Effect of the combination of clavulanic acid and cephalothin on an experimental infection with Yersinia enterocolitica in iron-overloaded mice.

Iron-overloaded mice were infected with a virulent strain of Yersinia enterocolitica by the oral route to study the effect of antimicrobial treatments. The effects of therapy were assessed by enumeration of viable yersiniae in Peyer's patches and in ileal contents. Combinations of cephalothin and clavulanic acid showed therapeutic effects, which were interpreted as in-vivo synergism, since each component alone was ineffective. Ceftazidime, which is relatively beta-lactamase resistant, showed in-vivo activity similar to that of the combination of cephalothin and clavulanic acid. These results suggest that clavulanic acid is able to protect cephalothin against Y. enterocolitica beta-lactamases in vivo, as has been shown previously in vitro.