The Impact of Breastfeeding on Nasopharyngeal Microbial Communities in Infants

Rationale: Breastfeeding elicits significant protection against respiratory tract infections in infancy. Modulation of respiratory microbiota might be part of the natural mechanisms of protection against respiratory diseases induced by breastfeeding. Objectives: To study the association between breastfeeding and nasopharyngeal microbial communities, including all cultivable and noncultivable bacteria. Methods: In this observational study, we analyzed the microbiota of infants that had received exclusive breastfeeding (n = 101) and exclusive formula feeding (n = 101) at age 6 weeks and 6 months by 16S-based GS-FLX-titanium-pyrosequencing. Measurements and Main Results: At 6 weeks of age the overall bacterial community composition was significantly different between breastfed and formula-fed children (nonmetric multidimensional, scaling, P = 0.001). Breastfed children showed increased presence and abundance of the lactic acid bacterium Dolosigranulum (relative effect size [RES], 2.61; P = 0.005) and Corynebacterium (RES, 1.98; P = 0.039) and decreased abundance of Staphylococcus (RES, 0.48; P 0.03) and anaerobic bacteria, such as Prevotella (RES, 0.25; P < 0.001) and Veillonella (RES, 0.33; P < 0.001). Predominance (>50% of the microbial profile) of Corynebacterium and Dolosigranulum was observed in 45 (44.6%) breastfed infants compared with 19 (18.8%) formula-fed infants (relative risk, 2.37; P = 0.006). Dolosigranulum abundance was inversely associated with consecutive symptoms of wheezing and number of mild respiratory tract infections experienced. At 6 months of age associations between breastfeeding and nasopharyngeal microbiota composition had disappeared. Conclusions: Our data suggest a strong association between breastfeeding and microbial community composition in the upper respiratory tract of 6-week-old infants. Observed differences in microbial community profile may contribute to the protective effect of breastfeeding on respiratory infections and wheezing in early infancy.