Pulmonary clearance of Mycoplasma pulmonis in rats with respiratory viral infections or of susceptible genotype.

We sought to determine whether or not increased severity of bronchopulmonary disease due to Mycoplasma pulmonis infection in rats with respiratory viral infections and in rats of susceptible genotype could result from altered pulmonary clearance. Pathogen-free rats were exposed to aerosols of radiolabeled M. pulmonis and the numbers of M. pulmonis colony-forming units, and amounts of radiolabel in the lungs were determined immediately after exposure or 4 hours later. Intrapulmonary killing of M. pulmonis during the 4-hour interval was determined from decreases in ratios of colony-forming units to radiolabel, and physical clearance was determined from decreases in radiolabel. Neither intrapulmonary killing nor physical clearance differed between control F344 rats and F344 rats inoculated with Sendai virus or sialodacryoadenitis virus, or between F344 and LEW rats. Rates of intrapulmonary killing and physical clearance were 64 +/- 3% and 44 +/- 2%, respectively (overall means +/- standard error).