Semi-nested polymerase chain reaction for detection of toxigenic Vibrio cholerae from environmental water samples

Molecular Characterization of Vibrio cholerae O1 Reveals Continuous Evolution of Its New Variants in India

Vibrio cholerae, the causing agent of cholera is still a major health challenge in most of the developing countries. In this study, V. cholerae strains collected from different cholera outbreaks in India over a period of past 7 years were found to have various toxigenic, pathogenic and regulatory genes viz. ctxAB, zot, tcp, hlyA, ace, ompU, ompW, rfbO1, toxT and toxR. The biotype specific genes rstR and rtxC revealed the El Tor biotype in majority of the isolates. However, variants among the isolates were found having genotype of both the biotypes. Sequencing of ctxB gene revealed the presence of altered ctxB of classical biotype with additional variations in isolates of 2007. Mismatch amplification mutation assay PCR also confirmed the isolates belonging to classical biotype. Antibiogram of the isolates revealed resistance for nalidixic acid, co-trimoxazole, streptomycin, and polymyxin B and susceptibility for tetracycline among most of the isolates from India. However, V. cholerae isolates from a recent outbreak in Eastern India were resistant to tetracycline. The study corroborated the continuous emergence and wide-spread of multidrug resistant El Tor variant strains in the Indian subcontinent.

Characterization of Vibrio cholerae from deep ground water in a cholera endemic area in Central India

A total of 8 out of 11 deep ground water samples collected from different villages in Central India were found contaminated with Vibrio cholerae non O1, non O139. In a multiplex PCR, isolates were found positive for ompW gene but negative for ctxAB and rfbO1 genes. However, isolates from two places were positive for tcp and zot genes, indicating their intestinal colonization and toxigenic potential. Antibiotic susceptibility studies revealed that all isolates were multidrug resistant. Although, none of the isolates was found PCR positive for the mobile genetic elements, class 1 integrons and SXT constins. The results of this study corroborated that deep ground water can also be an important reservoir of V. cholerae in plane endemic areas, suggesting a continuous monitoring of water samples for timely prevention of the disease.