1974 Volume 114 Issue 4 Pages 315-337
Microbiological and pathological examinations of the respiratory tract of young hamsters infected with Mycoplasma pneumoniae by inhalation of aerosol were carried out for up to a maximum of 98 days after infection. Mycoplasma pneumoniae organisms were found mainly in the pharynx and larynx for the first two weeks, then they continued to proliferate in the main bronchi or intrapulmonary bronchi for up to 98 days. On the third day after infection, inflammatory changes consisting mostly of infiltration with lymphocytes and monocytes appeared in the bronchial epithelium. These inflammatory changes proceeded to the peribronchial or interstitial tissues and reached a maximum on the 21st day after infection. After that, they showed a tendency to decrease and were replaced partially by atelectatic and emphysematous changes. These pathological processes seemed to be associated with the presence of Mycoplasma pneumoniae. On electron microscopic examination by the double staining and the ferritinantibody method, Mycoplasma pneumoniae organisms were found among cilia and microvilli of the bronchial epithelium during the first two weeks. Structures resembling mycoplasmas, which bound ferritin were also located among the debris of exfoliated cells from epithelium. As the inflammatory process spread, exfoliation and desquamation of bronchial epithelium and increase of mucus-secreting cells, became more marked and eventually vacuolation in the remaining epithelial cells, with an increased number of basal cells was seen throughout the epithelium. In the terminal stage the ciliary epithelium was replaced partially by squamous epithelium. These studies, especially the identification of intact mycoplasma organisms at the surface of the epithelial cells, suggested that this may be the site of growth of this organism in the respiratory tract.