Association of overexpression of efflux pump genes with antibiotic resistance in Pseudomonas aeruginosa strains clinically isolated from urinary tract infection patients.

There are several mechanisms for antibiotic-resistant Pseudomonas aeruginosa. The purpose of this study is to investigate the association between the expression of efflux pump-coding genes and antibiotic resistance in P. aeruginosa causing urinary tract infections (UTIs). We extracted the RNA from 105 clinical strains of P. aeruginosa isolated from UTI patients with full data on antibiotic MICs and assayed real-time quantitative reverse-transcription PCR. We investigated the gene expressions of four resistance nodulation cell division-type multi-drug efflux pump systems (MexAB-OprM, MexCD-OprJ, MexEF-OprN and MexXY(-OprA)) and the correlation of the MICs of nine antibiotics, risk factors and antibiotic resistance-related genes with expressions of mexB, mexC, mexE and mexY. Multivariate statistical data demonstrated a significant relationship between increased expression of mexB or mexC and complicated UTI (Odds ratio=8.03, P<0.001 and Odds ratio=8.86, P=0.032, respectively). We also found a significant association between the increased expression of mexC and resistance to levofloxacin (LVFX) (Odds ratio=4.48, P=0.035). In conclusion, increased expression of mexC leads to LVFX resistance in P. aeruginosa causing UTI. These results contribute to our knowledge of the efflux pump system and antibiotic resistance.