Sulfonamide chemotherapy was found to cure rats of an otherwise fatal form of experimental Friedländer's bacillus pneumonia when treatment was begun 6 hours after inoculation. Most of the pneumonic lesions cleared completely, but an occasional animal exhibited small residual abscesses in the previously consolidated lung.
The recovery process taking place in the lungs was studied histologically at various intervals during therapy. As in the case of pneumococcal pneumonia, the principal action of the sulfonamide was upon the bacteria in the advancing edema zone at the periphery of the pneumonic lesion. The bacteriostatic action of the drug appeared to stop the spread of the pneumonia, and the Friedländer bacilli were ultimately ingested and destroyed by the phagocytic cells in the alveolar exudate.
The phagocytosis of bacteria in the lung was shown to be unrelated to the presence of antibody in the blood.