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GIHEP Micro - Foodborne infection (i) (Food poisoning (epidemiology…
GIHEP Micro - Foodborne infection (i)
gastroenteritis
acute inflamm of stomach + intestines lining
caused by food poisoning, irritating food or drink, or psychological (stress)
Food poisoning
group of illnesses caused by ingestion of contaminated food or food that contains microorganisms/toxins/poisons
most commonly causes gastroenteritis, but also systemic illness (esp in some salmonella + listeriosis), neuro syndromes (e.g. botulism) + toxic states (mecurary, mushrooms)
epidemiology
common
many infectious causes
usually sporadic
may occur as outbreak
notifiable to public health
transmission = faecal oral contaminated food/water (esp shellfish, poultry, eggs - when undercooked or raw)
pathogenesis
ingestion of pre-formed toxin (S aureus, B cereus)
in vivo toxin production (B cereus, C perfrnigens)
multiplication/tissue invasion
clinical features of food poisoning causing gastroenteritis
acute onset
diarrhoea
vomiting
nausea
crampy abdo pain
Approach to food poisoning
Hx
onset of symptoms
duration
travel
food - takeaway, restaurant, buffet, picnic
were other people sick?
medications
can cause/contribute to diarrhoea (e.g. gastric acid suppressants)
Exam
may have fever, not always
usually otherwise normal unless its not food poisoning + actually an abdo pathology (e.g. appendicitis)
Investigations
vomitus not useful
faeces: selective culture for bacteria (MacConkey)
lactose fermenters (e.g. E coli = pink)
non-lactose fermenters (e.g. salmonella = yellow)
electron microscopy, ELISA, PCR for viruses
light microscopy for protozoa
food investigated in an outbreak, not for individual cases
Tx
supportive - fluid + electrolyte replacement
avoid antidiarrhoeals if possible (peristalsis to get rid of pathogen = good immune mechanism)
antibiotics not indicated in vast majority of cases
Prevention
education
hand hygiene
correct food storage + prep
notify public health to investigate outbreaks
appropriate control measures
hazard analysis critical control points (HACCP) = systematic preventative approach mandatory for all food premises (restaurants, hosp, schools)
Parasites
protozoa
giardia lamblia (giardiasis)
often waterborne
cryptosporidium (cryptosporidiosis)
can be a/w farm animals
5-10 organisms can cause infection
waterborne
parvum + hominis (formerly known as C parvum genotype 1) = most prevalent species in humans
oocysts allow it to survive outside body for long periods + be resistant to chlorine-based disinfectants
symptoms begin 2-10 days after infection - watery diarrhoea most common, also incl dehydration, weightloss, abdo cramps, pain, fever, nausea, vomiting
can be asymp
lasts 1-2 wks in immunocompetent host - self-limiting
severe disease in immunosuppressed - give anti-protozoal agents
entamoeba histolytica (amoebiasis)
a/w travel esp to tropics
amoebic dysentery
isopoda belli important in AIDS patients
rare causes of diarhoea incl intestinal tapeworms (cestodes)
taenia saginata (undercooked beef)
taenia solium (undercooked pork)
diphyllobothrium latum (undercooked fish)
viruses
calcivirus (e.g. norovirus)
rotavirus
Toxins (NOT INFECTIONS)
Ciguatera toxin (heat stable)
nausea, vomiting, diarrhoea, abdo pain
2-6hrs onset, followed by neuro paraesthesia + weakness, reversal of hot + cold
CV abnormalities in 2-5 days
consumption of reef fish (e.g. grouper, barracuda) - become contaminated during algal blooms containing dinoflagellates + produce heat stable toxin that becomes concentrates as it moves up the food chain
scombroid
buildup of histamine in food
shellfish + some mushrooms
flushing, diarrhoea, vomiting