Prevalence of bacterial respiratory pathogens in the nasopharynx in breast-fed versus formula-fed infants.

In several studies, breast-feeding has been associated with decreased frequency or duration of otitis media episodes. If a causal relationship exists, the mechanism of protection of breast-feeding has not been established. We hypothesized that infants who are breast-fed, compared with infants who are formula-fed, have a lower prevalence of nasopharyngeal colonization with the bacterial respiratory pathogens (Streptococcus pneumoniae, Haemophilus influenzae, Moraxella catarrhalis, Streptococcus pyogenes) commonly isolated from the middle ear effusions of children with acute otitis media. In two private pediatric practices, we obtained specimens from the nasopharynx for culture from 211 infants at 1 month of age and from 173 of these infants at 2 months of age. A swab was left in place in the nasopharynx for 45 s and was then immediately transferred onto appropriate culture media. Exclusively breast-fed (n = 84) and exclusively formula-fed (n = 76) infants were similar regarding the number of persons in the household, the number of children in the household, the number of siblings in day care, and the proportion with a recent upper respiratory tract infection. The two groups did not differ significantly in the proportions found to have one or more respiratory pathogens at 1 month of age (10.7 versus 18.4%; P = 0.12) or 2 months of age (34.8 versus 35.1%; P = 0.57). We conclude that during the first 2 months after birth, the exclusive receipt of breast milk appears not to substantially influence the prevalence of nasopharyngeal colonization with common bacterial respiratory pathogens.