Attempts to recoverMycoplasma suipneumoniaefrom experimental and natural cases of enzootic pneumonia in pigs

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Abstract
Two strains of enzootic pneumonia, which are regularly free from mycoplasmas other than Mycoplasma suipneumoniae, were transmitted experimentally to a total of 22 pigs. M. suipneumoniae was recovered in liquid medium from the lung lesions in 20 of these animals (91%).Twelve field outbreaks of enzootic pneumonia were likewise examined for M. suipneumoniae: from each outbreak, cases were selected where many mycoplasmas with the morphology of M. suipneumoniae were seen in touch preparations made from the lung lesions. M. suipneumoniae was recovered from only two of these outbreaks, but M. hyorhinis was obtained from nine of them.To establish whether the outbreaks yielding only M. hyorhinis were indeed enzootic pneumonia, material from five of them was used in disease-transmission experiments: enzootic pneumonia was induced in every instance, and M. suipneumoniae was recovered from three of the five transmitted strains.It is concluded that M. hyorhinis is commonly present in the lung lesions of enzootic pneumonia and that this mycoplasma may often prevent the isolation of M. suipneumoniae. The problem of recovering M. suipneumoniae in this situation is made more difficult by the fact that in no instance where M. suipneumoniae was isolated directly in liquid medium was it cultured in parallel on solid medium.