Effect of Silver Nanoparticles and Antibiotics on Antibiotic Resistance Genes in Anaerobic Digestion

Abstract

Water resource recovery facilities have been described as creating breeding ground conditions for the selection, transfer, and dissemination of antibiotic resistance genes (ARGs) among various bacteria. The objective of this study was to determine the effect of direct addition of antibiotic and silver nanoparticles (Ag NPs, or nanosilver) on the occurrence of ARGs in thermophilic anaerobic digesters. Test thermophilic digesters were amended with environmentally-relevant concentrations of Ag NP (0.01, 0.1, and 1.0 mg-Ag/L; corresponding to '0.7, 7.0, and 70 mg-Ag/kg total solids) and sulfamethoxazole (SMX) that span susceptible to resistant classifications (1, 5, and 50 mg/L) as potential selection pressures for ARGs. Tetracycline (tet(O), tet(W)) and sulfonamide (sulI, sulII) ARGs and the integrase enzyme gene (intI1) associated with Class 1 integrons were measured in raw sludge, test thermophilic digesters, a control thermophilic digester, and a control mesophilic digester. There was no apparent effect of Ag NPs on thermophilic anaerobic digester performance. The maximum SMX addition (50 mg/L) resulted in accumulation of volatile fatty acids and low pH, alkalinity, and volatile solids reduction. There was no significant difference between ARG gene copy numbers (absolute or normalized to 16S rRNA genes) in amended thermophilic digesters and the control thermophilic digester.

Critical review of the influences of nanoparticles on biological wastewater treatment and sludge digestion

“…As oxygen was absent in their study, no released silver ion was detected, which was recognized as the main reason for Ag-NPs showing no inhibitory effect on methanogenic activities. Similar result was reported by Miller et al (2012). Nevertheless, when sewage sludge was treated in the landfill bioreactors in the presence of Ag-NPs, the methanogenesis was adversely influenced (Yang et al, 2012b), and the toxicity of Ag-NPs was observed to be higher than its counterpart silver ion (Yang et al, 2013b(Yang et al, , 2013c.…”

Is anaerobic digestion a reliable barrier for deactivation of pathogens in biosludge?

“…Ultrasound generated the shear stress induced by cavitation while high temperature led to denaturation and loss of function of enzymes, nucleic acids, organelles and other cellular structures (Neumann et al, 2018). Microwave irradiation, UV, or nanoparticle were also reported to successfully improve the AD performance, achieving higher inactivation rate of fecal coliforms than single AD (Hong et al, 2006;Neto et al, 2006;Miller et al, 2013). The biotechnological development was less reported to integrate with AD compared to physiochemical technologies.…”

The Impacts of Triclosan on Anaerobic Community Structures, Function, and Antimicrobial Resistance

“…16 Triclosan-resistant bacteria exhibiting resistance to other antimicrobials were also found in a wastewater-impacted river. 17 The effect of triclosan on ARGs in anaerobic wastewater communities, where ARGs are abundant, [18][19][20] is poorly understood. Because ARGs are contaminants of concern 21 with negative public health consequences, 22 it is important to understand if triclosan can have an impact on the proliferation of ARGs in anaerobic wastewater communities where triclosan exposure can be high.…”