Staphylococcus aureus colonization and infection after discharge from a term newborn nursery

During a 6-month period, term infants underwent nasal and umbilical swabbing within 96 hours of delivery and again at 1 to 18 (mean 3.8) weeks after discharge. Swabs were inoculated onto horse blood agar and all S aureus isolates were phage typed. Two hundred three infants were enrolled and follow-up was obtained for 181 (89%). Thirty-two of 181 (17.6%) were initially colonized, of whom 12 (37.5%) were colonized on follow-up. Thirty-two of 181 became colonized subsequent to hospital discharge. No single phage type predominated. Twenty-five patients were diagnosed to have clinical illness--omphalitis (11), conjunctivitis (10), and pustulosis (5). Six of these were colonized with S aureus initially, although organisms of the same phage type were not recovered from cultures obtained at the time of clinical illness. There was no significant difference in the rate of infections in colonized (19%) versus non-colonized (12%) infants. In five patients where S aureus was recovered at the time of symptoms, all organisms were acquired subsequent to discharge. We conclude that nursery colonization with S aureus did not lead to clinical illness, and clinical illnesses previously ascribed to S aureus frequently occur in the absence of these bacteria.