Abstract
We have succeeded in demonstrating in sterile filtrates of broth cultures of four out of twenty-one strains of staphylococcus aureus isolated from various conditions, a powerful poison with a selective action for the skin. The poison is produced by the growth of these strains in any well buffered broth medium containing only a small amount of glucose. The medium from which our most powerful poisons were obtained was prepared by adding an equal volume of M/15 phosphate buffer solution pH 7.4 to ordinary sugar—free meat infusion broth containing 4 per cent Witte peptone, boiling, filtering and autoclaving. After inoculation with a suitable strain of staphylococcus, the poison can be demonstrated in the sterile Berkefeld filtrates of this broth after 24 hours growth, but our most toxic poisons were obtained after four to six days growth.
The toxicity of the filtrates was tested by intracutaneous inoculation in rabbits. One-tenth cc. of filtrates was inoculated intradermally and at the same time a control of 0.1 cc. of uninoculated broth was always injected in the same rabbit.
The reaction produced by the injection of a toxic filtrate becomes evident from two to six hours after injection as a bluishpurple area of 2 to 5 cm. in diameter, depending on the toxicity of the filtrate. The next day, the purple coltor assumes a yellow tinge, and there is usually added a deep red zone of 0.5 to 3 cm. surrounding the yellowish area. The circumsoribed yellowish area of 3 to 5 cm. becomes progressively yellower-as if necrotic. By the fifth day brown patches appear in the yellow area and increase in size until, at about the twentieth day, the whole lesion has become a dark brown scab. Four to eight weeks later the scab falls off leaving an ulcer. Microscopically the lesions show marked infiltration of polymorphonuclear leucocytes with necrosis of epidermis and underlying corium,
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