Relationship between maternal and neonatal Staphylococcus aureus colonization.

OBJECTIVE The study aimed to assess whether maternal colonization with Staphylococcus aureus during pregnancy or at delivery was associated with infant staphylococcal colonization. METHODS For this prospective cohort study, women were enrolled at 34 to 37 weeks of gestation between 2007 and 2009. Nasal and vaginal swabs for culture were obtained at enrollment; nasal swabs were obtained from women and their infants at delivery and 2- and 4-month postbirth visits. Logistic regression was used to determine whether maternal colonization affected infant colonization. RESULTS Overall, 476 and 471 mother-infant dyads had complete data for analysis at enrollment and delivery, respectively. Maternal methicillin-resistant S aureus (MRSA) colonization occurred in 10% to 17% of mothers, with the highest prevalence at enrollment. Infant MRSA colonization peaked at 2 months of age, with 20.9% of infants colonized. Maternal staphylococcal colonization at enrollment increased the odds of infant staphylococcal colonization at birth (odds ratio; 95% confidence interval: 4.8; 2.4-9.5), hospital discharge (2.6; 1.3-5.0), at 2 months of life (2.7; 1.6-4.3), and at 4 months of life (2.0; 1.1-3.5). Similar results were observed for maternal staphylococcal colonization at delivery. Fifty maternal-infant dyads had concurrent MRSA colonization: 76% shared isolates of the same pulsed-field type, and 30% shared USA300 isolates. Only 2 infants developed staphylococcal disease. CONCLUSIONS S aureus colonization (including MRSA) was extremely common in this cohort of maternal-infant pairs. Infants born to mothers with staphylococcal colonization were more likely to be colonized, and early postnatal acquisition appeared to be the primary mechanism.