Morphologic and Microbiologic Features of Trachea and Lungs in Germfree, Defined-Flora, Conventional, and Chronic Respiratory Disease-Affected Rats

SUMMARY The anatomic, microbiologic, and pathologic features of trachea and lungs of 146 laboratory rats from germfree, defined-flora, conventional, and 3 chronic respiratory disease ( crd )-affected colonies were determined. Peribronchial lymphocytic tissue was measured with quantitative histologic techniques. Chronic respiratory disease was usually characterized by tracheitis, bronchopneumonia, peribronchial lymphocytic infiltration, and bronchiectasis. Three organisms frequently isolated only from diseased rats were Mycoplasma sp., Diplococcus pneumoniae , and Pasteurella pneumotropica . Viral agents were not isolated. The crd could be transmitted to rats, but not to mice, by aerosol inoculation of tracheal and pulmonic suspensions from crd -affected rats. Using this information, a classification of respiratory diseases of rats was developed.