Behaviour of ceftazidime towards beta-lactamases

from Escherichia coli, Enterobacter cloacae, Proteus morganii and Pseudomonas aeruginosa, but the geometric mean of the inhibition constant Ki used to measure this interaction was 120 and almost 700 times higher with ceftazidime than with cefotaxime and cefuroxime, respectively. Two other beta-lactamases isolated from Pr. vulgaris and Klebsiella oxytoca also showed little or no interaction with ceftazidime. A complementary microbiological technique, the "double-disc" technique, indicated that ceftazidime was more stable than cefotaxime to all beta-lactamases tested. Moxalactam, however, appeared to have slightly greater stability.