Emergence of Oxacillinase-Mediated Resistance to Imipenem in Klebsiella pneumoniae
AUTOR(ES)
Poirel, Laurent
FONTE
American Society for Microbiology
RESUMO
Klebsiella pneumoniae strain 11978 was isolated in Turkey in 2001 and was found to be resistant to all β-lactams, including carbapenems. Cloning and expression in Escherichia coli identified five β-lactamases, including two novel oxacillinases. The β-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 β-lactamase (OXA-1) to which it is related. In addition, β-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 β-lactams of this clinical isolate resulted from peculiar β-lactamases and modification of outer membrane proteins.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=310167Documentos Relacionados
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