Identification of heat-stable enterotoxin-producing strains of Yersinia enterocolitica and Vibrio cholerae non-O1 by a monoclonal antibody-based enzyme-linked immunosorbent assay.

Using a mouse monoclonal antibody (MAb) 2F raised against Vibrio cholerae non-O1 heat-stable enterotoxin (NAG-ST) which also recognizes a shared epitope of Yersinia enterocolitica heat-stable enterotoxin (Y-ST), a competitive enzyme-linked immunosorbent assay (ELISA) was developed for independent detection of NAG-ST and Y-ST. There was good concordance between the Y-ST ELISA and the suckling mouse assay (SMA) for detection of Y-ST from test strains of Y. enterocolitica, and the Y-ST ELISA can effectively replace the SMA for routine detection of Y-ST. On the contrary, evaluation of the NAG-ST ELISA and the SMA using 139 strains of V. cholerae non-O1 showed discordant results and this was attributed to the presence of the suckling mice active factor(s) such as El Tor hemolysin and to the production of low amounts of NAG-ST. Concentration of culture supernatants of V. cholerae non-O1 followed by heating at 100 C was essential to obtain reproducible results by both the NAG-ST ELISA and the SMA. The ELISA developed in this study can be used for the identification of biologically active strains. While recently genetic methods such as polymerase chain reaction became available and were very reliable and simple techniques, the ELISA in this study has an advantage in detecting biologically toxic gene products of the strains. The genetic methods cannot differentiate silent STa genes which we often encounter in the case of Y. enterocolitica.