Biotype traits and antibiotic susceptibility of Vibrio cholerae serogroup O1 before, during and after the emergence of the O139 serogroup

Abstract

Sixty-nine strains of Vibrio cholerae 01 isolated at different times were analysed to investigate if there were any differences among the 01 strains isolated before, during and after the advent of the O139 serogroup. Of the 69 01 strains examined, 68 belonged to the Ogawa serotype while one belonged to the Inaba serotype. With the exception of one strain all other strains of V. cholerae 01 belonged to the eltor biotype. A single O1 strain isolated before the emergence of the O139 serogroup could not be classified as either eltor or classical biotype because it was resistant to both classical and eltor specific bacteriophages. Marked variations in the susceptibility to antibiotics of V. cholerae O1 isolated during the different periods were observed. In addition, strains of V. cholerae isolated after the epidemic of serogroup O139 in Calcutta showed an expanding R-type with resistance to a variety of drugs as compared to the 01 strains isolated before the advent of the O139 serogroup. From this study, it is clear that there is a substantial mobility in genetic elements of V. cholerae Ol which necessitates a continuous monitoring to keep abreast of the changing traits of the etiologic agent of cholera.