Early-life antibiotic exposure is associated with diverse long-term adverse health outcomes. Despite the immunomodulatory effects of gastrointestinal fungi, the impact of antibiotics on the fungal community (mycobiome) has received little attention. The objectives of this study were to determine the impact of commonly prescribed infant antibiotic treatments on the microbial loads and structures of bacterial and fungal communities in the gastrointestinal tract. Thirty-two piglets were divided into four treatment groups: amoxicillin (A), amoxicillin-clavulanic acid (AC), gentamicin-ampicillin (GA), and flavored placebo (P). Antibiotics were administered orally starting on postnatal day (PND) 1 until PND 8, except for GA, which was given on PNDs 5 and 6 intramuscularly. Fecal swabs were collected from piglets on PNDs 3 and 8, and sow feces were collected 1 day after farrowing. The impacts of antibiotics on bacterial and fungal communities were assessed by sequencing the 16S rRNA and the internal transcribed spacer 2 (ITS2) rRNA genes, respectively, and quantitative PCR was performed to determine total bacterial and fungal loads. Antibiotics did not alter the α-diversity (P = 0.834) or β-diversity (P = 0.565) of fungal communities on PND 8. AC increased the ratio of total fungal/total bacterial loads on PND 8 (P = 0.027). There was strong clustering of piglets by litter on PND 8 (P < 0.001), which corresponded to significant differences in the sow mycobiome, especially the presence of Kazachstania slooffiae. In summary, we observed a strong litter effect and showed that the maternal mycobiome is essential for shaping the piglet mycobiome in early life. IMPORTANCE This work provides evidence that although the fungal community composition is not altered by antibiotics, the overall fungal load increases with the administration of amoxicillin-clavulanic acid. Additionally, we show that the maternal fungal community is important in establishing the fungal community in piglets.
Keywords: Kazachstania slooffiae; antibiotics; fungi; mycobiome; porcine.