Efflux pumps expression and its association with porin down-regulation and β-lactamase production among <it>Pseudomonas aeruginosa </it>causing bloodstream infections in Brazil

• Main Authors: Xavier Danilo E, Picão Renata C, Girardello Raquel, Fehlberg Lorena CC, Gales Ana C
• Format: Article
• Language: English
• Published: BMC 2010-08-01
• Series: BMC Microbiology
• Online Access: http://www.biomedcentral.com/1471-2180/10/217

<p>Abstract</p> <p>Background</p> <p>Multi-drug efflux pumps have been increasingly recognized as a major component of resistance in <it>P. aeruginosa</it>. We have investigated the expression level of efflux systems among clinical isolates of <it>P. aeruginosa</it>, regardless of their antimicrobial susceptibility profile.</p> <p>Results</p> <p>Aztreonam exhibited the highest in vitro activity against the <it>P. aeruginosa </it>isolates studied (64.4% susceptibility), whereas susceptibility rates of imipenem and meropenem were both 47.5%. The MexXY-OprM and MexAB-OprM efflux systems were overexpressed in 50.8% and 27.1% of isolates studied, respectively. Overexpression of the MexEF-OprN and MexCD-OprJ systems was not observed. AmpC β-lactamase was overexpressed in 11.9% of <it>P. aeruginosa </it>isolates. In addition, decreased <it>oprD </it>expression was also observed in 69.5% of the whole collection, and in 87.1% of the imipenem non-susceptible <it>P. aeruginosa </it>clinical isolates. The MBL-encoding genes <it>bla</it>_SPM-1and <it>bla</it>_IMP-1were detected in 23.7% and 1.7% <it>P. aeruginosa </it>isolates, respectively. The <it>bla</it>_GES-1was detected in 5.1% of the isolates, while <it>bla</it>_GES-5and <it>bla</it>_CTX-M-2were observed in 1.7% of the isolates evaluated. In the present study, we have observed that efflux systems represent an adjuvant mechanism for antimicrobial resistance.</p> <p>Conclusions</p> <p>Efflux systems in association of distinct mechanisms such as the porin down-regulation, AmpC overproduction and secondary β-lactamases play also an important role in the multi-drug resistance phenotype among <it>P. aeruginosa </it>clinical isolates.</p>