Unusual infections in the immunocompromised host

In the past year a number of unusual infectious agents have caused significant, and sometimes fatal, infection in immunocompromised patients. Bacteria often considered to be of minimal pathogenicity such as Stomatococcus mucilaginosus or Centers for Disease Control group Ve may cause serious disease, especially in the setting of indwelling foreign bodies or neutropenia. In addition, prolonged treatment with antimicrobial agents may select unusually resistant bacteria, and this is highlighted by reports of the emergence of vancomycin-resistant gram-positive organisms. Invasive infections due to the dematiaceous fungi in neutropenic patients remain uncommon but pose great difficulty in treatment. Probably the most significant of the infections described is the development of invasive disease due to Candida krusei, particularly in patients receiving fluconazole therapy, and it is likely that further examples of the selection of unusual resistant fungal isolates by antifungal therapy will emerge.