Effect of amoxicillin on the gut microbiome of children with severe acute malnutrition in Madarounfa, Niger: a retrospective metagenomic analysis of a placebo- controlled trial

Background Children with severe acute malnutrition are treated with antibiotics as outpatients. We aimed to determine the effect of 7 days of amoxicillin on acute and long-term changes to the gut microbiome and antibiotic resistome in children treated for severe acute malnutrition.Methods We conducted a secondary analysis of a randomised, double-blinded, placebo-controlled trial (NCT01613547) of amoxicillin in children (aged 6-59 months) with severe acute malnutrition treated as outpatients in Madarounfa, Niger. We randomly selected 161 children from the overall cohort (n=2399) for initial 12-week follow-up from Sept 23, 2013 to Feb 3, 2014. We selected a convenience sample of those 161 children, on the basis of anthropometric measures, for follow-up 2 years later (Sept 28 to Oct 27, 2015). Children provided faecal samples at baseline, week 1, week 4, week 8, week 12, and, for those in the 2-year follow-up cohort, week 104. We conducted metagenomic sequencing followed by microbiome and resistome profiling of faecal samples. 38 children without severe acute malnutrition and six children with severe acute malnutrition matching the baseline ages of the original cohort were used as reference controls.Findings In the 12-week follow-up group, amoxicillin led to an immediate decrease in gut microbiome richness from 37 center dot 6 species (95% CI 32 center dot 6-42 center dot 7) and Shannon diversity index (SDI) 2 center dot 18 (95% CI 1 center dot 97-2 center dot 39) at baseline to 27 center dot 7 species (95% CI 22 center dot 9-32 center dot 6) species and SDI 1 center dot 55 (95% CI 1 center dot 35-1 center dot 75) at week 1. Amoxicillin increased gut antibiotic resistance gene abundance to 6044 reads per kilobase million (95% CI 4704-7384) at week 1, up from 4800 (3391-6208) at baseline, which returned to baseline 3 weeks later. 35 children were included in the 2-year follow-up; the amoxicillin-treated children (n=22) had increased number of species in the gut microbiome compared with placebo-treated children (n=13; 60 center dot 7 [95% CI 54 center dot 7-66 center dot 6] vs 36 center dot 9 [29 center dot 4-44 center dot 3]). Amoxicillin-treated children had increased Prevotella spp and decreased Bifidobacterium spp relative to age-matched placebo-treated children, indicating a more mature, adult-like microbiome.Interpretation Amoxicillin treatment led to acute but not sustained increases in antimicrobial resistance genes and improved gut microbiome maturation 2 years after severe acute malnutrition treatment.