Lack of microbiota accessible carbohydrates (MAC) can drive gut commensal extinctions. Infant formula lacks the MAC found in breastmilk, human milk oligosaccharides (HMOs). As a result, a switch from breastmilk feeding (high MAC) to formula (low MAC) may drive extinctions of infant gut commensals.
Methods : The prevalence of Bifidobacterium longum subsp. infantis, a bacterium that efficiently consumes HMOs, was compared in cohorts from Austria, Bangladesh, Finland, Gambia, Germany, Switzerland, and United States. Scientific literature reports that both Bangladesh and Gambia have long duration breastfeeding without a history of prevalent formula use; Bangladesh has a mean duration of breastfeeding of 31.9 months and Gambia has a median duration of breastfeeding >18 months. This contrasts with European countries and the US, who all have median duration of breastfeeding < 12 months and had a nadir in breastfeeding rates in the 1960s. Deterministic epidemiological models of B. infantis prevalence were created for each country to explore the potential effect of changing duration of breastfeeding on the prevalence of B. infantis.
Results : The highest prevalence of infant colonization with B. longum subsp. infantis was observed in countries without a history of disrupted breastfeeding patterns, Bangladesh and Gambia (80% and 91% colonization prevalence, respectively). The remaining countries had a prevalence of infant colonization with B. infantis ranging from 0.7% to 14%. The majority of infants in the European countries had gut communities dominated by Bifidobacterium ( >50% relative abundance Bifidobacterium) despite the low frequency of colonization with B. infantis. The R0 of B. infantis transmission varied by country.
The prevalence of infant colonization with B. infantis may be sensitive to breastfeeding duration in populations. Our data supports the concept that lack of MAC drives commensal extinctions, and suggests that deliberate intervention may be needed to restore B. infantis, a bacteria that benefits infant health. More studies are needed, particularly to determine whether species of Bifidobacterium other than B. infantis are sensitive to breastfeeding duration, and to understand the impact of different types of Bifidobacterium on infant health.
Funding Sources :
NIH awards F32HD093185 (DHT), AT007079 (DAM), and AT008759 (DAM)