Virulence factors

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Questions and Answers

Which pathogen is associated with producing Type IV pili for attachment?

Streptococcus pyogenes

Neisseria gonorrhoeae (correct)

Enterotoxigenic E. coli (ETEC)

Vibrio cholerae

What role do bacterial capsules predominantly play in terms of pathogen survival?

Increasing the mutation rate

Enhancing nutrient absorption

Facilitating cell division

Preventing phagocytosis by immune cells (correct)

Which component of some Streptococcus species aids in immune evasion?

Capsule polysaccharides

Mycolic acid

Fimbrae

M protein (correct)

What is the function of Type 1 fimbriae produced by Enterotoxigenic E. coli (ETEC)?

To facilitate adhesion to intestinal epithelial cells Signup and view all the answers

Which pathogen is known to cause cholera and is associated with methylphenylalanine?

Vibrio cholerae Signup and view all the answers

What happens to pH levels when cariogenic bacteria proliferate due to carbohydrate fermentation?

The pH drops rapidly Signup and view all the answers

How does the Herpes simplex virus evade the immune system?

By hiding in neurons and non-neuronal cells Signup and view all the answers

Which of the following is NOT a main virulence factor of Candida Albicans?

Exotoxins Signup and view all the answers

What role do cytotoxic T cells play in the interaction between pathogens and the host?

They trigger the production of escape mutations in pathogens Signup and view all the answers

Why are pathogens considered successful when they do not kill their host?

They achieve long-term residency and spread Signup and view all the answers

What role do adhesins play in bacterial infection?

They bind to specific receptors on host cells. Signup and view all the answers

Which type of pili is known for its ability to facilitate 'twitching' motility?

Type IV pili Signup and view all the answers

What is one consequence of a bacterium utilizing its adhesins effectively?

It is more likely to resist being removed from the host. Signup and view all the answers

Which of the following is NOT a known mechanism of virulence factors?

Enhanced nutrient absorption Signup and view all the answers

Streptococcus mutans is associated with which disease and adhesin?

Dental caries, Adhesin P1 Signup and view all the answers

What best defines a primary pathogen?

An environmental microbe causing disease in healthy individuals. Signup and view all the answers

How do exoenzymes contribute to bacterial virulence?

They help in breaking down host tissues. Signup and view all the answers

What is the primary mechanism of action for endotoxins?

They induce an inflammatory response. Signup and view all the answers

Which term refers to the degree or intensity of pathogenicity of a microorganism?

Virulence Signup and view all the answers

Which bacterial pathogen uses Type 1 fimbriae to cause Traveler's diarrhea?

Enterotoxigenic E. coli Signup and view all the answers

What are virulence factors primarily responsible for?

Resisting host immune responses and causing damage. Signup and view all the answers

Which type of pathogen is part of the normal microbiota but can cause disease under certain conditions?

Opportunistic pathogen Signup and view all the answers

What is required for a pathogen to survive in a host?

A source of nutrients and protection from harmful elements Signup and view all the answers

What does pathogenicity refer to?

The ability of the pathogen to cause disease. Signup and view all the answers

Which of the following is NOT a characteristic of virulence factors?

They are always harmful to the host. Signup and view all the answers

Which of the following components contribute to the chain of infection?

Agent, exposure, dose, susceptibility Signup and view all the answers

What condition is characterized by the presence of pus-forming bacteria in the blood?

Pyaemia Signup and view all the answers

Which virulence factor allows Staphylococcus aureus to evade phagocytosis?

Exoenzyme coagulase Signup and view all the answers

What are the minor changes in viral proteins resulting from point mutations called?

Antigenic drift Signup and view all the answers

Which of the following is a virulence factor associated with Streptococcus mutans?

Acidogenicity Signup and view all the answers

What is the primary function of leukocidins produced by certain pathogens?

Destroy phagocytes Signup and view all the answers

What mechanism allows some enveloped viruses to avoid the host's immune system?

Intracellular positioning Signup and view all the answers

What type of variation occurs through gene re-assortment resulting in significant protein changes in viruses?

Antigenic shift Signup and view all the answers

What role do fimbriae play for Porphyromonas gingivalis in oral health?

Stimulating immune response Signup and view all the answers

Study Notes

Pathogens and Disease

A pathogen is any microorganism that can cause disease in a host organism.
Primary pathogens can cause disease in healthy individuals.
Opportunistic pathogens are part of the normal microbiota and only cause disease in immunocompromised hosts.
Pathogenicity refers to the ability of a pathogen to cause disease.
Virulence is the degree or intensity of pathogenicity.
Virulence factors are mechanisms that determine the degree to which a pathogen causes damage, invasion, and infectivity.

Chain of Infection

The chain of infection is a model that describes the process of infection.
Virulence factors are a key element of the chain of infection.

How Pathogens Survive

To survive, pathogens need a suitable environment, a source of nutrients, and protection from harmful elements.

Mechanisms of Virulence Factors

Adhesion: Pathogens use various mechanisms to adhere to and colonize host cells. These mechanisms include:
- Pili: Hair-like structures that allow bacteria to attach to host cells using a ‘twitching’ motility.
- Fimbriae: Similar to pili but shorter and more numerous — they can be involved in attachment.
- Capsules: A protective layer that surrounds some bacteria, helping them evade phagocytosis and promote adhesion.
- Adhesins: Protein or glycoprotein molecules on the bacterial cell wall that bind to specific receptors on host cells.
Evasion of Phagocytosis: Defense mechanisms used by pathogens to avoid being engulfed and destroyed by phagocytes:
- Antiphagocytic factors: These factors prevent phagocytosis. For example:
  - M protein: Found in the fimbriae of some Streptococcus species, it alters the bacterial surface.
  - Mycolic acid: A waxy substance in the cell wall of Mycobacterium tuberculosis.
- Coagulase: An exoenzyme produced by Staphylococcus aureus that triggers the fibrinogen-to-fibrin cascade, coating bacteria in fibrin clots and preventing phagocytosis.
- Kinases: Exoenzymes that digest fibrin clots, allowing pathogens to escape and spread.
- Antigenic variation: Pathogens change their surface proteins to avoid recognition by the host's immune system.
- Leukocidins: Toxins that destroy phagocytes.
Immunoevasion: Mechanisms to evade the host's immune system:
- Destruction of T lymphocytes: Some pathogens target and destroy T lymphocytes.
- Intracellular position: Some pathogens reside inside host cells, where they are protected from the immune system.
Immunosuppression: Directly suppressing the immune system.
Toxigenicity:
- Exotoxins: Protein toxins secreted by bacteria.
- Endotoxins: Lipopolysaccharide (LPS) components of the outer membrane of Gram-negative bacteria.
Enzymatic: Pathogens produce exoenzymes that damage host tissues:
- Exoenzymes: Enzymes secreted by bacteria that break down host cell components.

Terminology Describing Pathogens in the Bloodstream

Bacteraemia: Presence of bacteria in the blood.
Pyaemia: Presence of pus-forming bacteria in the blood.
Toxaemia: Presence of toxins in the blood.
Septicaemia: Multiplying bacteria in the blood.

Viral Virulence

Adhesins: Viral adhesins, often found on the viral capsid or envelope, bind to specific cell receptors (tropism).
Antigenic variation:
- Antigenic drift: Result of point mutations that cause minor changes in spike proteins, leading to new strains.
- Antigenic shift: The gene re-assortment between different viral strains, leading to significant changes in spike proteins, potentially causing a pandemic.
Examples:
- Influenza virus: Spike protein hemagglutinin.
- HIV: Glycoprotein g20 .