Mycobacterium tuberculosis of the RD Rio Genotype Is the Predominant Cause of Tuberculosis and Associated with Multidrug Resistance in Porto Alegre City, South Brazil

Abstract

ABSTRACT 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 IS 6110 -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.