Rapid identification of colonization factor antigens (CFA/I and CFA/II) of enterotoxigenic E. coli (ETEC) and O-antigens of enteropathogenic E. coli (EPEC) by coagglutination test.

Specific antisera for CFA/I (O78), CFA/II (O6) or enteropathogenic (EPEC) somatic O-antigens (serogroups O26, O86a and O111) were adsorbed to Staphylococcus aureus (strain Cowan I) to produce coagglutination reagents. Conventional agglutination tests with bacterial cells showed that antiserum against strain C922a-1 reacted with strain C91f, whereas anti-C91f did not agglutinate cells of strain C922a-1. Antisera raised against strains 4334f and C91f agglutinated their bacterial cells. Anti-303d did not react with strains C922a-1, 91f, nor with 4334f. Similar results were obtained with tests performed with COA-reagents of the above strains. Homologous antisera diluted 1:1000 gave positive COA reaction, after being adsorbed to Cowan I. Such diluted antisera gave negative agglutination reaction in the conventional agglutination tests. The COA test is at least 100 times more sensitive than the conventional agglutination tests. Hence, preparation of COA reagents implies practically economical use of antisera. Furthermore, the COA technique is much more sensitive and rapid (less than 5 min) than immunodiffusion test which takes greater than or equal to 24 h to read and in which large molecular weight antigens fail to diffuse in to agarose. 30 CFA/I strains (100%) gave COA positive reaction and only 25 CFA/II strains (71,4%) were positive with CFA/II COA reagents. The coagglutination technique was also applicable to identification of enteropathogenic E. coli by using somatic O-antigens (O26, O86a and O111) antisera.(ABSTRACT TRUNCATED AT 250 WORDS)