Recent transmission of W-Beijing family Mycobacterium tuberculosis in rural eastern China

OBJECTIVE: To understand the degree of recent transmission of tuberculosis (TB) and determine the risk factors associated with recent transmission stratified by W-Beijing genotype in rural China. DESIGN: A cross-sectional study of bacteriologically confirmed TB patients registered in two rural counties of eastern China over a 1-year period. RESULTS: Of 351 patient isolates, spoligotyping identified 243 (69.2%) as W-Beijing family strains, and 53 (15.1%) and 15 (4.3%) as members of T1 Family and Family 33, respectively. Insertion sequence (IS) 6110 based restriction fragment length polymorphism typing revealed that 31 clusters together accounted for 80 of the 351 isolates. Strains with the W-Beijing genotype were more likely to be clustered than non-Beijing strains (42.3% vs. 8.3%, P < 0.001). The proportion of cases due to recent transmission was estimated at 23.1% (32.1% W-Beijing genotype vs. 2.8% non-W-Beijing genotype). Multivariate analysis showed that bacille Calmette-Guérin (BCG) vaccination (aOR 2.97), multidrug resistance (aOR 5.45) and body mass index (aOR 1.13) were independent predictors for clustering among W-Beijing isolates. CONCLUSIONS: The low clustering proportions highlight the role of endogenous reactivation of TB as a main concern in rural eastern China. Our findings also suggest that W-Beijing strains were associated with recent transmission in this population, where multidrug resistance and BCG vaccination may play an important role in the mechanism of TB transmission.