Virulence Factors Revision PDF

Virulence factors  Key terminology Pathogen - Any microorganism that is able to cause disease in a host organism. Primary pathogen - An environmental microbe that is able to cause disease in an otherwise healthy individual. Opportunistic pathogen - A member of...

Virulence factors  Key terminology Pathogen - Any microorganism that is able to cause disease in a host organism. Primary pathogen - An environmental microbe that is able to cause disease in an otherwise healthy individual. Opportunistic pathogen - A member of the normal microbiota and only causes disease in an immunocompromised host. Pathogenicity - Ability of pathogen to cause disease. Virulence - Degree or intensity of pathogenicity. Virulence factors - Mechanisms that determine the degree to which the pathogen causes damage, invasion and infectivity. (Help microorganisms to invade and avoid host defences). Antigenic drift - Result of point mutations causing minor changes in spike proteins. Antigenic shift - Gene re-assortment results in major changes in spike proteins. Cytokine - Small proteins important for controlling immune cell growth and activity.  Fimbriae: Invasion: Pili: -Alters surface of bacterium to -Start invasion process and Proteases = -Hair-like structures to prevent phagocytosis. allow for penetration of deeper Capsules: Degrade collagen in connective enable bacteria to attach tissues. -Protective coat tissue to promote spread. to host cells and -Specific to particular tissue colonise. Adhesion -Prevents phagocytosis from immune cells. structures. -Prevents adhesion of antibodies. Exoenxymes -Allow bacteria to move along host cell surface. -Aid in adhesion of bacteria. Bacterial cell wall: -Surface proteins that bind to target receptor molecules on host cell surface. Extracellular enzymes: -Allow bacteria to adhere closely allowing for -Secreted by cell and functions colonisation. outside of cell. Virulence factor mechanisms -Many bacteria use one or more adhesins. Endotoxins: Fimbriae: -Derived from gram-negative bacteria. -Some streptococcus -Stimulates general systemic inflammatory response. species contain M protein; -Stable at high temperatures. alter surface wall of bacteria Immune evasion -Part of outer membrane of bacterial cell wall. to inhibit phagocytosis -Low concentration- effect host inflammatory Antigenic variation: Toxins response against infection. -Avoid detection and -Biological poisons -High concentration- severe drop in blood pressure, destruction due to altering produced by some multi organ failure or death. Leukocidins: pathogens surface proteins. -Cytotoxin that is Exotoxins: Mycolic acid: able to destroy white -Potent protein molecules, produced inside -Produced in cell wall acts blood cells and Toxigenicity = as protective coat. pathogenic bacteria. phagocytes (immune Ability of a pathogen -Deters killings -Mainly gram-negative but some gram-positive. cells). produce toxins and mechanisms when -Target specific receptors on specific cells. cause damage to host phagocytosed. -Specific on action. -Lethal in low concentrations. cells.  Adhesins: Pleomorphism: -Different adhesins for -Can respond to various Gingipains: Fimbriae: different functions of; adhesion environmental conditions and -Exoenzymes (proteases) are produced by -Modify and stimulate immune to oral epithelial cells and adapt to biological niches. gingipains to break down structural proteins of responses in periodontium. biofilm formations. periodontium; collagen, elastin & fibronectin. -Effects cytokine secretion and -Contribute to periodontal disease. inhibition. Candida albicans Pathogenic yeast ORAL THRUSH ↑ Porphyromonas gingivalis Exoenxymes: Gram -‘ve anaerobe -Variety of exoenzymes produced. PERIODONTAL DISEASE -Contribute to; tissue damage, adhesion and releases iron as Virulence factor mechanisms nutrition for the yeast. in Oral Health Adhesin: -Adhesin P1 anchored to cell wall, aids in adhesion to tooth. -Polysaccharides on cell wall aid bacteria to adhere to tooth enamel. Streptococcus mutans Herpes simplex virus Gram +’ve facultative anaerobe Opportunistic pathogen: Pathogenic virus CARIES -Hide in neurons and non- HSV-1 neuronal cells and emerge as Cariogenicity = Surface glycoproteins: Ability to promote or pathogenic form when immune Acidogenic: -Coat with complement factors resistance is low in host. -Produces acid by breaking down carbohydrates. cause the development to prevent the immune system Cell surface receptors: from eliminating the virus. -Causes a decrease in oral cavity pH due to of tooth decay. -Many receptors used to gain increase in cariogenic bacteria — increased risk of entry and allow virus spread from tooth decay! cell-cell.