Gastrointestinal Diseases Flashcards
Acute gastroenteritis causes
Viral-> rotavirus, adenovirus, norovirus
Bacterial-> E.coli, salmonella, shigella, cholera, campylobacter, yersina
Toxin mediated-> c.diff, s.aures, b.cereus, c.perfingens
Parasitic-> cryptosporidium parvum, giardia lambia, entamoeba histolytica
Host defence against GI infection
Enzymes in saliva and small bowel
Acidic environment of stomach
Unspecific antibodies in stomach-> IgA, peyers patches
Bile
Physical movement prevents close approximation with intestinal wall
Mucin and mucus act as a barrier
Food associated diarrhoea causes
Spread from contaminated food
Viral-> rotavirus, adenovirus, rotavirus
Bacterial-> compylobacter, e.coli, salmonella, shigella, cholera, yersina
Toxin mediated-> s.aureus, b.cereus, c.perfringens
Travel associated diarrhoea causes
Spread from contaminated food or water
Viral-> rotavirus, adenovirus, norovirus
Bacterial-> e.coli, salmonella, shigella, cholera, compylobacter, yersina
Parasitic-> cryptosporidium parvum, giardia lambia, entamoeba histolytica
Investigations of gastroenteritis
History and examination Blood cultures Stool -> microscopy-> ova, cysts, parasites -> culture-> salmonella, shigella -> antigen detection-> rotavirus, adenovirus -> toxin testing-> c.diff
Symptoms of viral gastroenteritis
Faecal-oral spread, incredibly infectious
Explosive diarrhoea often with vomiting
Incubation of 24-48hrs
Supportive management
E.coli and E.coli 0157
Enterotoxigenic-> heat labile and heat stable toxins -> abdo pain, cramping,diarrhoea ->12hr intubation -> oral rehydration Enterohaemorrhagic-> e.coli 0157.H7 ->Variable presentation-> mild diarrhoea to haemolytic uraemia syndrome -> mediated by verocytotoxin -> 2-19 days intubation -> do not give antibiotics Enteroinvasive Enteropathogenic Enteroaggregative
Diagnosis of E.coli
Culture -> sorbitol no fermenter -> biochemistry to confirm E.coli Toxin detection -> PCR stool
Salmonella
Multiple sub species
-> s.enteritidis-> most common->usually self limiting diarrhoea
-> s.typhi and s.paratyphi-> most severe-> life threatening sepsis with possible secondary seeding
Occasional carrier state in gall bladder
Servere infections-> ciproflaxacin or ceftriaxone
Diagnosis of salmonella
Stool culture -> XLA, DCA agar -> black colonies -> s.enteritidis Blood cultures -> typhi and paratyphi -> special lab as high risk infections
Shigella
Different sub species
Dysentery-> most server disease
Haemorrhagic colitis, fluid loss and shock-> potentially life threatening-> bowel perforation
Incubation 1-3 days
Supportive therapy with good fluid rehydration
Faecal- oral
Diagnosis of shigella
Stool cultures
-> XLD, DCA agar
-> pink colonies
Subtype to species level
Campylobacter
Zoonotic bacterial infection with c.jejuni, c.coli
Malaise, abdo pain, fever, nausea, vomiting
Contaminated food or water-> raw chicken
Incubation 3-5 days
Supportive therapy
Usually self limiting
Diagnosis-> selective agar and microaerophillic conditions 45*c
Clostridium difficile
Spectrum of antibiotics associated diseases produced by toxin from c.diff
-> diarrhoea, pseudomembranous colitis, bowel perforation and death
Broad spectrum antibiotics are a major risk factor
Treat with -> metrondiazole or vancomycin and stop offending antibiotics
Pathophysiology of c.diff
Spores which survive for a long time in the environment
2 toxins
-> A enterotoxin
-> B cytotoxin
Both penetrate epithelial cells leading to cell death
ELISA to look for toxin and stool culture
Toxin mediated food poisoning
Mainly s.aureus, clostridium perfingens, b.cereus
Incubation of a few hours
Enterotoxin induced
-> s.aureus-> sudden onset abdo pain and vomiting
-> clostridium-> occasional necrotising enteritis
Parasites
Cryp. Parvum, giardia lambia, entamoeba histolytica
Faecaly contaminated water
Incubation 7-10 days
Cryp-> self limiting
Giardia and entamoeba-> metrondiazole
Stool analysis-> cyst and Protozoa in stool
Infection control
Single room Own toilet Damp dust daily Minimum, specific equipment Patient must be 48 hours healthy Or 72 hours if going to another health care facility or c.diff
H.pylori
Bacterial infection that causes-> chronic gastritis and duodenal ulcers
Initiation and continuation of inflammatory response
Eventually atrophy and metaplasia
Associated with gastric adenocarcinoma
2 antibiotics and a PPI
Clinical features of H.pylori
Epigastic pain Nausea Vomiting Haematemesis Blood in poo Symptoms usually resolve despite continuing infection
Diagnosis of H.pylori
Gram negative spiral curved bacillus Strict growth requirements Motile Urease positive great test Serology-> presence of antibody
