Mycoplasma pneumoniae: A mouse pneumonia model

Experimental pneumonia caused by Mycoplasma pneumoniae(MP) has been principally described in guinea pigs and hamsters and rarely in mice. To investigate the pathogenesis of MP infection we used the mouse model. Balb/c mice were anesthetized with metofane and 2.75 × 10^-7 cfu MP was introduced by intranasal(IN) inoculation on days 0, 1, and 2. Control mice received IN SP4 broth without MP. Five to ten mice were sacrificed on days 0,1,2,4,6,8,10,13 and 15. Sinus wash, bronchoalveolar lavage(BAL), serum and lung samples were taken from each mouse. A histopathological scoring system(HPS) for inflammatory changes in the lungs used a scale of 0 to 26(most severe). SP4 broth cultures were positive 100% of the time for all sinus wash and BAL samples. The mean c.f.u./ml log₁₀ on SP4 agar were from 4.1 to 6.4 on days 1-8 and >/= 1.5 on days 10-15 for BAL and sinus wash specimens. Serum PCR was negative. ELISA for Ig M and immunoblots for MP antibody were positive 20/34(58%) and 33/34(97%) at >/=8 days, respectively. IgG was negative. The mean HPS ranged from a maximum of 14 on day 4 to a minimum of 4 on day 13(range 0-21). Ten control mice had negative cultures, immunoblot and IgG or IgM antibody and an HPS of 0 or 1. This mouse model can be used to study the immunologic and therapeutic responses to MP infection and to provide a more rapid diagnostic approach.