Present address: National Institute of Science Education and Research, IOP Campus, Sachivalaya Marg, Bhubaneswar-751005, India.
Analysis of clonally related environmental Vibrio cholerae O1 El Tor isolated before 1992 from Varanasi, India reveals origin of SXT-ICEs belonging to O139 and O1 serogroups
Article first published online: 21 JUL 2009
© 2009 Society for Applied Microbiology and Blackwell Publishing Ltd
Environmental Microbiology Reports
Special Issue: Vibrio Ecology. Editors: Carla Pruzzo, Balakrish Nair, Jim Oliver and Rita Colwell
Volume 2, Issue 1, pages 50–57, February 2010
How to Cite
Mohapatra, S. S., Mantri, C. K., Mohapatra, H., Colwell, R. R. and Singh, D. V. (2010), Analysis of clonally related environmental Vibrio cholerae O1 El Tor isolated before 1992 from Varanasi, India reveals origin of SXT-ICEs belonging to O139 and O1 serogroups. Environmental Microbiology Reports, 2: 50–57. doi: 10.1111/j.1758-2229.2009.00051.x
- Issue published online: 8 FEB 2010
- Article first published online: 21 JUL 2009
- Received 1 April, 2009; accepted 22 June, 2009.
In this study, we report the presence of SXT in environmental Vibrio cholerae O1 El Tor strains isolated before 1992 from Varanasi, India. All isolates, except one, were resistant to Tm, and/or Sul, Sm, Fr, Na and Am. None contained plasmids. PCR and DNA sequencing revealed the presence of SXT containing dfrA1 and/or sulII, strAB in six isolates and dfr18, sulII and strAB in five isolates. Three clinical V. cholerae O1 isolated during 1992 contained the antibiotic resistance gene cassette aadA1 in the class 1 integron. Conjugation experiments, followed by PCR analysis of transconjugants, provided evidence of the transferable nature of SXT and associated antibiotic resistance genes, and its integration into the prfC site. Results of phylogenetic analysis of the intSXT gene of clonally similar V. cholerae showed a clear difference between dfr18+ and dfrA1+V. cholerae O1 isolates. This is the first report of the occurrence of SXT harbouring sulII, strAB, dfr18 and/or dfrA1 genes in environmental V. cholerae O1 isolated prior to 1992 from Varanasi, India, and suggests emergence of SXT+ antibiotic-resistant V. cholerae O139 and O1 from an environmental V. cholerae progenitor by acquisition of SXT and antibiotic-resistant gene clusters.