Genetic diversity of metallo-b-lactamases produced by carbapenem-resistant Pseudomonas aeruginosa

Abstract number: R2285

Rizk N., Zaki S.

Objectives: To investigate the prevalence of metallo-b-lactamases (MBLs) among clinical isolates of carbapenem resistant (CR) Pseudomonas aeruginosa (P. aeruginosa), and to characterize their molecular types.

Methods: A total of 134 non-repetitive clinical isolates of P. aeruginosa were collected and tested for carbapenem resistance by disk diffusion method with imipenem and meropenem. Minimum inhibitory concentrations (MICs) were determined by the microdilution technique according to CLSI guidelines. CR isolates were screened for the presence of MBLs by imipenem EDTA double disk synergy test. Isolates with screen positive results were confirmed by EDTA inhibition of imipenem hydrolysis with their crude cell extracts, and by PCR using primers for detection of bla IMP-1, bla IMP-2, bla VIM-1, bla VIM-2, bla SPM-1, and intI1 genes.

Results: Of the total 134 P. aeruginosa clinical isolates included in this study, 75(56%) isolates were CR, among them, MBL phenotype was detected in 30(40%) isolates by the double disk synergy test. EDTA sensitive hydrolysis of imipenem by crude cell extracts confirmed 14 (46.7%) isolates as MBL producers. PCR detected MBL genes among 15 (50%) isolates; 11(733%) isolates were positive for bla VIM-2, and 4(26.7%) isolates were positive for bla IMP-1. The integrase gene (intI1) was detected in all of the 15 genotypically MBL producing isolates. No isolate harbouring bla VIM-1, bla IMP-2, or bla SPM-1 was detected.

Conclusion: Continued screening for MBLs production among CR P. aeruginosa isolates will be essential to control dissemination by this important resistant mechanism, ensure optimal patient care, and the timely introduction of appropriate infection control procedures. PCR is an important step, since EDTA based screening tests can give false positive results.

Session Details

Date: 19/04/2008
Time: 00:00-00:00
Session name: 18th European Congress of Clinical Microbiology and Infectious Diseases
Location: Barcelona, Spain
Presentation type:
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