Correlation analysis between gyrA gene mutations and the tolerance to ofloxacin in Mycobacterium tuberculosis strains

Objective Utilizing of ofloxacin as a target to investigate the effect of drug-resistant threshold on the early laboratory determination of drug-resistant Mycobacterium tuberculosis;combined with DNA sequence analysis,to probe the correlation between gyrA genetic mutations and the tolerance to ofloxacin in Mycobacterium tuberculosis strains.Methods(1) Utilizing L-J medium slant containing ofloxacin to detect the sensitivity to ofloxacin against 101 isolates by way of absolute concentration.(2) Sequencing to detect the ofloxacin-resistant Mycobacterium tuberculosis gyrA genetic mutation characteristics.Results(1) 17 of 52 ofloxacin-resistant 5.0,and 2 of 49 ofloxacin-sensitive strains can grow in 10.0 and 2.0 μg/ml of ofloxacin onto the ofloxacin containing Lowenstein-Jensen slants.Those were respectively contributed about 32.69% of 52 and about 4.08% of 49 of the tested isolates.(2) The sequencing results showed that genetic mutations of OFLX-resistant Mycobacterium tuberculosis clinical isolates occur mainly on codon 90,91 and 94.In addition,10 of 101 Mycobacterium tuberculosis isolates was found to occur different deletion or insertion on gyrA base chains.101 clinical isolates of Mycobacterium tuberculosis was totally genetic point mutation on codon 95,and the mutation rate was 100%,detected occuring Conclusions(1) DeterminingTB drug resistance on upper and lower threshold plays an important role in laboratory early detection of TB drug resistance.(2) gyrA genetic mutations occurring in the OFLX-resistant Mycobacterium tuberculosis were variable,and highly relevant to ofloxacin-resistance,but lack of significant correlation with the tolerance to ofloxacin in M.tuberculosis strains.