The longitudinal trends of multidrug and extensively drug resistant tuberculosis in China

BackgroundContinuous understanding of the epidemiology of drug resistant TB, especially for multidrug/extensively drug resistant TB (MDR/XDR-TB) is essential to develop the appropriate strategies for preventing its epidemic. The present study aimed to investigate the longitudinal trend of the rates and dynamic change of MDR/XDR M.Tuberculosis and its transmission pattern to adjust the TB control activities in eastern rural China.MethodsThe data presented here spanned 8years and was derived from three population-based studies of drug-resistant TB in two eastern rural counties: DQ and GY in terms of socio-demographic characteristics of drug-resistant cases, as well as the microbiological and molecular features of their infected M.Tuberculosis strains in eastern rural China.ResultsOf the 990 smear-positive patients within the studied period, 413 (41.7%) cases showed resistance to any of the detected first- (INH, RIF and EMB) and second-line (OFL, LEV, KAN, AMK, and CAP) anti-TB drugs: 89 with MDR (9.0%). Of these MDR-TB isolates, 34 cases (38.2%) showed resistance to any of the second-line anti-TB drugs: 25 (28.1%) with resistance either to FQs or second-line injective drugs (Pre-XDR) and 9 (10.1%) showed simultaneous resistance to the two categories (XDR). Molecular analysis of pncA gene revealed 185 M.Tuberculosis cases contained the mutation associated with PZA resistance, with a significantly higher proportion in MDR compared with the others (35% vs. 16.8%, p=0.04). For the longitudinal perspective, MDR-TB (from 9.1% to 14.5%, p=0.001), Pre-XDR-TB (from 2.5% to 4.5%, p=0.01) and XDR-TB (from 0.9% to 3.6%, p=0.04) exhibited an upward trend, while there was a significant decreasing change in the proportion of totally first-line drug sensitivity (p=0.047). Non-linear regression analysis showed that MDR-TB, Pre-XDR-TB and XDR-TB increased significantly over the study period with a double time of 4.8year (95% CI: 3.69–5.92), 3.2year (95% CI: 2.16–5.94) and 3.3year (95% CI: 1.099–8.32). Being clustered, sputum smear result and previously treated history were factors increasing the trending of M/XDR-TB. The MIRU24 loci genotyping revealed the 21 clusters involving 48 (28.4%) drug-resistant cases in DQ and 28 clusters involving 59 (32.1%) drug-resistant cases in GY. Of these clusters, 11 were related to MDR/XDR-TB and 8 of these clustered genotypes were observed more than 5years of the study period.ConclusionThese results show that active transmission of MDR/XDR-TB is taking place and that the increasing trend in the observed rate of MDR/XDR-TB tends to be due to the variation in the distribution of patients with different socio-demographic features and the continued transmission of particular genetic clusters. Continuous surveillance of clinical isolates of M.Tuberculosis is needed to identify M/XDR-TB, especially in patients who have a history of TB and have received prior anti-TB treatment