Objective Dysbiosis of the infant gut microbiota may have long‐term health consequences. This study aimed to determine the impact of maternal intrapartum antibiotic prophylaxis (IAP) on infant gut microbiota, and to explore whether breastfeeding modifies these effects. Design Prospective pregnancy cohort of Canadian infants born in 2010–2012: the Canadian Healthy Infant Longitudinal Development (CHILD) Study. Setting General community. Sample Representative sub‐sample of 198 healthy term infants from the CHILD Study. Methods Maternal IAP exposures and birth method were documented from hospital records and breastfeeding was reported by mothers. Infant gut microbiota was characterised by Illumina 16S rRNA sequencing of faecal samples at 3 and 12 months. Main outcome measures Infant gut microbiota profiles. Results In this cohort, 21% of mothers received IAP for Group B Streptococcus prophylaxis or pre‐labour rupture of membranes; another 23% received IAP for elective or emergency caesarean section (CS). Infant gut microbiota community structures at 3 months differed significantly with all IAP exposures, and differences persisted to 12 months for infants delivered by emergency CS. Taxon‐specific composition also differed, with the genera Bacteroides and Parabacteroides under‐represented, and Enterococcus and Clostridium over‐represented at 3 months following maternal IAP. Microbiota differences were especially evident following IAP with emergency CS, with some changes (increased Clostridiales and decreased Bacteroidaceae) persisting to 12 months, particularly among non‐breastfed infants. Conclusions Intrapartum antibiotics in caesarean and vaginal delivery are associated with infant gut microbiota dysbiosis, and breastfeeding modifies some of these effects. Further research is warranted to explore the health consequences of these associations. Tweetable abstract Maternal #antibiotics during childbirth alter the infant gut #microbiome.

Our gut microbiota provide a number of important functions, one of which is the metabolism of dietary fiber and other macronutrients that are undigested by the host. The main products of this fermentation process are short-chain fatty acids (SCFAs) and other intermediate metabolites including lactate and succinate. Production of these metabolites is dependent on diet and gut microbiota composition. There is increasing evidence for the role of SCFAs in host physiology and metabolic processes as well as chronic inflammatory conditions such as allergic disease and obesity. We aimed to investigate differences in fecal SCFAs and intermediate metabolites in 163 infants at 3–5 months of age according to breastfeeding status. Compared to no exposure to human milk at time of fecal sample collection, exclusive breastfeeding was associated with lower absolute concentrations of total SCFAs, acetate, butyrate, propionate, valerate, isobutyrate, and isovalerate, yet higher concentrations of lactate. Further, the relative proportion of acetate was higher with exclusive breastfeeding. Compared to non-breastfed infants, those exclusively breastfed were four times more likely (aOR 4.50, 95% CI 1.58–12.82) to have a higher proportion of acetate relative to other SCFAs in their gut. This association was independent of birth mode, intrapartum antibiotics, infant sex, age, recruitment site, and maternal BMI or socioeconomic status. Our study confirms that breastfeeding strongly influences the composition of fecal microbial metabolites in infancy.

We report an open-label study of the effects of bilastine at 20, 40 and 80 mg daily for 2 weeks on the signs and symptoms of chronic spontaneous urticaria (CSU) in patients who had not responded sufficiently to licensed doses of other H 1 -antihistamines.The study was designed to mimic the real-life situation in which the antihistamine dose is increased gradually up to fourfold the licensed dose, depending on the effectiveness of the previous dose. Its limitations include the relatively small number of patients and uncontrolled design. LETTERS TO THE EDITOR | 2073