•Primary cutaneous Bacillus cereus infection frequently presents as a single necrotic bulla on the extremity of an immunocompromised patient. In lesional biopsy specimens and smears, the large gram-positive rods of B cereus may be mistaken for Clostridium species. This is a potentially serious error, as Bacillus species are resistant to penicillin and other β-lactam antibiotics. We studied a case in which large periodic acid-Schiff-staining organisms were seen in the biopsy specimen from a necrotic bulla on the finger of a neutropenic patient with diffuse large cell lymphoma. The tissue biopsy specimen subsequently yielded a pure culture of B cereus. Staining with periodic acid-Schiff was then performed on a series of bacterial species in human tissue and from smears of culture colonies. The following bacterial species were found to be consistently periodic acid-Schiff positive after diastase digestion: B cereus, Corynebacterium diphtheriae, Propionibacterium acnes, Klebsiella pneumoniae, and Micrococcus luteus.
Khavari PA, Bolognia JL, Eisen R, Edberg SC, Grimshaw SC, Shapiro PE. Periodic Acid-Schiff-Positive Organisms in Primary Cutaneous Bacillus cereus InfectionCase Report and an Investigation of the Periodic Acid-Schiff Staining Properties of Bacteria. Arch Dermatol. 1991;127(4):543-546. doi:10.1001/archderm.1991.04510010111013