Infections of the Gastrointestinal Tract

Infections of the Gastrointestinal Tract “the shits” Gastroenteritis • Associated with microorganisms. • True infections vs intoxication • Symptoms - diarrhoea, vomiting, abdo pain “nature and duration depends on…” • Pathogenesis - attach / irritate - invade locally - in vivo toxins • Portals - faecal oral route (role of food) Host / Microbe interaction • Ingestion of, and presence of “nasty” microbes on food is more common than you think….but disease is RARE. EXPOSURE low dose high dose no disease disease HOST DEFENCES- chem, mech, microbial ROLE OF FOOD - growth of org’s favours “high dose” Reservoirs of infection “..initial source of organism” • HUMAN - normal flora - INFECTED or carrier - CARRIER • ANIMAL • ENVIRONMENT Transmission Reservoir / faeces VECTOR Fingers, flies, fomites Vehicle food, water HOST DISEASE DOSE NO DISEASE Control of foodborne disease Interrupt transmission • slaughtering practices • personal hygiene • foodhandling / innocent foods Minimise dose • food storage • adequate cooking Causes of diarrhoea • • • • • Most undiagnosed / unknown Non infectious Intoxication Bacterial infection Viral infection Parasitic infection • Community acquired or nosocomial • Foodborne / water / other • sporadic / outbreak Common intoxications • • • • • Staphylococcus aureus “foodpoisoning” Food contamination Growth and pre-formed toxin Toxin is heat stable Rapid onset diarrhoea and vomiting Difficult to diagnose Common bacterial causes Campylobacter - 20 000 /year - chicken major source Salmonella - 6000 year - animals major source - large outbreaks - just diarrhoea - human only, small dose Shigella Nosocomial diarrhoea • • • • Clostridium difficile Follows antibiotic use ? Reservoir, common exposure Eradication difficult Spectrum of disease - diarrhoea - bloody diarrhoea - pseudomembranous colitis Miscellaneous microbial causes Rotavirus - young children - highly infectious - vomiting AND diarrhoea - “el nino effect” - resilient / waterborne - fatty stools, flatulence - widespread, animals - resilient and small - no treatment - AIDS - remember SYDNEY Giardia Cryptosporidium Miscellaneous microbial causes Rotavirus - young children - highly infectious - vomiting AND diarrhoea - “el nino effect” - resilient / waterborne - fatty stools, flatulence - widespread, animals - resilient and small - no treatment - AIDS - remember SYDNEY Giardia Cryptosporidium Hepatitis A “the other hepatitis” • Infection is by ingestion NOT by exposure to blood and body fluids. • Faecal oral exposure Intestinal cells viraemia liver • Outbreaks - shellfish, hospitals, care centres • Nausea, vomiting, jaundice, fatigue • Recovery is usual / fatality < 1/1000 • Vaccination - both passive and active