Combined VNTRs and MLST analysis improves typification of Leptospira interrogans isolates from Argentina.

VARNI VANINA; RUYBAL PAULA; MELENDEZ YAMIL; KOVAL ARIEL; BRIHUEGA BIBIANA; CAIMI KARINA

Mérida

Otro; VII Meeting of the International Leptospirosis Society; 2011

Activities associated with rural occupations continue to be an important risk factor for leptospirosis in Argentina. Previous data support that Icterohaemorragie remains the most prevalent serogroup associated to humans, Pomona to swines and bovines, Ballum to urban rodents and serovar Hardjo to cattle. Few leptospira surveys have been carried out and many of these studies reported high proportion of cases with agglutination titres against multiple serogroups. Focusing in new molecular typing strategies, the aim of this work was to perform a genotypic characterization of Leptospira interrogans from Argentinean isolates in order to increase the knowledge of the pathogen variants circulating in our country. We have analyzed isolates of L. interrogans from different hosts arisen from the prevalent region in Argentina. Two molecular typing strategies were applied: VNTRs and MLST. Sequence types (ST) were determined based on the sequences published in the world database: http://leptospira.mlst.net. A Maximum-Likelihood tree was constructed with MLST data, using MEGA5 and an eBURST analysis by PHYLOViZ softwares. VNTRs PCR products were analyzed using BioNumerics. The typing strategies data was combined in a Maximum-parsimony analysis, implemented in TNT software. Simpson?s index of diversity was calculated for each and the combination of genotyping methods. Both methods proved to have coincident results with those obtained by the reference serologic technique. The STs found were ST37, ST17 and ST58 that correspond to serovars Pomona, Icterohaemorragiae and Serjoe, respectively. New genetic variants were described within the clade defined for the serovar Pomona resulting in novel STs (STN1, STN3). eBUSRT algorithm showed ST37 as the founder genotype of a clonal complex that includes STN1 and STN3. Furthermore, ST37 high frequency suggests the importance of focusing studies on this clonal complex in Argentina. Both techniques combined increased the discrimination power allowing further intraserovar differenciation. Moreover, genetic variation within serovar Pomona was greater than serovar Icterohaemorragiae, being these serovars preponderant within pathogens collections studied from Argentina. This work represents the first report which combines VNTRs and MLST strategies for the molecular typing of Leptospira sp., particularly in Argentina, and allows to deepen the molecular characterization of isolates obtained in different national reference centres, mainly those from cattle origin due to their relevance in Public Health.