Virulence factors hard

Virulence and Virulence Factors

• 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.
• Virulence factors help microorganisms invade and avoid host defenses.

Pathogens

• Pathogens are microorganisms that cause disease in a host.
• Primary pathogens can cause disease in an otherwise healthy individual.
• Opportunistic pathogens only cause disease in an immunocompromised host.
• Pathogenicity is the ability of a pathogen to cause disease.

Chain of Infection

• The chain of infection involves agent, virulence, dose, exposure, and susceptibility.
• Virulence refers to the agent's ability to cause disease.
• Dose refers to the amount of the agent that causes disease.
• Exposure refers to how the host was exposed to the agent.
• Susceptibility refers to the host's vulnerability to the agent.

Molecular Koch’s Postulates

• Molecular Koch's postulates identify virulence factors encoded by genes of microorganisms.

Bacterial Adhesins

• Adhesins are bacterial virulence factors that allow bacteria to adhere to host cells.
• Adhesins allow for colonization and resist physical removal.
• Examples of bacterial adhesins include protein F, adhesin P1, type IV pili, type 1 fimbriae, and N-methylphenylalanine pili.

Capsules

• Some bacteria produce capsules that aid in adhesion and immune evasion.
• Capsules prevent phagocytosis by immune cells.
• Capsules deter phagocytosis by their size and composition.

Mycolic Acid

• Mycolic acid is a waxy substance produced by Mycobacterium tuberculosis.
• Mycolic acid acts as a protective coat to deter killing mechanisms during phagocytosis.

Fimbriae and Cell Walls

• Some pathogens produce virulence factors that enable evasion of the immune system.
• Streptococcus fimbriae contain M protein, which alters the bacterial surface and inhibits phagocytosis.
• Mycobacterium tuberculosis produces mycolic acid, a waxy substance in the cell wall, which acts as a protective coat and inhibits phagocytosis.

Porphyromonas Gingivalis

• Porphyromonas gingivalis (P. gingivalis) is a gram-negative bacterium that produces fimbriae and enzymes that break down tissues.
• P. gingivalis fimbriae modify and stimulate immune responses.
• P. gingivalis produces gingipains (proteases), which break down structural proteins in the periodontium, such as collagen, elastin, and fibronectin.

Streptococcus Mutans

• Streptococcus mutans is a bacterium associated with tooth decay.
• Streptococcus mutans' main virulence factors are adhesion, acidogenicity, and acid tolerance.
• Streptococcus mutans converts sugar and starch into acid.
• Streptococcus mutans causes a decrease in pH, which weakens tooth enamel and increases the risk of demineralization.

Herpes Simplex Virus

• Herpes simplex virus can hide in neurons and non-neuronal cells, persisting for years.
• Herpes simplex virus is pathogenic when immune resistance is low.
• Herpes simplex virus causes herpes labialis (cold sore).

Candida Albicans

• Candida albicans is a pathogenic yeast associated with opportunistic fungal infections in humans
• Candida albicans is found on dentures and in biofilms.
• Candida albicans produces exoenzymes (aspartyl proteases), known as 'Sap Proteins', which break down proteins.
• Candida albicans is pleomorphic, adapting to environmental changes and forming filamentous biofilms.
• Candida albicans produces hydrolytic enzymes that cause tissue invasion.

Adhesins as Virulence Factors in Candida albicans

• Adhesins are virulence factors that allow Candida albicans to change, adapt, invade, and colonize.

Conclusion

• Pathogens employ virulence factors to evade host defenses and increase virulence.
• The interaction between pathogens and host cells is dynamic, with pathogens evolving to avoid immune responses.
• The ongoing arms race between pathogens and hosts leads to the emergence of new pathogens that effectively exploit their hosts without causing death.