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 Details

Date: 16/05/2009
Time: 00:00-00:00
Session name: 19th European Congress of Clinical Microbiology and Infectious Diseases
Location: Helsinki, Finland, 16 - 19 May 2009
Presentation type:
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