Behaviour of cefmenoxime towards beta-lactamases.

Using several well-characterized beta-lactamases isolated from Gram-negative bacteria, the interactions of cefmenoxime, a new methoxy-imino-amino-2-thiazol cephalosporin were compared with those of cefotaxime, lamoxactam, cefoperazone and ceftazidime. On-line computerized microacidimetry allowed determination of the affinity of these compounds for the enzymes, which was characterized by Ki values. Microacidimetry showed poor interactions of cefmenoxime with penicillinase TEM-1 (low Vm, poor affinity) whereas it showed a high affinity for the cephalosporinases, as is also the case for cefotaxime or lamoxactam. Both cefmenoxime and cefotaxime showed relative susceptibility in Masuda's double disc technique.