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Open Access Highly Accessed Research article

A multi locus variable number of tandem repeat analysis (MLVA) scheme for Streptococcus agalactiae genotyping

Eve Haguenoer12, Gaelle Baty2, Christine Pourcel3, Marie-Frédérique Lartigue14, Anne-Sophie Domelier14, Agnès Rosenau1, Roland Quentin14, Laurent Mereghetti12 and Philippe Lanotte12*

Author Affiliations

1 Université François-Rabelais de Tours, UFR de Médecine, EA 3854 « Bactéries et risque materno-fœtal », Institut Fédératif de Recherche 136 « Agents Transmissibles et Infectiologie », Tours, France

2 CHRU de Tours, Service de Bactériologie-Virologie, Tours, France

3 Université Paris Sud 11, CNRS, UMR 8621, Institut de Génétique et Microbiologie, Orsay, 91405, France

4 CHRU de Tours, Service de Bactériologie et d'Hygiène Hospitalière Tours, France

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BMC Microbiology 2011, 11:171  doi:10.1186/1471-2180-11-171

Published: 27 July 2011

Abstract

Background

Multilocus sequence typing (MLST) is currently the reference method for genotyping Streptococcus agalactiae strains, the leading cause of infectious disease in newborns and a major cause of disease in immunocompromised children and adults. We describe here a genotyping method based on multiple locus variable number of tandem repeat (VNTR) analysis (MLVA) applied to a population of S. agalactiae strains of various origins characterized by MLST and serotyping.

Results

We studied a collection of 186 strains isolated from humans and cattle and three reference strains (A909, NEM316 and 2603 V/R). Among 34 VNTRs, 6 polymorphic VNTRs loci were selected for use in genotyping of the bacterial population. The MLVA profile consists of a series of allele numbers, corresponding to the number of repeats at each VNTR locus. 98 MLVA genotypes were obtained compared to 51 sequences types generated by MLST. The MLVA scheme generated clusters which corresponded well to the main clonal complexes obtained by MLST. However it provided a higher discriminatory power. The diversity index obtained with MLVA was 0.960 compared to 0.881 with MLST for this population of strains.

Conclusions

The MLVA scheme proposed here is a rapid, cheap and easy genotyping method generating results suitable for exchange and comparison between different laboratories and for the epidemiologic surveillance of S. agalactiae and analyses of outbreaks.