Person-to-person (MDR) multidrug-resistantTB transmission drives epidemic in China.

Person-to-person MDR-TB transmission drives epidemic in China.Recent data from a population-based, observational study in China revealed that patients were more likely to contract multidrug-resistant tuberculosis from person-to-person transmission than inadequate treatment. “Inadequate treatment was considered to be the most common way of developing MDR [tuberculosis (TB)]; however, our data show that most of the patients in our study population who had [MDR-TB] had been infected with MDR strains,” Chongguang Yang, PhD, postdoctoral associate of epidemiology of microbial diseases at Yale School of Medicine, and colleagues wrote in the Lancet Infectious Diseases. “We also found that a majority of transmission events occurred in settings such as residential communities or complexes and related public facilities.” Yang and colleagues performed variable-number-of-tandem-repeat (VNTR) genotyping and whole-genome sequencing on MDR-TB isolates collected from patients in Shanghai, China to establish transmission patterns and risk factors of MDR-TB in the area. Their analysis included data from 324 patients aged 15 years and older who were diagnosed with MDR-TB between Jan. 1, 2009 and Dec. 31, 2012. The researchers used a standardized questionnaire to determine patients’ social characteristics, history of TB exposure and locations where transmission may have occurred. According to the data, 59% of patients with MDR-TB were treatment-naive. Overall, 32% of the 324 MDR-TB strains were in 38 genomic clusters that differed by 12 single nucleotide polymorphisms or fewer, indicating recent transmission. The researchers combined treatment-naive cases (n = 191) with cases included in genomic clusters (n = 93) and estimated that up to 73% (95% CI, 67.3-77.3) of all MDR-TB cases were likely caused by transmission of MDR strains. Epidemiological links were identified in 69% of the genomically clustered cases, only four of which were traced to household contacts. The majority (n = 45) of cases were either linked to other cases from the same residential community or neighborhood street, or cases using the same public health facilities such as food markets.