Systematic investigation of baseline nosocomial transmission of tuberculosis in the Kyrgyz Republic, Central Asia.

Objectives: Controlling tuberculosis (TB) transmission is of paramount importance for combating the TB pandemic. Although TB hospitals are considered hotspots of transmission, systematic longitudinal studies examining the underlying incidence and possible risk factors of nosocomial TB transmission are lacking. The objectives of this study were to detect nosocomial transmission events over a 20-month period using whole genome sequencing (WGS) of Mycobacterium tuberculosis complex (MTBC) isolates collected from 563 patients with pulmonary TB hospitalized in the Kyrgyz Republic.

Methods: The WGS was performed on 698 MTBC isolates, including 563 first isolates recovered from participants within 4 weeks of hospitalization and 135 follow-up isolates from treatment control samples collected at least 4 weeks apart. All participants' roommates were recorded over the whole study period.

Results: The cohort represented >95% of TB patients hospitalized at the study sites during the follow-up period of 53 372 hospitalization days. Genome-based cluster analysis revealed that 173 of the 563 (30.7%) first isolates fell into 56 clusters (<5 single nucleotide polymorphism [SNPs]). Two nosocomial TB transmissions from index cases to their roommates were proven. And five potential transmissions were observed between patients who shared time, but not a room, in the hospital or where the index case was not identified. Most transmitted strains were more resistant than the previous one.

Discussion: Within-community transmission of MTBC is highly active in Kyrgyzstan. With 13.7 per 1000 patient years (95% CI: 1.6-49.5), we observed markedly higher rates of nosocomial transmission than reported in previous WGS-based studies.