Abstract
Colonization of the infant gut is believed to be critically important for a healthy growth as it influences gut maturation, metabolic, immune and brain development in early life. Understanding factors that influence this process is important, since an altered colonization has been associated with a higher risk of diseases later in life. Fecal samples were collected from 108 healthy neonates in the first half year of life. The composition and functionality of the microbiota was characterized by measuring 33 different bacterial taxa by qPCR/RT qPCR, and 8 bacterial metabolites. Information regarding gender, place and mode of birth, presence of siblings or pets; feeding pattern and antibiotic use was collected by using questionnaires. Regression analysis techniques were used to study associations between microbiota parameters and confounding factors over time. Bacterial DNA was detected in most meconium samples, suggesting bacterial exposure occurs in utero. After birth, colonization by species of Bifidobacterium, Lactobacillus and Bacteroides was influenced by mode of delivery, type of feeding and presence of siblings, with differences found at species level and over time. Interestingly, infant-type bifidobacterial species such as B. breve or B. longum subsp infantis were confirmed as early colonizers apparently independent of the factors studied here, while B. animalis subsp. lactis presence was found to be dependent solely on the type of feeding, indicating that it might not be a common infant gut inhabitant. One interesting and rather unexpected confounding factor was gender. This study contributes to our understanding of the composition of the microbiota in early life and the succession process and the evolution of the microbial community as a function of time and events occurring during the first 6 months of life. Our results provide new insights that could be taken into consideration when selecting nutritional supplementation strategies to support the developing infant gut microbiome.
Highlights
Composed of 1011 to 1012 micro-organisms per gram of feces, and estimated to harbor more than 500 bacterial species, the human gastrointestinal microbiota is a large and diverse community of microorganisms and is in close cross-talk with its host [1,2,3]
Since time was included in our model as a variable, our results showed that delaying the collection of meconium samples by one day increased the chance of detecting the following bacteria: Bifidobacterium; Bacteroides fragilis group; Enterococcus; Staphylococcus; L. gasseri subgroup; and B. adolescentis by 3.1 (p = 0.003); 2.35 (p = 0.01); 10.69 (p
The results we have reported so far were found to be dependent only on the mode of delivery, in this study we found that the presence of the L. reuteri subgroup, the L. gasseri subgroup and B. bifidum was dependent on the interaction between mode of delivery and the type of feeding (Table 5)
Summary
Composed of 1011 to 1012 micro-organisms per gram of feces, and estimated to harbor more than 500 bacterial species, the human gastrointestinal microbiota is a large and diverse community of microorganisms and is in close cross-talk with its host [1,2,3]. The infant gut was considered to be sterile, only becoming colonized after birth from the maternal microbiota, diet, and the environment [4,5,6,7]. Recent findings suggest that microbial exposure may start already during gestation and colonization starts with the early settlers derived from the maternal microbiota and environment immediately from birth [8,9,10,11]. The development of the infant gut microbiota is profoundly influenced by host genotype, gestational age, antibiotic use, mode of delivery, diet and the context in which the infant is born (rural vs urban, presence of siblings, pets and other factors) [4, 5, 12,13,14,15,16,17]. Previous studies have demonstrated that strains originating from the maternal gut and vagina are transferred to the infant’s gut in case of a vaginal delivery (VD) [18,19,20], while infants born by cesarean section (CS) are suggested to be initially colonized by bacteria from the environment such as from maternal skin, hospital staff or other neonates [21]
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