Correlation Of Active Efflux System And Quinolones Resistance In Lactic Acid Bacteria

14 lactic acid bacteria strains isolated from Xilinguole Pastoral in Inner Mongolia, China, were investigated in the present study. Double dilution method was used to determine the minimal inhibitory concentrations （MIC） to quinolones of the isolated strains. The results indicated that 14 lactic acid bacteria performed various levels of resistance to norfloxacin and ciprofloxacin, and the resistance rate to both norfloxacin and ciprofloxacin were all 100%. Among them,7 strains showed highly drug-resistant whose the MIC value to two kinds of quinolones were greater than 512 μg/mLProton pump inhibitor reserpine was combined with fluorescence spectrophotometry to detect the ciprofloxacin intakes of drug resistant strains and control strains.The results showed that there were active efflux systems in drug-resistant strains ZHZ18, ZHZ28, ZNN3 and ZNN4, and the effect can be inhibited by reserpine.Experiments of morphology, physiological and biochemical characteristics,16S rRNA sequence analysis were carried out on 4 strains which possessed obvious active efflux. The results showed that ZHZ18, ZHZ28 belonged to Enterococcus durans, ZNN3 and ZNN4 belonged to Enterococcus faecium.Chromosomal gene efrB which encoded ABC active transport protein, was found by PCR amplification in strains ZHZ18 and ZHZ28. The homology of base sequences between the test strains and E.faecalis were 76%. The homology of amino acid sequences translated by efrB gene between the test strains and Enterococcus durans in GeneBank with the accession number WP₀53109251 were 100%. There were 29 differences of the amino acid sequences between the test strains and the control strain E.faecalis. The protein encoded by efrB may be one of the active efflux proteins which mediated the quinolones resistance in test strains.