Arthritis in mice due to infection with Mycoplasma pulmonis. I. Clinical and microbiologic features.

Abstract

After iv inoculation with Mycoplasma pulmonis, 47 of 50 mice studied for two years developed chronic arthritis. The clinical course was marked by an acute onset with maximal involvement between two and four weeks after inoculation. Inflammation of joints then subsided to a relatively steady level. Changing patterns of swelling, erythema, and loss of mobility were prominent during both the acute and the chronic phrases. Up to 5 × 106 cfu/ml, the arthritic response was dependent on size of inoculum. Neither sex nor age (four to 18 weeks) of the mice significantly altered the response. Microbiologic aspects of the disease were studied in a group of 140 mice. From one to 46 weeks inclusive, 93% of the mice developed arthritis, and 27.2% of clinically arthritic joints were culture-positive. Of those that were culture-positive, the degree of clinical arthritis correlated significantly with the log number cfu of M. pulmonis per gram of tissue. No correlation was found between number of culture-positive joints and duration of infection. The significance of the culture-negative joints and the possible application of M. pulmonis infection as an experimental model of human rheumatoid arthritis were discussed.