Horizontal transmission of Candida parapsilosis candidemia in a neonatal intensive care unit

Abstract

This report describes the nosocomial acquisition of Candida parapsilosis candidemia by one of the six premature newborns housed in the same room of a neonatal intensive care unit at the Ospedale Santa Chiara, Pisa, Italy. The infant had progeria, a disorder characterized by retarded physical development and progressive senile degeneration. The infant, who was not found to harbor C. parapsilosis at the time of his admission to the intensive care unit, had exhibited symptomatic conjunctivitis before the onset of a severe bloodstream infection. In order to evaluate the source of infection and the route of transmission, two independent molecular typing methods were used to determine the genetic relatedness among the isolates recovered from the newborn, the inanimate hospital environment, hospital personnel, topically and intravenously administered medicaments, and indwelling catheters. Among the isolates collected, only those recovered from the hands of two nurses attending the newborns and from both the conjunctiva and the blood of the infected infant were genetically indistinguishable. Since C. parapsilosis was never recovered from indwelling catheters or from any of the drugs administered to the newborn, we concluded that (i) horizontal transmission of C. parapsilosis occurred through direct interaction between nurses and the newborn and (ii) the conjunctiva was the site through which C. parapsilosis entered the bloodstream. This finding highlights the possibility that a previous C. parapsilosis colonization and/or infection of other body sites may be a predisposing condition for subsequent C. parapsilosis hematogenous dissemination in severely ill newborns.

FIG. 1.

Electrophoretic separation of chromosome-sized DNA bands of C. parapsilosis strains. Lanes: M, S. cerevisiae used as a marker; 1, 2, 3, 7, and 8, C. parapsilosis isolates recovered, respectively, from the conjunctiva (Cp:c1) and blood (Cp:b1) of the newborn with progeria, from the sink area of the NICU (Cp:e1), and from two health care workers of the NICU (Cp:hcw1 and Cp:hcw2); 4, 5, and 6, genetically unrelated strains of C. parapsilosis isolated, respectively, from an outpatient (Cp:op1), from one health care worker of the NICU (Cp:hcw3), and from the environment of a different ward (Cp:e2); 9 and 10, ATCC 96144 and ATCC 96140, respectively, used as reference strains.

FIG. 2.

Schematic representation of the C. parapsilosis karyotypes (numbered 1 through 7) obtained for the isolates and reference strains (listed below the corresponding karyotype) by PFGE, showing the chromosome mobility groups (I, II, and III). Molecular sizes are given on the left. Line thickness corresponds to band density and intensity of ethidium bromide staining.

FIG. 3.

Electrophoretic separation of DNA products obtained by RAPD-PCR from C. parapsilosis strains with RPO2 as a primer. (A) Lanes: M, λ DNA-EcoRI/HindIII used as a marker; 1, 2, 3, 7, and 8, C. parapsilosis isolates recovered, respectively, from the conjunctiva (Cp:c1) and blood (Cp:b1) of the newborn with progeria, from the sink area of the NICU (Cp:e1), and from two health care workers of the NICU (Cp:hcw1 and Cp:hcw2); 4, 5, and 6, genetically unrelated strains of C. parapsilosis isolated, respectively, from an outpatient (Cp:op1), from the environment of a different ward (Cp:e2), and from one health care worker of the NICU (Cp:hcw3); 9 and 10, reference strains ATCC 96140 and ATCC 96144, respectively. Molecular sizes (in kilobases) are shown to the left of the gel. (B) Dendrogram showing the genetic similarity of the strain collection.