Pneumonitis in mice inoculated with Mycoplasma pulmonis: production of pulmonary lessions and persistence of organisms and antibodies.

Abstract

Specific pathogen-free (SPF) ICR mice were inoculated intranasally with Mycoplasma pulmonis strain m53 and were observed during one-year period for the formation of pulmonary lesions, persistence of mycoplasmas and production of antibodies. Of the nasal cavity, the isolation rate was 100% during 3 months following inoculation, decreasing thereafter. While the organisms persisted for a longer period in the trachea than in any other sites of the respiratory tract, they were isolated only at a lower rate from the lung. Gross pulmonary lesions were first observed on the 2nd day after inoculation and, in earlier stage of infection, the incidence of pneumonic lesions correlated with mycoplasmal isolation rate, becoming a maximum 90% on the 20th day. Later, however, such correlation was not observed, although the incidence of lung lesions remained at 50% for 10 months. While the CF antibody was detected already 5 to 10 days after inoculation turning to negative in 90% of inoculated animals one year later, the IHA antibody was detected 20 or more days after inoculation persisting at high titers for one year or over. The MI antibody was first detectcd 2 months after inoculation at titers much lower than those in CF and IHA. In non-inoculated mice having been kept for 10 weeks as cage mates with inoculated ones, were found to have mycoplasmas and antibodies without no gross lesions in the lung.