Triclocarban shifted the microbial communities and promoted the spread of antibiotic resistance genes in nitrifying granular sludge system

The fate of pharmaceuticals and personal care products (PPCPs) in sewer sediments:Adsorption triggering resistance gene proliferation

In recent years, large quantities of pharmaceuticals and personal care products (PPCPs) have been discharged into sewers, while the mechanisms of PPCPs enrichment in sewer sediments have rarely been revealed. In this study, three PPCPs (tetracycline, sulfamethoxazole, and triclocarban) were added consecutively over a 90-day experimental period to reveal the mechanisms of PPCPs enrichment and the transmission of resistance genes in sewer sediments. The results showed that tetracycline (TC) and triclocarban (TCC) have higher adsorption concentration in sediments compared to sulfamethoxazole (SMX). The absolute abundance of Tets and suls genes increased in sediments under PPCPs pressure. The increase in secretion of extracellular polymeric substances (EPS) and the loosening of the structure exposed a large number of hydrophobic functional groups, which promoted the adsorption of PPCPs. The absolute abundance of antibiotic resistance genes (ARGs), EPS and the content of PPCPs in sediments exhibited significant correlations. The enrichment of PPCPs in sediments was attributed to the accumulation of EPS, which led to the proliferation of ARGs. These findings contributed to further understanding of the fate of PPCPs in sewer sediments and opened a new perspective for consideration of controlling the proliferation of resistance genes.

Mitigation of Triclocarban Inhibition in Microbial Electrolysis Cell-Assisted Anaerobic Digestion

Triclocarban (TCC), as a widely used antimicrobial agent, is accumulated in waste activated sludge at a high level and inhibits the subsequent anaerobic digestion of sludge. This study, for the first time, investigated the effectiveness of microbial electrolysis cell-assisted anaerobic digestion (MEC-AD) in mitigating the inhibition of TCC to methane production. Experimental results showed that 20 mg/L TCC inhibited sludge disintegration, hydrolysis, acidogenesis, and methanogenesis processes and finally reduced methane production from traditional sludge anaerobic digestion by 19.1%. Molecular docking revealed the potential inactivation of binding of TCC to key enzymes in these processes. However, MEC-AD with 0.6 and 0.8 V external voltages achieved much higher methane production and controlled the TCC inhibition to less than 5.8%. TCC in the MEC-AD systems was adsorbed by humic substances and degraded to dichlorocarbanilide, leading to a certain detoxification effect. Methanogenic activities were increased in MEC-AD systems, accompanied by complete VFA consumption. Moreover, the applied voltage promoted cell apoptosis and sludge disintegration to release biodegradable organics. Metagenomic analysis revealed that the applied voltage increased the resistance of electrode biofilms to TCC by enriching functional microorganisms (syntrophic VFA-oxidizing and electroactive bacteria and hydrogenotrophic methanogens), acidification and methanogenesis pathways, multidrug efflux pumps, and SOS response.

Impact of earthworms on antibiotic resistance genes removal in ampicillin-contaminated soil through bacterial community alteration

The emergence of antibiotic resistance genes (ARGs) as contaminants in soil poses a significant threat to public health. Earthworms (Eisenia foetida), which are common inhabitants of soil, have been extensively studied for their influence on ARGs. However, the specific impact of earthworms on penicillin-related ARGs remains unclear. In this study, we investigate the role of earthworms in mitigating ARGs, specifically penicillin-related ARGs, in ampicillin-contaminated soil. Utilizing high-throughput quantitative PCR (HT-qPCR), we quantified a significant reduction in the relative abundance of penicillin-related ARGs in soil treated with earthworms, showing a decrease with a p-value of <0.01. Furthermore, high-throughput 16S rRNA gene sequencing revealed that earthworm intervention markedly alters the microbial community structure, notably enhancing the prevalence of specific bacterial phyla such as Proteobacteria, Firmicutes, Chloroflexi, and Tenericutes. Our findings not only demonstrate the effectiveness of earthworms in reducing the environmental load of penicillin-related ARGs but also provide insight into the alteration of microbial communities as a potential mechanism. This research contributes to our understanding of the role of earthworms in mitigating the spread of antibiotic resistance and provides valuable insights for the development of strategies to combat this global health issue.

Long-Term Triclocarban Exposure Induced Enterotoxicity by Triggering Intestinal AhR-Mediated Inflammation and Disrupting Microbial Community in Mice

Exposure to triclocarban (TCC), a commonly used antibacterial agent, has been shown to induce significant intestine injuries and colonic inflammation in mice. However, the detailed mechanisms by which TCC exposure triggered enterotoxicity remain largely unclear. Herein, intestinal toxicity effects of long-term and chronic TCC exposure were investigated using a combination of histopathological assessments, metagenomics, targeted metabolomics, and biological assays. Mechanically, TCC exposure caused induction of intestinal aryl hydrocarbon receptor (AhR) and its transcriptional target cytochrome P4501A1 (Cyp1a1) leading to dysfunction of the gut barrier and disruption of the gut microbial community. A large number of lipopolysaccharides (LPS) are released from the gut lumen into blood circulation owing to the markedly increased permeability and gut leakage. Consequently, toll-like receptor-4 (TLR4) and NF-κB signaling pathways were activated by high levels of LPS. Simultaneously, classic macrophage phenotypes were switched by TCC, shown with marked upregulation of macrophage M1 and downregulation of macrophage M2 that was accompanied by striking upregulation of proinflammatory factors such as Il-1β, Il-6, Il-17, and Tnf-α in the intestinal lamina propria. These findings provide new evidence for the TCC-induced enterotoxicity.

The proliferation of antibiotic resistance genes (ARGs) and microbial communities in industrial wastewater treatment plant treating N,N-dimethylformamide (DMF) by AAO process

The excessive use of antibiotics has resulted in the contamination of the environment with antibiotic resistance genes (ARGs), posing a significant threat to public health. Wastewater treatment plants (WWTPs) are known to be reservoirs of ARGs and considered to be hotspots for horizontal gene transfer (HGT) between bacterial communities. However, most studies focused on the distribution and dissemination of ARGs in hospital and urban WWTPs, and little is known about their fate in industrial WWTPs. In this study, collected the 15 wastewater samples containing N,N-dimethylformamide (DMF) from five stages of the anaerobic anoxic aerobic (AAO) process in an industrial WWTPs. The findings revealed a stepwise decrease in DMF and chemical oxygen demand (COD) content with the progression of treatment. However, the number and abundances of ARGs increase in the effluents of biological treatments. Furthermore, the residues of DMF and the treatment process altered the structure of the bacterial community. The correlation analysis indicated that the shift in bacterial community structures might be the main driver for the dynamics change of ARGs. Interestingly, observed that the AAO process may acted as a microbial source and increased the total abundance of ARGs instead of attenuating it. Additionally, found that non-pathogenic bacteria had higher ARGs abundance than pathogenic bacteria in effluents. The study provides insights into the microbial community structure and the mechanisms that drive the variation in ARGs abundance in industrial WWTPs.

Insights into the role of extracellular polymeric substances (EPS) in the spread of antibiotic resistance genes

Antibiotic resistance genes (ARG) are prevalent in aquatic environments. Discharge from wastewater treatment plants is an important point source of ARG release into the environment. It has been reported that biological treatment processes may enhance rather than remove ARG because of their presence in sludge. Attenuation of ARG in biotechnological processes has been studied in depth, showing that many microorganisms can secrete complex extracellular polymeric substances (EPS). These EPS can serve as multifunctional elements of microbial communities, involving aspects, such as protection, structure, recognition, adhesion, and physiology. These aspects can influence the interaction between microbial cells and extracellular ARG, as well as the uptake of extracellular ARG by microbial cells, thus changing the transformative capability of extracellular ARG. However, it remains unclear whether EPS can affect horizontal ARG transfer, which is one of the main processes of ARG dissemination. In light of this knowledge gap, this review provides insight into the role of EPS in the transmission of ARGs; furthermore, the mechanism of ARG spread is analyzed, and the molecular compositions and functional properties of EPS are summarized; also, how EPS influence ARG mitigation is addressed, and factors impacting how EPS facilitate ARG during wastewater treatment are summarized. This review provides comprehensive insights into the role of EPS in controlling the transport and fate of ARG during biodegradation processes at the mechanistic level.

The pH-specific response of soil resistome to triclocarban and arsenic co-contamination

Heavy metals as well as disinfectants affect the spread of antibiotic resistance genes (ARGs) in soil microbes, however, their cumulative impacts on the proliferation of ARGs are not well studied. In addition, both the chemical stability/availability and ARG profiles are affected by the soil pH, but it has never been considered in the systematic evaluation of soil resistome. In the present study, a microcosm experiment was conducted to study the combined effects of arsenic and triclocarban on the resistome in soil samples with variable pH (pH 4-7). The simultaneous additions of arsenic and triclocarban increase the ARG abundance at pH > 6, because of the intensive co-selective pressures triggered by the increase in concentrations of available arsenic and triclocarban. The occurrence of multidrug ARGs increases with the addition of arsenic and triclocarban, due to the preferred selection of their functional flexibility. The presence of arsenic and triclocarban is strongly related to the spread of MGEs affecting the soil resistome. Furthermore, pH alters the patterns of microbial inhabitants, increasing the relative abundance of Bacteroidota and Proteobacteria and contributing to the prevalence of tetracycline and sulfonamide ARGs at neutral pH. These findings have insight that the effects of arsenic and triclocarban co-contamination on the soil antibiotic resistome is pH dependent.

Triclocarban transformation and removal in sludge conditioning using chalcopyrite-triggered percarbonate treatment

Herein, a facile combination approach of chalcopyrite and sodium percarbonate (CuFeS2+ SPC) was established to augment both TCC removal efficiency and sludge dewatering. Results showed that utilizing the CuFeS2 dosage of 600 mg/g total solids (TS) under the optimal condition, along with the SPC dosage of 12.5 mg/g TS, an initial pH of 4.0, and a reaction duration of 40 min, led to a substantial reduction of 53.9% in the TCC content within the sludge, accompanied by a notable decrease of 36.9% in the water content. Compared to well-studied iron-based advanced oxidation processes, CuFeS2 + SPC treatment proved to be more cost-effective and environmentally friendly. Mechanistic findings demonstrated that •OH oxidation played a significant role in TCC removal, with O2•- and 1O2 acting as secondary factors. During the CuFeS2 + SPC process, the received •OH, O2•-, and 1O2 destroyed the main binding sites of extracellular polymeric substances to TCC, including tryptophan-like protein, amide, CO stretch, and -COO- functional groups. As a result, approximately 50% of TCC was partially degraded within the solid sludge phase after the attack of radicals. Meanwhile, the decreased macromolecular organic compounds in solid sludge attenuated the binding efficacy of TCC, giving rise to the transfer of partial TCC to the liquid phase. Ultimately, the TCC in sludge was successfully removed, and five transformation products were identified. This study significantly contributes to our understanding regarding TCC transformation and removal in the sludge conditioning process.

Performance of sewage sludge treatment for the removal of antibiotic resistance genes: Status and prospects

Wastewater treatment plants (WWTPs) receive wastewater containing antibiotic resistant bacteria (ARB) and antibiotic resistant genes (ARGs), which are predominant contributors to environmental pollution in water and soil. Of these sources, sludge is a more significant contributor than effluent. Knowing how sludge treatment affects the fate of ARGs is vital for managing the risk of these genes in both human and natural environments. This review therefore discusses the sources and transmission of ARGs in the environment and highlights the risks of ARGs in sludge. The effects of co-existing constituents (heavy metals, microplastics, etc.) on sludge and ARGs during treatment are collated to highlight the difficulty of treating sludge with complex constituents in ARGs. The effects of various sludge treatment methods on the abundances of ARGs in sludge and in soil from land application of treated sludge are discussed, pointing out that the choice of sludge treatment method should take into account various potential factors, such as soil and soil biology in subsequent land application. This review offers significant insights and explores the abundances of ARGs throughout the process of sludge treatment and disposal. Unintentional addition of antibiotic residues, heavy metals, microplastics and organic matter in sludge could significantly increase the abundance and reduce the removal efficiency of ARGs during treatment, which undoubtedly adds a barrier to the removal of ARGs from sludge treatment. The complexity of the sludge composition and the diversities of ARGs have led to the fact that no effective sludge treatment method has so far been able to completely eliminate the ecological risk of ARGs. In order to reduce risks resulting by transmission of ARGs, technical and management measures need to be implemented.

Insight into the evolution of microbial communities and resistance genes induced by sucralose in partial nitrification system with triclosan pre-exposure

Sucralose (SUC), an artificial sweetener widely used in food, beverages and pharmaceuticals, is frequently detected in various environmental matrices. Triclosan (TCS) is commonly used as a disinfectant and often co-exists with SUC in sewage environments. This study investigated the effects of SUC (0.1-10 mg/L) on the transmission of intracellular and extracellular antibiotic resistance genes (ARGs) in the partial nitrification systems with and without TCS pre-exposure. The reactors operated for 150 days, and SUC did not affect ammonia oxidation performance, while TCS led to the maintenance of partial nitrification. The types and abundances of extracellular ARGs in sludge and free ARGs in water increased significantly after TCS pre-exposure when faced SUC stress, which might be caused by a decrease in α-Helix/(β-Sheet + Random coil). SUC was more easily to enrich ARGs in partial nitrification systems with TCS pre-exposure, exacerbating the risk of ARGs transmission. The microbial community showed stronger relationships to cope with the direct stress of SUC, and the functional bacteria (Thauera and Nitrosomonas) in TCS pre-exposure system might be potential hosts of ARGs. This study might provide insights for better understanding the fates of SUC in partial nitrification systems and the ecological risks in wastewater containing TCS and SUC. ENVIRONMENTAL IMPLICATION: Sucralose (SUC) is often detected in the environment and considered as an emerging contaminant due to its soaring consumption and environmental persistence. Triclosan (TCS) is an antibacterial agent that often co-exists with SUC in personal care products and sewage environments. During 150 d, two partial nitrification reactors with and without TCS pre-exposure were established to study the effects of SUC on nitrification performance, antibiotic resistance genes (ARGs) and microbial communities. This study showed the refractory nature of SUC, and SUC led to the transmission of extracellular ARGs in partial nitrification system with TCS pre-exposure, exacerbating the risk of ARGs dissemination.

Interference of gut-brain-gonad axis originating from triclocarban exposure to parent zebrafish induces offspring embryonic development abnormality by up-regulation of maternal circSGOL1

Triclocarban (TCC) is a widely used antibacterial ingredient possessing acute toxicity effects; however, its chronic toxicity and underlying molecular mechanisms remain uncertain. Herein, we demonstrated that chronic TCC exposure affects the growth and development of adult zebrafish through inducing an intestinal flora disorder in the gut. The imbalance of intestinal flora caused functional barriers within the intestinal-brain-gonadal axis. This resulted in a series of anomalous nerve and motor behaviors, and reproductive toxicity as reflected in pathological damage to parental gonads and F1-larval developmental malformations. Abnormal development of F1 larvae was attributed to apoptosis induced by the up-regulation of circSGOL1. This up-regulation affected the activity and localization of the hnRNP A1 protein, which then promoted overexpression of pro-apoptotic related genes that ultimately lead to apoptosis during early embryonic development. Overall, these novel findings systematically elucidated the TCC toxicity mechanism in parent-offspring dyads, and provide important theoretical guidance for early risk warning and control of chronic TCC toxicity.

Unraveling the Role of Microalgae in Mitigating Antibiotics and Antibiotic Resistance Genes in Photogranules Treating Antibiotic Wastewater

Harnessing the potential of specific antibiotic-degrading microalgal strains to optimize microalgal-bacterial granular sludge (MBGS) technology for sustainable antibiotic wastewater treatment and antibiotic resistance genes (ARGs) mitigation is currently limited. This article examined the performance of bacterial granular sludge (BGS) and MBGS (of Haematococcus pluvialis, an antibiotic-degrading microalga) systems in terms of stability, nutrient and antibiotic removal, and fate of ARGs and mobile genetic elements (MGEs) under multiclass antibiotic loads. The systems exhibited excellent performance under none and 50 μg/L mixed antibiotics and a decrease in performance at a higher concentration. The MBGS showed superior potential, higher nutrient removal, 53.9 mg/L/day higher chemical oxygen demand (COD) removal, and 5.2-8.2% improved antibiotic removal, notably for refractory antibiotics, and the system removal capacity was predicted. Metagenomic analysis revealed lower levels of ARGs and MGEs in effluent and biomass of MBGS compared to the BGS bioreactor. Particle association niche and projection pursuit regression models indicated that microalgae in MBGS may limit gene transfers among biomass and effluent, impeding ARG dissemination. Moreover, a discrepancy was found in the bacterial antibiotic-degrading biomarkers of BGS and MBGS systems due to the microalgal effect on the microcommunity. Altogether, these findings deepened our understanding of the microalgae's value in the MBGS system for antibiotic remediation and ARG propagation control.

A holistic review on triclosan and triclocarban exposure: Epidemiological outcomes, antibiotic resistance, and health risk assessment

Triclosan (TCS) and triclocarban (TCC) are antimicrobials that are widely applied in personal care products, textiles, and plastics. TCS and TCC exposure at low doses may disturb hormone levels and even facilitate bacterial resistance to antibiotics. In the post-coronavirus disease pandemic era, chronic health effects and the spread of antibiotic resistance genes associated with TCS and TCC exposure represent an increasing concern. This study sought to screen and review the exposure levels and sources and changes after the onset of the coronavirus disease (COVID-19) pandemic, potential health outcomes, bacterial resistance and cross-resistance, and health risk assessment tools associated with TCS and TCC exposure. Daily use of antimicrobial products accounts for most observed associations between internal exposure and diseases, while secondary exposure at trace levels mainly lead to the spread of antibiotic resistance genes. The roles of altered gut microbiota in multi-system toxicities warrant further attention. Sublethal dose of TCC selects ARGs without obviously increasing tolerance to TCC. But TCS induce persistent TCS resistance and reversibly select antibiotic resistance, which highlights the benefits of minimizing its use. To derive reference doses (RfDs) for humans, more sensitive endpoints observed in populational studies need to be confirmed using toxicological tests. Additionally, the human equivalent dose is recommended to be incorporated into the health risk assessment to reduce uncertainty of extrapolation.

Personal Care Products as a Contributing Factor to Antimicrobial Resistance: Current State and Novel Approach to Investigation

Antimicrobial resistance (AMR) is one of the world's industrialized nations' biggest issues. It has a significant influence on the ecosystem and negatively affects human health. The overuse of antibiotics in the healthcare and agri-food industries has historically been defined as a leading factor, although the use of antimicrobial-containing personal care products plays a significant role in the spread of AMR. Lotions, creams, shampoos, soaps, shower gels, toothpaste, fragrances, and other items are used for everyday grooming and hygiene. However, in addition to the primary ingredients, additives are included to help preserve the product by lowering its microbial load and provide disinfection properties. These same substances are released into the environment, escaping traditional wastewater treatment methods and remaining in ecosystems where they contact microbial communities and promote the spread of resistance. The study of antimicrobial compounds, which are often solely researched from a toxicological point of view, must be resumed considering the recent discoveries, to highlight their contribution to AMR. Parabens, triclocarban, and triclosan are among the most worrying chemicals. To investigate this issue, more effective models must be chosen. Among them, zebrafish is a crucial study system because it allows for the assessment of both the risks associated with exposure to these substances as well as environmental monitoring. Furthermore, artificial intelligence-based computer systems are useful in simplifying the handling of antibiotic resistance data and speeding up drug discovery processes.

The spread of different resistance genes fractions in nitrification system under chronic exposure to varying alkyl chain length benzalkyl dimethylammonium compounds

Benzalkyl dimethylammonium compounds (BACs) are generally applied as surfactants and disinfectants. In this study, the nitrification systems were exposed to different alkyl chain lengths (C12-C16) and different levels of BACs (0-5 mg/L), respectively, totally 120 days and to explore the chronic effect of BACs on resistance genes (RGs). RGs were classified into four fractions based on activated sludge properties. Ammonia oxidation performance were not significantly affected by BACs, whereas BACs increased the absolute abundance of most intracellular RGs in sludge (si-RGs). Under the exposure of BACs, extracellular RGs in water (we-RGs) showed a decrease trend and si-RGs tended to be converted to we-RGs. Tightly bound-Tyrosine side chain was significantly correlated with most we-RGs, and we-intI1 might contribute to the propagation of RGs. Therefore, the risk of transmission of different fractions of RGs in the nitrification system under the stress of BACs should be taken seriously.

The synergistic mechanism of β-lactam antibiotic removal between ammonia-oxidizing microorganisms and heterotrophs

Nitrifying system is an effective strategy to remove numerous antibiotics, however, the contribution of ammonia-oxidizing bacteria (AOB), ammonia-oxidizing archaea (AOA) and heterotrophs for antibiotic removal are still unclear. In this study, the mechanism of β-lactam antibiotic (cefalexin, CFX) removal was studied in a nitrifying sludge system. Results showed that CFX was synergistically removed by AOB (Nitrosomonas, played a major role) and AOA (Candidatus_Nitrososphaera) through ammonia monooxygenase-mediated co-metabolism, and by heterotrophs (Pseudofulvimonas, Hydrogenophaga, RB41, Thauera, UTCFX1, Plasticicumulans, Phaeodactylibacter) through antibiotic resistance genes (ARGs)-encoded β-lactamases-mediated hydrolysis. Regardless of increased archaeal and heterotrophic CFX removal with the upregulation of amoA in AOA and ARGs, the system exhibited poorer CFX removal performance at 10 mg/L, mainly due to the inhibition of AOB. This study provides new reference for the important roles of heterotrophs and ARGs, opening the possibilities for the application of ARGs in antibiotic biodegradation.

Fate, toxicity and effect of triclocarban on the microbial community in wastewater treatment systems

Triclocarban (TCC), one of the typical antimicrobial agents, is a contaminant of emerging concern commonly found in high concentration in water environments. However, the fate and toxicity of TCC in wastewater treatment systems remain poorly understood. Here, we investigated how TCC impacts chemical oxygen demand and inorganic nitrogen transformation in a hydrolytic anaerobic-anoxic/oxic process. In the anaerobic section, the transformation of TCC was dominated by reductive dechlorination and supplemented by two amid bonds hydrolysis. In the anoxic and oxic sections, the hydrolysis of amid bonds dominated. The toxicity was reduced after the treatment (IC₅₀ from 0.09 to 0.54). TCC inhibited NH₄⁺-N removal in the anaerobic section and led to the NO₃^--N accumulation (2.84-4.13 mg/L) after treatment, with the abundance of N-removal bacteria decreased by 6%. Furthermore, the original ecological niche was gradually replaced by TCC-resistant/degradative bacteria, formating new microbial modules to resist the TCC stress. Importantly, fourteen genera including Methanosaeta, Longilinea, Dokdonella and Mycobacterium as potential bioindicators warning TCC and its intermediates were proposed. Overall, this study provides new insights into the fate of TCC in biological wastewater treatment systems and suggests a great importance for TCC control to ensure the health and resilience of ecosystems.