Bacterial pathogenesis

Bacterial pathogenesis

1. Koch's postulates

   • Take the bacterium from lesion and isolate it in pure culture; reinfect animal with same microbe and reisolate that microbe from the animal.
   • In order to establish the connection between microbe and disease.
   • Drawbacks include no host factors; emphasis on ability to culture microbe in lab; may lose virulence in lab; may not require organism to infect host; require animal model.

2. Transmission

   • Respiratory or saliva
     • Conjunctiva
     • Respiratory tract
   • Fecal-oral
     • Alimentary tract
   • Venereal
     • Urogenital
   • Vector
   • Vertebrae reservoir
   • Vector-vertebrae reservoir

3. Progression of infection

   • Entry
     • Transmission
   • Colonisation
     • Adhesion
       • Pili or fimbrial
         • Enterotoxigenic Escherichia coli or ETEC
         • Rod shaped
         • Hollow
         • helical structure of protein subunits
           • Called pilin
         • Can be polar or peritrichous
       • Capsule
         • Composed of
           • Polysaccharides
           • Polyproteins
         • Protects against host factors.
       • Non-fimbrial
         • Bordetella pertussis
           • Uses FHA, a 220lDa protein containing RGD motif
             • binds to human b1 integrins
         • Bartonella hanselae
           • Leads to endocarditis and cat scratch disease
           • BadA is a non-fimbriae adhesion protein
             • Binds to ECM
             • Binds to epithelial cell membrane
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