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Questions and Answers
How does phase variation contribute to bacterial virulence?
How does phase variation contribute to bacterial virulence?
- By altering surface antigens, allowing pathogens to evade immune detection. (correct)
- By directly neutralizing host antibodies through enzymatic degradation.
- By increasing the pathogen's susceptibility to phagocytosis.
- By enhancing the production of bacterial toxins, overwhelming the host immune system.
Which of the following is the MOST accurate distinction between pathogenicity and virulence?
Which of the following is the MOST accurate distinction between pathogenicity and virulence?
- Pathogenicity is the ability to colonize a host, whereas virulence is the degree of damage caused.
- Pathogenicity only applies to viral infections, whereas virulence is specific to bacterial infections.
- Pathogenicity is a qualitative term describing the ability to cause disease, while virulence is its quantifiable measure. (correct)
- Pathogenicity refers to the mechanism of infection, while virulence describes the host's immune response.
How does Protein A, produced by Staphylococcus aureus, function as a virulence factor?
How does Protein A, produced by Staphylococcus aureus, function as a virulence factor?
- It acts as a superantigen, causing a cytokine storm.
- It binds to the Fc region of immunoglobulins, inhibiting phagocytosis. (correct)
- It directly lyses host cells, releasing intracellular contents.
- It disrupts the complement cascade, preventing opsonization.
What is the primary mechanism by which endotoxin (LPS) contributes to the pathogenesis of Gram-negative bacterial infections?
What is the primary mechanism by which endotoxin (LPS) contributes to the pathogenesis of Gram-negative bacterial infections?
How do siderophores enhance bacterial virulence?
How do siderophores enhance bacterial virulence?
What is the role of IgA protease in bacterial pathogenesis, and which bacteria produce it?
What is the role of IgA protease in bacterial pathogenesis, and which bacteria produce it?
What is the function of injectisomes (Type III secretion systems) in Gram-negative bacteria?
What is the function of injectisomes (Type III secretion systems) in Gram-negative bacteria?
How do capsules contribute to the virulence of bacteria like Streptococcus pneumoniae and Neisseria meningitidis?
How do capsules contribute to the virulence of bacteria like Streptococcus pneumoniae and Neisseria meningitidis?
What is the significance of cord factor (trehalose dimycolate) in the pathogenesis of Mycobacterium tuberculosis?
What is the significance of cord factor (trehalose dimycolate) in the pathogenesis of Mycobacterium tuberculosis?
How do sulfatides contribute to the virulence of Mycobacterium tuberculosis?
How do sulfatides contribute to the virulence of Mycobacterium tuberculosis?
Flashcards
Virulence
Virulence
Quantifiable pathogenicity of an organism, useful in determining disease severity and temporal effects.
Infectious Dose 50 (ID50)
Infectious Dose 50 (ID50)
Quantifies the number of organisms needed to cause disease in 50% of those exposed.
Lethal Dose 50 (LD50)
Lethal Dose 50 (LD50)
Quantifies the number of pathogens needed to kill 50% of those exposed.
Virulence Factors
Virulence Factors
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Capsule
Capsule
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Endotoxin
Endotoxin
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Phase/Antigenic Variation
Phase/Antigenic Variation
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Protein A
Protein A
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Protein M
Protein M
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IgA Protease
IgA Protease
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Study Notes
Virulence vs. Pathogenicity
- Virulence and pathogenicity are often used interchangeably.
- Virulence quantifies an organism's pathogenicity.
- Virulence can assist physicians in determining the severity of disease associated with exposure and temporal effect.
- Viral load required for disease associated with SARS COVID Two (the causative agent of COVID 19) and increase in severe lens associated with variant strains is an example.
Quantifying Virulence
- Infectious Dose 50 (ID50) quantifies the number of organisms required to cause disease in 50% of those exposed.
- Lethal Dose 50 (LD50) quantifies the number of pathogens required to kill 50% of those exposed.
- Enteropathogenic E. coli has an LD50 of 1 million cells.
- Anthrax has an LD50 of less than 10 spores.
Virulence Factors
- Factors that contribute to virulence are associated with the process of infection, high heat, invasion, and adhesion.
- The interaction of host and pathogen drive a multifaceted strategy of microbial survival and immunological detection and elimination.
- Virulence factors include microbial strategies to evade and avoid the immune system.
- S. pneumoniae and N. meningitidis produce capsules as antiphagocytic factors.
- Bacterial toxins, such as endotoxin LPS, can result in shock, hypotension, and thrombosis.
- These effects are produced indirectly by macrophage activation, with release of cytokines
- The virulence factors of many bacterial infections are enhanced by the host response rather than by bacterial factors.
- Phase antigenic variation assist pathogens to evade elements of the host immune system by changing surface antigens, for instance, regulating or modifying the expression of surface antigens.
- Be familiar with virulence factors and the associated effect on the host pathogen interaction.
Specific Virulence Factors
- Protein A: Released by Staphylococcus.
- Binds the Fc portion of immunoglobulin G to prevent phagocytosis.
- Protein M: Released by Group A Streptococcus.
- Plays a major role in molecular mimicry, rheumatic heart disease, and rheumatic fever.
- Also prevents phagocytosis.
- "Protein M is for mimicry"
- IgA Protease: Released by S. pneumoniae, N. influenzae.
- Aids bacteria in colonizing their structure in GI and respiratory mucosa.
- Immunoglobulin prevents the bacteria from attaching to the mucus of the GI and respiratory tract.
- Injectisome: Utilized by Pseudomonas aeruginosa, E. coli, Salmonella, and Shigella.
- A small needle that bacteria use to deliver toxins into host cells, using a type three secretion system.
- Serpentine Cord: Used by Mycobacterium.
- Activates macrophages and releases tumor necrosis factor alpha, which will form the granuloma.
- Forms granulomas in mycobacterium infection by releasing tumor necrosis factor alpha.
- Sulfatides: Used by Mycobacterium.
- Physical surface protein that inhibits phagosome lysosome fusion.
- Allows Mycobacterium to survive inside the phagocytic WBC.
- K capsule: Used by E. coli.
- Reduces the symptoms of neonatal meningitis and Disinfection.
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