Efflux Inhibition in Clinical Isolates of Pseudomonas Aeruginosa Using Sertraline for Ciprofloxacin Resistance Breakdown

The efflux pump in Pseudomonas aeruginosa inhibits the effect of ciprofloxacin by releasing quinolones out of the cell. It is important to find compounds to inactivate or inhibit its activity to continue using the antibiotics. The present study was done to investigate using sertraline as an efflux pump inhibitor in P. aeruginosa to reduce antibiotic resistance.

P. aeruginosa strains were isolated from clinical sources and identified by routine microbiological methods. Resistance of the isolates to ciprofloxacin was evaluated by Kirby–Bauer test. Resistance breakdown was investigated by adding sertraline to the Moller Hinton agar medium and determining the zone of inhibition of ciprofloxacin. Minimum inhibitory concentration (MIC) by microplate dilution method and Minimum bactericidal concentration (MBC) by culture and MTT method were done for the isolates and ATCC 27853. The presence of the efflux pump was evaluated by the phenotypic method using sertraline and serial dilution method of the liquid medium in a microplate, on ciprofloxacin-resistant strains. The presence of the producing gene of this pump was determined by the genotyping method in resistant strains by performing PCR. The standard PAO1 strain of P. aeruginosa was used as a positive control.

This study was approved by the Ethics Committee of the Faculty of Medical Sciences of Islamic Azad University, Brojerd Branch (Code: IR.IAU.B.REC.1401.011).

Based on Kirby–Bauer test results, three strains were considered resistant to ciprofloxacin. MIC of drug-resistant strains was between 32 and 64 mg/ml and MBC was between 16 and 32 mg/ml. By performing electrophoresis on the PCR products, it was determined that the tested strains contained the mexA gene encoding the efflux pump. In the agar medium without sertraline, the zone of inhibition around the ciprofloxacin disc was zero, but after adding sertraline, the diameter of the halo increased to 25 mm. The minimum inhibitory concentration of ciprofloxacin in the isolates before adding 25 µg of sertraline was 128 µg/ml and after adding sertraline, it was 4 µg/ml.

It was concluded that sertraline inhibited the efficiency of the efflux pump in resistant P. aeruginosa isolates and reduced ciprofloxacin resistance.