Molecular-epidemiological study on the transmission of drug resistant tuberculosis and its influencing factors in rural areas of eastern China

Abstract

To investigate the contribution of recent transmission in the epidemic of drug-resistant Mycobacterium tuberculosis (M.TB) and related factors from biomedical and social-demographic perspectives in the Eastern rural areas of China. Identified by proportion method of drug susceptibility test, 223 drug resistant M.TB isolates and their hosts were included in the present study. These drug resistant tuberculosis isolates were first genotyped by Mycobacterial Interspersed Repetitive Units (MIRU), and those isolates with identical MIRU genotype were further classified by IS6110 restricted fragment polymorphism (RFLP). 'Cluster' was defined as two patients' M. TB isolates harboring the identical MIRU genotype and IS6110-based RFLP pattern simultaneously. Unique strains denoted those with the unparalleled MIRU genotype in the study collection. Socio-demographic and biomedical characteristics of host patients were compared between the clusters and unique groups through univariate and multivariate logistic regression analysis. Based on the MIRU-IS6110 pattern, there were 52 isolates belonged to the "cluster" group and 171 as the "unique" group. Drug resistant M.TB strain isolated from patients at the age of 30 - 60 year had a higher probability of being clustered, comparing to those from patients below 30 years of age (30.9% vs. 11.9%; OR = 3.297; 95%CI: 1.169 - 9.297). Such finding were also seen in the isolates from patients with previous treatment history compared to newly diagnosed patients (32.9% vs. 18.4%; OR = 2.163, 95%CI: 1.144 - 4.090). The multi-drug resistant M.TB strain was found to have been more frequently clustered when comparing to the mono-drug resistant M.TB (47.2% vs. 15.5%; OR = 4.773; 95%CI: 2.316 - 9.837). The transmission pattern of drug resistant tuberculosis was presented mainly by the sporadic distribution in small group within rural villages. Transmission of drug-resistant tuberculosis was seen in the population living in the Eastern rural areas of China, and causal contact within villages was considered as the main route of recent transmission. Patients at middle age and having previous tuberculosis treatment history might have increased the risk of transmission by patients with drug resistant tuberculosis.