Mutational and acquired carbapenem resistance mechanisms in multidrug resistant Pseudomonas aeruginosa clinical isolates from Recife, Brazil.

Felipe Lira De Sá Cavalcanti,Elena Román Paucar,Marcia Maria Camargo De Morais,Luis Martínez-Martínez,Tereza Cristina Leal-Balbino,Laura Álvarez Montes,Alain Antonio Ocampo-Sosa,Cristina Rodríguez Mirones

doi:10.1590/0074-02760150233

Abstract

An investigation was carried out into the genetic mechanisms responsible for multidrug resistance in nine carbapenem-resistant Pseudomonas aeruginosaisolates from different hospitals in Recife, Brazil. Susceptibility to antimicrobial agents was determined by broth microdilution. Polymerase chain reaction (PCR) was employed to detect the presence of genes encoding β-lactamases, aminoglycoside-modifying enzymes (AMEs), 16S rRNA methylases, integron-related genes and OprD. Expression of genes coding for efflux pumps and AmpC cephalosporinase were assessed by quantitative PCR. The outer membrane proteins were separated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The blaSPM-1, blaKPC-2 and blaGES-1 genes were detected in P. aeruginosaisolates in addition to different AME genes. The loss of OprD in nine isolates was mainly due to frameshift mutations, premature stop codons and point mutations. An association of loss of OprD with the overexpression of MexAB-OprM and MexXY-OprM was observed in most isolates. Hyper-production of AmpC was also observed in three isolates. Clonal relationship of the isolates was determined by repetitive element palindromic-PCR and multilocus sequence typing. Our results show that the loss of OprD along with overexpression of efflux pumps and β-lactamase production were responsible for the multidrug resistance in the isolates analysed.

Highlights

The increasing prevalence of multidrug-resistant (MDR) and extensively drug-resistant (XDR) Pseudomonas aeruginosa isolates is severely compromising the selection of appropriate treatments for the infections caused by these organisms and is causing high morbidity and mortality (Poole 2011, Ocampo-Sosa et al 2012)
The carbapenem resistance in P. aeruginosa in Brazil is still often associated with the production of class B β-lactamases; isolates producing class A carbapenemase (KPC) were found in this work
KPC enzymes are almost entirely attributed to enterobacteria, especially Klebsiella pneumoniae and E. coli, these β-lactamases have recently been observed in Pseudomonas spp in America (Villegas et al 2007)

Summary

Introduction

The increasing prevalence of multidrug-resistant (MDR) and extensively drug-resistant (XDR) Pseudomonas aeruginosa isolates is severely compromising the selection of appropriate treatments for the infections caused by these organisms and is causing high morbidity and mortality (Poole 2011, Ocampo-Sosa et al 2012). Overexpression of the MexAB-OprM and MexEF-OprN efflux system and chromosomal cephalosporinase AmpC can lead to carbapenem resistance among P. aeruginosa clinical isolates when associated with other mechanisms (Poole 2011).

Results

Conclusion