Abstract: Objective To study the relations between enterococcal GyrA gene mutation, enterococcal multi-drug resistance efflux pumps and fluoroquinolones resistant in enterococci. Methods All strains were identified using VITEK-2 compact and GPI cards. Mutation of GyrA gene in strains of 30 E.faecalis and 10 E.faecium of levofloxacin-resistant and ciprofloxacin-resistant were detected using PCR and single strand configuration polymorphism(SSCP), testing results and mutant types were confirmed by sequencing analysis. At the same time, the minimal inhibitory concentration(MIC) of 30 strains of enterococci against ciprofloxacin were tested using M-H agar including reserpine that final concentration was 20 μg/mL. Results All the 40 strains of enterococci resistant to Levo and Cip, were successful to amplify GyrA gene; 24 strains of E. faecalis and 4 E. faecium single-strand electrophoresis band appeared abnormal compared with ATCC 29212. The sequencing of 2 strains of E. faecalis had codon alterations at 87:GAA→GGA; 2 strains of E. faecium had the codon alteration at 83: AGT →TAT. Alterations of codons lead to the change of amino acids. Parts of E. faecalis' MICs were decreased adding reserpine in the M-H agar. Conclusion All 40 strains enterococci GyrA gene were detected by PCR-SSCP and confirmed by sequencing analysis, 70%(28 strains) had gene mutation. This result indicated GyrA gene mutations are main causes, which resulted in fluoroquinolones-resistance in enterococci. In addition, Multi-drug resistance efflux pumps were also existent in enterococci.

Key words: enterococci, fluoroquinolone, GyrA gene, multi-drug resistance efflux pumps, single strand configuration polymorphism