Coagglutination test for detection of heat labile enterotoxin producing Escherichia coli strains

A simple particle immunoassay based on the coagglutination (CoA) of Staphylococcus aureus strain Cowan 1 coated with heat labile enterotoxin (LT) specific antibodies was evaluated to detect LT in the cell lysates of blood agar grown Esch. coli. Among strains of Esch. coli isolated from 2661 patients with acute diarrhoea, isolates from 609 patients demonstrated LT production by CoA test. Most prevalent serogroups were 020, 078, 0128, 04, 0117, 068, 0158, 07, 0114, 0148 and 0145. A comparison of CoA with classical rabbit ileal loop and skin permeability factor assay for 100 strains showed 86, 69 and 83 LT positive strains respectively. CoA proved a more specific, simple, rapid and sensitive assay which may be useful for screening of large number of Esch. coli isolates in epidemiological investigations.