Bacterial pathogenesis

list kochs postulates

1) The microbe should be found in all cases and at all sites of the disease.
2) The microbe should be isolated from the infected persons and maintained in pure culture.
3) The pure cultured microbe should cause symptoms of the disease on inoculation into a susceptible individual.
4) The microbe should be reisolated from the intentionally infected host.

describe adherence as a virulence factor

adhesins on bacteria attach to sites on epithelium or mucous membranes.

describe invasion as a virulence factor

invasins mediate penetration of epithelial layer

once inside the epithelia, pathogen may
penetrate deeper tissues
• growth may be established at points distant from
point of entry
• entry to blood or lymphatic circulatory system
gives access to all organs & systems of the host
(SYSTEMIC DISEASE)

how to intracellular pathogens work?

survive
within immune system associated, phagocytic
cells (macrophages)
• “Trojan horse” tactic, enabling transport to
other tissues

what is the term for bacteria entering the blood stream

bacteraemia

name 5 secreted virulence factors

coagulase

protease

nuclease

leucocidins

haemolysins

what is an endotoxin and name 3 types

protein released from organism as it grown that has toxic affect,

neurotoxin, enterotoxin, cytotoxin

name 3 ways bacteria become pathogenic

transformation, transduction, conjunction

all horizontal gene transfer

what is transformation

uptake of naked DNA from environment

what is conjunction

direct transfer of plasmid dna between bacteria

what is conjunction

dna transfer mediated by bacteriophages

what are pathogenicity islands

• Regions of bacterial chromosomes
• Only in virulent strains of bacteria
• Carry multiple virulence genes (secretion systems, iron acquisition)
• Often located at bacteriophage and insertion sequence integration sites.
• Differ in G+C content compared to host genome