A survey of β-lactamases from 618 isolates of Klebsiella spp

β-Lactamases from 618 isolates of Klebsiella spp. (487 Klebsiella pneumaniae and 131 Klebsiella oxytoca) were identified by analytical isoelectric focusing. The strains were consecutive isolates from 618 different patients in five hospital centres between 1980 and 1984. Most of the chromosomal β-lactamases from the K. pneumoniae isolates had a pI of 7-1, and most of the K. oxytoca isolates had chromosomal β-lactamases of pIs 7-8, 5-3 and 5-5. Plasmid-mediated β-lactamases were produced by 91-8%of K. pneumoniae isolates and 9-9% of K. oxytoca isolates