Triclosan is the Predominant Antibacterial Compound in Ontario Sewage Sludge

Abstract

Sewage treatment plants (STPs) accumulate both antibiotic and nonantibiotic antimicrobial compounds that can select for antibiotic resistant bacteria. Herein, we aimed to identify the predominant antibacterial compounds impacting E. coli from Ontario sewage sludge consisting of thousands of unknown compounds. Among the 10 extracted sludge samples, 6 extracts exerted significant growth inhibition effects in E. coli. A total of 103 compounds were tentatively detected across the 10 sludge samples by suspect screening, among which the bacterial enoyl-ACP reductase (FabI) inhibitor triclocarban was detected at the highest abundance. A hypomorphic FabI knockdown E. coli strain was highly susceptible to the sludge extracts, confirming FabI inhibitors as the primary antibacterial compounds in the sludge. Protein affinity pulldown identified triclosan as the major ligand binding to a His-tagged FabI protein from the sludge, despite the higher abundance of triclocarban in the same samples. Effect-directed analysis was used to determine the contributions of triclosan to the observed antibacterial potencies. Antibacterial effects were only detected in F17 and F18 across 20 fractions, which was consistent with the elution of triclosan and triclocarban in the same two fractions. Further, potency mass balance analysis confirmed that triclosan explained the majority (58–113%) of inhibition effects from sludge extracts. This study highlighted triclosan as the predominant antibacterial compound in sewage sludge impacting E. coli despite the co-occurrence of numerous other antibiotics and nonantibiotics.

Defining the Chemical Additives Driving In Vitro Toxicities of Plastics

“…According to LC-MS/MS analysis, 6,361 compound features were found in the extract of PVC pipe A. To identify the PPARγ ligands associated with the PVC pipe extract, a bioanalytical method “protein A ffinity P urification with N ontargeted A nalysis (APNA)” was employed as described in our previous studies. − APNA uses a tagged protein (e.g., nuclear receptor) as “bait” to directly isolate protein ligands from environmental mixtures consisting of thousands of chemicals (see the workflow in Figure S8a). The method was first benchmarked with rosiglitazone by incubating with the His-tagged PPARγ-LBD.…”

Disclosing Environmental Ligands of hL-FABP and PPARγ: Should We Re-evaluate the Chemical Safety of Hydrocarbon Surfactants?

“…To identify environmental contaminants binding to hL-FABP/PPARγ in indoor dust and sewage sludge, APNA was employed. 24,26,29 His-tagged full length hL-FABP was overexpressed in E. coli cells. To perform APNA experiments, crude lysates (400 µL) of E. coli cells overexpressing His-tagged hL-FABP were incubated with 4 μL indoor dust or sewage sludge extracts.…”

“…This overcomes the major challenge of co-elution in EDA, and largely reduces false discovery rates. This method has been employed in our recent studies to identify chemical contaminants binding to multiple human 24,[27][28][29] and bacterial proteins 26 . A major advantage of APNA is the capacity to simultaneously isolate multiple ligands from complex environmental mixtures, which is ideal for the identification of PPARγ ligands.…”

“…A bioanalytical method "protein Affinity Purification with Nontargeted Analysis (APNA)" has been proposed in our previous studies for the screening of protein ligands in the environment. [24][25][26] Distinct from the conventional EDA method relying on LC fractionation, APNA uses a tagged protein (e.g., NR) as a "bait" to directly isolate protein ligands from environmental mixtures consisting of thousands of chemicals. This overcomes the major challenge of co-elution in EDA, and largely reduces false discovery rates.…”

Co-Exposure to Bisphenols, Parabens, and Antimicrobials and Association with Coronary Heart Disease: Oxidative Stress as a Potential Mediating Factor?

“…Despite short half-lives, these compounds are emerging as endocrine-disrupting chemicals (EDCs) of high concern due to their low-dose effects . They are released into the surroundings via municipal and industrial sewage; frequently occur in dust, water, and food; and are chronically exposed to humans. − The U.S. Food and Drug Administration has abandoned the use of BPA in baby bottles, sippy cups, and infant formula packaging, and has prohibited TCS and TCC from being used in over-the-counter soaps. , However, the annual industrial production of these compounds is still rising or maintained at high levels, , thereby posing an exposure risk to the public.…”