Characterization of biochemically atypical Vibrio cholerae strains and designation of a new pathogenic species, Vibrio mimicus.

Biochemically atypical strains classified as Vibrio cholerae were characterized by biochemical reactions, serology, antibiotic susceptibility testing, and deoxyribonucleic acid relatedness. Strains with the following atypical reactions were shown to be V. cholerae: mannose negative, mannitol negative, lysine decarboxylase negative, no growth in the presence of 5% NaCl, salicin and cellobiose positive. Sucrose-negative strains were shown to constitute a new species, Vibrio mimicus, whose type strain is 1721-77 (ATCC 33653). In addition to its negative sucrose reaction, V mimicus was differentiated from V. cholerae by its negative Voges-Proskauer, corn oil, and Jordan tartrate reactions and by its sensitivity to polymyxin. V. mimicus was isolated from shellfish and water, as well as from human diarrheal stools and ear infections. Most strains were typable with antisera against V. cholerae. Strains from three serogroups produced either a heat-labile or a heat-stable enterotoxin.