Role Of Mutation In DNA GyrA Gene In Fluoroquinolones Resistance Of Pseudomonas Aeruginosa

Objective: Pseudomonas aeruginosa (PA) is one of the most important causes of nosoeomial infections. It may be a particular problem in the clinical therapy as it has intrinsic and acquired resistance to antibiotics. Fluoroquinolones has potent antimicrobacterial activity against Pseudomonas aeruginosa, however with its extensive use clinically, the resistance rate of PA to these antibiotics rises year after year. Starting from the function mechanism of fluoroquinoiones, making use of PA which is isolated from the patients in Guangzhou, this paper probes into the pertinence of the major resistance mechanism of PA to fluoroquiolones (CPLX and NFLX) and its GyrA gyrA gene mutation, providing some clues for reasonable clinical use of antibiotics. Methods: 1. Taking the sputa or bronchial secretions from patients with pulmonary infection by the broncheofibroscopy to do routine culture, then isolating and confirming, obtained 145 PA strains. Micro-ilution broth method was used to determine the bacteria susceptibility to CPLX and NFLX ,and compared the resistance rate to them; 2. Using PCR-FLP, detected the mutation of PA gyrA gene at position 83, and studied the relationship between the point mutation and the resistance mechanism of PA to fluoroquinolones. Results: 1. Among the 145 PA strains obtained from isolated cultivation, there were 55 and 38 strains resistant to NFLX and CPLX respectively , the resistance rate being 37.9% and 26.2% according to micro-ilution method . There was significant difference between the resistance rate to NFLX and that to CPLX (P(O.05). 2. The ratios of resistant strains to NFLX and CPLX were 17. 5% (18 of 103) and 3. 88% (4 of 103) among the strains without mutation of gyrA gene at position 83 respectively. The ratios of resistant strains to NPLX and CPLX were 88. 1% (37 of 42) and 81. 0%(34 of 42) among the strains containing mutation of gyrA gene at position 83. The ratio of resistance strains to NPLX for without mutation of gyrA gene at 83 position and that for containing mutation of gyrA gene at position 83 had significant difference (P~0.01) . So did that of resistance strains to CPLX. Cono I us ion: 1. The susceptibility of CPLX to PA in Guangzhou is higher than that of NFLX. 2. The 83 th mutation of DNA gyrA gene is the main resistance mechanism of PA to fluoroquinolones. 3. PCR-RFLP method is a rapid, simple and economical method in studying the mechanisms of fluoroquinolones resistance. 4. Micro-ilution broth method can be conducted easily with accurate results. It is suitable for scientific research work and bacteria laboratories of skeleton hospitals, and able to provide veracious minimum bacteria' restraining concentration.