Gastrointestinal Infections: Toxins

Mind Map by hands97, updated more than 1 year ago
Created by hands97 over 6 years ago


Medical Microbiology Mind Map on Gastrointestinal Infections: Toxins, created by hands97 on 04/30/2013.

Resource summary

Gastrointestinal Infections: Toxins
1 C. Botulinum
1.1 Neurotoxin: Inhibits acetylcholine release from nerve endings, flaccid paralysis
1.1.1 Heavy (100kDa) & Light Chain (50kDa, metalloprotease, HexxH zinc-binding motif, cleaves SNARE complex, ie SNAP-25, synaptobrevin, or syntaxin)
1.2 Types A-G but food-bourne usually A,B,D, E (marine)
1.3 Therapy= antitoxins to mop up free toxin
1.4 Difficult to diagnose: Similar to stroke symptoms. Need to isolate toxin from faeces/CSF/serum, takes 2+ days to show!
1.4.1 Mouse bioassay (4 days), new PCR developed
1.5 G+ve, spore forming (survive high temps), anaerobe
1.6 Outbreaks through contaminated food- preserving/canning process inadequate
1.7 Incubation: 6hrs-16days
1.8 Vaccine for high risk workers,e.g. scientists
1.9 Infant botulism: Linden flowers implicated, natural sedative
2 S. aureus
2.1 G+, coccus, facultative anaerobe
2.2 Stable over range of pH/salt/temps
2.3 Staph enterotoxin, heat-resistant
2.4 Abdominal pain, vomiting, fever
2.5 Catalase +ve, coagulase/DNAse +ve
2.6 20-100ng enough to cause infection
2.7 Protein-rich foods, e.g. dairy/meat
2.8 Incubation: 1-6hrs, infection:<48hrs
2.9 Enter text here
3 B. cereus
3.1 Cereulide (emetic toxin), cyclic dodecadepsipeptide
3.1.1 Highly resistant to acid/proteolysis, heat
3.1.2 Bind 5HT3 receptor on vagus afferents (nerve fibres) to stimulate sickness
3.1.3 Inhibits fatty acid oxidation in mitochondria, possible liver toxicity
3.1.4 Encoded on a megaplasmid, via ces genes
3.1.5 PlcR regulated expression
3.2 103-108 infectious dose (high)
3.3 Can cause meningitis, UTIs, RTIs, HAIs!
3.3.1 RTIs: carries anthracis pX01 plasmid (but no pX02- required for capsule+positive regulator of toxin genes on pX01)
3.3.2 HAIs: amongst immunosuppressed patients, equipment contaminated e.g. ventilators, intravenous catheters, etc
3.3.3 Meningitis, meningoencephalitis, brain abscess, etc. Abdominal pain before bacteremia-->brain. Risk factors include intrathecal induction chemotherapy
3.3.4 UTIs: Contaminant on catheter (forms biofilm)--->pyelonephritis.
3.4 Diarhoeal toxins
3.4.1 Tripartite (Cytotoxin K & Nonhaemolytic Enterotoxin)


  • NHe most dominant!! L1, L2 (lytic) & B (binding) subunits (CytK), NHeA, NHeB, NHeC (NHe) NHe= pore former
3.4.2 Oligomeric B-barrel pore-forming (Haemoysin bl & CytK)
3.4.3 Cerelysin O
3.4.4 Haemolysin II HlyIIR, dimeric transcriptional regulator (repressor)
3.4.5 InhA2
3.4.6 phospholipase C
3.5 G+ve, facultative-to-aerobic, spore-forming (resistant to gamma radiation/pasteurisation), non-mannitol fermentor
3.6 Some strains produce negligible amounts of toxin & authorised for use as probiotic!
3.7 Vomiting infection: 8-10hours, diarrhoeal infection: 20-36hrs
4 C.perfringens
4.1 G+ve, spore-forming, anaerobic
4.3 Incubation: 8-14hrs, infection: 24hrs
4.4 Peaks in autumn (stews)
4.5 Toxins
4.5.1 CPE (enterotoxin) Bind claudin -3, -4, -8, -14 Oligomerises into hexamer (CH1) Influx of Ca2+ into cell--> apoptotic pathway CH2 Internalises occludin Histopathologic damage to cells--> diarrhoea Cytoplasmic C and N termini, 4 transmembrane domains
4.5.2 Iota toxin ADP-ribosyltransferase CD44 binding implicated
4.6 Non-motile
5 V. cholerae
6 C. Difficile
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