An Infectious Agent from Cases of Atypical Pneumonia Apparently Transmissible to Cotton Rats

Abstract

Cotton rats (Sigmodon hispidus) inoculated intranasally under ether anesthesia with sputum of lung from cases of atypical pneumonia produced lung lesions in 17 cases out of 78. Older animals were more susceptible. Lesions were "patchy red-gray" reaching maximum intensity at 6 or 8 days. Sera from recovered animals and human beings convalescent from atypical pneumonia neutralized the infectious agent. Though cultures of the agent on blood agar were negative it passed through Berkefeld N candles in 2 out of 6 expts.