Pathogenicity of some Mycoplasma and Acholeplasma species in the lungs of gnotobiotic calves.

Cloned cultures of 16 strains, representing nine different species of Mycoplasma and Acholeplasma, were inoculated intratracheally into gnotobiotic calves. Strains of M bovirhinis, M canadense, M verecundum, A axanthum and A modicum did not produce visible pneumonic lesions and were not reisolated from the lungs. Strains of M alkalescens and M arginini colonised the lower respiratory tract but failed to produce visible pneumonia. M bovigenitalium (strain M991/70) and M dispar (strain Gri226) both colonised the respiratory tract and induced pneumonic lesions estimated to involve up to 8 per cent (M bovigenitalium) and 17 per cent (M dispar) of the lung. Histologically M bovigenitalium produced a cuffing pneumonia and M dispar produced a interstitial alveolitis.