The Latin American & Mediterranean (LAM) spoligotype family is one of the most successful genotype of Mycobacterium tuberculosis worldwide and particularly prevalent in South-America. Within this family, a sublineage named Region of Difference Rio (RD Rio ) was reported initially in Brazil and is characterized by a genomic deletion of about 26.3 kb. This lineage seems to show a specific adaptation to the Euro-Latin American population. In this context, we sought to evaluate the LAM family and

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... e presence of the RD Rio genotype in samples from three Latin American countries including Paraguay, Venezuela and Argentina. To detect LAM strains reliably we applied a typing scheme using spoligotyping, 12 loci MIRU-VNTR, the Ag85C 103 SNP and the regions of difference RD Rio and RD174. IS6110-RFLP results were also used when available. Results: Genotyping of 413 M. tuberculosis isolates from three Latin-American countries detected LAM (46%) and the ill-defined T clade (16%) as the most frequent families. The highest clustering rate was detected in the sample population from the city of Caracas in Venezuela. We observed considerable differences in the presence of the RD Rio lineage, with high frequency in Caracas-Venezuela (55%) and low frequency in Buenos Aires-Argentina (11%) and Paraguay (10%). The molecular markers (RD174, Ag85C 103 , MIRU02-MIRU40 signature) of the RD Rio lineage were essentially confirmed. For the LAM family, the most polymorphic loci were MIRU40, MIRU31, MIRU10, MIRU26, MIRU16 and the least polymorphic MIRU24, MIRU20, MIRU04, MIRU23. Conclusions: Our results suggest a differential adaptation of LAM-sublineages in neighboring populations and that RD Rio strains spread regionally with different rates of distribution. The Ag85C SNP and RDs (RD174, RD Rio ) tested in this study can in fact facilitate molecular epidemiological studies of LAM strains in endemic settings and low-income countries.