Genetic organisation of transposase regions surrounding blaKPC carbapenemase genes on plasmids from K. pneumoniae and E. cloacae
Abstract number: P2009
Gootz T., Lescoe M.K., Dougherty B., Dib-Hajj F.
Objectives: We previously described several carbapenem-resistant (CR) K. pneumoniae from the NY-Presbyterian Hospital in NYC encoding KPC carbapenemases. Such strains are spreading to other regions of the US, South America, and the Middle East. We have determined the sequence of the flanking regions adjacent to the blaKPC and transposon genes of K. pneumoniae and E. cloacae isolates to better elucidate the mechanism of kpc transfer in these isolates.
Methods: Plasmids encoding the blaKPC gene were isolated from several CR isolates using high speed Maxi kits and characterised by standard restriction enzyme analysis. Plasmids (65 to 78 Kb) from non-clonal strains (PFGE) were purified and submitted for total DNA sequencing.
Results: Comparison of two plasmids from CR isolates revealed a conserved 10 kb region representing a probable mobile element of high G+C content (~62%). The region contains genes for three transposases and two transposase-associated proteins, the blaKPC, and a 67% G+C XerC-like recombinase gene that is often part of integrative and conjugative elements (ICE elements). The genetic environment of the element containing blaKPC-3 in the E. cloacae isolate indicated insertion adjacent to DNA containing a disrupted copy of a Tn3 transposase with nearly 100% identity to a penicillin resistance associated Haemophilus influenzae ICE element and, further downstream, plasmid conjugal transfer and transposase genes. A tnpR resolvase gene and the aad4 was located 11,000 bp upstream of blaKPC3. Further sequencing of the E. cloacae plasmid indicated the presence of a class I integron, but the blaKPC and flanking transposase genes did not appear to be part of this structure. Characterisation of the second plasmid from a CR K. pneumoniae encoding bla KPC-2 revealed an identical 10 kb region, but in this case the element disrupted a maturase gene from a group II self-splicing intron.
Conclusion: Endemic outbreaks of CR K. pneumoniae encoding KPC carbapenemases in NYC hospitals has become more common and this resistance gene is now found in many other species of Enterobacteriaceae and in Pseudomonas aeruginosa in several other parts of the world. Our data agree with previous studies indicating that portions of transposase genes flank the kpc structural genes located in plasmids from K. pneumoniae. In addition, we have found that some of these transposase genes are intact and in some cases may be part of more complex genetic elements.
|Session name:||18th European Congress of Clinical Microbiology and Infectious Diseases|
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