Isolation of Mycoplasma neurolyticum from Mice and its Pathogenicity

Abstract

Myco plasma neurolyticum was found to be harbored in the respiratory tracts of approximately one-half of the mice examined. There was not any significant difference in the isolation rate between mice with chronic respiratory disease (CRD) and apparently healthy ones. The organisms were isolated concomitantly with cultures of M. pulmonis. Though there were small differences in toxicity among the strain of isolates, all these organisms produced neurotoxin for mice, showing the typical rolling symptoms by intravenous injection with broth culture. The maximum amount of toxin produced by this organism was 2^5.5LD₅₀/ml, as determined by intravenous injection to mice with a 24-hr broth culture. The neurotoxicity of the organism was different according to the routes of inoculation, it was higher after intravenous, intraperitoneal and intracerebral inoculations, in this order. NO death occured when injected subcutaneously. Mice of ICR strain were administered intranasally with the culture of freshly isolated strain of M. neurolyticum or a virulent strain of M. pulmonis. M. neurolyticum failed to produce pneumonia, although it was recovered from the lungs of 4 of 10 mice 8 days after inoculation. On the other hand, M. pulmonis proliferated in the respiratory tracts and produced such a characteristic pneumonia as seen in CRD-affected mice. These results suggest that M. neurolyticum may have nothing to do with pneumonia production, though it has been isolated frequently from the respiratory tracts at naturally infected mice.