Frequency of the Mycobacterium tuberculosis RD genotype and its association with multidrug-resistant tuberculosis.

In recent decades, Mycobacterium tuberculosis with the RD genotype, frequently isolated from tuberculosis patients in Rio de Janeiro, has become part of the Latin American - Mediterranean (LAM) family and has been associated with multidrug-resistant tuberculosis (MDR-TB). The aim of this study was to investigate the frequency of M. tuberculosis RD in the state of Minas Gerais, Brazil, and its relationship with MDR-TB.For convenience, 172 susceptible and 63 MDR M. tuberculosis isolates were taken from pulmonary samples from patients diagnosed between January 2007 and December 2011. The DNA extracted from these isolates was analyzed by spoligotyping, PCR-RFLP to characterize fbpC/Ag85C103, multiplex PCR to detect RD and RD174, and MIRU-VNTR 24 loci.Among the 235 isolates, the RD pattern was identified in 122 (51.9%) isolates (IC 0.45-0.58), with 100 (42.5%) wild-type and 13 (5.5%) mixed pattern isolates, whereas RD174 was identified in 93 of the 122 RD positive samples (76.3%). The LAM family and the LAM9 lineage were the most frequently identified among the isolates in this study. Among the 63 MDR isolates, 41 (65.1%) were RD and 28 (44.4%) RD174.The association of both deletions with MDR proved to be statistically significant, corroborating the few reports that have associated RD with MDR.