Detection of Extended Spectrum β-Lactamases in Escherichia coli and Klebsiella pneumoniae

Abstract

The presence of extended spectrum β-lactamases (ESβLs) in 129 Escherichia coli and 128 Klebsiella pneumoniae strains was determined with the E test. β-lactamases were detected in 66 (51.2%) of E. coli and 107 (83.6%) of K. pneumoniae by the nitrocefin disk method. Putative ESβL production was observed in 15.5% of E. coli and 55.5% of K. pneumoniae with the E test. Among the putative ESβL-producer strains 11 were found to be susceptible to ceftizoxime, 6 to ceftazidime, 2 to ceftriaxone, cefotaxime and aztreonam, and one to cefoperazone according to the disk diffusion test. All putative ESβL-producers were resistant to cefodizime, thus it may be a good indicator of the presence of mainly TEM-type ESβL. The E test was also found to be practicable for the detection of ESβLs in clinical laboratory. Further studies are needed to clarify whether ESβL can be identified reliably in species that, in addition to plasmid mediated ESβL production, chromosomally encoded AmpC β-lactamases and other class A ESβLs by disk diffusion test.