Tropical disease in the immunocompromised host: melioidosis and pythiosis.

Melioidosis is an infection of humans and animals caused by a gram-negative motile bacillus, Pseudomonas pseudomallei. Forty-nine patients with melioidosis complicating diabetes mellitus, collagen vascular disorders, leukemia/lymphoma, and other hematologic malignancies are described. Twenty-nine of these patients had disseminated/septicemic infection, two developed toxic shock syndrome, and one with AIDS experienced recrudescent melioidosis. Patients with disseminated melioidosis often have a variety of defects in cellular immunity both in vitro and in vivo. In humans with recrudescent melioidosis, cellular immunity can be transferred by a transfer factor and by levamisole, a cellular immunopotentiating agent. The results of the treatment of our patients with disseminated/septicemic melioidosis with antimicrobial agents in combination have been successful. In recent years, four cases of fungal arteritis due to Pythium species and one case of keratitis due to Pythium were seen. Almost all patients with fungal arteritis had thalassemia; all presented with pain in the lower extremities and gangrenous lesions of the toes. Pythium species, an aquatic Phycomycetes, was identified in these cases as a human pathogen on the basis of clinical features, pathologic findings, and--of greatest importance--the isolation of the etiologic fungi. These five cases with remarkably similar presentations exhibited certain similarities with and differences from cases of mucormycosis, entomophthoromycosis, and peniciliosis.