engleski

Extended-spectrum beta-lactamases in clinical isolates of Klebsiella pneumoniae from Zagreb, Croatia

Forty clinical isolates of Klebsiella pneumoniae, from various clinical specimens, with reduced susceptibility to ceftazidime, were tested for extended-spectrum beta-lactamase (ESBL) production. ESBL production was demonstrated by 8 - fold reduction in MIC of ceftazidime combined with clavulanate (2 mg/L) compared to ceftazidime alone in all strains. The aim of the investigation was the biochemical and molecular characterization of the ESBL produced by K. pneumoniae strains and their Escherichia coli transconjugants. Transfer of ceftazidime resistance was demonstrated in 23 of 40 strains. Thirteen strains produced an extended spectrum beta-lactamase with the isoelectric point of 8.2 which was encoded by a selftransferable multiresistance plasmid of 150 kb. The substrate profile was similar to that of the SHV-5 isolated initially in Chile. Seven of these twelve strains had an additional TEM beta-lactamase. Six isolates and their transconjugants produced a plasmid - encoded ESBL with an isoelectric point close to 5.4 . The remaining twenty one strains produced an ESBL with an isoelectric point of 7.6 (thus probably SHV-2) which was encoded on a plasmid transferable to E. coli in four strains only. Four of those strains possessed an additional plasmid encoded TEM beta-lactamase with an isoelectric point close to 5.4 . The transconjugants harboured a multiresistance plasmid of 150 kb. Thus SHV-2 and SHV-5 enzymes appear to have been the most common ESBL in K. pneumoniae from Zagreb during 1994-1995.

extended-spectrum beta-lactamases; Klebsiella pneumoniae; cephalosporins

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