Susceptibility to beta-lactam agents of Yersinia enterocolitica biotype 4, serotype O3 isolated in various parts of the world.

Forty-eight human isolates of Yersinia enterocolitica of biotype 4, serotype O3 from various parts of the world were examined for susceptibility to 13 beta-lactam agents. The intracellular beta-lactamases of each of the 48 strains were examined. Isolates from Europe, Asia and Brazil (phage type VIII) or South Africa and Hungary (phage type IXa) produced both enzyme A and enzyme B, whereas isolates from New Zealand and Australia (phage type IXb) lacked the cephalosporinase enzyme B. Among the seven strains isolated in Canada belonging to phage type IXb, three strains expressed only enzyme A (group I) whereas the other four strains produced both enzymes A and B (group II). The high susceptibility to the combination of amoxycillin and clavulanate observed in one subtype was explained by the absence of the cephalosporinase enzyme B. A simple disk diffusion test with this antibiotic combination was shown to be effective in the detection of enzyme B in Y. enterocolitica 4/O3.