Synergy of amoxycillin combined with clavulanate and YTR 830 in experimental infections in mice.

YTR 830, a new beta-lactamase inhibitor, is synergistic with amoxycillin in vitro against a number of beta-lactamase-producing organisms. The combination of amoxycillin-YTR 830 was compared to amoxycillin-clavulanate in the treatment of experimental Staphylococcus aureus, Citrobacter freundii and Proteus mirabilis infections in mice. Both combinations were synergistic with amoxycillin against all three test organisms. The amoxycillin-clavulanate combination was superior against S. aureus and C. freundii while amoxycillin-YTR 830 was more effective against P. mirabilis. The difference in efficacy between the two drug combinations appears to relate to the degree of protection afforded the animals by the beta-lactamase inhibitor alone. YTR 830 is a promising new agent and should undergo further investigation.