Genetic structures at the origin of acquisition of the b-lactamase blaKPC gene

Abstract number: P2010

Naas T., Cuzon G., Villegas M.V., Lartigue M.F., Quinn J., Nordmann P.

Objectives: Emergence and dissemination of Enterobacteriaceae isolates harbouring carbapenemases is a significant threat to the management of nosocomial infections. The Ambler class A carbapenem-hydrolysing KPC b-lactamase, which hydrolyse all b-lactams except cephamycins, are increasingly reported in enterobacterial species, mostly in Klebsiella pneumoniae initially from the US (especially from New York City hospitals) but also from other countries from different continents, other enterobacterial species or from Pseudomonas aeruginosa. The aim of this work was to investigate the molecular determinants for this rapid spread.

Methods: Genetic structures surrounding the carbapenem-hydrolysing Ambler class A blaKPC gene were characterised by cloning, PCR analysis and sequencing in several KPC-positive K. pneumoniae and P. aeruginosa isolated from the US, Colombia and Greece. The strains were analysed for their DNA content (genomic or plasmid) by plasmid extraction, conjugation and electroporation assays.

Results: The blaKPC genes were associated with transposon-related structures. In K. pneumoniae YC isolate from the US, the b-lactamase blaKPC-2 gene was located on a novel Tn3-based transposon, Tn4401. Tn4401 was 10 kb in size, delimited by two 39-bp imperfect inverted repeat sequences, and harboured in addition to the b-lactamase blaKPC-2 gene, a transposase and a resolvase gene, and two novel insertion sequences, ISKpn6 and ISKpn7. Tn4401 has been identified in all isolates. Two isoforms of this transposon were found, Tn4401a found in K. pneumoniae YC and K. pneumoniae GR, from the US and Greece, respectively differed by a 100-bp deletion, located just upstream of the blaKPC-2 gene, as compared to Tn4401b found in the Colombian isolates. In all tested isolates, Tn4401 was flanked by a 5-bp target site duplication, signature of a recent transposition event, and was inserted in different ORFs located on plasmids varying in size and nature.

Conclusion: Tn4401 is likely at the origin of the carbapenem-hydrolysing b-lactamase KPC mobilisation to plasmids and its further spread to various sised plasmids identified in non-clonally related K. pneumoniae and P. aeruginosa isolates.

Session Details

Date: 19/04/2008
Time: 00:00-00:00
Session name: 18th European Congress of Clinical Microbiology and Infectious Diseases
Location: Barcelona, Spain
Presentation type:
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