EFFECTS OF GROWTH-PROMOTING ANTIMICROBIALS ON INHIBITION OF YERSINIA-ENTEROCOLITICA O-3 BY PORCINE ILEAL MICROFLORA

The survival of Yersinia enterocolitica serotype O:3 was examined in a n in vitro model of the porcine ileum in the presence of normal ileal microflora using a medium supplemented with the growth-promoting antim icrobials avoparcin, spiramycin, tylosin, carbadox and olaquindox, or without any antimicrobials, at 39 degrees C for 5 d. Growth of Y. ente rocolitica was inhibited in all trials in the following order: avoparc in < carbadox < spiramycin < no feed additives < tylosin < olaquindox. The media supplemented with avoparcin, carbadox and spiramycin suppor ted the survival of Y. enterocolitica up to 5 d. When incubated with t he normal ileal microflora without any growth-promoting antimicrobials , Y. enterocolitica could not be isolated after 4 d. With olaquindox a nd tylosin, Y. enterocolitica was not detected after 3 d.