Mycobacterium tuberculosis of the RDRio genotype is the predominant cause of tuberculosis and associated with multidrug resistance in Porto Alegre City, South Brazil.

Spoligotyping has shown Mycobacterium tuberculosis strains to be composed of different lineages, and some of them are not just geographically restricted but also affect specific ethnic populations and are associated with outbreaks and drug resistance. We recently described a particular subtype within the Latin American-Mediterranean (LAM) family, called RD(Rio), widespread in Brazil. Moreover, recent data also indicate that RD(Rio) is present in many countries on all continents and is associated with cavitary disease and multidrug resistance (MDR). To further explore the relationship between RD(Rio) and MDR, we conducted a study in a tuberculosis (TB) reference center responsible for the care of MDR patients in Rio Grande do Sul, the southernmost Brazilian state. From a collection of 237 clinical isolates, RD(Rio) alone was responsible for one-half of all MDR cases, including one large group composed of strains with identical IS6110-restriction fragment length polymorphism (RFLP) and having the LAM5 signature. We additionally had complete data records for 96 patients and could make comparisons between the presence and absence of RD(Rio). No difference in clinical, radiological or laboratory features was observed, but a significantly greater number of cases with MDR were described in patients infected with an RD(Rio) strain (P = 0.0015). Altogether, RD(Rio) was responsible for 38% of all TB cases. These data support and confirmed previous findings that RD(Rio) is the main agent responsible for TB in Brazil and is associated with drug resistance. Considering that RD(Rio) is a globally distributed genotype, such findings raise concern about the increase in MDR in certain human populations.

Characteristics of multidrug-resistant Mycobacterium tuberculosis in southern Brazil.

A major threat to tuberculosis (TB) control programs is the emergence of drug resistant Mycobacterium tuberculosis strains that cause TB that cannot be cured by standard anti-TB drug regimens. Because few data exist on MDR-TB in this region of the country, we performed an epidemiologic study that combined conventional and molecular analysis of MDR-TB cases from Rio Grande do Sul (RS) that were diagnosed in this period and included cases that were under treatment with second line drug schemes. Included were 121 MDR cases and sequencing of rpoB and katG showed that 106 (87.6%) strains were mutated in rpoB and 97 (80.2%) in katG. Spoligotyping demonstrated that the LAM genotype was predominant (n = 70, 57.8%) and included the largest group composed by 22 (18.1%) strains with the LAM5 ST93 genotype. Other main genotypes belonged to the families T (n = 22, 18.2%), U family (n = 16, 13.2%), Haarlem (n = 5, 4.1%) and X (n = 1, 0.8%). Genotyping by IS6110-RFLP analysis showed 51 distinct fingerprints, 38 (31.4%) of these observed only once and the other 13 patterns being shared among the rest of the isolates (n = 83, 68.6%). Among the 22 strains that were LAM5 ST93, only two had different IS6110-RFLP genotypes. In conclusion, there exists a high degree of M. Tuberculosis genotype clustering among MDR-TB cases in Rio Grande do Sul. Moreover, we observed a large MDR-TB outbreak.