Toxic effects for lambs of cytotoxic necrotising factor from Escherichia coli

The lethal effect, clinical signs and lesions caused by the intravenous inoculation into six lambs (seven to 10 days old) of a partly purified preparation of cytotoxic necrotising factor (CNF) from Escherichia coli, strain BM2-1, were investigated. Two control preparations were also tested in two lambs each: (i) the same as above but heated for one hour at 60 degrees C, a treatment which inactivates CNF and preserves residual endotoxic activity; and (ii) purified material from a CNF-defective mutant of BM2-1. Whereas none of the lambs in either of the control groups died or showed significant clinical signs or lesions, all the lambs inoculated with partly purified CNF developed severe clinical signs starting six hours after inoculation which consisted mainly of neurological signs and mucoid diarrhoea. The most striking lesions were oedema and haemorrhages in the central nervous system, and foci of coagulation necrosis in the myocardium. Mucus hypersecretion in the gastrointestinal tract was not associated with cellular inflammation.