RT Journal Article SR Electronic T1 Genetic Structures at the Origin of Acquisition of the β-Lactamase blaKPC Gene JF Antimicrobial Agents and Chemotherapy JO Antimicrob. Agents Chemother. FD American Society for Microbiology SP 1257 OP 1263 DO 10.1128/AAC.01451-07 VO 52 IS 4 A1 Naas, Thierry A1 Cuzon, Gaelle A1 Villegas, Maria-Virginia A1 Lartigue, Marie-Frédérique A1 Quinn, John P. A1 Nordmann, Patrice YR 2008 UL http://aac.asm.org/content/52/4/1257.abstract AB Genetic structures surrounding the carbapenem-hydrolyzing Ambler class A blaKPC gene were characterized in several KPC-positive Klebsiella pneumoniae and Pseudomonas aeruginosa strains isolated from the United States, Colombia, and Greece. The blaKPC genes were associated in all cases with transposon-related structures. In the K. pneumoniae YC isolate from the United States, the β-lactamase blaKPC-2 gene was located on a novel Tn3-based transposon, Tn4401. Tn4401 was 10 kb in size, was delimited by two 39-bp imperfect inverted repeat sequences, and harbored, in addition to the β-lactamase blaKPC-2 gene, a transposase gene, a resolvase gene, and two novel insertion sequences, ISKpn6 and ISKpn7. Tn4401 has been identified in all isolates. However, two isoforms of this transposon were found: Tn4401a was found in K. pneumoniae YC and K. pneumoniae GR from the United States and Greece, respectively, and differed by a 100-bp deletion, located just upstream of the blaKPC-2 gene, compared to the sequence of Tn4401b, which was found in the Colombian isolates. In all isolates tested, Tn4401 was flanked by a 5-bp target site duplication, the signature of a recent transposition event, and was inserted in different open reading frames located on plasmids that varied in size and nature. Tn4401 is likely at the origin of carbapenem-hydrolyzing β-lactamase KPC mobilization to plasmids and its further insertion into various-sized plasmids identified in nonclonally related K. pneumoniae and P. aeruginosa isolates.