In-vitro evaluation of β-lactamase inhibition by latamoxef and imipenem

Abstract

The in-vitro 50% inhibitory concentrations (IC50s) of latamoxef and imipenem against a set of plasmid-mediated β-lactamases including TEM-1, TEM-3, TEM-5 and TEM-10 were determined by an enzymatic method using nitrocefin as substrate. The IC50s of both antibiotics against extended-spectrum β-lactamases were below 0.2 mg/L. The conventional spectrum β-lactamase TEM-1 was not inhibited by either antibiotic at the highest concentration tested. Except for TEM-10 for which the IC50s of the two antibiotics were the same, imipenem showed significantly greater activity than latamoxef against TEM-3 and TEM-5. Clavulanic acid taken as a control demonstrated greater and wider inhibitory activity, but on the other hand it has no significant antibiotic activity.