The University of Alberta-based Synergy in Microbiota Research (SyMBIOTA) program, led by CHILD Cohort Study (CHILD) investigator Dr. Anita Kozyrskyj and Dr. James Scott (University of Toronto), continues to leverage CHILD biological samples and data to elucidate the dynamics among the human gut microbiome, environmental exposures and health outcomes. “Gut microbiome” refers to a community of microorganisms (such as bacteria, fungi, and viruses) that inhabit the digestive tract (or gut).
Three recent SyMBIOTA research studies explore: the impact of antibiotic use during childbirth and cesearean section delivery on an infant’s gut microbes; the impact of antibiotic use and exposure to household cleaning products on C. difficile colonization in infants; and the relationship between the metabolites in an infant’s gut and later risk of obesity in childhood.
The first study, published in the journal Microorganisms in August 2021, set out to explore the joint effect of multiple birth-related factors—delivery mode, antibiotic use during childbirth, and the onset of labour—on the abundance of a specific bacterium (Bifidobacterium) in the infant gut microbiome.
“Members of the genus Bifidobacterium are pioneer gut colonizers,” explain the authors. “They are considered foundational microbiota members that influence the early-life gut microbial community and exert positive effects on host health.”
The researchers studied associations between the microbes in the stool of 1,654 infants in CHILD with information about the conditions of their birth and found that the abundance of beneficial Bifidobacteria was decreased in infants born vaginally whose mothers received antibiotics during birth, even among breastfed infants, and was also decreased in infants born by cesarean delivery, with or without labour.
The second study, published in Antibiotics (Basel) in July 2022, investigated the effect of early-life exposure to antibiotics and household cleaning products on C. difficile colonization in infants.
“C. difficile is a major pathogen that is responsible for diarrhea in adults and older children,” explain the authors. “Infants colonized by C. difficile usually show no symptoms, but this colonization may serve as a reservoir for adult C. difficile infections, or it may indicate that the infant has lower resistance to colonization and that the maturation of its gut microbiota may be delayed. This, in turn, may make the child more vulnerable to allergies and asthma, which we already know are associated with early-life antimicrobial exposure.”
The researchers analyzed the stool of 1,429 infants in CHILD at 3–4 months of age and 1,728 infants in CHILD at 12 months of age, and studied associations with antimicrobial exposures collected from hospital birth charts and standardized questionnaires. They found that C. difficile colonization was significantly higher in infants exposed to both antibiotics and a higher usage of household cleaning products.
The third study, published in the International Journal of Obesity in July 2022, examined the relationship between the presence of specific metabolites in an infant’s gut, and a child’s risk of obesity at one and three years of age.
Using samples from 647 infants in CHILD, researchers analyzed a number of important metabolites in the infants’ stool at age 3-4 months and correlated them with information about these children’s body mass index (BMI) scores at ages 1 and 3 years. They found that a greater presence of one infant fecal metabolite (formate) lowered the BMI by age three, whereas the greater presence of a different metabolite (butyrate) increased a child’s BMI. However, the researchers also found that these differences in metabolites did not affect obesity risk among infants that were exclusively breastfed; in other words, exclusive breastfeeding appeared to counterbalance the obesity-influencing effects of these fecal metabolites.
“This study identifies an important area of future research in understanding the pathogenesis of obesity,” the authors observe.
“It is a great advantage to SyMBIOTA research that CHILD is such a well-characterized birth cohort,” observes Dr. Kozyrskyj. “It is enabling remarkable advances in our understanding of the gut microbiome, how it is influenced by our environment, and how it, in turn, influences our health. We plan to continue building on these discoveries, thanks to the generosity of the families in CHILD who continue contributing to the Study’s collection of biological samples and data.”
SyMBIOTA is one of seven CIHR-funded Canadian Microbiome Initiative teams. Visit the SyMBIOTA Lab website.