Abstract

COMPARISON BETWEEN PHENOTYPIC AND GENOTYPIC METHODS FOR THE DETECTION OF METALLO BETA LACTAMASES PRODUCING PSEUDOMONAS AERUGINOSA

Prof. Eman A. E. Abushady*, Asmaa M. M. Elgendy, Sabah M.M. Alkhawagah, Haneya A.A. Ali

ABSTRACT

Background: Pseudomonas aeruginosa is a frequent nosocomial pathogen that causes severe diseases in many settings. Carbapenem resistance may be conferred through various mechanisms, including the expression of carbapenemases. MBLs constitute the most clinically important group of carbapenemases, rapid and specific detection of the MBLs is crucial for the optimum treatment and control the spread of resistance. The aim of this study: was to compare between phenotypic and genotypic methods for the detection of MBLs-producing P. aeruginosa and to evaluate MBL E-test in comparison with MBLs-gene detection by PCR. Subjects and Methods: fifty P. aeruginosa isolates were collected from 138 patients in the intensive care units, different wards and outpatients. MBLs producing P. aeruginosa were identified based on conventional methods and antimicrobial
susceptibility testing, MBL E-test, IPM-EDTA combined disk method and IPM-EDTA double disk synergy test in addition to detection of blaVIM-2 and blaIMP-7 genes by PCR. Results: 40% of P. aeruginosa isolates were resistant to ceftazidime, 30% of them were resistant to carbapenems and 10% were susceptible. Eleven isolates were MBL-VIM-2 positive by PCR. Eight of them were resistant to carbapenems and ceftazidime and detected phenotypically as MBL-producers. All P. aeruginosa isolates were negative for blaIMP-7 gene. Eight isolates were positive by MBL E-test, ten by IPM- EDTA combined disk method and three by IPM-EDTA double disk synergy test. Conclusion: MBL E-test is a fast and accurate test for detection of MBL-production among the resistant strains, while PCR is useful in prevention of horizontal interspecies spread of hidden MBLs.

Keywords: P. aeruginosa, metallo-beta-lactamases, phenotypic and genotypic methods.