IN-VITRO EVALUATION OF BETA-LACTAMASE INHIBITION BY LATAMOXEF AND IMIPENEM

The in-vitro 50% inhibitory concentrations (IC(50)s) of latamoxef and imipenem against a set of plasmid-mediated beta-lactamases including T EM-1, TEM-3, TEM-5 and TEM-10 were determined by an enzymatic method u sing nitrocefin as substrate. The IC(50)s of both antibiotics against extended-spectrum beta-lactamases were below 0.2 mg/L. The conventiona l spectrum beta-lactamase TEM-1 was not inhibited by either antibiotic at the highest concentration tested. Except for TEM-IO for which the IC(50)s of the two antibiotics were the same, imipenem showed signific antly greater activity than latamoxef against TEM-3 and TEM-5. Clavula nic acid taken as a control demonstrated greater and wider inhibitory activity, but on the other hand it has no significant antibiotic activ ity.