Association of metals with early postnatal gut microbiota among infants admitted to the neonatal intensive care unit

The gut microbiota is closely related to infant health. However, the impact of environmental factors on the gut microbiota has not been widely investigated, particularly in vulnerable populations such as infants admitted to the neonatal intensive care unit (NICU). This study investigated the association between exposure to 12 metals and the composition of the gut microbiota in infants admitted to the NICU. Metal concentrations were determined in serum samples obtained from 107 infants admitted to the NICU at Hunan Children's hospital, China. Gut microbiota data were derived from 16S rRNA sequencing using stool samples. Generalized linear regression (GLR) models and Bayesian kernel machine regression (BKMR) analyses were used to estimate the associations between metals and both alpha-diversity indices and bacterial taxa. The GLR models showed that tin correlated negatively with the Shannon index (β = −0.55, 95% conficence interval [CI]: −0.79, −0.30, P_FDR< 0.001) and positively with the Simpson index (β = 0.26, 95% CI: 0.13, 0.39, P_FDR< 0.001). The BKMR analysis yielded similar results, showing that tin had the largest posterior inclusion probability for both the Shannon (0.986) and the Simpson (0.796) indices. Tin, cadmium, mercury, lead, and thallium were associated with changes in one or more taxa at the genus level. The BKMR analysis also revealed a negative correlation between metal mixtures and Clostridium_sensu_stricto, and tin contibuted mostly to the negative correlation. Early postnatal exposure to metals were associated with differences in the microbiome among infants admitted to the NICU. However, as the study was cross-sectional, these relationships must be confirmed in further studies.