Pathogenicity of certain Mycoplasma species in the bovine mammary gland

Strains of three of the species of mycoplasmas isolated from pneumonic calf lungs, Mycoplasma dispar, Mycoplasma bovirhinis and Acholeplasma laidlawii, were inoculated into the bovine mammary gland. Pathogenicity of the species was monitored by counting the inflammatory cells and mycoplasmas in milk. Six of the seven M dispar strains produced clinical mastitis, but the seventh strain, Vic12, was apparently avirulent. The four strains of M bovirhinis caused subclinical mastitis. None of the four strains of A laidlawii multiplied and they produced only a transient cell response in the milk.