Therapeutic Effectiveness of Prednisolone in Mycoplasma pulmonis-Infected Pneumonia in Mice

The present investigation was designed to analyze the therapeutic efficacy of prednisolone in the development of pulmonary lesions in Mycoplasma pulmonis-infected mice. Mice were treated every day from day 3 to day 9 after M. pulmonis inoculation with minocycline (group M), prednisolone (group P), or with minocycline and prednisolone (group MP) and a control group was left untreated. Mice from each group were sacrificed at days 7, 14, and 21. The macroscopic lung lesion scores of group MP at days 7, 14, 21, and of group M at day 7 were significantly lower (p < 0.05) compared with the control group. Pathological findings in group M and MP showed reduction of the polymorphonuclear leukocyte response in the alveoli compared with the controls. However, infiltration of lymphocytes around the bronchioles and blood vessels of group M was not less than that in group MP. The titer of CF antibody in group MP was the lowest of the four groups. Among the four groups, M. pulmonis was cultured in the joints of group P. These results suggest that combination therapy with minocycline and prednisolone was effective because the mice of group MP had a more marked reduction of infiltration of lymphocytes around the bronchioles and blood vessels as compared with group M. Simultaneously, with prednisolone alone therapy, a risk of dissemination of the mycoplasma organism and diminution of antibody production were suggested.