The Fate of a Virulent Hemolytic Streptococcus Injected into the Skin of Normal and Immunized Rabbits

1. Hemolytic streptococci, highly virulent for rabbits, when injected into the skin of normal animals increased greatly in number at the site of injection during the first 12 hours, diminished somewhat after 24 hours but still persisted after 21 days. They produced large abscesses within 24 hours, there was ulceration, and healing occurred after about 5 weeks. Histological observations confirmed the bacteriological evidence that the streptococci underwent great multiplication at the site of their injection. 2. Virulent hemolytic streptococci injected into the skin of normal rabbits appeared in small numbers within 1 hour in the lymph nodes. As multiplication proceeded in the skin, hemolytic streptococci were found in large numbers from 1 hour to 7 days after inoculation in the inguinal lymph nodes. 3. Hemolytic streptococci were recovered from deeper lymph nodes, that is, from the iliac nodes, but only in animals of which the inguinal lymph nodes contained bacteria in relatively large numbers. 4. Virulent hemolytic streptococci injected into the skin of normal rabbits in some instances entered the blood stream in considerable number, and occasionally caused death with bacteremia. Streptococci were recovered more frequently from the spleen and were present in this organ only when they had been recovered from the deep (iliac) lymph nodes. 5. When virulent hemolytic streptococci were injected into the skin of immunized rabbits, in a few instances they increased in number for a short time, but usually diminished rapidly and had entirely disappeared in 48 hours. The gross lesions were smaller than in normal rabbits. There was more phagocytosis, and redness and edema had disappeared after 48 hours. 6. When virulent streptococci were injected into the skin of immune rabbits they passed to the regional lymph nodes in relatively smaller numbers than in the previously normal controls and appeared in these nodes in considerable numbers only in animals in which there had been conspicuous multiplication at the site of inoculation. No streptococci could be found in the iliac lymph node, blood or spleen. 7. Virulent streptococci injected into the skin of normal animals multiply actively, resist phagocytosis, invade the tissues widely, enter adjacent and distant lymph nodes and in some instances are distributed by the blood stream to internal organs. After immunization associated with some sensitization, virulent streptococci are more readily ingested by phagocytes, remain sharply localized, are rapidly destroyed, fail to pass the nearest lymph nodes and do not enter the blood stream.