Genetic diversity of drug resistant Mycobacterium Tuberculosis in local area of Southwest China: a retrospective study.

Background: By 2014 although tuberculosis (TB) incidence had fallen by an average of 1.5% per year since 2000 and was 18% lower than the level of in 2000, 1.5 million people died for TB in that year. One of reason was that drug resistant Mycobacterium tuberculosis (DRTB) spread. This study aims to determine drug resistant characteristics and genotype of DRTB that isolated from patients in a tuberculosis referral hospital of southwest China.

Methods: Five hundred thirty-eight drug resistant tuberculosis samples were collected from July 2013 to March 2015. All the isolates were identified by genomic deletions in region of difference 105 (RD105) and genotyped by mycobacterial interspersed repetitive unit-variable number tandem repeat typing (MIRU-VNTR). Polymorphism and cluster analysis of each locus was carried out using Bionumerics Version 3.0 and phyloviz software.

Results: Five hundred thirty-eight TB strains included 503 Mycobacterium tuberculosis (MTB) isolates and 35 non Mycobacterium tuberculosis (NMTB) isolates. Of 503 isolates Beijing family type was 447 (88.9%, 447/503) and non-Beijing family type was 56 (11.1%, 56/503). Five hundred three DRTB isolates were divided into 345 genotypes, of which 265 isolates were single genotype and the remaining 238 strains were classified into 80 clusters with cluster rate of 47.3% and cluster ratio of 31.4%. Sixty-nine clusters belonged to Beijing family with cluster rate was 48.3% and clustering ratio was 32.9%. The non - Beijing family had 11 clusters with a cluster rate of 39.3% and the clustering ratio of 19.6%. Beijing genotype had a significant correlation with the age (P < 0.05), the retreatment patients (P < 0.05) and the city of Chongqing (P < 0.05), not with gender (P > 0.05). In the 9 Beijing genotype clusters each cluster contained some patients who lived in the same region.

Conclusions: Beijing genotype was the predominant in the patients with DRTB in our hospital. In Chongqing retreatment patients with Beijing genotype MTB may be patient with DRTB. Drug resistance test (DST), regular medication and strict follow-up are very important for patients with Beijing genotype MTB. In Chongqing control and treatment of DRTB should be paid attention. Transmission and relations of patients with DRTB need to be further research.