EXPERIMENTALLY-INDUCED PROLIFERATIVE ENTERITIS IN HAMSTERS - AN ULTRASTRUCTURAL-STUDY

Hamsters, three weeks old, were dosed orally with suspensions of intra cellular bacteria grown in rat enterocyte tissue culture cells IEC-18, which had been infected with suspensions of intracellular bacteria de rived from the lesions of proliferative haemorrhagic enteropathy occur ring naturally in two pigs. Each bacterial strain, identified as Ileal symbiont intracellularis, was passaged in the cell lines once, twice or five times, collected with the cells and used as inocula. Ten of 16 hamsters dosed with 916/91 passaged one or five times developed lesio ns of proliferative enteritis. In these 10 hamsters, marked hyperplasi a of ileal enterocytes associated with numerous intracellular curved b acteria was detected. An ultrastructural study of epithelial cells in the ileum of affected hamsters showed numerous intracellular bacteria in the cytoplasm. Similar bacteria were not seen in unaffected animals . Intracellular bacteria were usually seen in groups and could appear as electron dense or in a more electron lucent form. These bacteria we re clearly seen to enter cells from the intestinal lumen, via endocyti c vacuoles at the brush border. There was rapid breakdown of the entry vacuoles, leaving bacteria free in the cytoplasm where division was u sually observed. These bacteria were often seen in close association w ith normal or distended mitochondria and rough endoplasmic reticulum.