Rapid Detection of Carbapenem Resistance in Acinetobacter baumannii Using Matrix-Assisted Laser Desorption Ionization-Time of Flight Mass Spectrometry

Marie Kempf,Meryem Berrazeg,Jean-Michel Brunel,Sofiane Bakour,Abdelaziz Touati,Esma Mesli,Jean-Marc Rolain,Mourad Drissi,Christophe Flaudrops,Stefan Bereswill

doi:10.1371/journal.pone.0031676

Abstract

Rapid detection of carbapenem-resistant Acinetobacter baumannii strains is critical and will benefit patient care by optimizing antibiotic therapies and preventing outbreaks. Herein we describe the development and successful application of a mass spectrometry profile generated by matrix-assisted laser desorption ionization-time of flight (MALDI-TOF) that utilized the imipenem antibiotic for the detection of carbapenem resistance in a large series of A. baumannii clinical isolates from France and Algeria. A total of 106 A. baumannii strains including 63 well-characterized carbapenemase-producing and 43 non-carbapenemase-producing strains, as well as 43 control strains (7 carbapenem-resistant and 36 carbapenem-sensitive strains) were studied. After an incubation of bacteria with imipenem for up to 4 h, the mixture was centrifuged and the supernatant analyzed by MALDI-TOF MS. The presence and absence of peaks representing imipenem and its natural metabolite was analyzed. The result was interpreted as positive for carbapenemase production if the specific peak for imipenem at 300.0 m/z disappeared during the incubation time and if the peak of the natural metabolite at 254.0 m/z increased as measured by the area under the curves leading to a ratio between the peak for imipenem and its metabolite being <0.5. This assay, which was applied to the large series of A. baumannii clinical isolates, showed a sensitivity of 100.0% and a specificity of 100.0%. Our study is the first to demonstrate that this quick and simple assay can be used as a routine tool as a point-of-care method for the identification of A. baumannii carbapenemase-producers in an effort to prevent outbreaks and the spread of uncontrollable superbugs.

Highlights

Carbapenems, the most common of which are imipenem and meropenem, are among the drugs of choice for the treatment of nosocomial infections due to Acinetobacter baumannii [1]
The MALDI-TOF MS system was used for the detection of carbapenemase activity in a large collection of A. baumannii strains isolated in France and Algeria
The direct detection of carbapenemase activity using similar approaches involving MALDI-TOF was recently reported in two studies of P. aeruginosa and Enterobacteriaceae [16,17], but to our knowledge, this was the first time that the direct detection of carbapenemase activity was developed using imipenem as the carbapenem compound and including a large collection of A. baumannii clinical isolates and other bacterial strains

Summary

Introduction

Carbapenems, the most common of which are imipenem and meropenem, are among the drugs of choice for the treatment of nosocomial infections due to Acinetobacter baumannii [1] Their efficacies are increasingly becoming compromised because of the worldwide emergence of resistant isolates [2,3,4]. For A. baumannii, carbapenem resistance is principally mediated by the production of oxacillinases, mainly the blaOXA-23-like, blaOXA-24-like and blaOXA-58-like gene products [7,8,9,10,11,12,13]. Each of these enzymes is able to hydrolyze the amide bond of the b-lactam ring of carbapenems [6]. PCR-based methods remain the optimal tool for the identification of OXA-type carbapenemases, but the main disadvantages of such technologies include cost, the requirement for trained personal, and the inability to detect novel carbapenemase genes [15]

Methods

Results

Conclusion