Introduction: Candida albicans is an increasingly recognized cause of serious disease in premature infants. Relatively little is known about the properties of C. albicans playing a role in neonatal disease. Our group has collected a number of invasive and noninvasive isolates of C. albicans from premature infants, typed them into strains, and has begun to study the strains.

Objective: To characterize invasive and noninvasive strains of Candida albicans in an in vitro model of intravascular invasion.

Methods: HMEC-1 cells, an immortalized human microvascular endothelial cell line, were grown to confluence in wells containing clear plastic membranes with 8 micron pores. The membranes create an upper chamber, containing the monolayer, and a lower chamber (LC) within the well. C. albicans strains were inoculated into the upper chamber of the well at a density of 1 × 106yeast cells/ml and incubated in the wells for 24 hours. Samples of the LC were obtained at 24 hours incubation and plated on yeast peptone dextrose agar for quantitation.

Results: To date six strains have been analyzed. Two of the strains were isolated from patients with invasive disease. There was a large difference in endothelial cell monolayer/membrane penetration among C. albicans strains. The counts in the LC ranged from 0 to 4.6 × 104yeast cells/ml for the individual strains. The experiments were performed in triplicate and minimal variability was noted between wells inoculated with the same isolate. A high level of monolayer penetration was identified in one invasive isolate (1.5 × 104yeast cells/ml), the other invasive isolate demonstrated very low levels (3 yeast cells/ml).

Conclusions: C. albicans strains studied in an in vitro model of intravascular invasion demonstrated varying abilities to translocate through an endothelial monolyer. Additional strains will be analyzed to help determine the utility of this model to predict and study candidal strains with invasive potential.