Usefulness of phenotypic and genotypic methods for metallo-beta-lactamases detection in carbapenem-resistant Acinetobacter baumannii strains
Aleksandra Szejbach, Agnieszka Mikucka, Tomasz Bogiel, Eugenia Gospodarek
Med Sci Monit Basic Res 2013; 19:32-36
Background: Acinetobacter baumannii is an opportunistic microorganism with an increasing role in nosocomial outbreaks. For the last 2 decades, a growing number of carbapenem-resistant A. baumannii strains have been identified, including the metallo-beta-lactamases (MBLs) producers. The study aimed to investigate the genetic relatedness of, and MBLs production among, a collection of A. baumannii isolates from Poland.
Material/Methods: This study involved 78 clinical isolates of carbapenem-resistant A. baumannii. Strain typing of the isolates was performed using PCR-RAPD. The presence of MBLs was phenotypically determined using different double disc synergy tests (DDST), the imipenem/EDTA combination disk test (CDT) and Etest MBL. blaIMP and blaVIM genes were detected using a duplex PCR assay.
Results: The isolates were divided into 18 PCR-RAPD patterns. Among 18 examined isolates, 94.4% were MBL-positive by the phenotypic method relying on comparing the bacteria growth inhibition zones diameters between imipenem/EDTA and imipenem discs, 88.9% using Etest MBL, 66.7% using the double disc synergy test with ceftazidime, imipenem, meropenem and EDTA, and 88.9% using a corresponding method with 2-MPA. The existence of blaIMP was identified in 8 (10.3%) strains.
Conclusions: MBLs production was an important mechanism of carbapenem resistance among A. baumannii isolates in Poland. Laboratories should routinely screen for MBLs among A. baumannii isolates.
Keywords: Poland, Phenotype, Metals - metabolism, Genotyping Techniques - methods, Drug Resistance, Bacterial - genetics, Carbapenems - pharmacology, Acinetobacter baumannii - isolation & purification, Random Amplified Polymorphic DNA Technique, beta-Lactamases - genetics