ABSTRACT
Background: Vibrio cholerae is an autochthonous inhabitant of fresh and brackish water and estuarine system. Investigation of V. cholerae from the River Ganga seems important to find variation in CTX arrangement and genomic diversity. Objectives: To investigate V. cholerae O1 strains for the presence of virulence and regulatory genes, variation in number and organisation of the pre‑CTXФ and/or CTXФ, and for the genomic diversity. Materials and Methods: Polymerase chain reaction (PCR) was used to detect virulence and regulatory genes, type of rstR and location of CTXΦ on the chromosome. Southern hybridisation was conducted to see the number and arrangement of pre‑CTXΦ and CTXΦ. Ribotyping and pulsed‑field gel electrophoresis were used to find genetic relatedness. Results: Seven strains gave positive results by PCR for the gene encoding for ctxA, zot, ace, tcpA (El Tor), ompU, and toxR, except one strain that was negative for the ctxA. Three strains were positive for the tcpA (El Tor), ompU and toxR genes. Determination of CTX organisation showed that among the ctx‑positive strains, four harboured two copies of CTXETФ arranged in tandem and two harboured one copy of CTXETФ, and one ctx‑negative strain harboured only one copy of pre‑CTXETФ. Pulsotype and ribotype analysis showed existence of at least three pulsotype and ribotypes indicating diversity in genomic content among them. Conclusion: This study thus indicates that multiple clones (ribotypes/pulsotypes) of V. cholerae O1 carrying pre‑CTXΦ and/or CTXΦ and ctx‑negative strains were present in the water of the River Ganga, Varanasi, India.