Comparison of techniques for primary isolation of respiratory Mycoplasma pulmonis from rats.

Studies were performed to determine the optimal sites for primary isolation of Mycoplasma pulmonis from the respiratory system of laboratory rats. In a preliminary study, a group of 42 rats was cultured for respiratory M. pulmonis at several sites. Tracheal washes yielded the highest number of positive cultures (61.9%) and ground lung tissue yielded the lowest (19.0%), with the nasopharyngeal culture in the middle (52.38%). In a subsequent study, the tracheal wash was again the optimal method since 76.7% of 103 rats were positive for M. pulmonis, whereas culture of the nasopharyngeal area resulted in 53.9% positive cultures. In a third study, all 45 rats were positive for M. pulmonis when the tracheal wash method was used, whereas only 51% were positive when the nasopharyngeal area was cultured, indicating that the tracheal wash was the most reliable of the commonly used procedures. Other aspects of these experiments demonstrated the tympanic cavity of animals with otitis media to be an excellent source for obtaining material to culture for M. pulmonis.