Primary and acquired resistance to antituberculous drugs in strains of Mycobacterium tuberculosis isolated in Rwanda

This study was undertaken within the framework of a surveillance project on the resistance of Mycobacterium tuberculosis to first-line antituberculosis drugs in four provinces of Rwanda with a high prevalence of tuberculosis (TB). The purpose was to determine the prevalence of primary and acquired resistance of M. tuberculosis to major antituberculosis drugs. A cohort of patients (n=710) with pulmonary TB documented by positive microscopic examinations of exhaustive samples was recruited at 7 treatment centers. Sputum samples were cultured on Löwenstein-Jensen and Coletsos media. Sensitivity to antituberculosis drugs was tested using a BACTEC 460 radiometric system. M. tuberculosis was isolated in 644 of the 710 patients (90.7%). A total of 296 out of 573 tested for HIV infection (51.7% ) were positive. Primary resistance to one, two, three or four antituberculosis drugs was observed in 3.5%, 2.9%, 1.4% and 5.7% respectively. The prevalence of acquired resistance to antituberculosis drugs was 11.2%. Primary monoresistance to streptomycin was the most prevalent (2.3%) followed by resistance to ethambutol (1%). The combined rate of multiresistance was 11.6% with 7% involving new cases and 25.5% involving retreatment. This study showed that the rates of primary and acquired resistance to first-line antituberculosis drugs were high and that TB was associated with HIV infection. The National TB Control Program must implement measures to coordinate diagnosis and management of TB and HIV infection.