Characterization of Vibrio cholerae O139 isolated in Taiwan

Abstract

Vibrio cholerae O139 Bengal is the second aetiologic agent of the cholera epidemic that emerged in late 1992 in India which has subsequently spread to other nations. A few sporadic cases of V. cholerae O139 infection have been reported in Taiwan since 1997. The V. cholerae O139 strains isolated from clinical and environmental sources in Taiwan were characterized based on subspecies molecular typing, toxin production, and susceptibility to antibiotics and environmental stresses, and were compared to several O1 and other non-O1/non-O139 strains. Typing by pulsed-field gel electrophoresis revealed that the domestic O139 strains were identical to three of the four Japanese strains. Most of these domestic O139 strains were alpha-haemolytic and produced highly variable amounts of cholera toxin. The presence of cholera toxin gene was confirmed in all of these domestic strains by polymerase chain reaction. Meanwhile, most of the domestic O139 strains were resistant to nitrofurantoin, streptomycin, furazolidone and trimethoprim–sulfamethoxazole, while the O1 strains were not. Susceptibility of selected O139 strains to temperature stresses at 55°C and −20°C, acid treatment at pH 3·0, and N-alkyl dimethyl benzyl ammonium treatment did not differ significantly from other strains examined. Accordingly, these Taiwanese O139 strains were genetically close to the Japanese strains and also shared some common biological traits.