The histologic changes associated with the development of the acute inflammatory response to experimental cutaneous mucormycosis were studied at various times from 5 minutes to 24 hours after inoculation into normal rabbits and in rabbits with acute alloxan diabetes and acidosis. In normal animals the response by polymorphonuclear leukocytes began within a few minutes after inoculation, increased rapidly in extent and intensity and reached its peak within 6 to 12 hours. By that time there was also early proliferation of fibroblasts and of large mononuclear cells and these cellular reactions, together with the accumulated granulocytes, began to produce a demarcation of the lesions. Beginning 4 to 6 hours after inoculation the fungus showed some growth but this remained confined to the necrotic center of the lesions. In the diabetic rabbits the onset of the response by polymorphonuclear leukocytes was delayed by several hours, reduced in intensity and was apparently less effective. There was no proliferation of fibroblasts and the lesions were spreading rather than circumscribed. Fungus growth in the tissues began shortly after inoculation, was marked, progressed rapidly, and soon extended beyond the site of inoculation. The large mononuclear cells, however, appeared at about the same time and in equal number in the lesions of both diabetic and non-diabetic animals and showed no morphologic changes.
It is concluded that a significant delay and impaired effectiveness of the response by polymorphonuclear leukocytes, a lack of fibroblastic proliferation and an enhanced growth of the fungus lower host resistance to infection with it and are directly consequent on severe alterations in host metabolism.