Abstract:

Objective Analysis of mutation sites of drug resistance genes in 958 M.tuberculosis clinical isolates.Methods The positive mycobacterial cultures of 2718 patients were collected from various clinical specimens such as sputum, tissue, and pleural effusion in Xi’an Chest Hospital from January to December 2017. Forty-one cases of non-tuberculous mycobacterial infection and 2677 cases of Mycobacterium tuberculosis infection were distinguished by strains identification.The information including results of M.tuberculosis cultures and drug susceptibility test (“drug sensitivity test”) by MGIT 960 liquid and drug resistance test by gene chip in 958 patients were collected.The coincidence rate of mutation sites and phenotypic drug susceptibility test results were analyzed. The count data were analyzed by χ² test, and P<0.05 was considered statistically significant.Results The mutation rate of a single site was 19.52% (187/958) in all of the clinical isolates.The ropB gene mutation rates in the 5-, 21-, 41-, 61-83 age groups were 7.89% (9/114), 13.52% (63/466), 18.27% (38/208), and 9.41% (16/170), respectively. The mutation rate of the ropB in the middle-aged group was statistically different from that in the adolescent group (χ²=6.358, P=0.013) and the elderly group (χ²=5.994, P=0.018). The mutation rate at any one site was 19.45% (121/622) in the male population and 19.05% (64/336) in the female population.There was no significant difference between the male and female groups (χ²=0.023, P=0.932). There was a higher coincidence rate in mutation of rifampicin ropB 531 (C-T) (96.10%, 74/77) and isoniazid katG 315 (G-C) (98.45%, 127/129) and the phenotypic susceptibility. However, ropB 511 (T-C) was inferior coincidence rate to rifampicin phenotype (0.00%,0/10).Conclusion T here was a statistically significant difference in the mutation rate of ropB gene locus in patients of different age groups.The mutation rate of ropB gene happened in the middle-aged group was the highest. There was no significant difference in the mutation rate between the different gender groups.Diagnosis should be done by drug gene mutation combined with phenotypic susceptibility.

Key words: Mycobacterium tuberculosis, Microbial sensitivity tests, Molecular probe techniques, Point mutation, Comparative study