Genetic determinants of virulence, antibiogram and altered biotype among the Vibrio cholerae O1 isolates from different cholera outbreaks in India.

Cholera diarrhea is still a major health challenge for a large part of globe. Global replacement of Vibrio cholerae classical biotype by El Tor biotype, emergence of O139 serogroup and rapid spread of antibiotic resistant strains indicate the continuous evolution in V. cholerae. In this study, 114 V. cholerae O1 serotype Ogawa isolates, collected from different cholera outbreaks in different regions of India between 2004 and 2007 were subjected to biochemical, immunological and molecular characterization. All the isolates were PCR positive for various toxigenic, pathogenic and regulatory genes, viz. ompW, ctxB, rfbO1, tcp, zot, rtxC, ace, hlyA, ompU and toxR. The antibiogram studies of isolates revealed the resistance towards several antibiotics including nalidixic acid, co-trimoxazole, streptomycin, nitrofurantoin and polymyxin B. However, antibiogram of the strains confirmed susceptibility to tetracycline and chloramphenicol in all the isolates. This study also substantiated the wide spread of class 1 integrons and SXT elements (mobile genetic elements for antibiotic resistance) in clinical isolates in India. Sequencing of cholera toxin (ctxB) gene revealed the replacement of traditional ctxB of El Tor biotype with ctxB of classical biotype in all the O1 El Tor strains collected since 2004. In addition, in 2007, a new variant of O1 El Tor strain with further modifications in ctxB of classical biotype is discovered among the Indian isolates.

Goel AK ，Jiang SC 《-》

Epidemics of severe cholera caused by El Tor Vibrio cholerae O1 Ogawa possessing the ctxB gene of the classical biotype in Orissa, India.

We investigated the epidemic of cholera that occurred in Kashipur and Dasmantpur blocks of Orissa, reported during July-September 2007. Sixty-two rectal swabs and 28 water samples collected from diarrhea patients at different hospitals and villages were bacteriologically analyzed for the identification, antibiogram, and detection of toxic genes of Vibrio cholerae. The cholera outbreaks were caused by V. cholerae O1 Ogawa biotype El Tor in both Kashipur and Dasmantpur blocks. All the V. cholerae isolates from the clinical and environmental samples were sensitive to tetracycline, gentamicin, azithromycin, and chloramphenicol, but were resistant to ampicillin, ciprofloxacin, norfloxacin, co-trimoxazole, nalidixic acid, neomycin, and furazolidone, except the water isolates, which were sensitive to ciprofloxacin and norfloxacin. The multiplex PCR assay revealed that all the clinical and environmental V. cholerae isolates were positive for the ctxA and tcpA genes, showing biotype El Tor. Interestingly, 88% of the clinical and environmental isolates of V. cholerae were El Tor biotype with mutation at the ctxB gene of the classical strain, as confirmed by mismatch amplification of mutation (MAMA)-PCR assay. This is the first report of the El Tor variant of V. cholerae O1 Ogawa having the ctxB gene of the classical strain with altered antibiogram causing epidemics of cholera in Orissa, India.

Pal BB ，Khuntia HK ，Samal SK ，Kar SK ，Patnaik B ... -  《-》

Multidrug resistant Vibrio cholerae O1 El Tor carrying classical ctxB allele involved in a cholera outbreak in South Western India.

Cholera is a fatal diarrheal disease characterized with enormous fluid loss through stools. A total of 41 Vibrio cholerae isolates collected from a recent cholera outbreak in Solapur, South Western India were found to belong to serogroup O1, biotype El Tor and serotype Ogawa. Molecular analysis revealed the prevalence of different toxigenic and pathogenic genes in the isolates. All the isolates harboured rstR(El)(Tor) allele indicating the presence of CTXΦ(El)(Tor). However, cholera toxin (ctxB) gene sequencing and a ctxB allele specific PCR of the isolates confirmed the presence of ctxB of classical biotype. The antibiogram profile revealed the resistance for several antibiotics including nalidixic acid, polymyxin B, streptomycin, sulfamethoxazole, trimethoprim, rifampicin and vibriostatic agent 2,4-diamino-6,7-diisopropylpteridine (O/129). All the isolates were PCR positive for class 1 integron and SXT elements also. Fingerprinting analysis revealed the clonal relationship among the outbreak isolates. The results suggested the involvement of multidrug resistant V. cholerae El Tor biotype isolates having ctxB gene of classical biotype in the cholera outbreak.

Jain M ，Goel AK ，Bhattacharya P ，Ghatole M ，Kamboj DV ... -  《-》

Emergence of Vibrio cholerae O1 biotype El Tor serotype Inaba causing outbreaks of cholera in Orissa, India.

Pal BB ，Khuntia HK ，Samal SK ，Das SS ，Chhotray GP ... -  《JAPANESE JOURNAL OF INFECTIOUS DISEASES》

A large cholera outbreak due to a new cholera toxin variant of the Vibrio cholerae O1 El Tor biotype in Orissa, Eastern India.

Kumar P ，Jain M ，Goel AK ，Bhadauria S ，Sharma SK ，Kamboj DV ，Singh L ，Ramamurthy T ，Nair GB ... -  《JOURNAL OF MEDICAL MICROBIOLOGY》