Rooftop and surface garden soils in Bangladesh harbor diverse resistome profiles

Despite the growing expansion of urban agriculture, the diversity, composition, and antimicrobial resistance (AMR) profiles (i.e., resistome) of microbial communities in rooftop and surface garden soils in Bangladesh remain insufficiently characterized, limiting our understanding of their potential role as reservoirs and disseminators of AMR. In this study, shotgun metagenome sequencing was applied to 27 soil samples, including 7 from Dhaka rooftop gardens (DRG), 6 from Dhaka surface gardens (DSG), 8 from Gazipur rooftop gardens (GRG), and 6 from Gazipur surface gardens (GSG) to comprehensively characterize their resistome profiles. We identified 88 antibiotic resistance genes (ARGs), of which 19 (21.6%) were shared across all sites, and found significant differences in resistome composition by garden type (p = 0.04). Rooftop soils harbored more ARGs (DRG, 50; GRG, 48) than surface soils (DSG, 40; GSG, 41) and were dominated by glycopeptide resistance genes, collectively representing 62.43-74.07% of ARGs. Rooftop garden soils were also enriched in efflux pumps (adeF, 45.21% of rooftop ARGs) and ribosomal-protection-related oxazolidinone resistance gene O23S (62.13% in GRG). Conversely, surface soils featured a higher abundance of genes mediating antibiotic inactivation, such as CATA (11.64% in DSG) and fosBx1 (5.94% of surface ARGs), as well as those conferring co-resistance to biocides (qacG) and metals. The efflux pump gene adeF also remained a significant component of the surface resistome (24.33% of surface ARGs). Geographic location also modulated resistome composition. Garden soils from Gazipur emerged as notable hotspots, characterized by extremely high abundances of tetracycline efflux pumps (TET45) and multiple copper resistance genes and regulators (e.g., COPA, YCNJ, CSOR). Key ARG carriers included Bacillus licheniformis, B. paralicheniformis, Pseudomonas sabulinigri, and Paenibacillus spp. Spearman correlation analyses revealed strong positive associations (r = 1.0) between specific taxa and resistance mechanisms, as well as co-occurrence patterns among antibiotic, biocide, and metal resistance genes. Collectively, these results indicate that garden soils represent important reservoirs of ARGs, with resistome architecture influenced by both garden type and location, highlighting the necessity for sustainable management practices and a One Health approach to environmental resistome surveillance.