Most LAM Mycobacterium tuberculosis strains in Venezuela, but not SIT605, belong to the RDRio subfamily

Abstract

Tuberculosis is a global public health problem that is resurgent in Venezuela, with 13 thousand estimated new cases in 2018. Strains of the Mycobacterium tuberculosis RDRio, subfamily belong to the Latín American Mediterranean (LAM) family and are a major cause of TB in Rio de Janeiro, Brazil. LAM strains predominate in Venezuela, where spoligotype SIT605 is common, but surprisingly not found elsewhere. We sought to assess the presence of RDRio strains in tuberculosis patients in different regions of Venezuela and determine whether SIT605 also belongs to the RDRio subfamily. Using spoligotyping and MIRU-VNTR 24 loci, we identified 86 clinical LAM and SIT605 isolates from the Venezuelan capital Caracas and several Venezuelan states. Region of difference deletion loci RD174 and RDRio, and also IS1561 were used to identify strains of the RDRio subfamily, while IS6110 at position 932,204 and the Ag85C103 polymorphism were used to validate SIT 605 as a LAM family strain. We found that 69.8% of the isolates were RDRío, including 94.3% of strains isolated in Caracas, 17.9% isolated in the state of Carabobo, the two strains analyzed from Delta Amacuro, and one each from Sucre, Apure and Aragua states. RDRio was in 100% of: SIT17 (LAM 2); SIT20 (LAM 1); SITs 93, 1694, 1696, 960, 1367 (LAM 5); and SITs 216 (LAM 9); but only 75% of SIT42 (LAM 9) strains. Thus, most of the LAM strains in Venezuela belong to the RDRío subfamily. SIT 605 strains, although LAM, are not in the RDRío subfamily.