PRELIM 06 - Bacterial Mechanisms of Pathogenicity Flashcards
The ability to cause disease by overcoming host defenses
Pathogenicity
The degree of pathogenicity
Virulence
3 portals of entry
Mucous membranes, Skin, Parenteral
Epithelium lining the respiratory tract, GIT, GUT, and conjunctiva
Mucous membranes
Skin that is impenetrable by most microorganisms
Unbroken skin
Is a parasite that bores through intact skin
Hookworm
It grows on keratin in skin or infect the skin itself
Fungi
The number of pathogen cells or virions required to cause active infection in 50% of inoculated animals
ID50/Median infective dose
The number of pathogenic cells or virions required to kill 50% of infected animals
LD50/Median lethal dose
These bind surface receptors on the cells of certain host tissues
Adhesins/Ligands
Glycocalyx (Adherence factors)
Streptococcus mutans
Fimbriae (Adherence factors)
Actinomyces, Streptococcus pyogenes
Fimbriae, pili (Adherence factors)
Enteropathogenic Escherichia coli
Fimbriae, opacity associated proteins (Adherence factors)
Neisseriae gonorrhoeae
Tapered end as hook (Adherence factors)
Treponema pallidum
Produces adhesins that bind to laminin and fibronectin on skin cells (Adherence factors)
Staphylococcus aureus
Converts fibrinogen to fibrin that coagulates the blood to protect bacteria from phagocytosis and defenses (Enzymes)
Coagulase
Breaks down fibrin and digests clots (Enzymes)
Kinase
A kinase produced by Streptococcus pyogenes
Fibrinolysin/Streptokinase
Hydrolizes hyaluronic acid, which holds together cells in connective tissues (Enzymes)
Hyaluronidase
Breaks down collagen in connective tissues (Enzymes)
Collagenase
Destroys IgA (Enzymes)
IgA protease
Prevents phagocytic cells from adhering to the bacterium
Capsule