Loss of some virulence factors of enterotoxigenic Escherichia coli on repeated subcultures.

Thirty enterotoxigenic Esch. coli (ETEC) strains of predominant serogroups, isolated from patients with diarrhoea in Ludhiana, Punjab were investigated for expression of heat labile (LT) enterotoxin and colonization factor antigens (CFAs) on repeated subculture. These belonged to serogroup 078 (10), 080 (2), 0114 (6), 020 (3), 0128 (3), 0153 (2) and 08 (4) respectively. The isolates exhibited a differential response for expression of LT and CFAs on repeated subculturing. All the strains were positive for both LT and CFA up to six subcultures. Three strains of serogroup 0114 and one of 080 failed to express CFA while one strain each of serogroups 080, 0114, 020 and 08 failed to elaborate LT in the 8th subculture. Only 25 and 19 isolates were detected as stable producer of LT and CFAs up to 10th subculture.