Detection of extended spectrum beta-lactamases in Escherichia coli and Klebsiella pneumoniae

The presence of extended spectrum beta-lactamases (ES beta Ls) in 129 Esche richia coli and 128 Klebsiella pneumoniae strains was determined with the E test, beta-lactamases were detected in 66 (51.2%) of E.coli and 107 (83.6% ) of K pneumoniae by the nitrocefin disk method. Putative ES beta L product ion was observed in 15.5% of E. coli and 55.5% of K pneumoniae with the E t est. Among the putative ES beta L-producer strains 11 were found to be susc eptible to ceftizoxime, 6 to ceftazidime, 2 to ceftriaxone, cefotaxime and aztreonam, and one to cefoperazone according to the disk diffusion test. Al l putative ES beta L-producers were resistant to cefodizime, thus it may be a good indicator of the presence of mainly TEM-type ES beta L. The E test was also found to be practicable for the detection of ES beta Ls in clinica l laboratory. Further studies are needed to clarify whether ES beta L can b e identified reliably in species that, in addition to plasmid mediated ES b eta L production, chromosomally encoded AmpC beta-lactamases and other clas s A ES beta Ls by disk diffusion test.