High throughput profiling of antibiotic resistance genes in urban park soils with reclaimed water irrigation

Reclaimed water irrigation (RWI) in urban environments is becoming popular, due to rapid urbanization and water shortage. The continuous release of residual antibiotics and antibiotic resistance genes (ARGs) from reclaimed water could result in the dissemination of ARGs in the downstream environment. This study provides a comprehensive profile of ARGs in park soils exposed to RWI through a high-throughput quantitative PCR approach. 147 ARGs encoding for resistance to a broad-spectrum of antibiotics were detected among all park soil samples. Aminoglycoside and beta-lactam were the two most dominant types of ARGs, and antibiotic deactivation and efflux pump were the two most dominant mechanisms in these RWI samples. The total enrichment of ARGs varied from 99.3-fold to 8655.3-fold compared to respective controls. Six to 60 ARGs were statistically enriched among these RWI samples. Four transposase genes were detected in RWI samples. TnpA-04 was the most enriched transposase gene with an enrichment was up to 2501.3-fold in Urumqi RWI samples compared with control soil samples. Furthermore, significantly positive correlation was found between ARGs and transposase abundances, indicating that transposase might be involved in the propagation of ARGs. This study demonstrated that RWI resulted in the enrichment of ARGs in urban park soils.