Chronic exposure to triclosan sustains microbial community shifts and alters antibiotic resistance gene levels in anaerobic digesters

Abstract

Triclosan, an antimicrobial chemical found in consumer personal care products, has been shown to stimulate antibiotic resistance in pathogenic bacteria. Although many studies focus on antibiotic resistance pertinent to medical scenarios, resistance developed in natural and engineered environments is less studied and has become an emerging concern for human health. In this study, the impacts of chronic triclosan (TCS) exposure on antibiotic resistance genes (ARGs) and microbial community structure were assessed in lab-scale anaerobic digesters. TCS concentrations from below detection to 2500 mg kg(-1) dry solids were amended into anaerobic digesters over 110 days and acclimated for >3 solid retention time values. Four steady state TCS concentrations were chosen (30-2500 mg kg(-1)). Relative abundance of mexB, a gene coding for a component of a multidrug efflux pump, was significantly higher in all TCS-amended digesters (30 mg kg(-1) or higher) relative to the control. TCS selected for bacteria carrying tet(L) and against those carrying erm(F) at concentrations which inhibited digester function; the pH decrease associated with digester failure was suspected to cause this selection. Little to no impact of TCS was observed on intI1 relative abundance. Microbial communities were also surveyed by high-throughput 16S rRNA gene sequencing. Compared to the control digesters, significant shifts in community structure towards clades containing commensal and pathogenic bacteria were observed in digesters containing TCS. Based on these results, TCS should be included in studies and risk assessments that attempt to elucidate relationships between chemical stressors (e.g. antibiotics), antibiotic resistance genes, and public health.

Inhibition during Anaerobic Co-Digestion of Aqueous Pyrolysis Liquid from Wastewater Solids and Synthetic Primary Sludge

“…Sequencing was performed by a commercial company (Molecular Research, LP, Shallowater, TX, USA) using the Illumina MiSeq v3 300 base pair sequencing platform (Illumina, San Diego, CA, USA). Universal primers, 515F and 806R were used for PCR amplification to target the V4 variable region of the 16S rRNA gene as described elsewhere [27]. Raw un-joined sequence data were quality filtered and sequences were depleted from barcodes and primers.…”

Removal of antibiotic resistance genes in an anaerobic membrane bioreactor treating primary clarifier effluent at 20 °C

“…Chemical micropollutants are prevalent in wastewater and pose a variety of ecological risks including fish feminization and the spread of antibiotic resistance. [13][14][15][16][17][18] Results vary in the few existing publications regarding chemical micropollutant removal through AnMBRs. 19,20 Additional research is warranted to help determine if pre-or post-treatment is needed to achieve chemical micropollutant removal.…”

Sub-Pilot-Scale Autocatalytic Pyrolysis of Wastewater Biosolids for Enhanced Energy Recovery

“…Biosolids are treated using processes such as anaerobic digestion, but their residual energy is refractory and is not fully recovered before biosolids land application [6]. Additionally, organic contaminants of emerging concern in biosolids such as triclosan are potential issues as well [7][8][9][10][11]. Hence, post-treatment techniques to improve energy and resource recovery and reduce adverse environmental impacts are crucial to achieving sustainable WRRFs.…”