Molecular characterization of a beta-lactamase gene, blaGIM-1, encoding a new subclass of metallo-beta-lactamase.
As part of the SENTRY Antimicrobial Surveillance Program in 2002, five multidrug-resistant Pseudomonas aeruginosa clinical isolates were detected with metallo-beta-lactamase (MbetaL) activity. The isolates were recovered from different patients in a medical center located in Dusseldorf, Germany. The resistant determinant was isolated amplifying the region between the integrase and the aacA4 gene cassette. Sequencing revealed a novel MbetaL gene, designated bla(GIM-1). Additional analysis showed that GIM-1, comprising 250 amino acids and with a pI value of 5.4, differs in its primary sequence from that described for IMP, VIM, and SPM-1 enzymes by 39 to 43%, 28 to 31%, and 28%, respectively. The enzyme possesses unique amino acids within the major consensus sequence (HXHXD) of the MbetaL family. Kinetics analysis revealed that GIM-1 has no clear preference for any substrate and did not hydrolyze azlocillin, aztreonam, and the serine-beta-lactamase inhibitors. bla(GIM-1) was found on a 22-kb nontransferable plasmid. The new MbetaL gene was embedded in the first position of a 6-kb class 1 integron, In77, with distinct features, including an aacA4 cassette downstream of the MbetaL gene that appeared to be truncated with bla(GIM-1). The aacA4 was followed by an aadA1 gene cassette that was interrupted by a copy of the IS1394. This integron also carried an oxacillinase gene, bla(OXA-2), before the 3'-CS region. GIM-1 appears to be a unique MbetaL, which is located in a distinct integron structure, and represents the fourth subclass of mobile MbetaL enzymes to be characterized.
Castanheira
Mariana
M
Disciplina de Doencas Infecciosas e Parasitarias, Universidade FEderal de Sao Paulo, Brazil. maricastanh@yahoo.com
Toleman
Mark A
MA
Jones
Ronald N
RN
Schmidt
Franz J
FJ
Walsh
Timothy R
TR
D000595:Amino Acid Sequence; D015780:Carbapenems / Q000494:pharmacology; D017931:DNA Primers; D004269:DNA, Bacterial / Q000235:genetics; D024881:Drug Resistance, Bacterial; D004587:Electrophoresis, Agar Gel; D016521:Electrophoresis, Gel, Pulsed-Field; D005798:Genes, Bacterial / Q000235:genetics; D032023:Integrons / Q000235:genetics; D007525:Isoelectric Focusing; D007700:Kinetics; D008826:Microbial Sensitivity Tests; D008969:Molecular Sequence Data; D010641:Phenotype; D011550:Pseudomonas aeruginosa / Q000187:drug effects / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D001618:beta-Lactamases / Q000235:genetics*
D015780:Carbapenems; D017931:DNA Primers; D004269:DNA, Bacterial; D001618:beta-Lactamases; C495217:beta-lactamase GIM-1, Pseudomonas aeruginosa