JAC Advance Access originally published online on November 13, 2007
Journal of Antimicrobial Chemotherapy 2008 61(1):59-63; doi:10.1093/jac/dkm443
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Original research |
Ongoing epidemic of blaVIM-1-positive Klebsiella pneumoniae in Athens, Greece: a prospective survey
1 First Department of Propaedeutic Medicine, Medical School, University of Athens, Athens, Greece 2 Department of Microbiology, Medical School, University of Athens, Athens, Greece 3 Department of Microbiology, Laikon General Hospital, Athens, Greece 4 Department of Microbiology, Evangelismos General Hospital, Athens, Greece 5 Department of Microbiology, Hippokration General Hospital, Athens, Greece
Received 25 July 2007; returned 29 August 2007; revised 15 October 2007; accepted 19 October 2007
* Corresponding author. Tel: +30-210-7462152; Fax: +30-210-7462010; E-mail: ltzouvel{at}cc.uoa.gr
Objectives: To determine the current frequency and study the characteristics of VIM-1-producing Klebsiella pneumoniae isolates from bloodstream infections in Greek hospitals.
Methods: All blood isolates of K. pneumoniae were prospectively collected during 2004–06 in three teaching hospitals located in Athens. MICs of antibiotics were determined by the Etest. Extended-spectrum- (ESBL) and metallo-β-lactamase (MBL) production was examined by clavulanate- and EDTA-based techniques, respectively. Isolates were typed by PFGE of XbaI-digested genomic DNA. Detection of blaVIM-1 and mapping of the VIM-1-encoding integrons were performed by PCR and sequencing.β-Lactamase activities were analysed by IEF and imipenem hydrolysis was assessed by spectrophotometry. VIM-1-encoding plasmids were transferred to Escherichia coli by conjugation and transformation and characterized by Inc/rep typing and RFLP.
Results: Sixty-seven (37.6%) of 178 K. pneumoniae blood isolates were blaVIM-1-positive (VPKP); 77.8% of these were from ICUs. All VPKP isolates were multidrug-resistant. The MICs of carbapenems for VPKP varied from the susceptible range to high-level resistance overlapping with those of MBL-negative isolates. The EDTA-imipenem synergy methods had reduced sensitivity in detecting VPKP isolates when the MICs were in the susceptible range. ESBL production was common among VPKP isolates (n = 45, 67.2%) as indicated by resistance to aztreonam and confirmed by a clavulanate-based double-disc synergy test. The responsible ESBL was always an SHV-5-type enzyme as indicated by IEF. PFGE identified eight clusters (A–H) of VPKP isolates with related (>80%) patterns, as well as four unique types. Both inter-hospital spread of several clones and genotypic similarities among susceptible, ESBL-positive and VPKP isolates were also observed. Location of blaVIM-1 and expression of VIM-1 were studied in 12 isolates representing the eight PFGE clusters. In all isolates, blaVIM-1 was part of a class 1 integron that also carried aacA4, dhfrI, aadA and sulI. In eight isolates (clusters C, D, G and H), the blaVIM-1 integron was located in transferable IncN plasmids. A cluster F isolate carried a VIM-1-encoding, self-transferable plasmid that was not typeable by Inc/rep typing. VIM-1-encodingreplicons were not identified in three isolates (PFGE clusters A, B and E). VPKP isolates exhibited differences in imipenem-hydrolysing activities which, however, were not correlated with the respective carbapenem MICs.
Conclusions: A multiclonal epidemic of blaVIM-1-carrying K. pneumoniae is under way in the majorhospitals in Greece. Microorganisms producing both VIM-1 and SHV-5 constitute the prevalent multidrug-resistant population of K. pneumoniae in this setting.
Keywords: K. pneumoniae , carbapenem resistance , metallo-β-lactamases