Studies on sensitivity to streptomycin of the atypical pneumonia agent.

An agent from cases of primary atypical pneumonia associated with development of cold agglutinins (Eaton et al., 1944, 1945) has again been found in recent small outbreaks of this disease (Liu et al., 1955). By using the Coons technique with fluorescein labeled antibody, the site of infection was detected in the lungs of chick embryos following passage by the amniotic route. Previous reports have indicated that strain Mac of the agent, isolated in 1944, was partially inhibited in chick embryos and cotton rats by tetracyclines and erythromycin (Eaton, 1950, 1954) and slight reduction of the pulmonary lesions by streptomycin was also observed. However, serial chick embryo passage of strain Mac with 50 Ag/ml of streptomycin in the suspending medium had been done from time to time without significant loss of infectivity. A recently isolated strain F. H. seemed more sensitive to streptomycin because use of this drug to control bacterial contamination frequently resulted in loss of infectivity. On further investigation it was found that strain F. H., although closely related antigenically to strain Mac (Liu, 1957) did have a significantly greater sensitivity to streptomycin.