Overproduction of active efflux pump and variations of OprD dominate in imipenem-resistant Pseudomonas aeruginosa isolated from patients with bloodstream infections in Taiwan.

Cheng-Yen Kao,Kuei-Hsiang Hung,Po-Ren Hsueh,Shu-Sheng Chen,Jiunn-Jong Wu,Hsiu-Mei Wu,Jing-Jou Yan

doi:10.1186/s12866-016-0719-2

Abstract

BackgroundThe emergence of imipenem-resistant Pseudomonas aeruginosa (IRPA) has become a great concern worldwide. The aim of this study was to investigate resistance mechanisms associated with bloodstream isolated IRPA strains in Taiwan.ResultsA total of 78 non-duplicated IRPA isolates were isolated from patients with bloodstream infection. The average prevalence of imipenem-resistance in those isolates was 5.9 % during a 10-year longitudinal surveillance in Taiwan. PFGE results showed high clonal diversity among the 78 isolates. VIM-2, VIM-3, OXA-10, and OXA-17 β-lactamases were identified in 2 (2.6 %), 3 (3.8 %), 2 (2.6 %), and 1 (1.3 %) isolates, respectively. Active efflux pumps, AmpC β-lactamase overproduction, and extended-spectrum AmpC cephalosporinases (ESACs) were found in 58 (74.4 %), 25 (32.1 %) and 15 (19.2 %) of IRPA isolates, respectively. oprD mutations with amino acid substitution, shortened putative loop L7, premature stop codon caused by point mutation, frameshift by nucleotide insertion or deletion, and interruption by insertion sequence were found in 19 (24.4 %), 18 (23.1 %), 15 (19.2 %), 14 (17.9 %), and 10 (12.8 %) of isolates, respectively.ConclusionsThis study suggests that alterations in the OprD protein and having an active efflux pump are the main mechanisms associated with bloodstream isolated IRPA. Overproduction of AmpC, ESACs, and the presence of VIM- and OXA-type β-lactamases play additional roles in reduced susceptibility to imipenem in P. aeruginosa isolates in Taiwan.Electronic supplementary materialThe online version of this article (doi:10.1186/s12866-016-0719-2) contains supplementary material, which is available to authorized users.

Highlights

The emergence of imipenem-resistant Pseudomonas aeruginosa (IRPA) has become a great concern worldwide
Long-term surveillance and antimicrobial susceptibility of IRPA Based on the large scale screening of bacteremic P. aeruginosa isolates, 5.9 % of isolates appeared to be resistant to imipenem
All isolates were resistant to imipenem but 2 (2.6 %) and 3 (3.8 %) isolates were susceptible to meropenem and Minimal inhibitory concentration (MIC)

Summary

Introduction

The emergence of imipenem-resistant Pseudomonas aeruginosa (IRPA) has become a great concern worldwide. Pseudomonas aeruginosa is one of the most important nosocomial pathogens, which colonizes patients with trauma or a breach by tracheostomy, catheters, surgery, or severe burns. It is the major cause of chronic. Surveillance of antimicrobial susceptibility by the European Centre for Disease Prevention and Control reported that the average rate of resistance of P. aeruginosa against carbapenems was 17.1 % [11]. ESACs confer reduced susceptibility to cephalosporins and carbapenems [15, 16]

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