Genetic diversity of mycobacterium tuberculosis, drug resistance and atypical mycobacteria in Rwanda

Abstract

The genus Mycobacterium has two main groups, Mycobacterium tuberculosis complex (MTBC) and atypical mycobacteria. The MTBC species, the causative agents of tuberculosis (TB), has been further typed into different genotypes. Genotyping methods of M. tuberculosis help in identifying the most predominant circulating genotypes and their transmission dynamics and this helps in planning for a better tuberculosis drug resistance surveillance system. In Rwanda, little is known about the most predominant M. tuberculosis genotypes and there is limited data on drug resistance especially pyrazinamide drug resistance profile. Moreover, the distribution of atypical mycobacteria and their underlying epidemiological factors are also unknown. Our main goal is to characterize epidemiologically and genotypically M. tuberculosis, establish drug resistance and determine the distribution of atypical mycobacteria countrywide. Smear positives collected from suspected TB patients from Januray to July 2015 were submitted for primary culture on both solid and liquid culture media. All positive cultures on Lowenstein Jensen and BACTEC MGIT 960 liquid culture system were followed by phenotypic drug susceptibility testing (DST) to characterize resistance for first line anti-tuberculosis drugs. Isolates were tested for susceptibility to first line anti-TB drugs using Isoniazid, Rifampin, Streptomycin, and Ethambutol. Speciation of atypical mycobacteria was done using GenoType MTB DRplus Assay CM and AS. The present review presents preliminary results from primary culture, drug resistance and atypical mycobacteria. Out of 994 positive culture, MTBC accounted for 99.6% while atypical mycobacteria represented 0.4%. Of the 990 samples, 932 (94.1%) were new patients and 58 (5.9%) were patients with previous history of treatment for tuberculosis. MDR-TB was detected in 1.4% cases among new patients and 8.6% in previous treated patients. Among the mono-resistance pattern, Ethambutol represented the majority of all mono-resistance, averaging 17.4%. Non- Tuberclosis Mycobacteria (NTM) included M. celatum (0.1%), M. lentiflavum (0.1%), M. peregrinum (0.1%) and M. intracellulare (0.1%). In light of the present preliminary results, further investigations are needed to confirm the pan-resistance of Ethambutol. Molecular characterization is needed to decipher the most predominant M. tuberculosis genotypes, drug resistance and understand the extent of atypical mycobacteria in Rwanda. This would aid in strengthening TB treatment and control.