Practical approaches to diagnosing fungal infections in immunocompromised patients

Karin L. McGowan, Ph.D. from human skin and stool. Prior to sively to IC hosts. Burn patients are Director of Microbiology the 1980s, they were rarely reported to also at increased risk of acquiring disChildren's Hospital of Philadelphia cause infection (14, 16). Sepsis due to seminated Fusarium infections. AIDepartment of Pediatrics University of Pennsylvania Medical School Rhodotorula spp. occurs in IC pediatric though not all Fusarium infections in Philadelphia, Pennsylvania 19104 patients, especially children on longthe IC patients become disseminated, term steroid therapy who appear to be all of these infections are extremely predisposed to acquiring serious Rhodifficult to treat. Most isolates are reFungal infections frequently prove dotorula infection. A positive blood sistant to 5-fluorocytosine and require fatal to immunocompromised (IC) paculture from an IC patient that yields amphotericin B therapy. The prognosis tients. They are a frustration for both Rhodotorula is reason for concern, befor these patients is poor, and early iniclinicians and laboratorians because cause the overall mortality rate for this tiation of therapy offers the best chance they are difficult to diagnose, even with infection is 50 to 60%. for cure. Early therapy depends upon the best laboratory methods available. Trichosporon beigelii, the cause of laboratory awareness and rapid reMicrobiologists can, however, take white piedra, a superficial infection of porting of the results. practical steps to minimize the the hair shaft, is another yeast that The most common fungal infections problems encountered when dealing causes serious infections in IC patients in the immunocompromised are those with fungal infections in IC patients, or patients with hematologic maligcaused by Candida spp., Aspergillus nancies. T. beigelii can cause invasive spp., the Mucorales, and C. neoL a b o r a t o r y Awareness disease of the respiratory and gastroinformans, but significant changes in the The first step is to understand which testinal tracts, which leads to dissemipatterns of infection have occurred (3, organisms cause serious fungal infecnation (9). This organism shares 10). The incidence of candidemia at tions in IC patients, and in which cirantigenic determinants with the capsular cumstances they occur (Table 1). polysaccharide of Cryptococcus neoFungi that commonly cause infections formans (12, 13). Thus, compromised In This Issue in IC patients rarely cause serious inpatients with T. beigelii infections can fections in normal hosts. Many were have false positive serum cryptococcal once considered harmless colonizers, or antigen latex agglutination test results. Diagnosis of Fungai Infections. . . 33 saprophytes. Organisms such as Early detection of this pathogen is critImportance of direct microscopic, Drechslera, Cunninghamella, Penicilical, because a number of reported exam and serologic tests lium, and Pseudallescheria boydii are isolates have been resistant to amphoDiagnostic Significance of CMV now reported as causative agents in intericin B. fections that usually involve the In normal hosts, Fusarium infections Serology . . . . . . . . . . . . . . . . . . . . . 36 sinuses, lungs, and bloodstream. Neuare limited primarily to local infections Pitfalls in interpretation tropenia appears to be the most imporof the skin, nails and cornea. In bone Eschericheria hermannii Wound tant predisposing factor in these marrow transplant patients, Fusarium Infection . . . . . . . . . . . . . . . . . . . . . 38 patients, spp. frequently cause invasive fungal A rare, yellow-pigmented species Rhodotorula spp. have always been disease (2). In fact, invasive disease considered normal flora when recovered with this genus has been limited excluLetter to the Editors . . . . . . . . . . . 39