Association Of Mutation Patterns In Type Ⅱ Topoisomerase Genes And Fluoroquinolones Resistance Levels In Lactic Acid Bacteria

18 lactic acid bacteria strains isolated from natural fermented dairy in Darhan muminggan united banner and Siziwang banner Inner Mongolia, were investigated in the present study. Firstly, double dilution method was used to test the 18 lactic acid bacteria strains’minimal inhibitory concentration(MIC) to fluoroquinolones. The 18 lactic acid bacteria strains demonstrated various levels of resistance to levofloxacin, ciprofloxacin and norfloxacin when double dilution method was used.The resistance rate to levofloxacin, norfloxacin and ciprofloxacin were all 88.9%.As for levofloxacin and ciprofloxacin,lstrains behaved moderately sensitive andl strain behaved sensitive and the other strains showed drug-resistant. To norfloxacin,2 strains behaved moderately sensitive while other strains showed drug-resistant.Experiments of morphology, physiological and biochemical characteristics were carried on the tested strains. Then experiment of 16S rRNA sequence analysis were carried on in the study. Combined the results of physiological and biochemical identification, there were 3 strains belonged to Enterococcus faecium,2 strains belonged to Enterococcus durans,2 strains belonged to Pediococcus acidilactici.Futhermore, PCR amplification and gene sequencing test were conducted on gyrA, gyrB and parC of type II topoisomerase of these isolated strains. The results indicated that the gyrA and parC of resistant strains had 83 and 127 amino acid mutation were occurred respectively, which clearly demonstrateed that there were direct correlation between mutation patterns in gyrA and parC genes and fluoroquinolones resistance levels in lactic acid bacteria. It was one of the possible causes of drug-resistant which gyrB gene obtained the stop codon and occurred nonsense mutationa.