Development of a defined medium for Haemophilus somnus isolated from cattle.

Nutritional factors that influence the growth of Haemophilus somnus were examined, and a defined medium was developed. Optimal growth of H somnus in broth occurred under conditions of maximum aeration. Nutritional components required for or enhanced growth of most H somnus isolates in the defined medium included uracil, D-glucose, isotonic NaCl, Na2HPO4, nicotinamide, flavin mononucleotide, pantothenic acid, pyridoxine, and a variety of salts and amino acids. The defined medium supported optimum growth of 18 of 21 isolates of H somnus from cattle.