Genetic analysis of fluoroquinolone-resistant Acinetobacter baumannii isolates from Korea
Abstract number: 902_p1730
Acinetobacter baumannii has recognized as a important opportunistic pathogen of nosocomial infections and the resistance to fluoroquinolone among Acinetobacter spp. has rapidly emerged in Korea. The mechanism of resistance to fluoroquinolone has been associated mainly with mutations in quinolone-resistance-determinig regions (QRDR) of the gyrA gene of DNA gyrase and the parC gene of topoisomerase IV. The genetic analysis of fluoroquinolone resistance in A. baumannii isolates in Korea remain to be investigated. To investigate the prevalence of mutations in DNA gyrase and topoisomerase IV, we analysed the QRDRs of the gyrA and parC genes against ciprofloxacin-resistant A. baumannii isolates from Korean hospitals.
A total of 59 clinical isolates of A. baumannii were collected from nontertiary hospitals in 20022003. A. baumannii isolates were identified by the API 20NE kit and recA-RFLP analysis withTsp5091. MICs of ciprofloxacin and levofloxacin were determined according to the criteria of NCCLS. The QRDRs of gyrA and parC genes were amplified by PCR using specific primers. To detect mutations in the QRDRs, digestion of the PCR products with Hinf I were analysed and sequencing was performed by the dideoxy-chain termination method.
Ciprofloxacin and levofloxacin resistance rates of A. baumannii isolates were 89.8 and 78.0%, respectively. The MIC50 and MIC90 of ciprofloxacin and levofloxacin of these isolates were 32 and 128 and 8 and 16 mg/L, respectively. All of 53 ciprofloxacin-resistant A. baumannii had only a substitution of Ser83 with Leu in the GyrA protein. Other mutations in the gyrA gene, Gly81Val and Ala84;Pro, did not be detected. Among 53 A. baumannii isolates with alteration in Ser83 of GyrA, mutations with substitution of Ser80 to either Leu or Trp in the ParC were found in 41 and one isolate, respectively. Nine isolates had a substitution of Glu84 to Lys and two isolates contained no mutation in the ParC.
In this study, double mutation at codons Ser83 in GyrA and Ser80 in ParC were more frequently found among A. baumannii isolates with a ciprofloxacin MIC of 16 mg/L. In ParC protein, the novel substitution of amino acid, Ser80 to Trp, was detected."
|Session name:||XXIst ISTH Congress|
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