Background. In early 1990 fluconazole was introduced as a prophylactic antifungal agent after bone marrow transplantation. During the same year Candida krusei emerged as the chief candida pathogen among patients with bone marrow transplants. Methods. To determine whether there was a correlation between the introduction of fluconazole and the increased incidence of C. krusei, we conducted a retrospective study based on the medical, mycologic, and autopsy records of all adult inpatients who had undergone bone marrow transplantation (n = 296) or who had leukemia (n = 167) at the study center during 1989 and 1990. Results. The 84 patients who received antifungal prophylaxis with fluconazole had a sevenfold greater frequency of C. krusei infection than the 335 patients who did not receive fluconazole (8.3 percent vs. 1.2 percent, P = 0.002), despite having a lower frequency of disseminated C. albicans and C. tropicalis infections (0 vs. 6.0 percent, P = 0.02). Ten of the 11 C. krusei infections were controlled by a combination of amphotericin B and flucytosine. Colonization by C. krusei was found in 40.5 percent of the patients who received fluconazole but in only 16.7 percent of those who did not receive it (P<0.0001). Colonization was independently associated with the prophylactic use of both fluconazole (odds ratio, 3.50; P<0.001) and norfloxacin (odds ratio, 2.53; P = 0.04). C. krusei was not susceptible to fluconazole in vitro. Conclusions. In patients at high risk for disseminated candida infections, suppression of bacterial flora and the more common candida pathogens may permit some less pathogenic, but natively resistant candida species, such as C. krusei, to emerge as systemic pathogens. (N Engl J Med 1991;325:1274–7.).
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