Identification from stool culture can be confirmed by latex agglutination with specific antiserum. Tr - Fluid replacement

disease they give rise to are Sh. dysenteriae, Sh flexneri, Sh boydii and Sh sonnei Shigella spp has been implicated as a cause of 'gay bowel1 syndrome in homosexual men. There is no known animal reservoir (in contrast to many Salmonella spp.). Shigella bacteremia is uncommon except in immunocompromised host (e.g. HIV infection). Cl. Fs. - Following an incubation period of 2-3 days, high fever, headache malaise and anorexia occur, along with frequent small-volume stools progressing to passage of blood and pus and severe abdominal cramps, tenesmus and abdominal tenderness on palpitation. Diag - Stool culture and identification of the organism by specific serological testing. Tr. -Fluid replacement. Antibiotics - Suprafloxacin is drug of choice in most adults, co-trimoxazole and ampicillin are alternatives in children. Escerichia coli - This Gram-negative organism is a major cause obacterial gastroenteritis. The identification of E.coli 0157:H7 as an important enteropathogen has helped understanding of bacterial diarrhoea. Transmission and pathogenesis - The 0157: H 7 serotype of E.coli is non-invasive and produces a toxin similar to that of Shigella which kills Vero cells; this organism is therefore known as verotoxin-producing E.coli (VTEC). Infection follows consumption of undercooked beef or untreated milk. Cl. Fs. - (a) Infection is classically associated with hemorrhagic colitis, but may be asmyptomatic or produce diarrhoea only. Illness lasts upto 12 days and usually resolves spontaneously but may prove fatal. (b) Hemolytic uremic syndrome as a complication in about 5% or more serious variant, thrombotic thrombocytopenic purpura. (c) Ischemic colitis - Mucosal disease due to VTEC resembles ischemic colitis in the elderly. Diag - Identification from stool culture can be confirmed by latex agglutination with specific antiserum. Tr - Fluid replacement. Ciprofloxacin if severe or prolonged disease for adults, ampicillin or co-trimoxsazole for children. Vibrio cholerae - the causative organism of cholerae, is a short, curved motile Gram-negative bacillus. The major pathogenic strain possesses a somatic antigen (01) with two biotypes - classical El Tor More recently, a strain with somatic antigen 0139, the Bengal strain has appeared. Pathogenesis - The major factor distinguishing 01 and 0139 serotypes from other 'non-cholera1 vibrios is the ability to produce an enterotoxin. This consists of a ring of five E' subunits around a central 'A' unit. This pentameric ring structure binds to GM1 ganglioside on the enterocyte cell membrane and the A subunit stimulates enterocyte adenylate cyclase, leading to conspicuous secretion of small intestinal fluid and ultimately diarrhoea. Cl. Fs. - (a) Stage of evacuation - Sudden onset with frequent loose stools, first yellow soon become colourless, watery and copious with flakes of mucus (rice water stools). Copious and incessant watery vomit. Subnormal temperature. (b) Stage of collapse - Depletion of water and salts occurs rapidly, leading to severe dehydration and hypovolemic shock, and ultimately to death Diag - is mainly clinical. The organism can be grown from stool either directly or after alkaline enrichment. Tr. - (a) Fluid and electrolyte replacement: Mild case - Oral rehydration therapy with glucose-electrolyte solution. Constituents (g/litre): Sodium chloride 3.5 Sodium bicarbonate 2.5 Potassium chloride 1.5 Glucose 20 Other solutions containing glucose polymers (e.g. rice water) and electrolytes are highly