Abstract:

Objective To investigate the prevalence and molecular characteristics of Ofloxacin (Ofx)-resis-tant Mycobacterium tuberculosis (MTB) isolates from Changping District of Beijing, so as to provide reference for clinical prevention and treatment of drug-resistant tuberculosis.Methods Seven hundred and one strains of MTB clinical isolates in Changping Tuberculosis Dispensary were collected from 2016 to 2018. Conventional proportional method (referred to as “drug sensitivity test”, DST) was used to detect in vitro drug susceptibility of MTB isolates. Among those clinical isolates, 51 strains were detected as multi-drug resistant(MDR)MTB, 650 strains were not MDR. GyrA gene mutations of Ofx-resistant isolates were test by gene sequencing. The resistance rates of Ofx in each year were compared using Cochran-Armitage trend test. The difference was significant if P<0.05.Results Of 701 MTB isolates, 41 (5.8%) were resistant to Ofx. Statistical analysis revealed that the resistance rate of Ofx was significantly increased from 2.9% (7/243) in 2016 to 8.0% (18/226) in 2018 ( {\chi }_{\mathrm{trend}}^2 =5.567, P=0.018). In addition, the Ofx resistant rates were 37.2% (19/51) and 3.4% (22/650) in MDR and non-MDR clinical MTB isolates, respectively, with significant difference (χ ²=92.462, P<0.01). GyrA gene mutation was detected in 31 strains (75.6%) of 41 Ofx resistant MTB strains. The most common mutations were 94 codons (36.6%) and 90 loci (34.1%).Conclusion The Ofx resistant rate of the clinical isolates of MTB in Changping District shows an increasing trend from 2016 to 2018. The mutation of GyrA gene is the most predominant mechanism associated with Ofx resistance in this region.

Key words: Mycobacterium, tuberculosis, Ofloxacin, Drug resistance, Microbial sensitivity tests, DNA mutational analysis, Data interpretation, statistical, Small-area analysis