Occurrence of colonization factor antigens I & II in enterotoxigenic Escherichia coli associated diarrhoea in Iran & correlation with severity of disease.

The occurrence of colonization factor antigens I and II (CFA/I and II) and type 1 somatic pili was investigated in 197 enterotoxigenic Esch. coli (ETEC) isolated from 197 patients of diarrhoea (aged under 3 yr) during February 1985 to March 1986 in Tehran, Iran. Among ETEC strains, 154 strains were heat-stable enterotoxin (ST) producers, 27 strains were heat-labile enterotoxin (LT) producers, and 16 strains produced both toxins. Sixty five (33%) strains showed mannose-resistant haemagglutination (MRHA) of human and/or bovine erythrocytes; of these, 51 (86%) strains were positive for CFA/I and II. Seventy one (36%) strains also exhibited type 1 somatic pili. CFA/I was found in 4 (15%) LT producing, 24 (16%) ST producing, and 2 (13%) LT/ST producing strains. In contrast, CFA/II was only found in ST producing strains (17 strains) and those producing both toxins (4 strains). Patients having CFAs-positive ETEC strains had a significantly (P less than 0.001) higher number of stool evacuation per day and a longer duration of diarrhoea than those having CFAs-negative strains. Fifty nine patients had mixed infections of ETEC strains and other enteropathogens. CFA/I or II (CFAs)-positive and CFAs-negative ETEC strains were found in 17 and 42 patients with mixed infections respectively. The mean number of stool evacuations per day was much higher in patients with ETEC and rotavirus than those with only ETEC infection (P less than 0.001). However, severity of the disease was not affected by the presence or absence of CFA/I or II in ETEC strains found in these patients.