Bacterial Pathogens and Virulence Factors
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Questions and Answers

What is the primary treatment for bacterial GI tract infections?

  • Surgery
  • Antifungals
  • Antibiotics (correct)
  • Antivirals

Which causative agent is associated with the most severe cases of malaria?

  • Plasmodium falciparum (correct)
  • Plasmodium vivax
  • Plasmodium malariae
  • Plasmodium ovale

What is a common complication of endocarditis?

  • Diabetes mellitus
  • Pulmonary embolism
  • Heart failure (correct)
  • Kidney damage

Which microorganism is primarily responsible for meningococcal meningitis?

<p>Neisseria meningitidis (C)</p> Signup and view all the answers

Which type of infection is typically resolved without specific antiviral treatment?

<p>Viral gastroenteritis (D)</p> Signup and view all the answers

What is often the first site of infection for the malaria parasite?

<p>Liver (B)</p> Signup and view all the answers

What type of pathogens are involved in causing sepsis?

<p>Bacterial, viral, and fungal (A)</p> Signup and view all the answers

What is a common symptom of malaria due to parasite action in the bloodstream?

<p>Fever and chills (D)</p> Signup and view all the answers

What is the role of β-lactamases in antibiotic resistance?

<p>They degrade β-lactam antibiotics, making them ineffective. (A)</p> Signup and view all the answers

How can efflux pumps contribute to antibiotic resistance in bacteria?

<p>By pumping antibiotics out of the cell. (A)</p> Signup and view all the answers

What type of microorganism is Staphylococcus aureus?

<p>Bacteria (D)</p> Signup and view all the answers

What happens to bacteria when exposed to antibiotics that induces stress responses?

<p>They undergo mutations and gene duplication. (C)</p> Signup and view all the answers

Which virulence factor assists Streptococcus pyogenes in evading phagocytosis?

<p>Capsule (A)</p> Signup and view all the answers

What mechanism do bacteria utilize to modify their target sites and resist antibiotics like aminoglycosides?

<p>Alteration of ribosomal structures. (B)</p> Signup and view all the answers

What infection is primarily caused by Bordetella pertussis?

<p>Whooping cough (C)</p> Signup and view all the answers

How does the virulence factor 'pertussis toxin' affect the host?

<p>Disrupts G-protein signaling (C)</p> Signup and view all the answers

What is the primary effect of selective pressure from widespread antibiotic use?

<p>Encourages the proliferation of resistant strains. (B)</p> Signup and view all the answers

What does the capsule of Streptococcus pneumoniae prevent?

<p>Phagocytosis (B)</p> Signup and view all the answers

Which of the following is NOT a strategy bacteria use to resist antibiotics?

<p>Environmental detoxification. (B)</p> Signup and view all the answers

How do plasmids contribute to the spread of antibiotic resistance among different bacterial species?

<p>By transferring resistance genes between microbes. (B)</p> Signup and view all the answers

What disease is caused by Mycobacterium tuberculosis?

<p>Tuberculosis (C)</p> Signup and view all the answers

Which mechanism allows bacteria to bypass the effects of antibiotics?

<p>Metabolic pathway alteration. (C)</p> Signup and view all the answers

Which factor is associated with the pathogenesis of Staphylococcus aureus leading to toxic shock syndrome?

<p>TSST-1 (B)</p> Signup and view all the answers

What mechanism does Mycobacterium tuberculosis use to protect itself from destruction in phagolysosomes?

<p>Mycolic Acid (B)</p> Signup and view all the answers

What is the primary characteristic of salmonellosis?

<p>Diarrhea, fever, and abdominal cramps (D)</p> Signup and view all the answers

What is the first step of peptidoglycan synthesis?

<p>Cytoplasmic synthesis of precursors (A)</p> Signup and view all the answers

Which bacterium is known for causing severe diarrhea after antibiotic use?

<p>Clostridium difficile (B)</p> Signup and view all the answers

Which antibiotic inhibits the synthesis of NAM?

<p>Fosfomycin (A)</p> Signup and view all the answers

Which organism is often transmitted through the fecal-oral route and primarily affects children?

<p>Rotavirus (D)</p> Signup and view all the answers

Which virulence factor helps Neisseria gonorrhoeae evade mucosal immunity?

<p>Pili for attachment (B)</p> Signup and view all the answers

What is the role of bactoprenol in peptidoglycan synthesis?

<p>It transports precursors across the membrane (A)</p> Signup and view all the answers

What severe condition can result from infection with Shigella dysenteriae?

<p>Hemolytic Uremic Syndrome (HUS) (D)</p> Signup and view all the answers

What does vancomycin specifically target during peptidoglycan synthesis?

<p>Transglycosylation process (D)</p> Signup and view all the answers

What is the role of elementary bodies in Chlamydia trachomatis infections?

<p>Avoiding immune detection (B)</p> Signup and view all the answers

Which process links the glycan chains through peptide cross-bridges?

<p>Transpeptidation (A)</p> Signup and view all the answers

What symptom is common to infections caused by Campylobacter jejuni?

<p>Fever and diarrhea (C)</p> Signup and view all the answers

How do beta-lactam antibiotics affect bacterial cells?

<p>They inhibit penicillin-binding proteins (A)</p> Signup and view all the answers

Which of the following is NOT a virulence factor of Treponema pallidum?

<p>Induction of inflammation (D)</p> Signup and view all the answers

What structural feature of beta-lactam antibiotics mimics peptidoglycan precursors?

<p>Beta-lactam ring (B)</p> Signup and view all the answers

Which type of antibiotic mainly targets the crosslinking process during peptidoglycan synthesis?

<p>Beta-lactams (C)</p> Signup and view all the answers

Which statement correctly describes the Type III Secretion System?

<p>It involves direct injection of proteins into host cells. (A)</p> Signup and view all the answers

What is the primary purpose of antigenic variation in pathogens?

<p>To avoid detection by the host immune system. (D)</p> Signup and view all the answers

What mechanism do pathogens like Mycobacterium tuberculosis use to survive inside host cells?

<p>Resistance to lysosomal enzymes. (C)</p> Signup and view all the answers

Which pathogen is most notably associated with evading phagocytosis through the use of a polysaccharide capsule?

<p>Streptococcus pneumoniae (C)</p> Signup and view all the answers

How does the Herpes simplex virus diminish the host immune response?

<p>By inhibiting immune cell functions. (C)</p> Signup and view all the answers

What defines Enterohemorrhagic E. coli (EHEC)?

<p>It produces Shiga toxins. (C)</p> Signup and view all the answers

Which strategy involves a pathogen mimicking host molecules to avoid immune detection?

<p>Molecular mimicry. (D)</p> Signup and view all the answers

What is a defining characteristic of the Type II Secretion System?

<p>It transports proteins into the periplasm before secretion. (D)</p> Signup and view all the answers

Flashcards

Staphylococcus aureus

A bacterium commonly found on skin and in nasal passages, capable of causing infections like skin abscesses, pneumonia, and toxic shock syndrome.

Streptococcus pyogenes

A bacterium that causes strep throat, skin infections, and potentially serious complications like rheumatic fever.

Bordetella pertussis

A bacterium responsible for whooping cough, a highly contagious respiratory illness.

Streptococcus pneumoniae

A bacterium that can cause pneumonia, meningitis, ear infections, and sepsis. Often found in the normal respiratory flora.

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Mycobacterium tuberculosis

A slow-growing bacterium that causes tuberculosis, primarily affecting the lungs. It spreads through the air.

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Protein A

A virulence factor found in Staphylococcus aureus. It binds to antibodies and prevents them from attacking the bacteria.

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Capsule

A protective layer found in some bacteria, like Streptococcus pneumoniae. It prevents phagocytosis by immune cells.

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Mycolic Acid

A waxy substance found in the cell wall of Mycobacterium tuberculosis. It helps the bacteria resist destruction by macrophages.

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Type II Secretion System

This system transports proteins first into the periplasm and then across the outer membrane. It's used to secrete toxins and pili.

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Type III Secretion System

This is a needle-like structure that bacteria use to inject effector proteins directly into host cells. These proteins can interfere with the host immune system or manipulate host cells.

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Antigenic Variation

Pathogens can change their surface antigens, preventing the immune system from recognizing them. This allows them to evade detection and destruction.

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Immune Suppression

Some pathogens can suppress the host immune response by inhibiting the function of immune cells like T-cells and macrophages.

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Inhibition of Phagocytosis

Many bacteria produce capsules or structures that prevent them from being engulfed by phagocytes.

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Intracellular Survival

Some pathogens can survive and replicate inside host cells, evading the immune system by preventing the formation of phagolysosomes or resisting lysosomal enzymes.

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Molecular Mimicry

Some pathogens mimic host molecules to avoid immune detection.

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Escherichia coli (E. coli)

A Gram-negative bacterium, some strains can produce Shiga toxins causing serious illness like hemolytic uremic syndrome (HUS).

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Horizontal Gene Transfer

The transfer of genetic material (like resistance genes) between bacteria, not just from parent to offspring. This can happen through plasmids, transposons, or bacteriophages.

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Selective Pressure

The environment favors organisms with certain traits, making them more likely to survive and reproduce. Antibiotics create this pressure, favoring resistant bacteria.

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Gene Duplication and Mutation

Bacteria can copy their genes and sometimes make mistakes, leading to new versions of genes that may help them resist antibiotics.

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β-Lactamase

An enzyme that breaks down β-lactam antibiotics like penicillin. It's like a bacteria's weapon against these drugs.

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Target Modification

Bacteria change their internal structures (like ribosomes) so antibiotics can't bind and work.

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Efflux Pumps

Pumps built into bacteria that push antibiotics out before they can cause harm. Like a bouncer kicking out an unwelcome guest.

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Bypass Pathways

Bacteria find alternate ways to do things when antibiotics block their usual processes, like building their cell walls.

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Alteration of the Target Site

Bacteria change the part of their body that an antibiotic targets, so the drug can no longer bind effectively.

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Peptidoglycan Synthesis

The process of building the rigid cell wall of bacteria, essential for their survival. It involves specific steps and targets for antibiotics.

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NAG and NAM

N-acetylglucosamine (NAG) and N-acetylmuramic acid (NAM) are the building blocks of peptidoglycan. NAM is linked to a pentapeptide chain to form precursors.

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Fosfomycin

An antibiotic that blocks the first step in NAM synthesis, preventing the creation of peptidoglycan precursors.

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Bactoprenol

A lipid carrier that transports the peptidoglycan precursors (NAG-NAM-pentapeptide) across the bacterial membrane.

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Bacitracin

An antibiotic that blocks the recycling of bactoprenol, stopping the transport of peptidoglycan precursors across the membrane.

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Transglycosylation

The process of linking NAG and NAM subunits together to form long glycan strands, a key step in peptidoglycan synthesis.

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Vancomycin

An antibiotic that blocks transglycosylation by binding to the D-Ala-D-Ala terminus of the NAM pentapeptide, preventing the formation of glycan strands.

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Transpeptidation

The final step in peptidoglycan synthesis where peptide cross-bridges link the glycan strands together, creating a strong and rigid structure.

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Salmonella enterica

A bacteria that causes salmonellosis, characterized by diarrhea, fever, and abdominal cramps.

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Shigella dysenteriae

A bacteria that causes shigellosis, leading to dysentery (bloody diarrhea), abdominal pain, and fever.

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Campylobacter jejuni

A bacteria that causes bacterial gastroenteritis, often from consuming undercooked poultry.

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Clostridium difficile

A bacteria that causes antibiotic-associated diarrhea and pseudomembranous colitis, often during antibiotic use.

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Chlamydia trachomatis Virulence

This bacteria infects epithelial cells, particularly in the genitourinary tract, replicating inside host cells.

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Neisseria gonorrhoeae Virulence

Uses pili to attach to host cells, has IgA protease to evade mucosal immunity, and undergoes antigenic variation to escape detection.

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Treponema pallidum (Syphilis) Virulence

This bacteria evades the immune system by moving rapidly through tissues and lacking easily targeted antigens.

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What are the three main ways STIs evade the immune system?

  1. Hiding inside host cells (Chlamydia), 2. Evading antibodies (Neisseria), 3. Rapid movement and lacking targets (Treponema)
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GI Infection Treatment

Treating a GI infection depends on the cause. Bacterial infections are often treated with antibiotics. Viral infections often resolve on their own with supportive care. Parasitic infections are treated with specific medications like metronidazole.

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Antibiotic Resistance

A growing concern in treating bacterial GI infections. Some bacteria are becoming less responsive to antibiotics, making infections harder to treat.

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Malaria Causative Agent

Plasmodium species, especially P. falciparum, are the parasites that cause malaria. These parasites are spread by mosquitos.

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Malaria Progression

Malaria progresses in stages. The parasite enters the bloodstream, infects liver cells, then infects red blood cells, causing them to rupture and leading to classic malaria symptoms like fever and chills.

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Endocarditis

An infection of the heart's inner lining or valves, often caused by bacteria like Staphylococcus aureus or Streptococcus viridans.

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Sepsis

A systemic response to infection, often caused by bacteria like Staphylococcus aureus or E. coli. It can be life-threatening.

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Viral Myocarditis

An inflammation of the heart muscle caused by viruses like Coxsackievirus or parvovirus.

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Meningitis Causative Agent

Meningitis, an infection of the meninges, can be caused by various pathogens, including Neisseria meningitidis (meningococcal meningitis).

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Study Notes

Staphylococcus aureus

  • Bacteria
  • Found on skin and nasal passages
  • Can become invasive, causing infections
  • Opportunistic, exploiting breaches in skin or immune suppression
  • Virulence Factors:
    • Protein A: Binds to Fc region of antibodies, evading immune response
    • Exotoxins: Hemolysins, leukocidins, superantigens like TSST-1
    • Coagulase: Induces clot formation, shielding bacteria from phagocytosis
    • Biofilm Formation: Protects against antibiotics and immune cells

Streptococcus pyogenes

  • Bacteria
  • Pathogenesis: Pharyngitis, cellulitis, necrotizing fasciitis, post-infection sequelae (e.g., rheumatic fever)
  • Spreads via respiratory droplets or direct contact
  • Virulence Factors:
    • M protein: Resists phagocytosis and promotes adhesion
    • Streptolysins (O and S): Destroy host cells
    • Exotoxins: Pyrogenic exotoxins (superantigens causing streptococcal toxic shock)
    • Capsule: Prevents phagocytosis

Bordetella pertussis

  • Bacteria
  • Pathogenesis: Causes whooping cough by colonizing respiratory epithelial cells
  • Spread via respiratory droplets
  • Virulence Factors:
    • Pertussis toxin: Disrupts G-protein signaling, increasing cAMP levels
    • Filamentous hemagglutinin: Facilitates adhesion to epithelial cells
    • Adenylate cyclase toxin: Inhibits immune cell function

Streptococcus pneumoniae

  • Bacteria
  • Pathogenesis: Causes pneumonia, meningitis, otitis media, and sepsis.
  • Part of normal flora, becomes pathogenic under certain conditions
  • Virulence Factors:
    • Capsule: Prevents phagocytosis
    • Pneumolysin: Creates pores in host membranes
    • IgA protease: Degrades host antibodies

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Description

This quiz covers significant bacterial pathogens such as Staphylococcus aureus, Streptococcus pyogenes, and Bordetella pertussis. Understand their virulence factors, modes of infection, and clinical significance. Test your knowledge on these infectious agents and their impact on human health.

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