Clinical Isolates of Vibrio cholerae O1 El Tor Ogawa of 2009 from Kolkata, India: Preponderance of SXT Element and Presence of Haitian ctxB Variant

Abstract

BackgroundIncrease in the number of multidrug resistant pathogens and the accompanied rise in case fatality rates has hampered the treatment of many infectious diseases including cholera. Unraveling the mechanisms responsible for multidrug resistance in the clinical isolates of Vibrio cholerae would help in understanding evolution of these pathogenic bacteria and their epidemic potential. This study was carried out to identify genetic factors responsible for multiple drug resistance in clinical isolates of Vibrio cholerae O1, serotype Ogawa, biotype El Tor isolated from the patients admitted to the Infectious Diseases Hospital, Kolkata, India, in 2009.Methodology/Principal FindingsOne hundred and nineteen clinical isolates of V. cholerae were analysed for their antibiotic resistance phenotypes. Antibiogram analysis revealed that majority of the isolates showed resistance to co-trimoxazole, nalidixic acid, polymixin B and streptomycin. In PCR, SXT integrase was detected in 117 isolates and its sequence showed 99% identity notably to ICEVchInd5 from Sevagram, India, ICEVchBan5 from Bangladesh and VC1786ICE sequence from Haiti outbreak among others. Antibiotic resistance traits corresponding to SXT element were transferred from the parent Vibrio isolate to the recipient E. coli XL-1 Blue cells during conjugation. Double-mismatch-amplification mutation assay (DMAMA) revealed the presence of Haitian type ctxB allele of genotype 7 in 55 isolates and the classical ctxB allele of genotype 1 in 59 isolates. Analysis of topoisomerase sequences revealed the presence of mutation Ser83 → Ile in gyrA and Ser85→ Leu in parC. This clearly showed the circulation of SXT-containing V. cholerae as causative agent for cholera in Kolkata.ConclusionsThere was predominance of SXT element in these clinical isolates from Kolkata region which also accounted for their antibiotic resistance phenotype typical of this element. DMAMA PCR showed them to be a mixture of isolates with different ctxB alleles like classical, El Tor and Haitian variants.

<i>Vibrio cholerae</i> O1 Ogawa Strains Carrying the <i>ctxB7</i> Allele Caused a Large Cholera Outbreak during 2014 in the Tribal Areas of Odisha, India

“…The HCT-producing variants of V. cholerae were reported for the first time from the cholera outbreak in Odisha during 2007, later from Haiti during 2010, and subsequently from Asia and Africa (15,16). A few reports have described the isolation of HCT-producing variant V. cholerae O1 strain or the identification of this strain as the causative pathogen of small outbreaks from West Bengal, Bihar, and southern India (6,13,14). There have been similar reports on the isolation of HCT-producing V. cholerae from Zambia (11) and from Mexico during the 2013 cholera outbreak (12).…”

“…Additionally, new ctxB genotypes were observed in Zambia and Mexico during 2013, which represent variants of ctxB7 in HCT-producing V. cholerae (11,12). The ctxB7 variant V. cholerae O1 was first reported from the tribal areas of Odisha, India, during 2007 (6,13). These HCT variant strains of V. cholerae O1 were also reported from the Maharashtra (14) and Bihar states of India during 2012 (15).…”

Vibrio isolates from cases of acute diarrhea and their antimicrobial susceptibility pattern in a tertiary care hospital

“…Resistance to fluoroquinolones has been reported in studies from India [10], however most of the isolates were found to be susceptible to fluoroquinolones (Norfloxacin) in the present study. A number of multidrug resistance strains are also emerging in clinical isolates of V. cholera 01; serotype Ogawa, including resistance to trimethoprim-sulphamethoxazole and ampicillin [11]. Other studies have showed the current emerging toxigenic Inaba strains of Eltor biotype, than the earlier classical biotype [12].…”

Phenotypic Analysis Reveals that the 2010 Haiti Cholera Epidemic Is Linked to a Hypervirulent Strain

“…The AET strains have a gyrA mutation for nalidixic acid resistance and integrating conjugative elements (ICE) that confer multiple drug resistance, including to streptomycin and chloramphenicol (3,7,8). The ICEVchIn5 present in ϳ77% of strains has recently been shown to also encode a repressor of V. cholerae natural competence (9,10).…”

“…This clonal variant of V. cholerae with tcpA N89S , rtxA°, and ctxB7 alleles was first detected in Kolkata, India, in 2004 (7). It was also identified as the cause of outbreaks in Orissa, India, in 2007 (19), in Cameroon, Zimbabwe, and South Africa in 2009, and in Nepal in 2010 (8,13,14,18). The strain has been the predominant cause of cholera in India and Bangladesh at least to 2012 (7,20,21).…”