Spatial distribution of antibiotics and antibiotic resistance genes in tidal flat reclamation areas in China

Tidal flat areas are important resources for land development and are becoming antibiotic resistance receivers that trigger major health concerns. The spatial distributions of forty-nine antibiotics, nine antibiotic resistance genes (ARGs), one mobile gene element (MGE) gene, and nine available metals in the soils and sediments along the coastlines of the Yellow Sea in China were quantified. Hierarchical linear model analysis was used to explore relationships between the antibiotics and ARGs across multiple effects resulting from human activities and environmental factors. Fish farm sediments and farmland soils showed high levels of quinolones (QNs) (maximum 637 ng·g−1), sulfonamides (SAs) (maximum 221 ng·g−1), and corresponding ARGs. Significant positive correlations (P from 5.47 × 10−14 to 0.0487) were observed between the antibiotics (QNs, SAs, and chlortetracycline) and their corresponding ARGs (qnrA, qnrD, aac(6')-Ib-cr, dfrA, sul2, and tetA), indicating the selective pressure from antibiotics in soils and sediments. Nine available metals had positive correlations with at least one ARG, indicating heavy metal pollution could enhance the ARGs. Sheep and poultry husbandry and marine aquaculture contribute the most to the antibiotic resistance in the coastlines. In conclusion, antibiotic pollutions have promoting effects at sub-inhibitory concentrations and more attention should be given to inhibit the enrichment of ARGs during tidal flat reclamation processes. The study also suggests the induction effects from metal pollutions, MGE spread, and the antibiotic pollutions from the usage in livestock and aquaculture.