Study on mechanism of resistance in acinetobacter baumannii to quinolones

  Objective   To study the mechanism of resistance in acinetobacter baumannii to quinolones.

  Methods   Bacterial susceptibility test to quinolones were done by the Kirby-Bauer method for 35 isolates.Outer membrane protein was analyzed by SDS-PA GE.A ccumulation of ciprofloxacin by A.baumannii was determined by direct fluor escence method.The gene of gyrA was amplified by polymerase chain reaction(PCR)and the products were sequenced.

  Results   20 isolates were resistant to quinolones in 35 isolates.The analysis of outer membrane proteins showed that a protein of 29ku disappeared and 26ku protein enhanced in resistant isolates.The accumulation of ciprofloxacin in resistant isolates decreased.After treatment with NaN₃, the drug uptake increased to the normal level.DNA sequencing analysis revealed there was not any mutation in the gyrA gene.

  Conclusion   Active drug efflux and outer membrane protein permeability decreasement were the factors contributing to the quinolone resistance of A baumannii.