GPC-1, a novel class A carbapenemase detected in a clinical Pseudomonas aeruginosa isolate.

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GPC-1, a novel class A carbapenemase detected in a clinical Pseudomonas aeruginosa isolate.

J Antimicrob Chemother. 2020 Jan 20;:

Authors: Schauer J, Gatermann SG, Hoffmann D, Hupfeld L, Pfennigwerth N

Abstract
OBJECTIVES: To investigate the carbapenem resistance mechanism of a carbapenem-resistant clinical Pseudomonas aeruginosa isolate.
METHODS: A carbapenem-resistant P. aeruginosa isolate was recovered from a tracheal swab from a patient of a general ward in central Germany. Various phenotypic tests confirmed production of a carbapenemase that could not be identified further by PCR. A novel bla gene was identified by WGS and its carbapenemase activity was verified by heterologous expression in an Escherichia coli cloning strain. Kinetic parameters of the novel β-lactamase were determined by spectrophotometric measurements using purified enzyme.
RESULTS: WGS confirmed the presence of a novel class A carbapenemase. The novel bla gene was named GPC-1 (GPC standing for German Pseudomonas Carbapenemase) and exhibited 77% amino acid identity to BKC-1. WGS also showed that blaGPC-1 was located on the chromosome surrounded by multiple ISs as part of a 26 kb genetic island. Heterologous expression of GPC-1 in E. coli TOP10 led to increased MICs of penicillins, oxyimino-cephalosporins, aztreonam and imipenem, but not of meropenem or ertapenem. Spectrophotometric measurements supported the MIC studies, but detected a slight hydrolysis of ertapenem and meropenem when using high concentrations of purified enzyme.
CONCLUSIONS: The biochemical characterization of GPC-1 emphasizes the ongoing emergence of novel carbapenemases. Strains expressing a weak carbapenemase like GPC-1 might go unrecognized by routine diagnostics due to low MICs for the bacterial strains producing such enzymes.

PMID: 31960033 [PubMed - as supplied by publisher]