Background: We experience a case of blood stream infection due to C. parapsilosis in a patient following cardiac surgery. Here we describe the characteristics of serial isolates of C. parapsilosis demonstrated increasing resistance to fluconazole in vitro. Methods: The five isolates of C. parapsilosis were obtained from a patient operated on mitral valve. Antifungal susceptibility was determined by NCCLS microdilution method and E test. Strain identity was determined by pulse field gel electrophoresis. Population analysis was performed to determine whether the phenotype switch is a clonal event or associated with substrain selection. Fluconazole resistant isolates were subcultured in medium without fluconazole to examine stability. Results: The initial isolate(CP1) was fluconazole susceptible(MIC 2 μg/ml), however, the isolates(CP2 CP5) developed resistance after a brief usage of fluconazole. DNA typing revealed development of resistance in a persistent strain. On population analysis, CP1 formed colonies on plates containing 64 μg/ml fluconazole at frequencies of 10-4. Clinical isolates CP2, 5 and resistant subclone derived from CP1 demonstrated a homogenous population of resistant cells on plates containing 64 μg/ml fluconazole. The induced resistance was reversible through serial transfers in fluconazole-free media over a period of 30 days. Conclusions: Fluconazole-heteroresistant phenotype of C. parapsilosis was observed in blood stream isolates from a cardiac surgery patient. Fluconazole resistance can be developed by a selection from heteroresistant clones by exposure to fluconazole.
Full conference title:
13th Annual Focus on Fungal Infections
- FFI 13th (2003)