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Open Access Research article

Multi-locus variable number tandem repeat analysis of 7th pandemic Vibrio cholerae

Connie Lam1, Sophie Octavia1, Peter R Reeves2 and Ruiting Lan1*

Author Affiliations

1 School of Biotechnology and Biomolecular Sciences, University of New South Wales, Gate 9 High St, Sydney, New South Wales, 2052, Australia

2 School of Molecular Biosciences, University of Sydney, Sydney, New South Wales, 2006, Australia

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BMC Microbiology 2012, 12:82  doi:10.1186/1471-2180-12-82

Published: 24 May 2012

Abstract

Background

Seven pandemics of cholera have been recorded since 1817, with the current and ongoing pandemic affecting almost every continent. Cholera remains endemic in developing countries and is still a significant public health issue. In this study we use multilocus variable number of tandem repeats (VNTRs) analysis (MLVA) to discriminate between isolates of the 7th pandemic clone of Vibrio cholerae.

Results

MLVA of six VNTRs selected from previously published data distinguished 66 V. cholerae isolates collected between 1961–1999 into 60 unique MLVA profiles. Only 4 MLVA profiles consisted of more than 2 isolates. The discriminatory power was 0.995. Phylogenetic analysis showed that, except for the closely related profiles, the relationships derived from MLVA profiles were in conflict with that inferred from Single Nucleotide Polymorphism (SNP) typing. The six SNP groups share consensus VNTR patterns and two SNP groups contained isolates which differed by only one VNTR locus.

Conclusions

MLVA is highly discriminatory in differentiating 7th pandemic V. cholerae isolates and MLVA data was most useful in resolving the genetic relationships among isolates within groups previously defined by SNPs. Thus MLVA is best used in conjunction with SNP typing in order to best determine the evolutionary relationships among the 7th pandemic V. cholerae isolates and for longer term epidemiological typing.