Lec 6 (Clostridia)- summary.docx

3 Pages

Microbiology and Immunology
Course Code
Microbiology and Immunology 2500A/B
John Mc Cormick

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Clostridia - Gram + rods - Soil & intestinal tracts - Obligate anaerobes (veg. cells killed by O) (>80 species) - Endospore formers (Terminal endospores)- made when stressed - Exosporium Protein Spore coat Core wall – peptidoglycan Cortex – dna, cytoplasm, ribosomes - Dipicolinic Acid complex with Ca2+ → dehydrate cortex – gel consistency (pasteurizing won’t kill- 60-70 C ; autoclaving kills 121C) 1. C. difficile- Pseudomembranous colitis - also called antibiotic associated diarrhea - can exist as: a) asymptomatic carrier, b) mild-moderate diarrhea, c) life-threatening pseud colitis - exists in large intestine in low numbers - nosocomial pathogen - mode of transmission = fecal-oral route Pseudomembranous colitis: - recent antibiotic → kill normal flora & stress so form endospore → then germinate, grow, make toxins - does not invade – BUT toxins do damage - A-B Toxins- large clostridial cytotoxins - A domain: active with enzymatic activity- get this inside host cell - B domain: binding and uptake - A domain enzyme inactivates host G-proteins → rearrange cytoskeltn → cell death/inflamma’n - Epithelial layers peel off “pseudomembrane” and inflammation – yellow lesions - offensive smelling diarrhea - constitutional symptoms Diagnosis - history- taken antibiotics? - endoscopy, lab tests Treatment - discontinue antibiotic - give specific antibiotic Metronidazole (anaerobe antibiotic) - avoid anti-diarhheal- want to get rid of toxins - *NEW*: Restore microbiota from healthy patient- Effective- but need to screen donors 2. C. tetani- Tetanus - aka lockjaw - tetanus toxoid vaccine (TDap group) – 100% protected- problem in developing countries Tetanus - colonization of deep wound (anoxic conditions needed) - A-B neurotoxin- enters motor neuron, moves retrograde into CNS & affects inhibitory neuron - A domain- protease cleaves proteins
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