Variants of ctxB alleles of Vibrio cholerae O1 caused sequential cholera outbreaks in the tribal areas of Odisha, India

Abstract

Cholera localized outbreaks/epidemics accounting for high morbidity and mortality have been reported in different years both from the coastal and tribal districts of Odisha. In the present study, the emergence and spread of two sequential cholera outbreaks reported in July to October 2012 from Rayagada and Kalahandi districts of Odisha was investigated. Environmental water samples from different sources and rectal swabs from diarrhoea patients were analysed for identification, antibiogram profiles and molecular studies using DMAMA-PCR assays. The pulsed field gel electrophoresis (PFGE) was done on some selected Vibrio cholerae O1 strains isolated from these cholera outbreak areas. Results showed 42% of rectal swabs and 2.3% of water samples collected from both the districts were positive for Vibrio cholerae O1 Ogawa biotype El Tor carrying both ctxB1 and ctxB7 genotypes. The common resistance profile of V. cholerae O1 strains was ampicillin, nalidixic acid, furazolidone and co-trimoxazole. The PFGE analysis on selected V. cholerae O1 strains of ctxB1 and ctxB7 genotypes showed three pulsotypes with 96% similarity matrix exhibiting the relationship with their respective water sources. Hence, continuous surveillance is highly essential to monitor the antibiogram profile and changing pattern of ctxB genotypes of V. cholerae O1 in this region. HIGHLIGHTS The study reports the presence of V. cholerae O1 Ogawa biotype El Tor in 42% of rectal swabs and 2.3% of environmental water samples respectively.; The DMAMA-PCR assay revealed that the cholera outbreak in Rayagada district was predominantly due to ctxB1 allele; whereas it was due to ctxB7 allele of V. cholerae O1 El Tor variant strains reported in Kalahandi district.;

Keywords

• antibiogram profiles
• ctxb genotypes
• pulsotypes
• vibrio cholerae