Meconium microbiota types dominated by lactic acid or enteric bacteria are differentially associated with maternal eczema and respiratory problems in infants

Background: Culture-dependent methods have shown that meconium, the newborn's first intestinal discharge, is not sterile, but the diversity of bacteria present in this material needs to be further characterized by means of more sensitive molecular techniques.

Objective: Our aims were to characterize molecularly the meconium microbiota in term infants, to assess whether it contributes to the future microbiota of the infants' gastrointestinal tract, and to evaluate how it relates to lifestyle variables and atopy-related conditions.

Methods: We applied high-throughput pyrosequencing of the 16S rRNA gene to study the meconium microbiota in twenty term newborns from a Spanish birth cohort. For comparison, we characterized the microbiota in fecal samples from seven pregnant women days before delivery and in two series of infant samples spanning the first seven months of life. We also compared our data with vaginal and skin microbiota characterized in independent studies. Different types of meconium microbiota were defined based on taxonomic composition and abundance and their associations with different factors were statistically evaluated.

Results: The meconium microbiota differs from those in adult feces, vagina and skin, but resembles that of fecal samples from young infants. Meconium samples clustered into two types with different bacterial diversity, richness and composition. One of the types was less diverse, dominated by enteric bacteria and associated with a history of atopic eczema in the mother (P = 0.038), whereas the second type was dominated by lactic acid bacteria and associated with respiratory problems in the infant (P = 0.040).

Conclusions & clinical relevance: Our findings suggest that the meconium microbiota has an intrauterine origin and participates in gut colonization. Although based on a small population sample, our association analyses also suggest that the type of bacteria detected in meconium is influenced by maternal factors and may have consequences for childhood health.