[Comparison of two enrichment methods and five selective media for the isolation of Yersinia enterocolitica from tonsils of slaughter pigs (author's transl)].

115 tonsils of healthy slaughter pigs were culturally examined for presence of Yersinia (Y.) enterocolitica. For this purpose each sample was enriched both in phosphate buffered saline solution (pH 7.6; stored at 4 degrees C and plated every week, thrice all together) and modified Rappaport broth (plated after an incubation of two days at 22 degrees C). Each such enrichment was plated on 5 different selective media: Yersinia selective agar proposed by Wauters (1973), deoxycholate-citrate-mannitol agar (Saari and Jansen, 1979), pectin agar (Bowen and Kominos), MacConkey and Leifson agar as used in the routine, diagnostic of Enterobacteriaceae. Each agar plate was incubated at 28 degrees C for two days. By cold enrichment method were isolated 11 strains of human pathogenic Y. enterocolitica (9 X O-group I syn. serotype O:3; 2X O-group V syn. serotype O:9). With the modified Rappaport medium were recovered 33 strains (24X O-group I, 9 X O O-group V). The most recoveries were done over the Yersinia selective agar with 65.2%, then followed deoxycholate-citrate-mannitol agar with 57.6%, Leifson agar with 45.5%, MacConkey agar with 42.3% and pectin agar only with 18.2% of the isolations. Not only the type of enrichment medium has a marked effect in the recovery efficiency of Y. enterocolitica out of samples but also number and type of the used selective media on which the enrichment is plated.