Description of IMP-31, a novel metallo-β-lactamase found in an ST235 Pseudomonas aeruginosa strain in Western Germany. (2nd April 2015)

• Record Type: Journal Article
• Authors: Pfennigwerth, Niels; Geis, Gabriele; Gatermann, Sören G.; Kaase, Martin
• Is Part Of: Journal of antimicrobial chemotherapy. Volume 70:Number 7(2015:Jul.)
• Page Start: 1973
• Page End: 1980
• Publication Date: 2015-04-02
• Subjects: carbapenemases -- MBLs -- integrons -- enzyme kinetics; Anti-infective agents -- Periodicals; Chemotherapy -- Periodicals; 615.58
• DOI: 10.1093/jac/dkv079
• Languages: English
• ISSNs: 0305-7453

Abstract

Abstract: Objectives: The objective of this study was to characterize a novel IMP-type metallo-β-lactamase (MBL) found in an MDR clinical isolate of Pseudomonas aeruginosa . Methods: The P. aeruginosa isolate NRZ-00156 was recovered from an inguinal swab from a patient hospitalized in Western Germany and showed high MICs of carbapenems. MBL production was analysed by Etest for MBLs, an EDTA combined disc test and an EDTA bioassay. Typing of the isolate was performed by MLST. Genetic characterization of the new bla IMP gene was performed by sequencing the PCR products. A phylogenetic tree was constructed. The novel bla IMP gene was expressed in Escherichia coli TOP10 and the enzyme was subjected to biochemical characterization. Results: The P. aeruginosa isolate NRZ-00156 expressed the ST235 allelic profile and was resistant to all the β-lactams tested except aztreonam. The isolate was positive for MBL production and harboured a new IMP allele, bla IMP-31, located on a disrupted class I integron [also carrying the bla OXA-35, aac(6′)-Ib, aac(3)-Ic and aphA15 genes]. Its closest relative was IMP-35, with 96.7% amino acid identity. Expression of bla IMP-31 demonstrated that E. coli TOP10 producing IMP-31 had elevated resistance to all the β-lactams tested except aztreonam. Kinetic data were obtained for both IMP-31 and IMP-1. In comparison with IMP-1, IMP-31 showed weaker hydrolytic activity against all the β-lactams tested, which resulted from lower k cat values. Conclusions: The characterization of the new IMP-type gene bla IMP-31 from an ST235 P. aeruginosa isolate indicates an ongoing spread of highly divergent IMP-type carbapenemases in clinical P. aeruginosa strains and highlights the continuous need for the prevention of nosocomial infections caused by MDR Gram-negative bacteria.