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home - Colon - Colonic Infection - E. coli Written by Dr Sebastian Zeki
Knowledge

Recognises the range of important inflammatory conditions of the
intestine other than inflammatory bowel disease
Knows the range of potential aetiologies including infection and
ischaemia
Understands how diverticular disease can give rise to complications mini-CEX, SCE 1
Knows how diseases can affect the peritoneum and how such
conditions can present both in the acute and chronic situation
Knows the range of both acute and chronic intestinal infections and
their various presentations
Knows the means of investigations of infectious diseases and
understands the principles and use of antimicrobial therapy

Skills
Makes a full clinical assessment of patients presenting with infective
and inflammatory conditions
Recognises the potential urgency of the clinical situation. Selects
appropriate investigations and treatments

Behaviours
Manages patients with inflammatory and infective conditions carefully,
competently and sympathetically.

E. coli

Enterotoxigenic Ecoli (ETEC) Enteropathogenic Ecoli (EPEC) Enteroinvasive Ecoli (EIEC) The pathogensis is closely related to shigella.Clinical Manifestations include Watery diarrhoea which can become bloody. Often asymptomatic.Diagnosis can be done by DNA probe- this is not routinely available. Short incubation period Diarrhoea can be mild watery to cholera like in volume Nausea commonVomiting uncommon Usually 24 hours but can last up to 5 days LT- (heat-labile toxins) ST-(heat-stable Adenylate cyclase + Intracellular cyclic AMP Increases Secretion of chloride from intestinal crypt cells and inhibition of absorption of NaCl at the villus tips. Water secretion ST activates enterocyte cGMP with chloride secretion and inhibition of NaCl absorption. DiagnosisRabbit ileal loop bioassay for secretory toxin for LT Suckling mouse bioassay for secretory toxin for STDNA probes for LT and ST genes at reference lab Treatment:Oral rehydration therapyUsually self limiting course 2. Induce signal transduction 1. Localized adherence of the organisms to the enterocyte 3. Mobilize intracellular calcium, activate protein kinase C and the myosin-light-chain kinase, and induce tyrosine phosphorylation of proteins. 4. Intensive adher-ence of the organ-isms to the entero-cyte Increased perme-ability of intestinal tight junctions. Clinical manifestationsCan get severe diarrhoea and vomiting esp in childrenMost common in neonatesOften asymptomatic in adults DiagnosisDNA probe or PCR of the EPEC adherence factor (EAF) in reference labs Alterations in water and electrolyte secretion 3-4 days incubation Haemorrhagic colitis+Abdominal painWithout fever Pseudomembra-neous colitis without c. diff Asymptomatic 25% need hospitalizationIf uncomplicated resolves in 1 week 5-10 days after onset of diarrhoea 9% 50% need dialysis in acute phase3 to 5% mortality5 to 10 % permanent and serious renal or neurologic complications TTPHUS:ARF;MAHA;ThrombocytopeniaShiga toxins may have a predilec-tion for the renal circulation. Fever and neurologic sx SourcesBeefHuman contactFaecal contamination of foods Enterohaemorrhagic Ecoli (EHEC) Diagnosis is by stool isolation which is highest in the first 6 days after diarrhoea.E. coli O157:H7 ferments sorbitol slowly so screen on sorbitol-MacConkey (SMAC) agar. Confirm with indole.Determine if pathogenic by: Serotype; virulence bioassay;DNA probing or PCR.Treatment is supportive.Patients should be monitored for microangiopathy.There is no role for antibiotics.It is contentious as to whether this causes HUS. Prevention of EHEC:Contact precautions for patients.Reduce faecal soilage of meat during slaughter and processing.Hay feed animals 5 days prior to slaugh-ter to reduce E. coli carriage (changes colonic pH).Cook food to internal meat temperature> 68.3ºC. Enteropathogenic Ecoli Written by Dr Sebastian Zeki Enteroaggregative Ecoli (EAEC) This is more common in developing countries and accounts for 4.5% acute diarrhoea.The pathogenesis is unknown.The diagnosis is by tissue culture adherence assay; not DNA probes.Treatmentt is supportive only, no need for antibiotics.

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