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Human milk microorganisms contribute not only to the healthy development of the immune system in infants, but also in shaping the gut microbiota. We evaluated the effect of the maternal diet during pregnancy and during the first month of lactation on the human milk microbiota in a cross-sectional study including 94 healthy lactating women. Microbiota composition was determined by 16S rDNA profiling and nutrient intake assessed through food questionnaires. Thirteen genera were present in at least 90% of all samples, with three genera present in all samples: Streptococcus, Staphylococcus, and Corynebacterium. Cluster analysis indicated two distinct compositions: one marked by a high abundance of Streptococcus (cluster 1), and other by a high abundance of Staphylococcus (cluster 2). A global association with milk microbiota diversity was observed for vitamin C intake during pregnancy (p = 0.029), which was higher for cluster 2 individuals (cluster 2 median = 232 mg/d; cluster 1 = 175 mg/d; p = 0.02). Positive correlations were found between Bifidobacterium in the milk and intake of polyunsaturated and linoleic fatty acids during the lactation period (p < 0.01). We show that maternal diet influences the human milk microbiota, especially during pregnancy, which may contribute in shaping the gut microbiota.

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This review summarizes recent findings on the changes that occur during pregnancy in the composition of the vaginal and gut microbiome and their association with metabolic, hormonal, and immunological factors. Despite many studies on the topic, the vaginal and gut microbial profiles and their influence on the course of pregnancy are still unclear. We present data suggesting that, contrary to traditional understanding, the placenta is not sterile but has a microbial community. We review and discuss new findings on changes in the richness and diversity of the microbiota of pregnant women with term or preterm births, obesity, and gestational diabetes mellitus. Several factors influence the bacterial profile of these women and may explain, at least in part, some of the discrepant findings between studies. The development of and access to new molecular biology methods and techniques has expanded the possibilities of research. This will contribute to a better understanding of the microbiome and its role in normal and pathological pregnancies.

The initial colonization of the human microbiota is of paramount importance. In this context, the oropharyngeal administration of colostrum is a safe, viable, and well-tolerated practice even by the smallest preterm infants. Therefore, this study evaluated the effects of oropharyngeal administration of colostrum on the establishment of preterm infants’ oral microbiota. A longitudinal observational study was carried out with 20 premature neonates, divided into two groups: one receiving the protocol (Oropharyngeal Administration of Colostrum; OAC) and the other one receiving Standard Caare (SC). Saliva samples were collected from the newborns weekly during the study period (from the day of birth until the 21st day of life) for analysis of oral microbiota through 16S rRNA gene sequencing. We observed that the colonization of the oral microbiota of preterm newborns preseanted a higher relative abundance of Staphylococcus on the 7th day of life, mainly in the OAC group. Additionally, an increased abundance of Bifidobacterium and Bacteroides was observed in the OAC group at the first week of life. Regarding alpha and beta diversity, time was a key factor in the oral modulation of both groups, showing how dynamic this environment is in early life.

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Few studies reported the relation of intestinal microbiome composition and diversity in pediatric patients with primary sclerosing cholangitis (PSC) and ulcerative colitis (UC). In this cross-sectional study, we selected patients younger than 19 years old from the pediatric gastroenterology and hepatology outpatient clinic of a tertiary hospital to describe the intestinal microbiome of pediatric patients with PSC associated or not to UC. Patients were divided in PSC, PSC+UC, and UC diagnosis. A stool sample was collected from each patient (n=30) and from a healthy relative/neighbor (n=23). The microbiome composition was assessed using MiSeq (Illumina) platform. Differences in microbial composition were found between PSC and PSC+UC groups. The relative abundance of Veillonella and Megasphaera genera were increased depending on patients’ age at diagnosis. Veillonella was also increased in patients who were in an active status of the disease. Both genera were positively correlated to total bilirubin and gamma-glutamyl transferase. As a conclusion, the disease, the age and the disease activity status seem to influence the intestinal microbiome, highlighting the difference of intestinal microbiome profile for patients depending on age at diagnosis. We also showed an increase of Veillonella in patients with PSC and PSC+UC, and a positive correlation of dysbiosis and higher gamma-glutamyl transferase and total bilirubin in PSC+UC patients. Our findings are promising in the diagnosis, prognosis, and future therapeutic perspectives for PSC patients.

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