Vertical and horizontal transmission of Candida albicans in very low birth weight infants using DNA fingerprinting techniques

Background: Very low birth weight infants (VLBW, <= 1500 g) are at increased risk for invasive disease caused by fungi, and colonization is an important risk factor. This study was designed to examine the effect of maternal flora on Candida colonization of VLBW infants. Methods: Body site samples were collected within 24 hours of delivery from mothers who gave birth to VLBW infants, from their infants at birth, and then weekly for 12 weeks or until death or discharge. Yeast isolates were identified as Candida albicans by standard methods and typed by DNA fingerprinting using a C albicans strain-specific DNA probe (CARE-2). Results: Sixty-six percent (50/76) of mothers were colonized with yeast and 51% (39/76) of their infants had a Candida species isolated at least once. Of 46 infants born to C. albicans-colonized mothers, 18 (39%) became colonized with C albicans. Twenty-two percent (17/76) of the infants in the study were colonized with C albicans by 1 week of age; 76% of these infants (13/17) were born to C. albicans-colonized mothers suggesting vertical transmission. DNA fingerprinting was performed on these 13 mother-infant pairs and 11 pairs demonstrated identical band patterns, confirming vertical transmission. However, of all infants colonized with C albicans by the first week of age, just 65% (11/17) had a maternal source, and among all infants colonized at any time point, only 4 1 % (11/27) became colonized by vertical transmission. Conclusions: Both vertical and horizontal transmission contribute to Candida colonization of VLBW infants in the neonatal intensive care unit.