Frequency and Distribution of Tuberculosis Resistance-Associated Mutations between Mumbai, Moldova, and Eastern Cape

Abstract

f Molecular diagnostic assays, with their ability to rapidly detect resistance-associated mutations in bacterial genes, are promising technologies to control the spread of drug-resistant tuberculosis (DR-TB). Sequencing assays provide detailed information for specific gene regions and can help diagnostic assay developers prioritize mutations for inclusion in their assays. We performed pyrosequencing of seven Mycobacterium tuberculosis gene regions (katG, inhA, ahpC, rpoB, gyrA, rrs, and eis) for 1,128 clinical specimens from India, Moldova, and South Africa. We determined the frequencies of each mutation among drug-resistant and -susceptible specimens based on phenotypic drug susceptibility testing results and examined mutation distributions by country. The most common mutation among isoniazid-resistant (INH r ) specimens was the katG 315ACC mutation (87%). However, in the Eastern Cape, INH r specimens had a lower frequency of katG mutations (44%) and higher frequencies of inhA (47%) and ahpC (10%) promoter mutations. The most common mutation among rifampin-resistant (RIF r ) specimens was the rpoB 531TTG mutation (80%). The mutation was common in RIF r specimens in Mumbai (83%) and Moldova (84%) but not the Eastern Cape (17%), where the 516GTC mutation appeared more frequently (57%). The most common mutation among fluoroquinolone-resistant specimens was the gyrA 94GGC mutation (44%). The rrs 1401G mutation was found in 84%, 84%, and 50% of amikacin-resistant, capreomycin-resistant, and kanamycin (KAN)-resistant (KAN r ) specimens, respectively. The eis promoter mutation ؊12T was found in 26% of KAN r and 4% of KAN-susceptible (KAN s ) specimens. Inclusion of the ahpC and eis promoter gene regions was critical for optimal test sensitivity for the detection of INH resistance in the Eastern Cape and KAN resistance in Moldova. (This study has been registered at ClinicalTrials.gov under registration number NCT02170441.) I n 2014, an estimated 9.6 million people developed tuberculosis (TB), and 1.5 million people died of their infection (1). Although global TB incidence rates have fallen an average of 1.5% per year since 2000, the rise of drug-resistant TB (DR-TB) globally has complicated TB control efforts (1). The World Health Organization (WHO) estimates that as many as 1 in every 20 new, active TB infections is now drug resistant (1). One of the major roadblocks in combating this growing problem has been the lack of diagnostic technology for DR-TB. Current growth-based culture and drug susceptibility testing (DST) methods can take several weeks to months to yield results (2). While waiting on culture results, physicians are forced to treat their patients empirically, adjusting treatment regimens only once DST results become available. As a result, many undiagnosed DR-TB patients are being given medications that are ineffective, which amplifies resistance, increases the risk of mortality, and increases the risk of transmitting DR-TB infections in the community.Rapid molecular diagnostic assays for DR-TB have the p...

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