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GIHEP Micro - Foodborne infection (ii) Bacterial 1 (Campylobacter spp…
GIHEP Micro - Foodborne infection (ii) Bacterial 1
Campylobacter spp
4 spp a/w human disease
C jejuni
C coli (cattle, swine, birds)
C fetus
C lari (seabirds esp)
normal flora of cattle, swine, birds (shed + contaminate water)
sources
contaminated food (undercooked/poorly handled poultry)
contaminated water
livestock
household pets
most commonly a/w undercooked chicken, with a peak in summer (BBQ season)
person-person spread rare
most common cause of bacterial food poisoning in developed countries (esp C jejuni)
risk factor = PPI (less acid)
pathogenesis
not fully understood
adheres to jejunum + ileum
cytotoxin causes local damage
mucosal invasion
occasionally severe haemorrhagic necrosis of the SI may occur
may also have large bowel involvement with crypt abscess formation in severe cases (dDx = UC)
occasionally bacteraemia may occur with focal manifestations
incubation period = 2-4 days, can be up to 8-9 days
24hr prodromal illness: fever, headache
diarrhoea may be bloody, abdo pain may be severe
resolves in 5-7 days
complications
toxic megacolon
bacteraemia (extremes of age, immunosuppressed)
Guillain Barre syndrome (<1 in 1000)
Abs cross react with myelin sheath - ascending neuropathy
Lab dx
faeces/blood culture
microaerophilic
oxidase +ve
curved gram -ve bacilli
grey colonies on selective charcoal containing media
hydrolyses hippurate (blue colour)
faeces PCR
Tx
rehydration
antibiotics not routine - only if bacteraemic or immunosuppressed - azithromycin or ciprofloxacin (fluoroquinolone - blackbox tendonitis warning) if susceptible
prevention
food hygiene (proper cooking + storing)
hand hygiene (after animal/meat contact)
notifiable to public heath
S Aureus
salads, cream filled pastries, meats/sandwiches
high attack rate
outbreaks esp in summer
pre-formed enterotoxin ingested in the food
incubation = 1-8hrs (v short due to pre-formed toxin), lasts 8-24hrs
vomiting predominates, occasionally diarrhoea
up to 30% of people colonised
C Perfringens
incorrectly stored cooked meat, gravy, dairy products
toxin production in vivo (multiplication in SI, sporulation, enterotoxin production)
incubation = 8-24 hrs, lasts 1-3 days
produce diarrhoea, occasionally vomiting
C Botulinum
sources
improperly canned/home bottled products (inadequate heating during canning process)
raw honey (don't give to under 1s - infant botulism
preformed neurotoxin
incubation = 12-36 hrs
possibly diarrhoea + vomiting
ptosis 1st, then descending flaccid paralysis, mechanical ventilation required, high mortality (20%)
lasts wks to months
tx with antitoxin
Bacillus Cereus
type 1: Emetic syndrome
ingestion of preformed toxin
fried rice: allowed to cool slowly @ room temp/held for long period predisposes to germination of organism from spores with toxin release
incubation 1-6hrs, lasts 2-10hrs
predominantly vomiting, abdo cramps, may have diarrhoea
type 2: Diarrhoeal syndrome
toxin production in gut
meats, salads, chicken soup, maybe spices - contained with spores which germinate in bowel
incubation = 6-14hrs (longer as toxin has to be made), lasts 8-24 hrs
diarrhoea mainly
non-typhoidal salmonella
shigella
vibrio cholerae
Yersinia enterocolitica + pseudotuberculosis
Listeria monocytogenes
systematic
usually a/w underlying condition
pregnancy (esp 3rd trimester)
steroids