Short-comings of irgasan ticarcillin chlorate broth for the enrichment of Yersinia enterocolitica biotype 2, serotype 9 from meat.

Recovery of Yersinia enterocolitica serotype 0:9 from artificially contaminated minced pork with the enrichment medium irgasan ticarcillin chlorate broth (ITC) was poor. This was due to the lower growth rate of this serotype in comparison with serotype 0:3. Tests on the behaviour of serotype 0:3 and 0:9 towards some selective agents in ITC broth showed that the minimal inhibitory concentration of chlorate was much lower for serotype 0:9 than for serotype 0:3. Omitting chlorate in the ITC enrichment stimulated the growth of pure cultures. Reduction of MgCl2 and malachite green to 80% of the original concentration further increased the growth, so that after 48 h of incubation similar counts (10(7)-10(8) cfu/ml) as for serotype 0:3 were obtained.