Relationship of Maternal to Neonatal Colonization with Coagulase-Negative Staphylococci

ABSTRACT

Infections with coagulase-negative staphylococci (C-S) have become problems of major clinical importance among very low birthweight infants in neonatal intensive care units. Colonization with slime-producing strains of C-S may be a risk factor for these infants in the development of invasive infections. The present study evaluated the maternal genital tract as a possible source for neonatal colonization with C-S. Specific objectives were to determine the incidence of vaginal colonization with C-S in pregnant women with special reference to slime-producing strains and whether transmission of C-S occurs from mother to infant during the process of vaginal delivery. Antenatal vaginal cultures were done on 465 women at different gestations of pregnancy. Additionally, 101 women and their newborn infants were cultured after vaginal delivery. Fifty-one percent of women were colonized with C-S during pregnancy, and no significant differences in colonization rates by trimester were found. Slime-positive isolates from pregnant women increased significantly from the first to the third trimester (40 to 68%; chi-square, 11.21, p < 0.005). However, the proportion of slime-positive strains among the 30 infants who were colonized with C-S at birth was 40% (12 of 30). Although 30 infants were colonized with C-S at birth, only three were shown to have acquired the organism by maternal transmission determined by similarity of species, biotype, antibiotic sensitivity pattern, slime production, phage type, and plasmid pattern profile. Therefore 27 infants (26% of the total) most likely acquired C-S from environmental sources, including nursery attendants. Colonization from environmental sources was a much more common occurrence than colonization from maternal transmission. Approximately 40% of C-S strains colonizing infants on the first day of life are slime positive.