The authors demonstrated the transferability of antibiotic resistance genes in nosocomial strains of Klebsiella pneumoniae, isolated from newborn children at the Paediatric University Hospital in Bratislava. Strains were resistant to cefotaxime, ceftazidime and aztreonam. The determinants of resistance (carbenicillin, cephaloridine, cefotaxime, ceftazidime and aztreonam) were transferred to recipient strains of Escherichia coli K-12 and Proteus mirabilis P-38. The transfer of resistance determinant from donor strains was demonstrated by the analysis of the resistance spectrum in transconjugant clones of recipient strains by the method of indirect selection. The ability of production of extended spectrum b-lactamases (ESBL) was demonstrated by the double disc diffu- sion test. Synergy between clavulanate and cefotaxime, clavulanate and ceftazidime and/or clavu- lanate and aztreonam indicated production of ESBL by these strains.

        Key words: Klebsiella pneumoniae – extended-spectrum b b-lactamase – transferable resistance.