As expected, all meropenem-Defactinib susceptible isolates that overexpressed mexB, presented normal expression of both ampC and oprD when compared to that of PAO1. Higher percentage of mexB overexpression was observed among isolates that were also not susceptible to cefepime, amikacin, gentamicin and ciprofloxacin. Of note, 85.7% and 28.6% of SPM-producing P. aeruginosa showed

increased transcriptional levels of mexY and mexB, respectively. MDV3100 ic50 It is worth to mention that MexAB-OprM and/or MexXY-OprM overexpression was observed among isolates that were susceptible to most antimicrobials tested. This finding was expected since efflux pump overexpression in P. aeruginosa usually confers modest increase in the MICs of www.selleckchem.com/products/pp2.html antimicrobial agents that are ejected by these systems. Discussion and Conclusions P. aeruginosa

is the fifth most frequent pathogen of bloodstream infections and the first one causing pneumonia in Latin America according to the SENTRY Antimicrobial Surveillance Program [13]. In the last decades, the emergency of multi-drug resistant P. aeruginosa has been observed worldwide. Some of antimicrobial agents have become less effective against these organisms reducing the available therapeutic options for treatment of these infections. In this study 52.5% of the P. aeruginosa isolates studied were resistant to carbapenems. Our findings are in accordance of previous studies that showed high rates of antimicrobial resistance, including carbapenems, among P. aeruginosa clinical isolates collected from Brazilian institutions [14]. The genetic diversity observed among the P. aeruginosa isolates studied indicates that spread of clones and emergency of distinct genotypes have occurred in our hospital. The high rate of carbapenem Org 27569 resistance can be partially explained by the spread of an endemic SPM-producing clone. It also justifies the susceptibility rate to aztreonam since MBL producers are not able to hydrolyze this antimicrobial agent. This finding corroborates with those previously reported that described a single SPM producer clone spread out in the Brazilian

territory [15]. The overexpression of efflux systems may impact on clinical outcome of P. aeruginosa infections since they are capable of pumping out many classes of antimicrobial agents used for treatment of these infections [16]. However, it has not been clearly established the correlation between increase in the transcriptional level of an efflux-encoding gene and antimicrobial resistance leading to possible therapeutic failure [17]. In the present study, we have evaluated the transcriptional levels of four efflux-encoding genes as well as ampC and oprD among 59 P. aeruginosa clinical isolates. This collection represents the total number of patients with bloodstream infection due to P. aeruginosa in a six-month period in Hospital São Paulo, Brazil.