Tutorial Bacterial Diarrhoeal Diseases The pathogenic bacteria that can give rise to diarrhoea are :

Food poisoning pathogens: Staphylococcus aureus : Certain strains of Staph. aureus produce a heat-stable enterotoxin which if ingested gives rise to acute toxic food poisoning which often occurs in epidemics.

Salmonella : Salmonella food poisoning is caused by members of genus Salmonella other than the four serotypes that cause enteric fever ( S. typhi, S. paratyphi A,B and C ). Food may be contaminated during its preparation and serving. Human carriers, cases, domestic animals and rodents are sources of infection. Cows milk, milk products,and meat are infection sources.

Cl.perfringes Certain strains of Cl.perfringes cause toxic food poisoning. Such strains occur in faeces of man and animals. Vehicle of infection is pre-cooked meat stored at temperatures allowing multiplication of Cl.perfringes. Following ingestion a sufficiently large numbers of organisms,patient suffers from abdominal discomfort,cramps & diarrhoea 8-14 hours later. The illness is apyrexial & lasts only 1-3 days.

Bacillary Dysentry Bacilli Bacillary dysertry is an endemic bacterial infection all over the world. Severity of infection is related to Shigella spp.Severe illnesses are caused by Sh. dysenteriae. Clinical picture produced by serotypes of Sh..flexneri and Sh. boydii is less severe. Dysentery caused by Sh. sonnei is so mild that the infection amounts to a social inconvenience only.

Cholera Vibrios Include V. cholerae and ElTor vibrio. Cholera is essentially a water-borne infection and sources of infection are cases and carriers. Active immunization is not very useful, hence abandoned in all countries. The disease can be seen all over the world from time to time.

Gastroenteritis pathogens: Gastroenteritis is caused by entero- pathogenic strains of E. coli, affecting children (first year). Epidemics occur in nurseries. Babies artificially fed are more likely to suffer than breast-fed babies. Sources of infection: cases, carriers. Spread: by fomites, feeding bottles

Diarrhoea in Typhoid fever Patients with typhoid and paratyphoid fevers sometimes can present with diarrhoea which is not the predominant symptom.

Other Bacteria These include the following:- Campylobacter jejuni Campylobacter jejuni: isolated from 5-14% of diarrhoea cases. Yersinia enterocolitica Yersinia enterocolitica: Spread : ingestion of contaminated food.

Laboratory Diagnosis of Diarrhoeal Diseases Specimens collected : Stool and rectal swabs. Food specimens in food poisoning. Transport media: Sea water or alkaline peptone water for vibrios. Cary-Blair transport medium for other organisms

Media inoculated Media inoculated : *Blood agar, *Salt agar, *D.C.A., *Mc Conkey, *Selenite F, * T.C.B.S., *Alkaline petone water, *Cooked meat medium, *Willis and Hobbs (Cl. Perfringes ) *Butzlers medium (C.jejuni) *Media for Yersinia same as for N.L.F. bacteria  Identification  Identification by biochemical reactions and serological tests as appropriate.