S11C11P6-Bacterial Infections

S11C11P6-1: The epidermis is necrotic and, on the left, partially denuded. The necrotic epidermis is brightly acidophilic. Some of the cells of the rete ridges retain some nuclear architecture, but the nuclei are pyknotic (a marker for dying cells). A wedge-shaped area of necrosis in the dermis abuts upon the necrotic epidermis. The dermal connective tissue is poorly defined and smudgy; it is acelluar in the zone of necrosis. The vessels are congested, and some contain thrombi. The lesion is a cutaneous infarct; the pathogen is pseudomonas (pseudomonas septicemia).

S11C11P6-2: This small dermal vessel is packed with red blood cells; it is occluded. A few histiocytes are present among the red blood cells. Neutrophils are not a feature of the reaction in the lumen, or the wall of the vessel. The zone of basophilia (green arrows) is contributed by a heavy growth of bacteria (bacilli; pseudomonas organisms). The lesions of pseudomonas septicemia characteristically are necrotizing; they have the qualities of an infarct. Organisms commonly are confined to the walls and adventitia of vessels; vessels show thrombosis and necrosis.

S11C11P6-3: This lesion of bullous impetigo shows a subcorneal bulla with angulated defects among keratinocytes of the granular layer. There are perivenular infiltrates of lymphocytes in the upper portion of the reticular dermis. Lymphocytes and histiocytes have migrated into the epidermis in areas of inter-cellular edema. The histologic patterns overlap with those of both pemphigus foliaceus and staphylococcal scalded skin syndrome. In contrast to the findings in the latter two disorders, the lesions of bullous impetigo often contain stainable cocci on a Brown-Brenn stain (a modified Gram stain).

S11C11P6-4: At a higher magnification, there are scattered dyskeratotic cells near the granular layer. In this disorder, a staphylococcal toxin affects adhesive molecules which normally join, and hold together, neighboring keratinocytes in the superficial portion of the epidermis.

 

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