Novel MLST scheme for genetic characterization of worldwide Leptospira sp strains collections.

CAIMI KARINA; VARNI VANINA; LAUTHIER JUAN JOSÉ; TOMASINI NICOLÁS; HARTSKEERL RUDY; RUYBAL PAULA

New Orleans

Conferencia; 11th International Conference on Molecular Epidemiology and Evolutionary Genetics of Infectious Diseases; 2012

Leptospirosis is neglected infectious disease and a zoonosis of global distribution that has been recently identified as a public and animal health problem. Several molecular typing methods based on Multilocus Sequence Typing analysis have been developed for Leptospira sp. The aim of this study was to propose an MLST scheme with a minimum number of loci that allow to get the maximum genotypic diversity of this pathogen. For this purpose, 48 reference strains and 17 non-epidemiologically related isolates from diverse hosts and Argentinean regions were typed by 12 loci that correspond to the two most commonly used MLST schemes. The optimal number of loci was obtained using MLSTest software developed by the Molecular Epidemiology Unit (UNSa). Both MLSTest and START2 softwares were used to evaluate allelic and profile frequencies and to perform different MLST statistical analyses. The goeBURST algorithm was used to detect Clonal Complexes (CCs) between STs. Phylogenetic relationships among concatenated of the selected loci were inferred using the maximum-likelihood (ML), Kimura-2 parameter nucleotide substitution model tested with 500 bootstrap replications (MEGA5). The application of the 12 loci scheme to the collection rendered 57 different Sequence Type (STs) where 7 loci was the optimal number. These were selected according to the number of polymorphisms, the typing efficiency, their discriminatory power and the ratio of dN/dS substitutions per nucleotide site. goeBURST analysis established nine CCs where one of them has a clear founder genotype with three Single Locus Variants formed by STs that correspond mostly to argentinean isolates. The CCs obtained showed a clear correlation between geographical origin and hosts from which the isolates were obtained. The ML dendrogram constructed from concatenated sequences using the 7 loci selected, identified three major clusters corresponding to L. interrogans Pomona and, Icterohaemorrhagiae and L. kirschneri.