Transmission of Mycobacterium tuberculosis in a tuberculosis outbreak in a university in Jiangxi province from perspective of etiology in 2022

Objective To evaluate the performance of two genotype methods in responding the tuberculosis (TB) outbreak in school, by analysis of the transmission of Mycobacterium tuberculosis in an outbreak in a university in Jiangxi province from the perspective of etiology.

Methods In 2022, smear microscopy, culture, and Xpert MTB/RIF were carried out in TB case screening in the TB outbreak response in the university. Mycobacterial interspersed repetitive unit-variable number tandem repeats (MIRU-VNTR) and whole genome sequencing (WGS) were performed for 16 isolated strains of M. tuberculosis. Drug resistance and genotyping characteristics were analyzed to identify the transmission chain.

Results In the16 culture positive strains, 13 were identified as M. Tuberculosis. All the 13 strains were identified to belong Beijing genotype by using VNTR and Lineage 2 family by WGS. A total of 3 recent transmission chains were identified by either VNTR or WGS. Chain 1, the largest transmission chain, included 9 strains with rrs A514C mutation associated with streptomycin resistance.Chain 2 included 3 strains with rpoB H445N mutation associated with rifampicin resistance, while chain 3 only included 1 strain with rpoB D190A mutation. The result of epidemiological survey to identify the disease outbreak by the area distribution of the cases was not entirely consistent with that of pathogen genotyping in this study.

Conclusion VNTR and WGS are useful tools to identify the recent transmission of TB. Molecular epidemiological method can be complementary to traditional epidemiology method for the more accurate identification of the recent TB transmission.