Genetic relationships between Candida albicans strains isolated from dental plaque, tracheal secretions, and bronchoalveolar lavage fluid from mechanically-ventilated intensive care unit patients

Candida albicans often resides in the oral cavity of healthy humans as a harmless commensal organism. This opportunistic fungus can cause significant disease in immunocompromised patients, such as those undergoing mechanical ventilation in the intensive care unit (ICU). The goal of this study was to determine the genetic relationship between strains of C. albicans recovered from different oral sites within individual patients compared to strains from different patients. Samples were collected from dental plaque, tracheal secretions, and the lower airway by bronchoalveolar lavage of patients undergoing mechanical ventilation. Three pulsed-field gel electrophoresis (PFGE) typing methods were used to determine the genetic relatedness of the C. albicans strains isolated from the samples: electrophoretic karyotyping (EK), and restriction endonuclease analysis of the genome using SfiI (REAG-S) and Bss HII (REAG-B). Strains of C. albicans isolated from different sites from the same patient were genetically indistinguishable, whereas strains from different patients usually separated into different genotypes. Among the three methods, REAG-B proved to be the most discriminatory method to differentiate strains. The finding of genetically indistinguishable strains from different sites along the airway from the same patient suggests that the oral cavity may serve as an important reservoir for C. albicans in mechanically-ventilated patients.