Interaction of cefpirome and a cephalosporinase from Citrobacter freundii GN7391

The interaction of cefpirome and a cephalosporinase from Citrobacter freundii, including hydrolysis and inhibition, was studied in comparison with those of cefotiam, cefotaxime, and ceftazidime. Cefpirome was hydrolyzed by the enzyme more rapidly at Vmax than were cefotaxime and ceftazidime. However, the low affinity of the enzyme for cefpirome caused a reduction in the hydrolytic rate of cefpirome at a low drug concentration (0.1 microM). The high stability of cefpirome at a low concentration explains the high antimicrobial activity of the agent against cephalosporinase-producing bacteria.