Effects of heavy metals on the development and proliferation of antibiotic resistance in urban sewage treatment plants

Sewage treatment plants (STPs) are considered as hotspots for the emergence and proliferation of antibiotic resistance. However, the impact of heavy metals contamination on dispersal of antibiotic resistance in STPs is poorly understood. This study simultaneously investigated the effect of removal of metal and antibiotic resistance as well as mobile elements at different treatment units of STPs in Delhi, India. Results showed that treatment technologies used in STPs were inefficient for the complete removal of metal and antibiotic resistance, posing an ecological risk of co-selection of antibiotic resistance. The strong correlations were observed between heavy metals, metal and antibiotic resistance, and integrons, implying that antibiotic resistance may be exacerbated in the presence of heavy metals via integrons, and that metal and antibiotic resistance share a common or closely associated mechanism. We quantified an MRG rcnA, conferring resistance to Co and Ni, and identified that it was more abundant than all MRGs, ARGs, integrons, and 16S rRNA, suggesting rcnA could be important in antibiotic resistance dissemination in the environment. The associations between heavy metals, metal and antibiotic resistance, and integrons highlight the need for additional research to better understand the mechanism of coselection as well as to improve the removal efficacy of current treatment systems.

Automated summary

Sewage treatment plants (STPs) are considered hotspots for antibiotic resistance, but the impact of heavy metal contamination on the dispersion of antibiotic resistance in STPs is not well understood. This study reveals that the removal technologies used in STPs are inefficient in completely removing metal and antibiotic resistance, posing a risk of co-selection of antibiotic resistance. The study also identifies significant correlations between heavy metals, metal and antibiotic resistance, and integrons, suggesting a potential mechanism for the exacerbation of antibiotic resistance in the presence of heavy metals.