Strain Characterization of Candida parapsilosis Fungemia by Molecular Typing Methods

Abstract

 The present study used two molecular typing methods to investigate a cluster of eight cases of Candida parapsilosis fungemia in a hospital in Rio de Janeiro, Brazil. Candida parapsilosis is an important opportunistic pathogen that is frequently involved in outbreaks of nosocomial fungemia. Identification of a common source of infection and determination of genetic relatedness among the strains involved in outbreaks are important for infection control. Candida parapsilosis strains were isolated from the bloodstream of patients housed in an intensive-care unit (n=5) and in individual rooms (n=3). An additional strain of Candida parapsilosis was isolated from a hyperalimentation infusion flask, which was implicated by molecular typing to be the source of infection. All strains were identified using morphological and biochemical methods. The genetic relationship between patients' strains and the hyperalimentation infusion strain was assessed by electrophoretic karyotype (EK) analysis and random amplification of polymorphic DNA (RAPD). Both methods resulted in patterns that allowed differentiation of the isolates. Candida parapsilosis fungemia, in three of the eight patients, resulted from a common source of infection, as demonstrated by molecular typing methods. Image analysis of EK patterns indicated that these strains were closest to Candida parapsilosis Group II, a grouping that is a less frequent clinical isolate than the major Group I strains.