Genetic analysis of metallo-beta-lactamase producing Klebsiella pneumoniae and Pseudomonas aeruginosa isolates in the intensive care unit of a university general hospital in Greece

Abstract number: p1413

Koratzanis  E., Galani  I., Souli  M., Chryssouli  Z., Giamarellou  H.


During a study for the evolution and horizontal transfer of metallo-B-lactamase(MBL) genes from commensal to pathogenic gram-negative bacteria in patients of an intensive care unit of a tertiary care university hospital, we analysed the integrons carrying the MBL gene in K. pneumoniae and P. aeruginosa isolates.


Isolates from surveillance cultures as well as isolates considered pathogenic from the same patient that exhibited a positive EDTA-imipenem disk synergy test were studied. Susceptibility testing was performed by the disk diffusion technique and MICs were determined by the broth microdilution method according to NCCLS guidelines. EDTA-disc synergy test, was used to screen for MBL production. PCR and PCR-RFLP analysis and Southern hybridization were used to identify and analyse the blaVIM-containing integrons.


All isolates exhibited reduced susceptibility or resistance to imipenem (0.5–>8 mg/ml) and a positive EDTA-synergy test. Strains were resistant to ceftazidime, ceftriaxone and cefotaxime. Class I integrons associated with VIM-type MBL genes were found in all strains. Preliminary PCR-based experiments and RFLP analysis revealed the presence of 5 different integrons (1500–5500 bp) carrying blaVIM-1 in K. pneumoniae isolates. The predominant type is that of 1500 bp probably corresponding to an integron containing only blaVIM-1 gene cassette. A new integron containing blaVIM-1 and aac (6´)-IIc that has been characterized by our group in an Enterobacter cloacae clinical isolate was also found in a K. pneumoniae isolate. Interestingly, the same patient was also colonized by a Citrobacter freundii carrying the same integron. PCR and Southern hybridization revealed the presence of 2 integrons (both >2 kb) carrying blaVIM-2 in all of the P. aeruginosa isolates. The size and RFLP analysis revealed no similarities between the integrons of P. aeruginosa and those of K. pneumoniae.


MBLs of the VIM-type represent an emerging threat in Greek hospitals. All isolates of our study harboured blaVIM-1 (K. pneumoniae) or blaVIM-2 (P. aeruginosa), in class I integrons. We observed: 1) the diversity of blaVIM-1 containing integrons in different K. pneumoniae isolates of the same patient and the integration of the same class I integrons in K. pneumoniae nosocomial isolates of different patients and 2) no similarities of VIM-containing integrons from P. aeruginosa and K. pneumoniae isolates even those isolated from the same patient.

Session Details

Date: 01/08/2007
Time: 00:00-00:00
Session name: XXIst ISTH Congress
Location: Oxford, UK
Presentation type:
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