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Antimicrobial Agents and Chemotherapy, January 2004, p. 15-22, Vol. 48, No. 1
0066-4804/04/$08.00+0     DOI: 10.1128/AAC.48.1.15-22.2004
Copyright © 2004, American Society for Microbiology. All Rights Reserved.

Emergence of Oxacillinase-Mediated Resistance to Imipenem in Klebsiella pneumoniae

Laurent Poirel,1 Claire Héritier,1 Venus Tolün,2 and Patrice Nordmann1*

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,1 Department of Microbiology, Istanbul Medical Faculty, Capa, Istanbul, Turkey2

Received 20 March 2003/ Returned for modification 7 July 2003/ Accepted 22 September 2003

Klebsiella pneumoniae strain 11978 was isolated in Turkey in 2001 and was found to be resistant to all ß-lactams, including carbapenems. Cloning and expression in Escherichia coli identified five ß-lactamases, including two novel oxacillinases. The ß-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 blaOXA-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 blaOXA-48. Another plasmid that encoded a second oxacillinase gene, blaOXA-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 ß-lactamase (OXA-1) to which it is related. In addition, ß-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 ß-lactams of this clinical isolate resulted from peculiar ß-lactamases and modification of outer membrane proteins.

* Corresponding author. Mailing address: Service de Bactériologie-Virologie, Hôpital de Bicêtre, 78 rue du Général Leclerc, 94275 Le Kremlin-Bicêtre cedex, France. Phone: 33-1-45-21-36-32. Fax: 33-1-45-21-63-40. E-mail: nordmann.patrice{at}bct.ap-hop-paris.fr.

Antimicrobial Agents and Chemotherapy, January 2004, p. 15-22, Vol. 48, No. 1
0066-4804/04/$08.00+0     DOI: 10.1128/AAC.48.1.15-22.2004
Copyright © 2004, American Society for Microbiology. All Rights Reserved.



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