title: Description of IMP-31, a novel metallo-β-lactamase found in an ST235 Pseudomonas aeruginosa strain in Western Germany.
abstract: OBJECTIVE
  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 blaIMP gene was performed by sequencing the PCR products. A phylogenetic tree was constructed. The novel blaIMP 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, blaIMP-31, located on a disrupted class I integron [also carrying the blaOXA-35, aac(6')-Ib, aac(3)-Ic and aphA15 genes]. Its closest relative was IMP-35, with 96.7% amino acid identity. Expression of blaIMP-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 kcat values.
  
  
  CONCLUSIONS
  The characterization of the new IMP-type gene blaIMP-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.
authors.affiliation: Department of Medical Microbiology, Ruhr-University Bochum, Universitätsstraße 150, 44801 Bochum, Germany niels.pfennigwerth@rub.de.
authors.forename: Niels
authors.initials: N
authors.lastname: Pfennigwerth
authors.affiliation: Institute for Medical Laboratory Diagnostics Bochum GmbH, Castroper Straße 45, 44791 Bochum, Germany.
authors.forename: Gabriele
authors.initials: G
authors.lastname: Geis
authors.affiliation: Department of Medical Microbiology, Ruhr-University Bochum, Universitätsstraße 150, 44801 Bochum, Germany.
authors.forename: Sören G
authors.initials: SG
authors.lastname: Gatermann
authors.affiliation: Department of Medical Microbiology, Ruhr-University Bochum, Universitätsstraße 150, 44801 Bochum, Germany.
authors.forename: Martin
authors.initials: M
authors.lastname: Kaase
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D015780:Carbapenems / Q000494:pharmacology*; D016000:Cluster Analysis; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics; D024901:Drug Resistance, Multiple, Bacterial; D005858:Germany; D006801:Humans; D007700:Kinetics; D008826:Microbial Sensitivity Tests; D008969:Molecular Sequence Data; D058885:Multilocus Sequence Typing; D010802:Phylogeny; D011552:Pseudomonas Infections / Q000382:microbiology; D011550:Pseudomonas aeruginosa / Q000145:classification / Q000187:drug effects* / Q000201:enzymology* / Q000302:isolation & purification; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid; D001618:beta-Lactamases / Q000235:genetics* / Q000378:metabolism*
chemical_list: D000900:Anti-Bacterial Agents; D015780:Carbapenems; D004269:DNA, Bacterial; D001618:beta-Lactamases
keywords: MBLs; carbapenemases; enzyme kinetics; integrons