Potentiation of human polymorphonuclear leukocyte phagocytosis and intracellular bactericidal activity by amoxycillin/clavulanic acid.

The use of broad spectrum β-lactamase inhibitors in association with β-lactam agents provides one strategy to overcome the enzymatic resistance. Clavulanic acid is a potent inhibitor of a wide range of bacterial β-lactamases and its potentiating effect on amoxycillin has been established both in vitro and in clinical trials. Since the efficacy of an antimicrobial agent in the therapy of infections depends on the interaction of bacteria, antibiotic and phagocytes, we investigated the effect of amoxycillin/clavulanic acid on the in vitro interaction between human polymorphonuclear cells (PMNs) and β-lactamase producing strains of Klebsiella pneumoniae and Staphylococcus aureus. Clavulanic acid did not have any significant influence upon the PMN phagocytosis and killing against intracellular bacteria interestingly, the presence of the suicide inhibitory with its β-lactamase inhibitory properties, potentiated the activity of amoxycillin against the β-lactamase producing strains of K. pneumoniae and S. aureus in such a manner that bacteria became significantly more susceptible to either phagocytosis or microbicidal activities of human phagocytes, compared to both the control and amoxycillin systems.