Efflux pumps expression and its association with porin down-regulation and [beta]-lactamase production among Pseudomonas aeruginosa causing bloodstream infections in Brazil

• Published in: BMC microbiology Vol. 10; pp. 217 - 433
• Main Authors: Xavier, Danilo E, Picão, Renata C, Girardello, Raquel, Fehlberg, Lorena CC, Gales, Ana C
• Format: Journal Article
• Language: English
• Published: BioMed Central Ltd 12.08.2010
• Subjects: Analysis; Beta lactamases; Cross infection; Drug resistance in microorganisms; Health aspects; Nosocomial infections; Porins; Risk factors
• ISSN: 1471-2180; 1471-2180
• DOI: 10.1186/1471-2180-10-217

Multi-drug efflux pumps have been increasingly recognized as a major component of resistance in P. aeruginosa. We have investigated the expression level of efflux systems among clinical isolates of P. aeruginosa, regardless of their antimicrobial susceptibility profile. Aztreonam exhibited the highest in vitro activity against the P. aeruginosa 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 [beta]-lactamase was overexpressed in 11.9% of P. aeruginosa isolates. In addition, decreased oprD expression was also observed in 69.5% of the whole collection, and in 87.1% of the imipenem non-susceptible P. aeruginosa clinical isolates. The MBL-encoding genes bla.sub.SPM-1 and bla.sub.IMP-1 were detected in 23.7% and 1.7% P. aeruginosa isolates, respectively. The bla.sub.GES-1 was detected in 5.1% of the isolates, while bla.sub.GES-5 and bla.sub.CTX-M-2 were 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. Efflux systems in association of distinct mechanisms such as the porin down-regulation, AmpC overproduction and secondary [beta]-lactamases play also an important role in the multi-drug resistance phenotype among P. aeruginosa clinical isolates.