Use of an enzyme-linked immunosorbent assay (ELISA) to measure the expression of the K88 fimbrial antigen by enterotoxigenic Escherichia coli (ETEC).

A solid-phase enzyme-linked immunosorbent assay (ELISA) has been developed to detect and quantify the K88 fimbrial adhesin antigen. The assay was used to detect cell-bound antigen present in bacterial suspensions and cell-free K88 antigen present in extracts. Comparable amounts of K88 antigen were detected with whole bacteria and in the equivalent extracts. The assay was used to compare the expression of the K88 antigen by one laboratory strain (K12:K88ab) and three wild-type strains (O8:K87:K88ab:H19, O8:K87:K88ac:H19 and K88ad) of enterotoxigenic Escherichia coli (ETEC) during cultivation with eight medium types and two medium forms. Determination of the expression of K88 during unshaken batch culture revealed a correlation between growth phase and expression, with maximal concentrations being detected during late log to early stationary phase. Colony blotting experiments demonstrated that expression of the K88 antigen was under quantitative and not qualitative control.