title: Emergence of oxacillinase-mediated resistance to imipenem in Klebsiella pneumoniae.
abstract: Klebsiella pneumoniae strain 11978 was isolated in Turkey in 2001 and was found to be resistant to all beta-lactams, including carbapenems. Cloning and expression in Escherichia coli identified five beta-lactamases, including two novel oxacillinases. The beta-lactamase OXA-48 hydrolyzed imipenem at a high level and was remotely related (less than 46% amino acid identity) to the other oxacillinases. It hydrolyzed penicillins and imipenem but not expanded-spectrum cephalosporins. The bla(OXA-48) gene was plasmid encoded and not associated with an integron, in contrast to most of the oxacillinase genes. An insertion sequence, IS1999, was found immediately upstream of bla(OXA-48). Another plasmid that encoded a second oxacillinase gene, bla(OXA-47), located inside a class 1 integron was identified in K. pneumoniae 11978. OXA-47 had a narrow spectrum of hydrolysis activity and did not hydrolyze ceftazidime or imipenem, as is found for the beta-lactamase (OXA-1) to which it is related. In addition, beta-lactamases TEM-1 and SHV-2a were expressed from the same K. pneumoniae isolate. Analysis of the outer membrane proteins of this isolate revealed that it lacked a porin of ca. 36 kDa. Thus, the high-level resistance to beta-lactams of this clinical isolate resulted from peculiar beta-lactamases and modification of outer membrane proteins.
authors.affiliation: Service de Bactériologie-Virologie, Université Paris XI, Hôpital de Bicêtre, Assistance Publique/Hôpitaux de Paris, Faculté de Médecine Paris-Sud, 94275 Le Kremlin-Bicêtre, France.
authors.forename: Laurent
authors.initials: L
authors.lastname: Poirel
authors.forename: Claire
authors.initials: C
authors.lastname: Héritier
authors.forename: Venus
authors.initials: V
authors.lastname: Tolün
authors.forename: Patrice
authors.initials: P
authors.lastname: Nordmann
mesh_terms: D000595:Amino Acid Sequence; D001425:Bacterial Outer Membrane Proteins / Q000737:chemistry / Q000235:genetics; D001426:Bacterial Proteins / Q000737:chemistry; D002352:Carrier Proteins / Q000302:isolation & purification / Q000378:metabolism*; D003001:Cloning, Molecular; D017931:DNA Primers; D004269:DNA, Bacterial / Q000737:chemistry; D024881:Drug Resistance, Bacterial; D006868:Hydrolysis; D015378:Imipenem / Q000378:metabolism / Q000494:pharmacology*; D007525:Isoelectric Focusing; D007700:Kinetics; D007711:Klebsiella pneumoniae / Q000187:drug effects* / Q000201:enzymology* / Q000235:genetics; D008826:Microbial Sensitivity Tests; D008969:Molecular Sequence Data; D010957:Plasmids / Q000235:genetics; D013845:Thienamycins / Q000378:metabolism / Q000494:pharmacology*; D018440:beta-Lactam Resistance; D001618:beta-Lactamases / Q000302:isolation & purification / Q000378:metabolism*
chemical_list: D001425:Bacterial Outer Membrane Proteins; D001426:Bacterial Proteins; D002352:Carrier Proteins; D017931:DNA Primers; D004269:DNA, Bacterial; D013845:Thienamycins; D015378:Imipenem; D001618:beta-Lactamases; C108449:oxacillinase