Meta-analysis addressing the characterization and risk identification of antibiotics and antibiotic resistance genes in global groundwater

Antimicrobial resistance (AMR) is one of the significant global issues to public health. Compared to other aquatic environments, research on AMR in groundwater is scarce. In the study, a meta-analysis was conducted to explore the characteristics and risks of antibiotics and antibiotic resistance genes (ARGs) in global groundwater, using a data set of antibiotic concentrations collected from publications during 2000-2021 and a large-scale metagenomes of groundwater samples (n = 330). The ecotoxicological risks of antibiotics in the global groundwater were evaluated using mixture risk quotient with concentration addition model to consider the synergistic effects of multiple antibiotics. Bioinformatic annotations identified 1413 ARGs belonging to 37 ARG types in the global groundwater, dominated by rifamycin, polyketide, and quinolone resistance genes and including some emerging ARGs such as mcr-family and carbapenem genes. Relatively, the level of ARGs in the groundwater from spring was significantly higher (ANOVA, p < 0.01) than those from the riparian zone, sand and deep aquifer. Similarly, metal resistance genes (MRGs) were prevalent in the global groundwater, and network analysis suggested the MRGs presented non-random co-occurrence with the ARGs in such environments. Taxonomic annotations showed Proteobacteria, Actinobacteria, Eukaryota, Acidobacteria and Thaumarchaeota were the dominant phylum in the groundwater, and the microbial community largely shaped profile of ARGs in the environment. Notably, the ARGs presented co-occurrence with mobile genetic elements, virulence factors and human bacterial pathogens, indicating potential dissemination risk of ARGs in the groundwater. Furthermore, an omics-based approach was used for health risk assessment of antibiotic resistome and screened out 152 risk ARGs in the global groundwater. Comparatively, spring and cold creek presented higher risk index, which deserves more attention to ensure the safety of water supply.