08NED12 - Bacteria continued Pathogens & pathogenicity...

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Bacteria continued Normal flora species/locations Good species/bad relatives Obligate—must infect Facultative—can infect Opportunistic—immune compromised Role of structure in infection: 1)  Bacteria use fimbriae, flagella (modified), pili, slimes or capsules (mod. glycocalyx) Fimbriae: Neisseria (gonorrhea), shigella (dysentery), pseudomonas (lung infections) glycocalyx: Vibrio (cholera) 2)  Surface proteins Adhesins —attach to surfaces 3)  Pores and “injection” systems Allow bacteria to deliver factors to host cells to disable cells or to take over cells Type III secretion system—molecular syringe Invasins —remodel actin cytoskeleton so bacteria can enter or prevent digestion by immune cells Adhesion is the key Portals of entry: Mucus membranes are a popular region for invasion skin:  staphylococcus, streptococcus, tetanus wounds, breaks, bites, punctures—collectively known as  parenteral gastrointestinal tract: gram—rods: salmonella, shigella, vibrio, E. coli (hepA, rota, polio, echo) respiratory:  easiest; with GI, the most common strep throat, meningitis, diptheria, pertussis, pneumonia (Klebsiella, Mycoplasma),  Mycobacterium tuberculosis, staph urogenital: syphilis, gonorrhea, strep and staph  Almost every pathogen has a preferred route—some are exclusive, some are not Steps: 1-colonize 2-find nutritionally compatible niche 3-avoid immune system
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4-replicate 5-exit and spread Microorganisms damage cells in 4 ways Use host nutrients Cause direct damage in immediate vicinity Produce toxins Induce hypersensitivity in immune system Host response helps things along Viruses and bacteria Coughs, runny nose Diarrhea Open lesions or sores
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08NED12 - Bacteria continued Pathogens & pathogenicity...

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