Mutation of gyrA gene in 98 strains ofloxacin-resistant Mycobacteria tuberculosis clinical isolates in Henan province

The purpose was to analyze the characteristics of fluoroquinolone resistance gene gyrA mutation in M.tuberculosis in Henan Province.A total of 126 M.tuberculosis clinical isolates were conducted to test drug susceptibility,98 resistance strains were chosen,while 28 susceptible strains,H37Rv and H37Ra was selected as comparison.According to DNA sequencing,the primers were designed and PCR amplification was done.All strains were performed gyrA quinolone resistance determining region(QRDR) DNA sequencing.Results showed that gyrA mutation were found in 81 isolates(84%),30 isolates were single mutation among them,and other 51 isolates(63%,51/81) were double mutations in gyrA.The ofloxacin-resistant Mycobacterium tuberculosis in our province was high in double mutations in gyrA QRDR.Ala74Ser mutation,which previously had seldom been found in M.tuberculosis,was found.The gyrA mutation occurred in frequence gyrA94(84%),gyr90(71.6%),gyrA91(19.8%),and gyrA74(14.8%);no close relationship was observed between gyrA mutation type and ofloxacin MIC.By introducing M.tuberculosis H37Rv and M.tuberculosis H37Ra reference strains,interference from codon 95 AGC: ACC polymorphism was successfully avoided.This study indicates that 84% of the ofloxacin-resistant resistant M.tuberculosis strains have gyrA genetic mutations.The 84% ofloxacin-resistant isolates indicates the high rate of gyrA QRDR double point mutations.