beta-Lactamase Id of ceftazidime-resistant Pseudomonas aeruginosa strains.

4.2% Pseudomonas aeruginosa strains isolated in our hospital were resistant to ceftazidime. The 174K strain was also resistant to azthreonam but susceptible to imipenem and was studied as representative of these strains. It produced a single beta-lactamase (pI 8.6) which had all the characteristics of the chromosomal beta-lactamase Id and was the only beta-lactamase present. This enzyme hydrolyses slowly ceftazidime and imipenem. It could be a factor of imipenem resistance if the antibiotic influx into the bacteria was decreased or if the beta-lactamase Id was synthesized at a high level.