A survey of beta-lactamases from 618 isolates of Klebsiella spp.

beta-Lactamases from 618 isolates of Klebsiella spp. (487 Klebsiella pneumoniae 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 beta-lactamases from the K. pneumoniae isolates had a pI of 7.1, and most of the K. oxytoca isolates had chromosomal beta-lactamases of pIs 7.8, 5.3 and 5.5. Plasmid-mediated beta-lactamases were produced by 91.8% of K. pneumoniae isolates and 9.9% of K. oxytoca isolates. The beta-lactamase types identified most frequently were SHV-1 in the former species, and TEM-1 in the latter species. Of the K. pneumoniae isolates, 101 produced both of these plasmid-mediated beta-lactamases, while one strain produced an extended-spectrum SHV-like beta-lactamase. Of the 131 K. oxytoca isolates, 20 were hyper-producers of chromosomal beta-lactamase. The susceptibility of this genus to beta-lactam antibiotics is controlled almost exclusively by beta-lactamases, the production of which may differ from one strain to another; thus the empirical therapeutic use of beta-lactam antibiotics is not recommended for this genus.