Diversity of conjugative blaCTX-M-carrying plasmids from Klebsiella pneumoniae strains in Slovenian hospitals
Abstract number: O306
Mesko Meglic K., Koren S., Livermore D.M., Andlovic A., Jeverica S., Krizan-Hergouth V., Mueller-Premru M., Seme K., Woodford N.
Objectives: Diverse strains of K. pneumoniae with blaCTX-M were noted during a nationwide survey in Slovenia in 2005 and 2006. All had group 1 CTX-M genes, with blaCTX-M-15 identified by sequencing. Efficient in vitro transfer suggested that plasmids carrying blaCTX-M-15 were spreading horizontally in our hospitals and, here, we characterised the plasmids responsible in the major K. pneumoniae strains identified during the survey.
Methods: Plasmids from representative K. pneumoniae strains with CTX-M-15 enzyme were extracted by alkaline lysis and compared by ApaI, PstI and EcoRI restriction analysis. They were transferred into E. coli DH5a by electroporation. Transformants were selected on cefotaxime-containing agar and were screened by PCR for beta-lactamase genes, the aminoglycoside resistance genes aac(6')-Ib and aac3-IIb, and the plasmid-mediated quinolone resistance genes qnrA/B/S.
Results: Twelve isolates were characterised, representing 5 major strains (A-D, and F) found in the most-affected hospitals. Restriction analysis divided their plasmids into several groups. Representatives of strain A (n = 4) had essentially the same plasmid (group 1), as did the two representatives of strain D (group 2a). One strain F isolate had a plasmid (group 2b) very similar to plasmid 2a from strain D, indicating possible horizontal transfer. Plasmids of group 3 were retrieved from representatives of strains B and C, again indicating probable transfer. Plasmids from three other strains differed substantially from each other and from plasmids 1, 2a, 2b and 3. Nevertheless, on all plasmids, blaCTX-M genes were linked to an upstream ISEcp1 element, known to be involved in their mobilisation. All encoded multi-resistance: all but one group 1 and one ungrouped plasmid carried aac(6')-Ib; blaOXA-1 and aac(3)-IIa were detected on all except group 1 plasmids; blaTEM was found on group 1, 2b, one group 3 and two ungrouped plasmids. blaSHV and qnrA/B/S genes were not detected.
Conclusion: The considerable diversity of plasmids encoding CTX-M-15 enzyme in major Slovenian K. pneumoniae strains suggested only limited transfer, even when multiple strains were present in the same hospital. Evidence of plasmid transfer was between strains B and C, and possibly between strains D and F, although these plasmids were not strictly identical. Analysis of resistance genes encoded by the plasmids revealed diversity, with groupings coinciding largely with those based on restriction profiles.
|Session name:||19th European Congress of Clinical Microbiology and Infectious Diseases|
|Location:||Helsinki, Finland, 16 - 19 May 2009|
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