We aimed to examine the effects of antibiotic and probiotic usage on the gut microbiota structure and the presence of antibiotic-resistance genes (ARGs) in infants during the first six months of life. Questionnaires and fecal samples were collected within three days of birth, two months, and six months to assess antibiotic and probiotic exposure. Gut microbiotas were sequenced via 16S rRNA, and ARGs were conducted by qPCR, including beta-lactam (mecA, bla_TEM), tetracycline (tetM), fluoroquinolone (qnrS), aminoglycoside (aac(6′)-Ib), and macrolide (ermB). Infants were categorized by antibiotic and probiotic usage and stratified by delivery mode, microbial composition, and ARG abundances were compared, and potential correlations were explored. A total of 189 fecal samples were analyzed in this study. The gut microbiota diversity (Chao1 index) was significantly lower in the “only probiotics” (PRO) group compared to the “neither antibiotics nor probiotics” (CON) group at six months for the CS stratification (p = 0.029). Compositionally, the abundance of core genus Bifidobacterium_pseudocatenulatum was less abundant for the antibiotic during delivery (IAP) group than that in the CON group within the first three days (p = 0.009), while core genus Enterococcus_faecium was more abundant in the PRO than that in the CON group (p = 0.021) at two months. ARGs were highly detected, with Enterococcus hosting tetM and Escherichia associated with bla_TEM within three days of birth, though no correlation was found between Bifidobacterium and ARGs. These findings emphasized the critical importance of carefully managing antibiotic and probiotic exposures in early life, with implications for promoting lifelong health through preserving a healthy infant gut ecosystem.

The aim of the study was to investigate the association between maternal dietary iron intake during pregnancy and the gut microbiota characteristics of both the mother and neonate in a well-characterized cohort. A total of 95 mother-neonate dyads were included in our study, with basic information collected through questionnaires. A semi-quantitative Food Frequency Questionnaire (FFQ) was used to assess maternal dietary intake during pregnancy, and maternal dietary iron intake was categorized into <20 mg/d and ≥20 mg/d groups. Fecal samples were collected from the mother in the third trimester and the neonate, allowing for assessment of the community profile and diversity of gut microbiota via 16S rRNA amplicon sequencing. Then, a comparison between different maternal dietary iron intake groups was conducted, adjusting for delivery mode (VD, vaginal delivery; CS, cesarean section) and other potential confounding factors. No significant differences in community profile and diversity were observed for the maternal gut microbiota in different dietary iron intake groups. In neonate fecal samples, the Shannon (P = 0.044) and Simpson (P = 0.010) diversity indices of the gut microbiota were higher in the maternal dietary iron intake ≥20 mg/d group, while Simpson diversity presented the same tendency in vaginal delivery (P = 0.041) after stratification. The relative abundance of the core genus Bifidobacterium showed a significant difference between groups (4.69 [1.19–12.77] vs. 13.98 [3.44–27.28]; P = 0.044). The abundance of Lactobacillus was different in the ≥20 mg/d group under both delivery modes (VD: beta = 2.9, w = 4.13; CS: beta = 2.77, w = 3.8). Our findings suggest that adequate dietary iron intake during pregnancy may promote beneficial bacterial colonization and increase the biodiversity of the neonate gut microbiota.