Culture supernatants from V. cholerae O1 ElTor strains isolated from different geographic areas induce cell vacuolation and cytotoxicity

Objective: To investigate whether the HlyA-induced vacuolating effect is produced by V. cholerae O1 ElTor strains isolated from different geographic origins, including Mexico. Material and Methods: Supernatant-induced haemolysis, vacuolating activity and cytotoxicity in Vero cells were recorded. PCR, RFLP analysis and molecular cloning were performed. Results: All ElTor strains analyzed induced cellular vacuolation. Ribotype 2 strains isolates from the U.S. gulf coast yielded the highest titer of vacuolating activity. Eight of nine strains were haemolytic, while all strains were PCR positive for the hlyA gene. We cloned the hlyA gene from two ElTor strains, a toxigenic (2514-88, ctxAB⁺) and a non-toxigenic Mexican strain (CM 91-3, ctxAB^-). Supernatant from those recombinant E. coli strains induced haemolysis, cell vacuolation and cytotoxicity. RFLP-PCR analysis revealed similarities in the hlyA gene from all strains tested. Conclusion: The HlyA-induced vacuolating effect is a widespread phenotype of epidemic V. cholerae O1 ElTor strains.