Stool microbial composition is associated with recent and future diarrhea and fever events in breastfed Danish...

Gastroenteritis is an important cause of ailment among infants in high-income countries, including Denmark. There are many cases of diarrhea among Danish children for which no etiological agent is detected. This study investigated the associations between gastroenteritis-related morbidities (diarrhea, fever, and vomiting) and gut microbial community in well-nourished, breastfeeding Danish infants. Infant stool samples, morbidity questionnaires, and diet/breastfeeding questionnaires were collected at three time points during the first 8.5 months of life. The V4-V5 region of the 16S rRNA gene was amplified from stool DNA extracts, sequenced with Illumina MiSeq, and analyzed using QIIME2. PERMANOVA, linear mixed-effects modeling, and ANCOM-BC2 were used to identify associations between infant gut microbiome and gastroenteritis-related morbidities across all visits. Logistic regression and random forest models were employed to determine whether early gut microbial alpha diversity or abundance, respectively, could predict morbidity later in infancy. Alpha diversity was negatively associated with diarrhea. Granulicatella abundance was positively associated with diarrhea. From 3.5 to 6 months of age, Bacteroidales abundance was negatively associated with fever. Faith's phylogenetic diversity, Staphylococcales abundance, and Haemophilus abundance during 3.5 months of life were positively associated with future diarrhea during ages 3.5-8.5 months. Pielou's evenness and Actinobacteriota abundance within 3.5 months of life had negative and positive associations, respectively, with fever during ages 3.5-8.5 months. This study reveals diarrhea is associated with stool Granulicatella in well-nourished, breastfeeding Danish infants, as it is in children from low-income countries, and that the early gut microbiome may contribute to risks of diarrhea and fever morbidities later in infancy.CLINICAL TRIALSThis trial was registered at ClinicalTrials.gov as NCT03254329.

Gastroenteritis continues to cause much morbidity among infants in high-income countries, and the relationship with the gut microbiome is not fully understood, especially for well-nourished and breastfeeding infants. In the study presented here, infant stool Staphylococcales abundance (comprised of Staphylococcus and Gemella) and Haemophilus abundance during the first few months of life were positively associated with later diarrhea in well-nourished and breastfeeding Danish infants. Meanwhile, the abundance of Granulicatella (a facultative anaerobe with pathogenic potential) was greater in stool from infants who had recent diarrhea, suggesting further research is needed to determine its possible role in diarrhea and recovery from diarrhea. Fever usually did not co-occur with diarrhea or vomiting. Early life Actinobacteriota abundance was positively associated with later fever. This phylum was represented here by both pathobionts (Actinomyces) and mutualists (bifidobacteria), which may have contributed to fever differently-pathobionts through infection and mutualists through promotion of effective immune response to infection.