Breast milk microbiota of healthy women living in the Russian Federation

Abstract

Introduction. Mother’s breast milk is considered to be the best source of infant nutrition and, paradoxical as it may sound, the only product of the infant diet, which composition is still poorly known to us. This article presents the findings of a study on the breast milk microbiota conducted in the Russian Federation for the first time.Aim. To study the composition of the breast milk microbiota of healthy women living in the Russian Federation and identify the impact of various factors on its diversity.Materials and methods. A molecular genetic study on 56 colostrum samples and 12 mature breast milk samples from 56 healthy donors using a method based on sequencing of bacterial 16S rRNA gene was conducted.Results. In a batch of 56 colostrum samples, 22 species and 242 genera of bacteria were identified. Firmicutes, Proteobacteria, Actinobacteriota were the most predominant species of bacteria in healthy women with a normal body mass index, from a physiological pregnancy, who did not take antibiotics, after natural delivery at term; Streptococcus, Staphylococcus and Gemella were the most predominant at the level of delivery. Statistical analysis of the impact of nationality, age, number of children in the family and duration of hospitalization (PERMANOVA) showed no significant differences in the proportions of bacteria in the colostrum of women (p > 0.05). The gender of the child was the only factor that turned out to be significant. The biodiversity of colostrum of girl-delivered mothers were higher (Shannon index) than that of boy-delivered mothers. In addition, the mature breast milk microbiota (1 month after delivery) has lower alpha diversity as compared to colostrum.Discussion. The analysis of our results and reports from foreign colleagues showed significant similarities and differences, which, certainly, were explained by a number of reasons related to methodological and geographical differences, the method, timing and even the time of day when breast milk samples were collected.Conclusion. In general, the colostrum of healthy women had a fairly stable bacterial composition, and its rich biodiversity fully demonstrated high quality of the first microbial inoculum for the newborn intestine. Our results provide valuable insights into the healthy breast milk microbiota in women living in the Russian Federation and can be used as reference ranges, as well as for comparison with similar indicators in women from other countries.