Antituberculosis Drug Resistance in Pulmonary Isolates of Mycobacterium tuberculosis, Cuba 2012–2014

Abstract

INTRODUCTION Systematic surveillance of antituberculosis drug resistance allows identifi cation of multidrug-resistant and extensively drug-resistant isolates of Mycobacterium tuberculosis. Surveillance studies of antituberculosis drug resistance systematically conducted in Cuba for over 15 years have revealed low circulation of multidrugresistant tuberculosis, under 1% in new cases. OBJECTIVE Characterize antituberculosis drug resistance in isolates of M. tuberculosis recovered from patients with pulmonary tuberculosis in Cuba in 2012-2014. METHODSThe nitrate reductase assay was used to test 997 isolates of M. tuberculosis for sensitivity to isoniazid and rifampicin. Isolates identifi ed as multidrug resistant were tested for sensitivity to isoniazid, rifampicin, streptomycin, ethambutol, ofl oxacin, amikacin, kanamycin and capreomycin by the proportion method, as well as genetic resistance mutations in rpoB, katG, inhA, gyrA, rrs and embB genes, using GenoType MTBDRplus and MTBDRsl commercial kits. RESULTS Some 95.6% of isolates from new cases and 89.6% of isolates from previously treated patients were sensitive to isoniazid and rifampicin. Multidrug resistance was found in 0.8% of new and 5.2% of previously treated patients, a statistically signifi cant difference. One extensively drug-resistant isolate was detected among previously treated cases. All isolates examined with the molecular method had mutations in the rpoB gene, which is associated with resistance to rifampicin; only seven showed mutations in the katG gene and one in the inhA gene associated with isoniazid resistance. In one isolate, we found mutations in both gyrA and rrs genes, which are associated with resistance to fl uoroquinolones and second-line injectable drugs and therefore, extensive resistance.CONCLUSIONS Results corroborate the low frequency of multidrugresistant and extensively resistant M. tuberculosis strains in Cuba and highlight the need for continuous improvement of surveillance of antituberculosis drug resistance in Cuba.