Bacterial Infection and Pathogenesis infection Conception factors pathogen

Bacterial Infection and Pathogenesis

infection • Conception • factors pathogen virulence、amount、route host non-specific immunity environment

source • exogenous infection patient carrier animal • endogenous infection normal flora latent pathogen

transmission portals of entry of pathogen • • • respiratory tract gastrointestinal tract skin sex attach multiple

types of bacterial infection • inapparent infection • apparent infection acute infection chronic infection local infection systemic infection

types of systemic infection • • • bacteremia toxemia endotoxemia septicemia pyemia）

pathogenesis • • • pathogenicity virulence LD 50 / ID 50 毒力基因的表达及其调节 pathogenicity isoland，PAI） two-component signal transduction system cell signal transduction

bacterial pathogenicity • virulence invasiveness toxin • numbers • portals of entry

invasiveness • adherence） pilus: type I pili，P pilus CFA/I，CFA/II adhesin • capsule，microcapsule • bacterial biofilm • invasive enzyme

E. coli Type 1 fimbriae (adhesin) Mannose Bladder

biofilm 20 mm

biofilm

exotoxin • Definition: a soluble protein toxin usually secreted from a living bacterium. • Origin and release: produced by Gram-positive bacteria as well as Gram-negative cells • Physical and chemical properties: proteins and usually heat-labile.

exotoxin • neurotoxin • cytotoxin • entrotoxin

endotoxin • Origin and release: produced only by Gram-negative bacteria and released only when bacteria lyze. • Chemical and physical properties: lipopolysaccharide of the outer membrane of Gram-negative bacteria; heat-stable

Biological activity of endotoxin • • • fever leukopenia endotoxemia shock DIC Enhance the non-specific immunity