Use of electrophoretic karyotyping in the evaluation of Candida infections in a neonatal intensive-care unit

OBJECTIVE: To evaluate a possible common-source outbreak of Candida infections in the neonatal intensive-care unit. Systemic Candida infections increased from 6 to 11 cases (0.71 to 1.34 per 1,000 patient-days). In addition, Candida parapsilosis infections increased from 1 in 1992 to 10 in 1993. DESIGN AND SETTING: Tertiary-care, teaching, pediatric institution with a 40-bed neonatal intensive-care unit (NICU). Clinical characteristics, associated conditions, and antimicrobial therapy were obtained from the medical records of all NICU patients with positive blood cultures for Candida during 1992 and 1993. Nineteen Candida isolates from 15 infants were studied retrospectively using contour-clamped homogeneous electric-field (CHEF) electrophoresis. RESULTS: CHEF revealed eight karyotypes of C parapsilosis. Five isolates recovered from four patients shared one karyotype. The remaining isolates from seven infants all had distinctly different karyotypes. CONCLUSIONS: The evidence was insufficient to implicate a single source of infection, even though four patients in the same unit had identical strain types. However, identical strains of C parapsilosis were associated geographically, suggesting that nosocomial acquisition of C parapsilosis through indirect patient contact in the NICU was possible. The CHEF technique yields unique patterns that may be used to delineate clinical isolates and to study the molecular epidemiology of candidal infections.