Polymyxin E-1 (colistin sulphate) (neuro-)intoxication in young ostriches (Struthio camelus spp.)

Colistin (polymyxin E) is a cyclic polypeptide with a potent bactericidal action against most gramnegative bacilli. When used parenterally, polymyxins should be given with great care as they have a very small safety range, and easily induce neurotoxicity and nephrotoxicity. A dose of 39.5 mg/kg body weight colistin sulphate injected subcutaneously induced rapid (within 1 to 3 h) mortality in young ostriches. Clinical signs of apathy, lethargy and hypotonia indicative of neurotoxicity of the compound were observed. At postmortem, vascular congestion of brain vessels was seen while, on histology, severe acute oedema was present in the epicardium and the intestinal serosa. Congestion of villi, swelling and vacuolization of the plexus of Auerbach, as well as intermuscular and perivascular oedema of the heart, were also observed. In view of our observations in ostriches and in other species studied, a dose of >5 mg/kg body weight polymyxin E is not considered safe for parenteral administration in ostriches.