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GIHEP Micro - Foodborne infection (ii) Bacterial 2 - E Coli gastroenteritis
GIHEP Micro - Foodborne infection (ii) Bacterial 2 - E Coli gastroenteritis
ETEC (enterotoxigenic)
travellers' diarrhoea
underdeveloped countries, poor sanitation
site of infection = SI
non-invasive
2 types of toxins, 1 or both expressed
symptoms: watery (non-bloody), diarrhoea, fever, nausea
ranges from minor discomfort to severe cholera-like syndrome
colonisation: specialised pili (colonisation factor antigens) bind to Rs on epithelial cell surfaces of SI
enterotoxins
LT (heat labile, similar to cholera toxin)
ST (heat stable) causes an increase in cGMP = secretion of fluid + electrolytes resulting in diarrhoea
VTEC (verotoxigenic)
aka enterohaemorrhagic (EHEC)
serotype O+H
O157:H7 = the most common isolate, but other serotypes sometimes implicated, esp O26
produces shigella-like verotoxin (cytotoxin results in cell death by disrupting protein synthesis)
site of infection = colon, where adherence is rapidly followed by invasion of intestinal epithelial cells
acute inflamm response + tissue destruction produce diarrhoea with little fluid, lots of blood + sheets of mucus containing polymorhonuclear cells (approx 3 days duration)
main reservoir = cattle + other ruminants
survive for long periods in environment
transmission to humans
consumption of contaminated food, water, minced beef products,(should be well cooked to minimise risk)
exposure to contaminated environment involving direct or indirect contact with animals or their faeces
outbreaks often linked to undercooked minced beef, petting animals, water, unpasteurised milk, creches, residential institutions, contaminated wells
incubation period: 24-72 hrs
no. of notifications increasing in Ire
bloody diarrhoea +/- vomiting
more severe in extremes of age
lasts 3 days
complications
HUS
in 10% of under 10s
ARF, thrombocytopenia, microangiopathic haemolytic anaemia
antibiotics not indicated, a/w increased toxin release
rehydration B
EPEC (enteropathogenic)
infection site = SI
attaches to intestinal mucosa, loss of villi
invasion of host cells + interference with normal cellular signal transduction - symptoms
person-person spread
watery diarrhoea, vomiting, fever
major cause of infantile gastroenteritis esp in developing countries + under 6 months/old
high mortality rate due to severe dehydration
may cause outbreaks
EIEC (enteroinvasive)
infection site = colon
invasive - penetrate + multiply in epithelial cells of colon causing widespread cell destruction
doesn't produce toxin
clinical syndrome = shigella dysentery - dysentery-like diarrhoea with fever
abdo pain, watery diarrhoea, dysentery-like illness
EAEC (enteroaggregative)
attach to tissue culture cells in an aggregative manner
persistent diarrhoea in young children
adhere to GI mucosa + cause non-bloody diarrhoea without invading or causing inflamm
EAST (enteroaggregative stabile heat) toxin + haemolysin (role in virulence not proven)
significance of EAEC strains in human disease controversial