Inhibition of beta-lactamases from Yersinia enterocolitica by plant extracts

Strain IP134 of Yersinia enterocolitica, which produces two chromosomal-mediated beta-lactamases, was used to detect the presence of beta-lactamase inhibiting agents in plants. Aqueous and alcoholic extracts were obtained from the aerial parts of 179 phanerogamous species, belonging to 39 botanical families. In an assay to detect synergy, eight plants representing a wide taxonomic distribution showed beta-lactamase inhibitory activity. An iodometric assay confirmed the inhibition of beta-lactamases in six of these plants, and revealed beta-lactamase inhibition to be masked by antibacterial activity in two additional plant extracts. Thus, beta-lactamase inhibitory activity was present in 4.5% of the tested species, 1.1% of which had simultaneous antibacterial activity detectable.