycosides, tetracyclines, macrolides, Chloramphenicol) to inhibit protein synthesis, interfering with bacterial growth.
- Metabolism: Various antibacterial drugs interfere with bacterial metabolic processes like folic acid synthesis (e.g., sulfonamides, and trimethoprim), or the production of other essential metabolites.
- Nucleic Acid Synthesis: Antibiotics targeting bacterial DNA replication or RNA polymerase (e.g., quinolones, rifamycins) ultimately hindering bacterial growth.
Two Main Mechanisms of Action
- Bactericidal: Killing the microorgansim directly, by targeting essential structural components (cell wall, membranes).
- Bacteriostatic: Inhibiting bacterial growth, relying on the host's immune system to eliminate them.
Spectrum of Activity
- Narrow spectrum: Effective against a limited range of species.
- Broad spectrum: Effective against a wide range of species.
General Unwanted Effects
- Alteration of Gut Flora: Introducing secondary infections, superinfection (potentially more severe bacterial infections).
- Hypersensitivity Reactions: Allergies due to antigenicity of the antibiotic; could manifest as anaphylaxis.
- Gastrointestinal effects: Diarrhea, antibiotic-associated colitis (inflammation).
How long should antibiotic be taken
- Full course of recommended dosage and time as prescribed.
- Length can vary based on the severity of infection or condition.
Virology
- Virus: An intracellular parasite requiring a host cell to replicate, thus unable to reproduce outside of a host cell. Composed of nucleic acid core (DNA or RNA) that is surrounded by a protein coat or capsid. Some viruses have an external lipid envelope.
Antiviral Drugs
- Selective Toxicity: Difficult to achieve to avoid harm to hosts, because of the close structural similarity of viral and host components.
- Acyclovir: Incorporated into viral DNA synthesis.
- Relenza: Inhibits viral penetration into host cells.
- HIV and HAART: Reverse transcriptase inhibitors prevent viral replication and aids host immune system response to recover.
- Interferons: Naturally produced in infected host cells that defend against viral infections.
References
- A list of relevant publications and resources is provided.
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Description
Test your knowledge on the mechanisms of antibiotic resistance and the various classes of antibiotics. This quiz covers topics such as Mycoplasma and Archaea resistance, drug action, and the significance of plasmids. Explore how these factors contribute to the effectiveness of antibiotics and resistance in microbial cells.
