Distribution of typical antibiotic resistance genes in underlying surface sediments from urban commercial public squares and their potential hosts.

Increasing attention has been paid to antibiotic resistance genes (ARGs) in environments. However, no available literature could be found on ARGs contamination in urban underlying surface sediments. In this study, sediments from commercial public squares around Nanjing (China) were selected for the investigation of target ARGs distribution, showing that intracellular ARGs (iARGs) in particles were the dominant with their relative abundances in descending order of 4.82 × 10 copies/16S rRNA (<0.063 mm), 4.18 × 10 copies/16S rRNA (0.063-0.125 mm), 3.70 × 10 copies/16S rRNA (0.25-0.5 mm), 3.44 × 10 copies/16S rRNA (0.5-1 mm), 3.20 × 10 copies/16S rRNA (0.125-0.25 mm) and 9.53 × 10 copies/16S rRNA (1-2 mm), which was different with that of extracellular ARGs (eARGs). The influence of street sweeping on ARGs levels indicated that the species and relative abundances for both iARGs and eARGs in sediments from different sites were not consistent with the corresponding population densities. The correlation between ARGs and dominant bacterial communities implied that both Firmicutes and Bacteroidetes were positively correlated with ARGs (P < 0.01). The role of solar UV disinfection demonstrated that UV irradiation could inactivate antibiotic resistance bacteria (ARB) slightly with 0.5-1.0 log reduction, implying a considerable risk of ARB after solar irradiation. Our results suggested that it would need the more effective sweeping modes for the cleaning of small particles (<0.25 mm) and the higher disinfection to ARGs potential hosts (like Firmicutes and Blastocatella).