EVALUATION OF THE EXPRESSION OF MexY EFFLUX PUMP IN FLUOROQUINOLONE-RESISTANT Pseudomonas aeruginosa Tonani, L.1; Clímaco, E.C.1; Darini, A.L.C1 1-Faculdade de Ciências Farmacêuticas de Ribeirão Preto - Universidade de São Paulo, Ribeirão Preto, SP, Brasil. Keywords: Hospital infection, efflux pump, Pseudomonas aeruginosa, multidrug resistence. 1. Introduction 3. Results Pseudomonas aeruginosa is the most important Susceptibility rates of the studied isolates showed pathogenic non-fermenting bacteria, especially in 36.6% (15/41) for ciprofloxacin and norfloxacin nosocomial infections. This specie is often and 34,2% (14/41) for levofloxacin. These results associated (MDR) are in accordance to SENTRY data published by phenotype. One of the main MDR mechanisms in Gales et al. (2002) that showed 38,6% and 36% of P. aeruginosa is MexXY-OprM efflux pump, susceptible P. aeruginosa to ciprofloxacin and which confers resistance against antipseudomonal levofloxacin, respectively. penicillins, and Results from evaluation of MexY expression if showed that there was statistical significance reduced to multidrug resistance cephalosporins, susceptibility to quinolones meropenem, overexpressed. The aim of this work is to (P<0,05) in the relationship between determine if the over expression of MexY pump is fluoroquinolone susceptibility profile and 2-∆CT responsible for the increasing of fluoroquinolone values, with P value of 0.0006, for ciprofloxacin resistence in P. aeruginosa strains. and norfloxacin, and of 0.0013, for levofloxacin (Figure 1). 2. Methods It was used 41 P. aeruginosa isolates recovered Figure from pacients of University Hospital of Federal according University of Juiz de Fora. Firstly, the fluoroquinolones. 1. Distribution of to 2-∆CT clustered susceptibility against susceptibility profiles of these isolates were investigated by disc diffusion according to CLSI criteria. Expression assay of MexY gene was carried out by real time PCR, using Fast EvaGreen system, after RNA purification with RNAeasy kit and reverse transcription. Analyzing of real-time PCR data was realized by comparative 2-∆Ct method, using RpsL 4. Conclusion housekeeping gene expression to normalize MexY gene fluoroquinolones expression. susceptibles Results and of The results suggest that there was a high non- correlation between MexY overexpression and susceptibles isolates were compared by t test method of non-parametric and independent resistance phenotype to fluoroquinolone. Acknowledgments samples, to determine whether the difference is statistically significant. We thank FAPESP for financial support.