Growth requirements for Moraxella bovis.

Moraxella bovis isolates do not necessarily require complex growth media. Minimal growth requirements were approached by selecting mutants that grew on progressively simpler solid media. Isolate 137T was selected until it could be cultured on a medium containing sodium L-glutamate, with thiamine, nicotinamide, pyridoxine and inorganic salts. All 5 field strains isolated in 1983 showed the same requirements and no prior selection was needed. One of these 5 field strains (H388) was selected to require nicotinamide as the only added vitamin, and culture 137H was selected to grow without added vitamins. In contrast, type strains NCTC 8561 and NCTC 9426 could not be cultured on glutamate medium supplemented with a mixture of 8 growth factors. However, 35 out of 38 M. bovis cultures collected in this laboratory grew on that medium. A more complex medium (TG) contained 8 g glutamate and 2 g tryptone per litre of basal salts. Medium TG supported growth by both type strains and all 38 laboratory cultures. Growth on TG medium was promoted by adding 0.1 mg l-1 of pyridoxine, nicotinamide and thiamine. M. bovis strains from type-culture collections or those that have been subcultured on complex media only, may not have retained their native nutritional requirements.