Experimental Yersinia enterocolitica enteritis in rabbits

Abstract

Young rabbits weighing 500-800 g were inoculated orogastrically with clinical isolates of Y. enterocolitica (serotype 0:3; enterotoxigenic; HeLa [human cervical carcinoma] cell invasive) at a dose of 1.4 .times. 1010 bacteria suspended in 10% NaHCO3 solution. Diarrhea developed in 41 (87%) of 47 rabbits, with a mean .+-. standard deviation onset at 5.4 .+-. 2.4 days. The attack rate and onset of diarrhea were correlated with inoculum size. The 50% infectious dose was 2.9 .times. 108 bacteria. Bacterial colonization occurred in almost all rabbits, regardless of inoculum size. Seroconversion was demonstrated in 30 (71%) of 42 rabbits with or without diarrhea. Histopathological alterations were present in the jejuna, ilea and colons of rabbits with diarrhea; the most pronounced changes were generally noted in the ilea. Crypt abscesses localized at the depth of the intestinal glands were observed consistently and were composed of a bacterial nidus admixed with and enveloped by inflammatory cells comprised of eosinophils, neutrophils and mononuclear cells. rabbits inoculated with a raw fish isolate of Y. enterocolitica (serotype 0:6,30; non-enterotoxigenic; HeLa cell non-invasive) did not exhibit infection clinically, bacteriologically or pathologically.