Transmission of multidrug-resistant Mycobacterium tuberculosis in Shanghai, China: a retrospective observational study using whole-genome sequencing and epidemiological investigation

Summary

Background

Multidrug-resistant tuberculosis (MDR-TB) is a significant threat to tuberculosis elimination worldwide. Understanding the transmission pattern is crucial for its control. We used a genomic epidemiological approach to assess the recent transmission of MDR-TB and potential risk factors for transmission.

Methods

In a population-based retrospective study, we performed variable-number-of-tandem-repeat (VNTR) genotyping, followed by whole-genome sequencing (WGS) of isolates from all MDR-TB patients in Shanghai, China, 2009-2012. We measured strain diversity within and between genomically clustered patients. Genomic and epidemiologic data were combined to construct transmission networks.

Findings

367 (5%) of 7982 patients with tuberculosis had MDR tuberculosis and 324 (88%) of these had isolates available for genomic analysis. 103 (32%) of the 324 MDR strains were in 38 genomic clusters that differed by 12 or fewer single nucleotide polymorphisms (SNPs), indicating recent transmission of MDR strains. Patients who had delayed diagnosis or were older than 45 years had high risk of recent transmission. 235 (73%) patients with MDR tuberculosis probably had transmission of MDR strains. Transmission network analysis showed that 33 (87%) of the 38 clusters accumulated additional drug-resistance mutations through emergence or fixation of mutations during transmission. 68 (66%) of 103 clustered MDR strains had compensatory mutations of rifampicin resistance.

Interpretation

Recent transmission of MDR strains, with increasing drug-resistance, helps drive the MDR-TB epidemic in Shanghai, China. WGS provides a measure of the heterogeneity of drug-resistant mutations within and between hosts and enhances our ability to determine the transmission patterns of MDR-TB.

Funding

National Science and Technology Major Project, National Natural Science Foundation of China, and US National Insitutes of Health.