Increased Use of Quaternary Ammonium Compounds during the SARS-CoV-2 Pandemic and Beyond: Consideration of Environmental Implications

Photochemical transformation of benzalkonium chloride in seawater

The fate and risks of quaternary ammonium compounds (QACs) have gained increasing attention due to their widespread use during and after the COVID-19 pandemic. This study investigates the photodegradation of benzalkonium chloride (BAC C12) in seawater, revealing that its degradation rate (0.0928 h-1) is slower compared to pure water, where the rate is 0.132 h-1. Chloride (Cl-) and bromide (Br-) ions promote degradation by generating halogen radicals (Cl·, Br· and ClBr·-), nitrate ions (NO3-) can generate reactive oxygen species (ROS) and nitrogen-containing free radicals (e.g., ·NO2) via direct photolysis or indirect photosensitization reactions, while Fe3+, Mn2+ and Cu2+ accelerate the reaction by promoting ROS production to accelerate the reaction. The effect of dissolved organic matter (DOM) on degradation is concentration-dependent: at low concentrations, it inhibits degradation through photocompetition, while at high concentrations, it promotes degradation via photosensitization and electron transfer. Quenching reactions and probe experiments indicate that ·OH is the dominant species (contributing over 50 %), followed by ¹O₂ (more than 10 %) and halogen radicals (over 5 %), all of which play significant roles in degradation. Quantum chemical calculations and mass spectrometry identify key degradation pathways, including alkyl chain cleavage, benzene ring substitution (primarily at C2 and C5), and N-demethylation. ECOSAR simulations indicate that the chlorine and hydroxyl substitution products are more toxic. These findings provide a scientific basis for the environmental risk assessment and mitigation strategies of QACs.

Natural antimicrobials synergistically coupled with nanomotors: An innovative strategy for biofilm eradication

Biofilms are one of the most important problems occurring in industrial environments, especially in food industry. The possibility of foodborne disease outbreaks as a result of biofilm-food cross-contamination is a distinct concern, along with the substantial costs associated with food spoilage and biofilm control. Besides, despite daily cleaning and disinfection, many bacteria grow in machines and surfaces in food processing plants, some of them forming biofilms. A promising procedure for disinfection and biofilm elimination could be the use of hybrid antimicrobial nanomaterials endowed with motion (i.e., nanomotors). Herein, we report Janus nanoparticles based on the conjunction of platinum and mesoporous silica nanoparticles, functionalized with a derivative of a natural antimicrobial compound, vanillin. The engineered nanomotors combine H2O2-triggered self-propulsion with the antimicrobial activity of vanillin, allowing enhanced physical penetration into the 3D matrix formed by the exopolymeric substances generated in monospecies (Staphylococcus aureus) and multispecies (S. aureus and Escherichia coli) biofilms and the subsequent elimination of pathogenic cells.

Effect of cationic antiseptics on the vectorial electron and proton transfer in chromatophores of photosynthetic bacteria

The effect of the cationic antiseptics octenidine and miramistin on electron transfer reactions in photosynthetic bacterial chromatophores of Cereibacter sphaeroides has been studied using direct electrometric and flash photolysis techniques. When the ubiquinone pool and cytochrome bc1 complex were oxidized, the addition of octеnidine at a concentration of 100 µM completely inhibited the generation of transmembrane electric potential difference (Δψ) caused by protonation of the doubly reduced secondary quinone acceptor QB in the reaction center and, accordingly, vectorial charge transfer within the bc1 complex in response to a second laser flash. The lack of an effect of octenidine and miramistin on the rapid rise of Δψ (τ < 0.1 µs) due to charge separation between the primary electron donor P870 and the primary quinone acceptor QA was accompanied by an acceleration of Δψ decay kinetics over a period of ~ 10 ms in the presence of the former. The effect of miramistin was less pronounced. Overall, the data obtained by the two methods are qualitatively similar. The different effects of octanidine and miramistin are undoubtedly due to their structural features and may be related to their disordering influences on both the QB-binding site of the reaction center and the structure of the bilayer phospholipid membrane of chromatophores. These results are also important for understanding the molecular mechanisms of action of cationic antiseptics on both charge transfer reactions and thylakoid membrane integrity in oxygenic photosynthetic organisms.

Occupational Exposure Patterns to Disinfectants and Cleaning Products and Its Association With Asthma Among French Healthcare Workers

BACKGROUND

Disinfectants and cleaning products (DCPs) are important asthma risk factors among healthcare workers. However, healthcare work involves heterogenous cleaning tasks and co-exposure to many chemicals. These multidimensional aspects have rarely been considered. We aimed to identify patterns of occupational exposure to DCPs and study their associations with asthma.

METHODS

CONSTANCES is a French population-based cohort of ≈220,000 adults. Current asthma and asthma symptom score were defined by questionnaire at inclusion (2012-2021). Healthcare workers completed a supplementary questionnaire on their current/last held occupation, workplace, and cleaning activities that were used in unsupervised learning algorithms to identify occupational exposure patterns. Logistic and negative binomial regression models, adjusted for potential confounders, were used to assess associations with asthma outcomes.

RESULTS

In 5512 healthcare workers, four occupational exposure clusters were identified: Cluster1 (C1, 42%, reference), mainly characterized by low exposed nurses and physicians; C2 (7%), medical laboratory staff moderately exposed to common DCPs (chlorine/bleach, alcohol); C3 (41%), nursing assistants and nurses highly exposed to a few DCPs (mainly quaternary ammonium compounds); and C4 (10%), nurses and nursing assistants highly exposed to multiple DCPs (e.g., glutaraldehyde, hydrogen peroxide, and acids). Among women (n = 3734), C2 (mean score ratio [95% CI]: 1.31 [1.02; 1.68]) and C3 (1.18 [1.03; 1.36]) were associated with higher asthma symptom score, and an association was suggested between C3 and current asthma (odds ratio 1.22 [0.99; 1.51]).

CONCLUSION

In a large population of healthcare workers, four DCP exposure patterns were identified, reflecting the heterogeneity of healthcare jobs. Two patterns, including one characterized by laboratory workers, were associated with greater asthma symptoms in women.

Influence of Cleaning on Indoor Air Concentrations of Volatile and Semivolatile Organic Compounds in Residences

Cleaning activities can affect indoor air composition long after the cleaning is completed. Utilizing data from detailed observational monitoring campaigns, conducted over 21 weeks, we explore the influence of cleaning activities in two normally occupied, single-family houses. To study emissions and chemistry, we quantified more than 200 volatile organic compounds (VOCs) using a proton-transfer reaction time-of-flight mass spectrometer and 52 semivolatile organic compounds (SVOCs) using a semivolatile thermal-desorption gas chromatograph. During regular professional home cleaning, we observed postcleaning concentration enhancements in ∼60% of measured VOCs and ∼80% of measured SVOCs. Most of these concentration enhancements were not clearly linked to either primary emission from cleaning products or secondary formation through reactive chemistry. Instead, we infer that shifts in the sorptive properties of indoor surfaces account for most of these observations. Cleaning-associated enhancements mostly ebbed within a few hours, with some VOCs and lower-volatility SVOCs persisting more than 5 h, longer than would be expected for removal of inert species by ventilation. The use of carpet cleaner was associated with direct emission of 2-butoxyethanol, which persisted at elevated concentrations for days after the initial event. Home cleaning is potentially relevant for the health of professional cleaners and residents.

Perspectives on safety of quaternary ammonium compounds (QACs)

Quaternary ammonium compounds (QACs) are widely used to kill pathogenic microbes (including COVID-19), providing a substantial public health benefit. This review is an update to our previous publications that summarized and interpreted the current knowledge of the safety of the two most widely used QACs, alkyl dimethyl benzyl ammonium chloride (ADBAC) and didecyl dimethyl ammonium chloride (DDAC). A literature search was conducted for studies published since 2000 that addressed possible toxicity of ADBAC and DDAC as well as investigations into human exposure. The current database of high-quality animal toxicology studies with ADBAC/DDAC showed that adverse cellular changes are limited to effects at the point of contact. (1) Non-guideline animal toxicology investigations, (2) studies of the effect of QACs on subcellular functions, and (3) the sole report of systemic effects in humans might not be informative for human health risk assessment. Because of their widespread use, human exposure to QACs is frequent. Various reports measured QACs in media in the home and workplaces. Risk calculations performed based upon these exposure estimates performed as part of this review demonstrated that none of the exposure scenarios examined are predicted to pose adverse health risks to exposed individuals.

Organic Cation Transporter Mediates the Uptake of Quaternary Ammonium Compounds in Arabidopsis

Quaternary ammonium compounds (QACs), widely used in consumer products and pharmaceuticals, are increasingly released into soils and can accumulate in plants, posing significant ecological and health risks. While plant uptake mechanisms for QACs remain poorly characterized, this study identifies organic cation transporter 1 (OCT1) as a potential mediator of QAC absorption in Arabidopsis. Root uptake experiments demonstrated reduced QAC accumulation under treatments with metabolic and OCT inhibitors. Transcriptional upregulation of AtOCT1 in QAC-exposed wild-type plants, along with functional validation through yeast heterologous expression systems, implicated this transporter in cationic pollutant absorption. Comparative analysis revealed 12%-42% lower root QAC concentrations in AtOCT1 mutants compared to wild-type plants, while overexpression lines exhibited 9.4%-43% increases in accumulation alongside enhanced sensitivity. Molecular docking simulations demonstrated stronger binding affinities between AtOCT1 and QACs compared to its native substrate L-carnitine, with microscale thermophoresis confirming direct interactions. Quantitative structure-activity relationship analysis identified electronic energy, molecular weight, and polarizability as critical determinants of AtOCT1-mediated transport efficiency. These findings establish the biological and structural role of AtOCT1 in cationic pollutant uptake, advancing mechanistic understanding of transporter-mediated plant accumulation of ionizable organic pollutants.

Reviewing the complexities of bacterial biocide susceptibility and in vitro biocide adaptation methodologies

Decreased bacterial susceptibility to biocides raises concerns due to their influences on antibiotic resistance. The lack of standardized breakpoints, established methods, and consistent terminology complicates this research. This review summarizes techniques for studying biocide resistance mechanisms, susceptibility testing, and in-vitro adaptation methods, highlighting their benefits and limitations. Here, the challenges in studying biocide susceptibility and the need for standardized approaches in biocide research are emphasized for commonly studied biocide classes.

Secondary exposure and risk assessment of biocides as disinfectant sprays for COVID-19 prevention

The importance of disinfection has recently increased owing to the spread of infections, such as coronavirus disease 2019 (COVID-19). However, exposure to the biocidal products used for disinfection poses health risks. This study aimed to determine the safe use of biocides and the potential for secondary exposure in the general population. To obtain information on the exposure factors on site, an interview survey was conducted for 2 weeks and 10 days using a questionnaire. Toxicology studies were performed to determine the toxicity of each chemical in various biocidal products. The inhalation and dermal exposure algorithms in ConsExpo 4.0, a software developed by the Dutch National Institute for Public Health and the Environment (RIVM), were used to assess the risk of active substances in biocidal products. The average amounts of disinfectants and pesticides used in indoor environments per unit time were 5948.50 ± 72,434.76 mg and 201.61 ± 305.91 mg, respectively. Ethanol had the highest inhalation hazard quotient (HQinh) of 1.48E+02 while sodium dichloroisocyanurate had the lowest value of 1.74E-10. The HQinh/HQder ratios for the 10 active substances ranged from 1.51E+00 to 2.73E+05 were greater than 1, indicating that inhalation exposure had a greater effect than dermal exposure. The hazard index (HI) of the 10 active substances, excluding ethanol, was less than 1, indicating the absence of potential health risks. Therefore, to reduce the health risks associated with secondary exposure, disinfection should be performed during periods when individuals are away from the site to be disinfected, such as after regular working hours, and individuals should be encouraged to enter this site the following day instead of after the disinfection exercise. Methods, such as applying an active substance from a biocidal product to a cloth or fabric to carry out the disinfection protocol, should also be considered.

A review of microbial degradation of perfluorinated and polyfluoroalkyl substances (PFAS) during waste biotransformation processes: influencing factors and alleviation measures

Per- and polyfluoroalkyl substances (PFASs) are stable synthetic compounds that pose significant risks to humans and tend to accumulate during the biotransformation of municipal waste. Although physical and chemical methods can effectively remove PFASs, their high costs and susceptibility to secondary contamination have limited broader adoption. Microbial degradation of PFASs is an environmentally friendly and cost-effective approach, making it a highly promising method for removing PFASs in municipal waste biotransformation. This paper summarizes recent advancements in the mechanisms of PFASs removal in common waste biotransformation processes, such as composting, anaerobic digestion and biological wastewater treatment. Microorganisms remove PFAS from municipal waste mainly through adsorption and biodegradation. We suggest that the type of PFAS, the coexistence of multiple emerging pollutant and PFAS, and the nutrients provided by municipal waste are the key factors influencing microbial degradation of PFAS. We consider that in situ enrichment of microorganisms capable of degrading PFAS is an effective way to mitigate the inhibitory effect of PFAS on waste biotransformation. Also, the addition of adsorbent materials, the application of voltage, and the addition of quorum-sensing signalling molecules in combination with biodegradation can improve the effectiveness of biodegradation of PFAS. In this study, we look forward to the future research direction to understand the key metabolic pathways of microbial degradation of PFAS using isotope tracer method. This review provides new insights for efficient biotransformation of municipal waste and effective removal of PFAS.

Quaternary ammonium compounds in wastewater during the COVID-19 pandemic: occurrence, exposure evaluation and risk assessment

Quaternary ammonium compounds (QACs) are widely used as active ingredients in cleaning products and personal care products, which could enter domestic wastewater through various daily human activities. During the COVID-19 pandemic, elevated usage of QACs was reported; however, whether the increase could pose potential risks to the environment and human health is still unknown. To evaluate the population exposure and risks of QACs, influent and effluent wastewater samples were collected from December 15, 2022, to January 31, 2023, in a wastewater treatment plant. QACs were detected at mean ΣQAC concentrations of 711 ng L-1 in influent and 50.4 ng L-1 in effluent. Dialkyldimethyl ammonium compounds (DADMACs) and benzylalkyldimethyl ammonium compounds (BACs) accounted for the largest mean proportion of 48.5% and 66.1% in influent and effluent, respectively. The evaluated daily ΣQAC exposure ranged from 0.309 to 2114 mg per 1000 residents during the sampling period. Most QACs could be removed, with mean removal efficiency in the range of 62.6-100%. DADMAC-14:14, DADMAC-16:16 and BAC-C12 in effluent displayed higher risks to aquatic organisms based on risk quotient calculation. The estimated daily intakes of QACs were below the reference dose, suggesting negligible health concerns. The environmental occurrence and physico-chemical properties were further integrated in the toxicological priority index approach to rank the monitored QACs. DADMAC-16:16 exhibited the highest score, indicating its priority in further environmental and toxicological research.

Degradation of N-methylbenzylamine and N,N-dimethylbenzylamine in anaerobic biological reactors and formation of N-nitrosomethylbenzylamine and N-nitrosodimethylamine during subsequent chloramination

As water reuse demand increases, wastewater treatment plants must manage byproducts effectively while ensuring safety. The excessive use of benzalkonium chloride disinfectants can lead to the accumulation of benzylamines, such as N-methylbenzylamine (MBA) and N,N-dimethylbenzylamine (DMBA). Biological anaerobic treatment is becoming more popular due to concerns over energy consumption and carbon emissions. Our study examined the biodegradation of MBA and DMBA during anaerobic treatment and their effects on toxic byproduct formation during subsequent chloramination, as well as their impact on bioreactor performance, degradation pathways, and microbial communities. Our results showed that anaerobic bioreactors had minimal impact on overall treatment performance despite the presence of MBA and DMBA. MBA proved resistant to biodegradation, whereas DMBA underwent significant biodegradation. Notably, during chloramination, MBA effluent formed nitroso-MBA with a 1 % molar yield, whereas DMBA effluent had significant N-nitrosodimethylamine formation, with molar yields reaching 10 ± 1 % and 97 ± 7 % of the influent and residual DMBA concentrations. We observed significant differences in microbial communities between the DMBA reactor and the MBA and control reactors. Proposed degradation pathways and the involvement of specific microbial communities were detailed. These findings highlight the importance of thoroughly evaluating biologically treated effluent to manage the risks of toxic byproducts in water reuse.

Biocides as drivers of antibiotic resistance: A critical review of environmental implications and public health risks

The widespread and indiscriminate use of biocides poses significant threats to global health, socioeconomic development, and environmental sustainability by accelerating antibiotic resistance. Bacterial resistance development is highly complex and influenced significantly by environmental factors. Increased biocide usage in households, agriculture, livestock farming, industrial settings, and hospitals produces persistent chemical residues that pollute soil and aquatic environments. Such contaminants contribute to the selection and proliferation of resistant bacteria and antimicrobial resistance genes (ARGs), facilitating their dissemination among humans, animals, and ecosystems. In this review, we conduct a critical assessment of four significant issues pertaining to this topic. Specifically, (i) the role of biocides in exerting selective pressure within the environmental resistome, thereby promoting the proliferation of resistant microbial populations and contributing to the global spread of antimicrobial resistance genes (ARGs); (ii) the role of biocides in triggering transient phenotypic adaptations in bacteria, including efflux pump overexpression, membrane alterations, and reduced porin expression, which often result in cross-resistance to multiple antibiotics; (iii) the capacity of biocides to disrupt bacteria and make the genetic content accessible, releasing DNA into the environment that remains intact under certain conditions, facilitating horizontal gene transfer and the spread of resistance determinants; (iv) the capacity of biocides to disrupt bacterial cells, releasing intact DNA into the environment and enhancing horizontal gene transfer of resistance determinants; and (iv) the selective interactions between biocides and bacterial biofilms in the environment, strengthening biofilm cohesion, inducing resistance mechanisms, and creating reservoirs for resistant microorganisms and ARG dissemination. Collectively, this review highlights the critical environmental and public health implications of biocide use, emphasizing an urgent need for strategic interventions to mitigate their role in antibiotic resistance proliferation.

Synergistic effects of quaternary ammonium compounds and antibiotics on the evolution of antibiotic resistance

The usage of quaternary ammonium compounds (QACs) as disinfectants has surged dramatically during the COVID-19 pandemic and thereafter. QACs can promote antimicrobial resistance, but the combined effects of QACs and antibiotics in driving resistance evolution were yet revealed. This study aimed to evaluate antibiotic resistance of wastewater microorganisms under coexposure to typical antibiotics and the most widely used QAC, dodecyl dimethyl benzyl ammonium chloride (DDBAC). DDBAC exhibited synergistic effects with multiple antibiotics (ampicillin, azithromycin, ciprofloxacin, kanamycin, polymyxin B) in enhancing activated sludge resistance by 1.53-6.67 folds, compared with antibiotics exposure alone. DDBAC-ampicillin coexposure enriched multidrug and aminoglycoside ARGs with relatively high horizontal gene transfer potential. The synergistic mechanism was further explored using sludge-isolated pathogenic E. coli. DDBAC at 1-10 mg/L alone did not induce notable resistance, but synergized with ampicillin on enhancing resistance by 6.56-22.90 folds. Based on mutation analysis and transcriptomics, DDBAC-enhanced resistance evolution was attributable to efflux pump upregulation, target modification, and inhibition of ATP synthesis (a less reported mechanism). Five DDBAC-induced, resistance-conferring mutant genes were highly enriched in globally collected E. coli strains from wastewater outflow (n = 537) than soil/sediments (n = 714, p < 0.05). Considering the strong adsorption and persistence of QACs, their coexistence with antibiotics poses elevated antimicrobial resistance risks, particularly in wastewater treatment systems with long solid retention time and sewage sludge applied farmland.

A survey of 27 quaternary ammonium compounds in surface water, drinking water, stormwater runoff, swimming pool water, and rainwater from New York State, USA

Quaternary ammonium compounds (QACs), including benzylalkyldimethylammonium (BACs), dialkyldimethylammonium (DDACs), and alkyltrimethylammonium compounds (ATMACs), are widely used as disinfectants in industrial and consumer products. Nevertheless, little is known about their occurrence in aquatic environments. We surveyed 7 BACs, 6 DDACs, 6 ATMACs, and 8 hydroxyl‑ and carboxyl- metabolites of BACs (BACm) in various types of water (N = 233) from New York State, USA. The geometric mean (GM) concentration of ∑All (sum concentration of all QACs) varied among different water types in the following decreasing order: stormwater runoff (1140 ng/L) > swimming pool water (109) > river water (49.3) > rainwater (40.5) > lake water (23.7) > tap water (23.3) > bottled water (11.8). DDACs were the major class of QACs in all water types (except for bottled water), accounting for 51-62% of ∑All. Several metabolites of BACs were found in waters for the first time (GM: nondetectable to 82.4 ng/L). Surface water samples collected from the Hudson River and Onondaga Lake contained elevated QAC concentrations. The average annual discharge of QACs through the Hudson River into the Atlantic Ocean was up to 21,000 kg. The risk quotients of QACs in surface water reached up to 5260, highlighting potential ecological risks exerted by these chemicals. This study provides critical information for the risk assessment and management of QACs in the aquatic environment.

Quaternary ammonium compounds in medicinal herbs and health risk assessment

The rising global demand for medicinal herbs has increased human consumption, raising concerns about potential health risks related to quaternary ammonium compounds (QACs), especially among infants due to frequent use in certain cultures. To perform a market survey, an LC-ESI-MS/MS method was developed to detect five QACs, including Benzalkonium Chlorides (BACs) and Dialkyl Dimethyl Ammonium Chloride (DDAC), in dry medicinal herbs. The method employed QuEChERS extraction with acetonitrile and achieved chromatographic separation with a poroshell C18 column. Method validation was conducted according to Eurachem and SANTE/11312/2021 guidelines, showing high sensitivity and selectivity, with recoveries between 70% and 110% and RSDs below 5%. The method was applied to market samples, resulting in 33% exceedances of the maximum residue limits. In this study also dietary exposure risks for adults, toddlers and infants were evaluated. Preliminary risk assessment indicated acceptable dietary exposure risks.

The Slow Pandemic: Emergence of Antimicrobial Resistance in the Postadvent of SARS-CoV-2 Pandemic

Background: The unprecedented outbreak of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic has dramatically changed the global approach to public health, emphasizing the importance of measures to control and prevent infections. In response to the COVID-19 crisis, stringent hygiene practices and surface disinfection have become the norm, with an unprecedented surge in the use of disinfectants and antiseptics (DAs). Main Text: While these measures have been crucial in curbing the spread of the virus, an emerging concern has taken center stage: the potential impact of the prolonged and widespread use of antimicrobial compounds in these products on the development of antibiotic resistance. Antimicrobial resistance (AMR) has long been recognized as one of the most pressing global health threats. Quaternary ammonium compounds (QAC) such as benzalkonium chloride, benzethonium chloride, and cetylpyridinium chloride, which are extensively used in DAs formulations, have gained less attention in the context of AMR. Conclusion: A high abundance of QACs was detected in wastewater, and certain bacteria such as Pseudomonas aeruginosa, Acinetobacter baumannii, and Enterococcus species developed resistance to these compounds over time. We analyzed the available evidence from the scientific literature, examining the presence and concentrations of QACs in different water sources, and their resistance mechanisms. This review aimed to shed light on the multifaceted challenges that arise from the dual battle against the COVID-19 pandemic and the ongoing global fight against AMR.

Generation of DBPs from dissolved organic matter by solar photolysis of chlorine: Associated changes of cytotoxicity and reactive species

Since elevated amounts of chlorine disinfectant were discharged into surface water, more attention should be paid to the reactions between dissolved organic matter (DOM) and chlorine under sunlight. However, disinfection byproducts (DBPs) formed from DOM by solar photolysis of chlorine, and changes of cytotoxicity during this process remain unclear. In this study, it was found that solar photolysis of chlorine significantly promoted the formation of aliphatic chlorinated DBPs and aromatic chlorinated DBPs (including chlorobenzoquinone) by 44.7-109 % and 81.7-121 %, respectively compared with dark chlorination. Unknown total organic chlorine contained in low molecular weight fraction (<1 kD) significantly positively correlated to the cytotoxicity of water samples. Several factors (bicarbonate, dissolved oxygen, pH, nitrate, ammonia, bromide, and iodide) affecting the radical chemistry, and the formation of DBPs under solar photolysis of chlorine were also investigated. Reactive species including HO•, Cl•, O3, and reactive nitrogen species (RNS) were responsible for forming different DBPs. Especially O3 increased the formation of most categories of DBPs tested in this study, and RNS contributed to the formation of nitrogenous DBPs. This study provided more understanding of the adverse impact of overused chlorine, and reaction mechanisms between reactive species and DOM.

Unignorable environmental risks: Insight into differential responses between biofilm and plastisphere in sulfur autotrophic denitrification system upon exposure to quaternary ammonium compounds

Concerns of quaternary ammonium compounds (QACs) and microplastics (MPs) as emerging containments accumulating in wastewater treatment plants (WWTPs) have attracted much attention. Plastisphere with distinctive microbial communities might also be the repository for pathogens and resistance genes (RGs). Thus, the effects of three representative QACs with different concentrations on biofilm and plastisphere were studied in sulfur autotrophic denitrification (SAD) system. Over 100 days, 1-5 mg/L QACs exerted few impacts on system stability, whereas 15 mg/L QACs seriously lowered the microbial activity and the inhibitory effects ranked: benzylalkyldimethylethyl ammonium compound > dialkyldimethyl ammonium compound > alkyltrimethyl ammonium compound. Dosing of QACs in SAD system not only altered the microbial community structure and assembly, but also induced higher levels of intracellular RGs and extracellular RGs in plastisphere than in biofilm. Although the free RGs abundances in water slightly lowered, they might also pose great ecological risks. Pathogens identified as the potential hosts of RGs were more prone to colocalizing in plastisphere. Mobile genetic elements directly contributed to the three-fraction RGs transmission in SAD system. This study offered new insights into the differential responses of biofilm and plastisphere under QACs stress and guided for the disinfectants and MPs pollution containment in WWTPs.

Moroccan Hospital Cockroaches: Carriers of Multidrug-Resistant Gram-Negative Bacteria

Antimicrobial resistance in Gram-negative bacteria (GNB) is a growing global health concern, particularly in hospital environments, where cockroaches act as vectors for resistant strains. This study aimed to analyze antimicrobial resistance and biofilm formation in GNB isolated from cockroaches collected in the hospital environment. Cockroaches were collected, and bacterial isolation was performed from their gut contents and external surfaces. GNB strains were tested for antibiotic susceptibility using the disk diffusion method and examined for Extended-spectrum β-lactamases (ESBLs) and carbapenemases production. Molecular characterization of ESBLs and carbapenemases in GNB involved PCR amplification of antibiotic resistance genes, while biofilm formation was studied using a microplate assay. Seventy-five cockroaches were collected from which 165 GNB were isolated. The prevalence of ESBL-producing and carbapenemase-producing GNB was 6.7 and 1.8%, respectively. The predominant ESBL gene was blaCTX-M-28, while blaNDM-1 was the only carbapenemase gene detected. The qnrS1 gene was found in one NDM-1-producing Klebsiella pneumoniae and three ESBL-producing Escherichia coli. The qacΔE1 gene was detected in an NDM-1-producing Citrobacter freundii and a CTX-M-28-producing E. coli, whereas one NDM-1-producing Enterobacter cloacae carried both qacΔE1 and acrA genes. Strains harboring qacΔE1 and/or acrA genes exhibited biofilm-forming capabilities, with biofilm formation observed in 81.81% of ESBL-producing isolates and 100% of carbapenemase-producing isolates. The study underscores the role of cockroaches in carrying and disseminating ESBL- and carbapenemase-producing GNB in hospital settings. The coexistence of disinfectant resistance genes and antibiotic resistance suggests co-selection mechanisms, while biofilm formation enhances bacterial survival. These findings underline the urgent need for infection control strategies.

Common antimicrobials disrupt early zebrafish development through immune-cardiac signaling

The global production and use of antimicrobial chemicals surged during and after the COVID-19 pandemic, yet their developmental toxicity in aquatic organisms at environmentally relevant concentrations remains poorly understood. Here, we investigate and compare the developmental effects of two restricted antimicrobial chemicals-triclosan (TCS) and triclocarban (TCC)-and three alternative antimicrobials-benzalkonium chloride (BAC), benzethonium chloride (BEC), and chloroxylenol (CX)-on zebrafish embryos (Danio rerio) at concentrations of 0.4, 4, and 40 μg L-1. We find that BAC induces the most severe reduction in hatching rates, followed by TCS, TCC, BEC, and CX. BAC also exhibits the strongest inhibition of heart rate, with toxicity levels comparable to those of TCS and TCC. All tested chemicals, except CX, cause significant teratogenic effects. Transcriptomic analysis reveals substantial disruptions in immune-related coagulation cascades and mitogen-activated protein kinase signaling pathways. Further validation via protein-protein interaction network analysis and real-time quantitative polymerase chain reaction confirms that altered expression of key hub genes in these pathways impacts bone and heart development, as well as immune system function, potentially driving developmental toxicity. This study provides the first systematic comparison of developmental toxicity among currently used antimicrobials at environmentally relevant concentrations, revealing that the alternative antimicrobial BAC poses greater developmental risks than the banned TCS and TCC. These findings raise concerns about the safety of BAC as a widespread substitute and highlight the necessity for more rigorous environmental risk assessments of alternative antimicrobials before their large-scale application.

Designing Effective Antimicrobial Agents: Structural Insights into the Antibiofilm Activity of Ionic Liquids

Research concerning biofilm control is critical due to the pervasive and resilient nature of biofilms, which pose significant challenges across the industrial, environmental, and healthcare sectors. Traditional antimicrobial treatments are often ineffective against these robust structures. Here, we explore the antimicrobial properties of ionic liquids (ILs) and their efficacy in biofilm disruption. By examining the structural variations of ILs, we highlight the key role of hydrophobicity, noting that longer alkyl side chains in IL cations enhance biofilm disruption and bacterial death. However, upon reaching a certain optimal chain length─usually C12 to C14─the antimicrobial activity of ILs starts to decrease. Furthermore, the symmetry and size of anions significantly impact biofilm elimination. This Perspective addresses a critical gap in biofilm research, revealing the structure-activity relationships of ILs and providing a foundation for designing more effective biofilm-disrupting agents.

Effects of different quaternary ammonium compounds on intracellular and extracellular resistance genes in nitrification systems under the pre-contamination of benzalkyl dimethylammonium compounds

As the harm of benzalkyl dimethylammonium compounds (BACs) on human health and environment was discovered, alkyltrimethyl ammonium compound (ATMAC) and dialkyldimethyl ammonium compound (DADMAC), which belong to quaternary ammonium compounds (QACs), were likely to replace BACs as the main disinfectants. This study simulated the iterative use of QACs to explore their impact on resistance genes (RGs) in nitrification systems pre-contaminated by BACs. ATMAC could initiate and maintain partial nitrification. DADMAC generated higher levels of reactive oxygen species and lactate dehydrogenase, leading to increased biological toxicity in bacteria. The abundance of intracellular RGs of sludge was higher with the stress of QACs. DADMAC also induced higher extracellular polymeric substance secretion. Moreover, it facilitated the transfer of RGs from sludge to water, with ATMAC disseminating RGs through si-tnpA-04 and DADMAC through si-intI1. Sediminibacterium might be potential hosts for RGs. This study offered insights into disinfectant usage in the post-COVID-19 era.

The activity of indigo carmine against bacteriophages: an edible antiphage agent

Bacteriophage infections in bacterial cultures pose a significant challenge to industrial bioprocesses, necessitating the development of innovative antiphage solutions. This study explores the antiphage potential of indigo carmine (IC), a common FDA-approved food additive. IC demonstrated selective inactivation of DNA phages (P001, T4, T1, T7, λ) with the EC50 values ranging from 0.105 to 0.006 mg/mL while showing no activity against the RNA phage MS2. Fluorescence correlation spectroscopy (FCS) revealed that IC selectively binds to dsDNA, demonstrated by a significant reduction in the diffusion coefficient, whereas no binding was observed with ssDNA or RNA. Mechanistically, IC permeates the phage capsid, leading to genome ejection and capsid deformation, as confirmed by TEM imaging. Under optimal conditions (50 °C, 220 rpm), IC achieved up to a 7-log reduction in phage titer, with kinetic theory supporting the enhanced collision frequency induced by agitation. Additionally, IC protected E. coli cultures from phage-induced lysis without affecting bacterial growth or protein production, as demonstrated by GFP expression assays. IC's effectiveness and environmental safety, combined with its FDA approval and cost-effectiveness, make it a promising antiphage agent for industrial applications. KEY POINTS: • Indigo carmine effectively inactivates a broad spectrum of bacteriophages, offering protection to bacteria in industrial cultures. • A novel application of indigo carmine as a food-grade, environmentally safe, and FDA-approved antiphage agent protecting bacterial cultures. • Antiphage activity arises from indigo carmine's interaction with DNA within the phage capsid without harming bacterial cells or compromising protein production in bacterial cultures.

Occurrence and ecological risk of disinfection byproducts in urban water body during the pandemic in the Pearl River Delta

As the economic center of southern China, the Pearl River Delta region (PRDR) pays special attention to public health issues. During the pandemic, intensive disinfection was carried out in the city to prevent the spread of the virus, which resulted in disinfectant residuals elevating and produced large amounts of toxic disinfection byproducts (DBPs) in the urban water environment. For the purpose of surveying the concentration and distribution of urban water DBPs during the outbreak, 57 samples were collected from three urban water matrices in the PRDR, and were analyzed for the common seven types of DBPs, to elucidate their occurrence and ecological risk. Total 31 DBPs were detected, and the average concentrations of various DBPs in the three matrices were in the order of: surface water (1.9-27.5 μg/L) < effluent from wastewater treatment plant (30.5-114.8 μg/L) < hospital wastewater (5.5-168.9 μg/L). Both trihalomethanes (THMs) and haloacetic acids (HAAs) were the two most major DBPs in all three water categories. By comparing the concentration levels of DBPs in different areas, the concentration levels of DBPs in PRDR were not high. In some hospital wastewater, the TOC content may be able to be used as an associative indicator of DBPs content. The results of the risk quotient indicate that HAAs and haloacetonitriles (HANs) pose some ecological risk.

Factors affecting mass inflow of quaternary ammonium compounds into Japanese sewage treatment plants

Quaternary ammonium compounds (QACs), ecotoxic organic chemicals linked to multidrug resistance, are being used increasingly, for example to prevent the transmission of infections such as covid-19, in households, hospitals, and industry. To understand the locations, fluctuations, and fractions of QACs entering sewers, we monitored 14 QACs (benzalkonium chloride [BAC]-C8, C10, C12, C14, C16, and C18; dialkyldimethylammonium chloride [DDAC]-C8, C10, and C12; alkyltrimethylammonium chloride [ATAC]-C12, C16, and C18; benzethonium chloride; and cetylpyridinium chloride), and a disinfectant (chlorhexidine) in influent at four Japanese sewage treatment plants (STPs) five times throughout a year. Mass inflows were relatively stable throughout the year, indicating that the recent seasonal covid-19 epidemic did not greatly influence them. The differences in mass inflows among the STPs were normalized successfully by sewered residential population (most relative SDs were <30%), implying households to be the main source. Per-capita mass inflows accounted for 58%-73% of the per-capita consumption of BAC-C12 + C14 + C16, 28%-59% of that of DDAC-C10, 52%-70% of that of ATAC-C12, 86%-99% of that of ATAC-C16, and 64%-82% of that of ATAC-C18, indicating that a large proportion of their consumption entered sewers. The high contribution of ATAC-C16 agreed with its limited use in primary and secondary industries, little of whose wastewaters enter sewers, whereas the low contribution of DDAC-C10 is attributable to its substantial use in animal husbandry. Our first observation of fractions of QACs entering sewers will advance the management of environmental risks.

Deciphering the inhibitory mechanisms of didecyldimethylammonium chloride on microalgal removal of fluoxetine: Insights from the alterations in cell surface properties and the physio-biochemical and molecular toxicity

The COVID-19 pandemic has increased the co-occurrence of quaternary ammonium compounds (QACs) and antidepressants in aquatic environments. Microalgae are sustainable and cost-effective candidates for removing emerging pollutants. QACs have a robust ability to adsorb on cell surface and alter membrane permeability, but little is known about the influence of QACs on microalgal bioremediation of co-existing pollutants like antidepressants. In this study, the influence mechanisms of didecyldimethylammonium chloride (DDAC) on the removal of fluoxetine (FLX) by C. pyrenoidosa were explored. The results showed that C. pyrenoidosa exhibited high removal efficiency of single FLX (75.23 %-88.65 %) mainly through biodegradation (57.12 %-67.19 %). However, the coexisting medium and high concentrations of DDAC considerably decreased the biodegradation amount (10.50 %-33.30 %) and removal efficiency (29.47 %-52.89 %) of FLX by C. pyrenoidosa. In contrast, the presence of DDAC increased extracellular and intracellular FLX concentrations due to the enhanced extracellular polymeric substance content, cell surface hydrophobicity, and cell membrane permeability. Meanwhile, DDAC showed synergistic effects with FLX on microalgal growth through exacerbated oxidative damage and photosynthesis inhibition. Moreover, transcriptomics revealed that the dysregulations of key genes involved in the DNA replication and repair, ribosome biogenesis, photosynthesis-antenna proteins, peroxisomes, and glutathione metabolism pathways were important molecular mechanisms underlying the synergistic toxicity. Furthermore, the principal component analysis suggested that the enhancement of extracellular and intracellular FLX concentrations induced by the coexistence of DDAC increased the mixture's toxicity, resulting in the decreased biodegradation amount and ultimately a reduction in the removal efficiency of FLX. Our results highlight the significance of recognizing the influence of QACs on microalgal remediation and ecological risks of antidepressants.

Effects of quaternary ammonium disinfectants on human pathogenic bacteria in anaerobic sludge digestion: Dose-response and resistance variation

Sewage sludge is a critical reservoir for biological pollutants, and its harmless disposal remains a major issue. Quaternary ammonium compounds (QACs) as typical household disinfectants are inevitably concentrated in sewage sludge, and have the potential to affect human pathogenic bacteria (HPBs) that remain poorly understood. This study found that the relative abundance of HPBs in digesters was decreased by 10 - 20 % at low QACs dose, but increased by 238 - 591 % at high QACs dose. Mechanistic analysis revealed that low QACs doses promoted functional hydrolytic/fermentative bacteria and their metabolism by stimulating extracellular polymeric substances secretion and enhancing resistance to QACs. Conversely, high QAC doses decreased microbial biomass and developed QACs and antibiotic resistance of HPBs by increasing cell membrane permeability and triggering oxidative stress, resulting in deteriorating sanitation performance. These findings provide advanced insights into the potential function and hazards of exogenous QACs on the biosafety of digestate.

Source and bioavailability of quaternary ammonium compounds (QACs) in dust: Implications for Nationwide Exposure in China

Quaternary ammonium compounds (QACs), widely used in various disinfectants products during the COVID-19 Pandemic, raised the concerns on their exposure and health effect. To date, the sources of QACs in indoor environments have been largely ignored. Additionally, there is no information on the nationwide human exposure assessment of QACs in China after the COVID-19. Herein, analysis of QACs in household products, including personal care (n = 27), cleaning (n = 6) and disinfection products (n = 11) from different manufacturing companies further confirmed there are extensive application of QACs in household products, raising their potential exposure to humans. QACs were frequently detected in indoor dust samples (n = 370) from 111 cities of 31 provinces/municipalities across China, with median concentration of 6778 ng/g. Benzalkyldimethylammonium compounds (BACs) and alkyltrimethylammonium compounds (ATMACs) were identified as the dominant QACs in dust samples, with the proportions of 44 % and 46 %, respectively. The in vivo bioavailability experiment (C57BL/6 male mice) showed that the relative bioavailability (RBA) of QACs through dust ingestion ranged from 5.08 % to 66.3 % and 60.3 % to 118 % in the low and high-dose group, respectively. Compared to the pre-adjustment scenario of RBA values, the exposure risk of QACs was overestimated by 2.23 - 5.14 times.

Downstream effects of the pandemic? Spatiotemporal trends of quaternary ammonium compounds in suspended particulate matter of German rivers

During the SARS-CoV-2 pandemic, the preventive use of antimicrobials such as quaternary ammonium compounds (QACs) surged worldwide. As cationic and surface-active biocides, QACs are only partly removed during wastewater treatment and may cause adverse ecological effects in the downstream environment. To understand the environmental consequences of increased disinfectant use during the pandemic, we investigated spatiotemporal QAC concentration trends in the suspended particulate matter (SPM) of three diverse German rivers. Covering pooled annual SPM samples from 2006-2021 and monthly samples from 2018-2021 collected by the German Environmental Specimen Bank, 31 QACs were quantified by high performance liquid chromatography-mass spectrometry. ∑QAC concentrations in annual samples differed by more than tenfold between rivers in the order Saar (average 6.7 µg/g) > Rhine (0.9 µg/g) > Mulde (0.3 µg/g). The strongest potential pandemic imprint was however observed in the Mulde (+67 %) and Rhine (+22 %). Besides pandemic dynamics, also seasonal variation and mineral content of SPM tentatively affected QAC concentrations. Exceedance of predicted no-effect concentrations for sediment suggest ecotoxicological risks for long-chained QACs already before the pandemic. Our study thus highlights the importance of monitoring the environmental effects of antimicrobial use during pandemics and calls for an urgent minimization of non-essential applications.

Pulmonary surfactant biogenesis blockage mediated polyhexamethylene guanidine disinfectant induced pulmonary fibrosis

The widespread use of disinfectants and inhalation exposure to aerosolized forms is closely associated with adverse health effects on the respiratory system and pulmonary fibrosis, but the mechanism remains unclear. Here, we investigated the time-course pulmonary fibrosis effects of polyhexamethylene guanidine (PHMG) disinfectant inhalation exposure and elucidated its underlying mechanism. Specifically, scRNA-seq analysis revealed an initial increase in epithelial cell numbers after 4 weeks of PHMG exposure during induced pulmonary fibrosis, followed by a subsequent decrease after 8 weeks of exposure. Mechanistically, PHMG disrupted autophagic flux leading to intracellular accumulation and blocked pulmonary surfactant biogenesis in alveolar type II epithelial (AT2) cells both in vitro and in vivo. Furthermore, intervention studies using metformin confirmed that autophagy dysfunction mediated the blockage of pulmonary surfactant biogenesis in AT2 cells, playing a pivotal role in PHMG-induced pulmonary fibrosis. Our elucidation of these toxicological mechanisms provides valuable insights into the pathogenesis of pulmonary fibrosis triggered by environmental PHMG exposure, thereby offering a promising therapeutic target for mitigating and treating PHMG-associated pulmonary fibrosis.

Mass loading, removal and emission of 27 quaternary ammonium compounds, including metabolites of benzalkonium, in a wastewater treatment plant in New York state, USA

Benzylalkyldimethylammonium (BACs), dialkyldimethylammonium (DDACs), and alkyltrimethylammonium compounds (ATMACs) are quaternary ammonium compounds (QACs) widely used in industrial and consumer products. Nevertheless, little is known about their fates in wastewater treatment plants (WWTPs). We detected 7 BACs, 6 DDACs, 6 ATMACs, and 8 hydroxy- and carboxyl- metabolites of BACs (BACm) in wastewater collected from a WWTP in New York State. The median concentrations of ∑All (sum concentration of all 27 analytes) in influent and final effluent were 31900 and 545 ng/L, respectively, which corresponded to a removal efficiency of 98 %. C14-BAC, C10-DDAC, C18-DDAC, and C16-ATMAC were the major compounds found in influent (collectively accounting for 62 % of ∑All), suggestive of their prevalent usage in consumer products. BACm were detected for the first time in wastewater (median: 1720 ng/L in influent), and they comprised 8-11 % of ∑All in wastewater, which highlighted the importance of monitoring QAC metabolites in wastewater. The mass loadings of QACs into the WWTP were in the range of 1480-10700 mg/d/1000 inhabitants, whereas the corresponding emission rates were in the range of 119-7720 mg/d/1000 inhabitants. QACs present in final effluents may exert low to moderate risks on aquatic organisms, which warrants more attention.

Impact of the COVID-19 Pandemic on the Use of Quaternary Ammonium Compound Disinfectants in Healthcare Facilities Within Selected States in the United States of America

Introduction Quaternary ammonium compounds (QACs) are the active ingredient in the majority of disinfectants approved for use against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the causative agent of the coronavirus disease 2019 (COVID-19). Although widely used, they have been linked to infertility and birth defects in animals, and have been shown to increase proinflammatory cytokines, decrease mitochondrial function, and disrupt sterol biosynthetic pathways in a dose-dependent manner in humans. This study examined if there was an increased use of QAC-based disinfectants among healthcare settings in response to the COVID-19 pandemic and aims to bring to light the negative health outcomes that this rise in QAC exposure may pose.  Methods This hypothesis was explored using a telephone survey tool with both open-ended and closed-ended questions to assess changes in disinfection practices within hospitals, private practices, and dental practices. To ensure that the data were most representative of the United States, all states were ranked based on 28 health metrics tracked by the Kaiser Family Foundation. Those that ranked closest to the national average were Arizona, Florida, Illinois, Michigan, Pennsylvania, and Virginia. Healthcare facilities within these states were called at random and asked about changes in disinfection practices, specifically regarding the disinfectant type, product concentration, changes in the frequency of cleaning, and changes in the cleaning method. Additional data such as demographics, hospital ward type, and practice type were also obtained. Results QAC-based disinfectants were one of the most commonly used products in the surveyed hospitals, private practices, and dental practices both before and throughout the pandemic. Among all the medical facilities surveyed, approximately 80 to 90% indicated an increase in the frequency of cleaning. Within private practices, approximately 80 to 90% increased both spraying and wiping, while within dental practices, 75% increased wiping and only 60% increased spraying. Over 80% of hospitals reported an increase in all methods of disinfection within each ward type. The number of dental practices using QAC-containing disinfectants increased due to the pandemic. In hospitals, the class of disinfectant varied considerably by ward, but overall fewer of them used QAC-based disinfectants and more relied on peroxide-containing disinfectants. Conclusions This study identified increases in the disinfection frequency and changes to disinfection products within healthcare settings as a result of the COVID-19 pandemic. The predominant use of QAC-based products and the increased frequency of disinfection are important findings as they indicate heightened exposure. Emerging literature has identified adverse health outcomes in both animals and humans from contact with QACs. Increased disinfection during a pandemic or disease outbreak is critical to control the spread of disease; however, further research is needed to investigate whether the use of QAC-containing disinfectants to combat COVID-19 results in unintended disease burden in the healthcare workers.

A multi-pronged approach to assessing antimicrobial resistance risks in coastal waters and aquaculture systems

Antimicrobial resistance (AMR) is a global challenge that has impacted aquaculture and surrounding marine environments. In this study, a year-long monitoring program was implemented to evaluate AMR in two different aquaculture settings (i.e., open cage farming, recirculating aquaculture system (RAS)) and surrounding marine environment within a tropical coastal region. The objectives of this study are to (i) investigate the prevalence and co-occurrence of antibiotic-resistant bacteria (ARB), antibiotic resistance genes (ARGs), antibiotics (AB) and various associated chemical compounds at these study sites; (ii) explore the contributing factors to development and propagation of AMR in the coastal environment; and (iii) assess the AMR risks from different perspectives based on the three AMR determinants (i.e., ARB, ARGs and AB). Key findings revealed a distinct pattern of AMR across the different aquaculture settings, notably a higher prevalence of antibiotic-resistant Vibrio at RAS outfalls, suggesting a potential accumulation of microorganisms within the treatment system. Despite the relative uniform distribution of ARGs across marine sites, specific genes such as qepA, blaCTX-M and bacA, were found to be abundant in fish samples, especially from the RAS. Variations in chemical contaminant prevalence across sites highlighted possible anthropogenic impacts. Moreover, environmental and seasonal variations were found to significantly influence the distribution of ARGs and chemical compounds in the coastal waters. Hierarchical cluster analysis that was based on ARGs, chemical compounds and environmental data, categorized the sites into three distinct clusters which reflected strong association with location, seasonality and aquaculture activities. The observed weak correlations between ARGs and chemical compounds imply that low environmental concentrations may be insufficient for resistance selection. A comprehensive risk assessment using methodologies such as the multiple antibiotic resistance (MAR) index, comparative AMR risk index (CAMRI) and Risk quotient (RQ) underscored the complexity of AMR risks. This research significantly contributes to the understanding of AMR dynamics in natural aquatic systems and provides valuable insights for managing and mitigating AMR risks in coastal environments.

Designing Antibacterial-Based Quaternary Ammonium Coatings (Surfaces) or Films for Biomedical Applications: Recent Advances

Antibacterial coatings based on quaternary ammonium compounds (QACs) have been widely investigated in controlled release applications. Quaternary ammonium compounds are low-cost and easily accessible disinfectants that have been extensively used, especially after the COVID-19 outbreak. There has been a growing interest in developing a clearer understanding of various aspects that need to be taken into account for the design of quaternary ammonium compounds to be used in the biomedical field. In this contribution, we outline the mechanism of action of those materials as well as the key design parameters associated with their structure and antibacterial activity. Moreover, emphasis has been placed on the type of antibacterial coatings based on QACs and their applications in the biomedical field. A brief outlook on future research guidelines for the development of dual-function antibacterial coatings is also discussed.

Exposure effects of benzalkonium chloride (BAC) on gonadal physiology and fertility suppression in medaka (Oryzias latipes)

Benzalkonium chloride (BAC), a commonly used quaternary ammonium compound in various products like antiseptics, cosmetics, and disinfectants, has raised concerns due to its potential to contaminate aquatic environments and subsequently affect the reproductive performance of the organisms within those ecosystems. The article underscores a critical concern regarding the impact of BAC on aquatic ecosystems, particularly its effect on fish reproductive quality, using medaka (Oryzias latipes) as a model organism. Firstly, while measuring lethal dose of BAC in adult medaka, we observed a dose dependent mortality in BAC treated fish (100 and 200 ppm: 100%; 60 ppm: 51.7%; 30 ppm or less: no mortality at 24 h post treatment (hpt)) and calculated the LD50 at 96 hpt as 39.291 ppm (95% confidence interval: 28.817-53.570 ppm). Further, we assessed the molecular, cellular and histological changes through long-term exposure. Enlarged sperm pockets and reduced spermatocyte were seen in BAC exposed testis while no significant structural changes were observed in the ovaries. Following BAC exposure, drastic alterations in the gene expression and cellular localization related to sex, estrogen signaling, and autophagy were also noted from gonads and liver. Subsequently, using a short-term exposure analysis, we confirmed the sex and time responsive transcriptional kinetics and found that BAC sequentially affected the gonadal somatic cells followed by germ cell differentiation. Finally, using reproductively competent male and female medaka, we conducted progeny production and performance analysis and depicted a drastic reduction in fecundity, and fertilization and hatching rate, indicating adverse effects of BAC on reproductive success. Cumulatively, these findings emphasize the consequences of widespread use of BAC on reproductive security of aquatic animals and highlights the need for further research to comprehend the potential harm posed by such compounds to aquatic animal health and ecosystem integrity.

Highly Effective Biocides against Pseudomonas aeruginosa Reveal New Mechanistic Insights Across Gram-Negative Bacteria

Pseudomonas aeruginosa is a major nosocomial pathogen that persists in healthcare settings despite rigorous disinfection protocols due to intrinsic mechanisms conferring resistance. We sought to systematically assess cationic biocide efficacy against this pathogen using a panel of multidrug-resistant P. aeruginosa clinical isolates. Our studies revealed widespread resistance to commercial cationic disinfectants that are the current standard of care, raising concerns about their efficacy. To address this shortcoming, we highlight a new class of quaternary phosphonium compounds that are highly effective against all members of the panel. To understand the difference in efficacy, mechanism of action studies were carried out, which identified a discrete inner-membrane selective target. Resistance selection studies implicated the SmvRA efflux system (a transcriptionally regulated, inner membrane-associated efflux system) as a major determinant of resistance. This system is also implicated in resistance to two commercial bolaamphiphile antiseptics, octenidine and chlorhexidine, which was further validated herein. In sum, this work highlights, for the first time, a discrete inner-membrane specific mechanism for the bolaamphiphile class of disinfectants that contrasts with the prevailing model of indiscriminate membrane interactions of commercial amphiphiles paving the way for future innovations in disinfectant research.

Temporal concentrations of Quaternary ammonium compounds in wastewater treatment effluents during the COVID-19 pandemic, 2020-2021

Quaternary ammonium compounds (QAC) are high production chemicals used in many commercial and household disinfection products. During the SARS-CoV-2 (COVID-19) pandemic, QACs were included on lists of COVID-19 disinfectants. Increased QAC use could lead to higher levels of QACs in wastewater treatment plant (WWTP) effluents, which could subsequently be released into the environment. To evaluate QACs in WWTP effluent, three WWTPs in the northeastern United States were monitored from May 2020 through August 2021. Target QACs included six benzylalkyldimethyl ammonium compounds (BAC), three dialkyldimethyl ammonium compounds (DADMAC), two ethylbenzylalkyldimethyl ammonium compounds (EBAC), and benzethonium. At least one QAC was detected in every sample with individual concentrations up to 1600 ng L-1. BAC-C14 was detected most frequently, found in 93% of effluent samples; BAC-C12, BAC-C16, EBAC-C12 and EBAC-C14 were all detected in greater than 80% of samples. Few temporal patterns were observed in QAC concentrations with respect to weekly COVID-19 cases: at WWTP 2, DADMAC-C8:C10 and DADMAC-C10 were positively correlated, and DADMAC-C8 negatively correlated. There were several seasonal trends at WWTP 1, including significant differences of ƩDADMAC, which were higher in fall than summer; ƩBAC was higher during the fall than both spring and summer; and ƩQAC where higher during the fall than spring.

Virucidal Coatings Active Against SARS-CoV-2

Three types of coatings (contact-based, release-based, and combined coatings with both contact-based and release-based actions) were prepared and tested for the ability to inactivate SARS-CoV-2. In these coatings, quaternary ammonium surfactants were used as active agents since quaternary ammonium compounds are some of the most commonly used disinfectants. To provide contact-based action, the glass and silicon surfaces with covalently attached quaternary ammonium cationic surfactant were prepared using a dimethyloctadecyl[3-(trimethoxysilyl)propyl]ammonium chloride modifier. Surface modification was confirmed by attenuated total reflection infrared spectroscopy, X-ray photoelectron spectroscopy (XPS), scanning electron microscopy, and contact angle measurements. The grafting density of the modifier was estimated by XPS and elemental analysis. To provide release-based action, the widely used quaternary ammonium cationic disinfectant, benzalkonium chloride (BAC), and a newly synthesized cationic gemini surfactant, C18-4-C18, were bound non-covalently to the surface either through hydrophobic or electrostatic interactions. Virus titration revealed that the surfaces with combined contact-based and release-based action and the surfaces with only release-based action completely inactivate SARS-CoV-2. Coatings containing only covalently bound disinfectant are much less effective; they only provide up to 1.25 log10 reduction in the virus titer, probably because of the low disinfectant content in the surface monolayer. No pronounced differences in the activity between the flat and structured surfaces were observed for any of the coatings under study. Comparative studies of free and electrostatically bound disinfectants show that binding to the surface of nanoparticles diminishes the activity. These data indicate that SARS-CoV-2 is more sensitive to the free disinfectants.

Biocompatible hydrogels based on quaternary ammonium salts of chitosan with high antimicrobial activity as biocidal agents for disinfection

The paper reports new hydrogels based on quaternary ammonium salts of chitosan designed as biocidal products. The chitosan derivative was crosslinked with salicylaldehyde via reversible imine bonds and supramolecular self-assemble to give dynamic hydrogels which respond to environmental stimuli. The crosslinking mechanism was demonstrated by 1H NMR and FTIR spectroscopy, and X-ray diffraction and polarized light microscopy. The hydrogel nature, self-healing and thixotropy were proved by rheological investigation and visual observation, and their morphology was assessed by scanning electron microscopy. The relevant properties for application as biocidal products, such as swelling, dissolution, bioadhesiveness, antimicrobial activity and ex-vivo hemocompatibility and in vivo local toxicity and biocompatibility on experimental mice were measured and analyzed in relationship with the imination degree and the influence of each component. It was found that the hydrogels are superabsorbent, have good adhesivity to skin and various surfaces and antimicrobial activity against relevant gram-positive and gram-negative bacteria, while being hemocompatible and biocompatible. Besides, the hydrogels are easily biodegraded in soil. All these properties recommend the studied hydrogels as ecofriendly biocidal agents for living tissues and surfaces, but also open the perspectives of their use as platform for in vivo applications in tissue engineering, wound healing, or drug delivery systems.

Reproductive & developmental toxicity of quaternary ammonium compounds†

Quaternary ammonium compounds are a class of chemicals commonly used as disinfectants in household and healthcare settings. Their usage has significantly increased in recent years due to the COVID-19 pandemic. In addition, quaternary ammonium compounds have replaced the recently banned disinfectants triclosan and triclocarban in consumer products. Quaternary ammonium compounds are found in daily antimicrobial and personal care products such as household disinfectants, mouthwash, and hair care products. Due to the pervasiveness of quaternary ammonium compounds in daily use products, humans are constantly exposed. However, little is known about the health effects of everyday quaternary ammonium compound exposure, particularly effects on human reproduction and development. Studies that investigate the harmful effects of quaternary ammonium compounds on reproduction are largely limited to high-dose studies, which may not be predictive of low-dose, daily exposure, especially as quaternary ammonium compounds may be endocrine-disrupting chemicals. This review analyzes recent studies on quaternary ammonium compound effects on reproductive health, identifies knowledge gaps, and recommends future directions in quaternary ammonium compound-related research. Summary Sentence  Quaternary ammonium compounds, a class of disinfecting compounds that have skyrocketed in usage during the COVID-19 pandemic, are emerging as reproductive and developmental toxicants.

Fate of quaternary ammonium compounds upon the UV/monochloramine process: Kinetics, transformation pathways and the formation of N-nitroso-N-methyl-N-alkylamines

Quaternary ammonium compounds (QACs) are widely detected in the aquatic environment due to their extensive use in a wide array of antibacterial products during the pandemic. In the current study, UV/monochloramine (UV/NH2Cl) was used to degrade three typical QACs, namely benzalkonium compounds (BACs), dialkyl dimethyl ammonium compounds (DADMACs), and alkyl trimethyl ammonium compounds (ATMACs). This process achieved high efficiency in removing BACs from water samples. The transformation products of QACs treated with UV/NH2Cl were identified and characterized using a high-resolution mass spectrometer, and transformation pathways were proposed. The formation of N-nitroso-N-methyl-N-alkylamines (NMAs) and N-nitrosodimethylamine (NDMA) were observed during QAC degradation. The molar formation yield of NDMA from C12-BAC was 0.04 %, while yields of NMAs reached 1.05 %. The ecotoxicity of NMAs derived from QACs was predicted using ECOSAR software. The increased toxicity could be attributed to the formation of NMAs with longer alkyl chains; these NMAs, exhibited a one order of magnitude increase in toxicity compared to their parent QACs. This study provides evidence that QACs are the specific and significant precursors of NMAs. Greater attention should be given to NMA formation and its potential threat to the ecosystem, including humans.

Development of quaternized agar-based materials for the coronavirus inactivation

The COVID-19 pandemic has revealed weaknesses in healthcare systems and underscored the need for advanced antimicrobial materials. This study investigates the quaternization of agar, a seaweed-derived polysaccharide, and the development of electrospun membranes for air filtration in facemasks and biomedical applications. Using the betacoronavirus MHV-3 as a model, quaternized agar and membranes achieved a 90-99.99 % reduction in viral load, without associated cytotoxicity. The quaternization process reduced the viscosity of the solution from 1.19 ± 0.005 to 0.64 ± 0.005 Pa.s and consequently the electrospun fiber diameter ranged from 360 to 185 nm. Membranes synthesized based on polyvinyl alcohol and thermally cross-linked with citric acid exhibited lower water permeability. Avoiding organic solvents in the electrospinning technique ensured eco-friendly production. This approach offers a promising way to develop biocompatible and functional materials for healthcare and environmental applications.

Synthesis and antimicrobial activity testing of quaternary ammonium silane compounds

With increasing health awareness of the pathogenic effects of disease-causing microorganisms, interest in and use (of medical textiles, disinfectants in medical devices, etc.) of antimicrobial substances have increased in various applications, such as medical textiles and disinfectants (alcohol-based and nonalcoholic), in medical devices There are several concerns with alcohol-based disinfectants, such as surface deformation of medical devices due to high alcohol content and damage to skin tissue caused by lipid and protein denaturation of cell membranes. Quaternary ammonium compounds (quats) were preferred because they have the potential to prepare water-based disinfectants. In this study, novel (3-chloropropyl)triethoxysilane (CPTMO) and (3-chloropropyl)triethoxysilane (CPTEO) based quaternary ammonium silane compounds (silane-quats) were developed using quats with carbon chain lengths of C12, C14, C16 and C18. Titration (ASTM D2074) was used to calculate the yield of the synthesis and the structures of the products were characterised by Fourier transform infrared spectroscopy (FTIR), nuclear magnetic resonance spectroscopy (13C NMR, 1H NMR) and gas chromatography-mass spectrometry (GC-MS).The in vitro antimicrobial activity of the synthesized samples was evaluated against Gram-positive (Staphylococcus aureus (S. aureus), Enterococcus hirae (E. hirae)) and Gram-negative (Escherichia coli (E. coli), Pseudomonas aeruginosa (P. aeruginosa)) bacteria and fungi (Candida albicans (C. albicans), Aspergillus brasiliensis (A. brasiliensis)) using the minimum inhibitory concentration (MIC) test. According to MIC tests, the silane-quats with the highest antimicrobial effects were dimethylhexadecyl[3-(trimethoxysilyl)propyl]ammonium chloride (SQ3), which had an MIC of < 16 μg/ml (ppm) against E. coli, S. aureus, E. hirae, C. albicans, and A. brasiliensis and 32 μg/ml against P. aeruginosa. The MIC test results also showed antimicrobial activity at least 2 times greater than that of the commercially available disinfectant benzalkonium chloride (BAC). Findings suggest that SQ3 (C16) holds promise as an effective medical disinfectant, presenting a novel approach to combating microbial infections in healthcare settings.

Whatever does not kill them makes them stronger: Using quaternary ammonia antimicrobials to alleviate the inhibition of ammonia oxidation under perfluorooctanoic acid stress

Perfluorooctanoic acid (PFOA), benzalkyl dimethylammonium compounds (BAC) and antibiotic resistance genes (ARGs) have negative effects on biological sewage treatment. The performance of nitrification systems under stress of PFOA (0.1-5 mg/L) or/and BAC (0.2-10 mg/L) was explored during 84-day experiments using four sequencing batch reactors, in this study. Low (0.1 mg/L) concentration PFOA had a positive influence on ammonia removal, while medium and high (2 and 5 mg/L) concentrations PFOA caused severe inhibition. Meanwhile, PFOA stress resulted in the enrichment of ARGs in water (w-ARGs). BAC (0-10 mg/L) had no obvious influence on ammonia removal. However, BAC promoted the reduction of ARGs and the bacterial community was the main participator (48.07%) for the spread of ARGs. Interestingly, the joint stress of PFOA and BAC increased the ammonia-oxidizing bacteria (AOB) activity from 5.81 ± 0.19 and 6.05 ± 0.79 mg N/(g MLSS·h) to 7.09 ± 0.87 and 7.23 ± 0.29 mg N/(g MLSS·h) in medium and high concentrations, compared to single stress of PFOA, which was observed for the first time. BAC could reduce bioavailability of PFOA through competitive adsorption and decreasing sludge hydrophobicity by the lower β-Sheet and α-Helix in tightly bound protein. Furthermore, the joint stress of PFOA and BAC was able to intensify the proliferation of w-ARGs and extracellular ARGs in sludge, and developed the most active horizontal gene transfer mediated by intl1 compared to single stress of PFOA or BAC. The batch tests verified the detoxification capacity of BAC on nitrification under 2.5 mg/L PFOA (48 h exposing), and the maximum alleviation of AOB activity was achieved at BAC and PFOA mass ratio of 2:1. In summary, BAC could be used to alleviate the inhibition of PFOA on ammonia oxidation, providing an efficient and sustainable approach in wastewater treatment.

Differential Expression Analysis Reveals Possible New Quaternary Ammonium Compound Resistance Gene in Highly Resistant Serratia sp. HRI

During the COVID-19 pandemic, the surge in disinfectant use emphasised their pivotal role in infection control. While the majority of antimicrobial resistance research focuses on antibiotics, resistance to biocides, which are present in disinfectants and sanitisers, is escalating. Serratia sp. HRI is a highly resistant isolate, and through the study of this organism, the molecular mechanisms of resistance may be uncovered. Serratia sp. HRI was treated with the disinfectant benzalkonium chloride in preparation for RNA sequencing. Through mining of the RNA-Seq differential expression data, an uncharacterised Major Facilitator Superfamily (MFS) efflux pump gene was found to be up-regulated at least four-fold at four different time points of exposure. Real-time PCR revealed this uncharacterised MFS efflux gene was up-regulated after exposure to benzalkonium chloride and two additional disinfectants, didecyldimethylammonium chloride (DDAC) and VirukillTM. Additionally, expression of this gene was found to be higher at 20 min versus 90 min of exposure, indicating that the up-regulation of this gene is an initial response to biocide treatment that decreases over time. This suggests that MFS efflux pumps may be an initial survival mechanism for microorganisms, allowing time for longer-term resistance mechanisms. This work puts forward a novel biocide resistance gene that could have a major impact on biocide susceptibility and resistance.

Antilisterial effect of alkyl polyglycosides biosurfactant and modes of action

Several outbreaks of Listeria monocytogenes originated mainly from contaminated contact surfaces. Thus, this study investigated the antilisterial effect of natural surfactants in terms of their use as a 2-in-1 sanitizing washer on a food contact surface and evaluated their modes of action. The antilisterial activity of alkyl polyglycosides (APGs), namely capryl glucoside (CA), coco glucoside (CG), and decyl glucoside (DG), was evaluated based on the minimum inhibitory concentration (MIC) and the minimum bactericidal concentration (MBC) using broth dilution assay. The results showed that CG had the strongest antilisterial activity. Therefore, CG was selected for further investigation. The time-kill assay showed a lethal effect of 0.5 % (w/w) CG by inactivating 4 Log reduction (99.99 %) of L. monocytogenes within 3 s. Furthermore, 1 % (w/w) CG with slight mechanical force in washing (by shaking) was efficient for sanitizing a stainless-steel coupon surface based on its ability to cause a total reduction of deposited L. monocytogenes (99.9 %) within 10 min. Scanning electron microscopy and applying Fourier-transform infrared spectroscopy revealed that CG chemically disrupted the cell wall and plasma membrane of L. monocytogenes within 5 min after a gentle wash. The results showed it had potent antimicrobial activity and was bactericidal against L. monocytogenes. Overall, our results supported the use of CG as a natural antibacterial surfactant to alter the chemical sanitizer and the possibility of its practical use in the food industry and for household use.

Exposure to zinc and dialkyldimethyl ammonium compound alters bacterial community structure and resistance gene levels in partial sulfur autotrophic denitrification coupled with the Anammox process

Dialkyldimethyl ammonium compound (DADMAC) is widely used in daily life as a typical disinfectant and often co-exists with the heavy metal zinc in sewage environments. This study investigated the effects of co-exposure to zinc (1 mg/L) and DADMAC (0.2-5 mg/L) on the performance, bacterial community, and resistance genes (RGs) in a partial sulfur autotrophic denitrification coupled with anaerobic ammonium oxidation (PSAD-Anammox) system in a sequencing batch moving bed biofilm reactor for 150 days. Co-exposure to zinc and low concentration (0.2 mg/L) DADMAC did not affect the nitrogen removal ability of the PASD-Anammox system, but increased the abundance and transmission risk of free RGs in water. Co-exposure to zinc and medium-to-high (2-5 mg/L) DADMAC led to fluctuations in and inhibition of nitrogen removal, which might be related to the enrichment of heterotrophic denitrifying bacteria dominated by Denitratisoma. Co-exposure to zinc and high concentration DADMAC (5 mg/L) stimulated the secretion of extracellular polymeric substances and increased the proliferation risk of intracellular RGs in sludge. This study provided insights into the application of PSAD-Anammox system and the ecological risks of wastewater containing zinc and DADMAC.

Sex-Specific Effects of Environmental Exposure to the Antimicrobial Agents Benzalkonium Chloride and Triclosan on the Gut Microbiota and Health of Zebrafish (Danio rerio)

The use of disinfectants containing benzalkonium chloride (BAC) has become increasingly widespread in response to triclosan (TCS) restrictions and the COVID-19 pandemic, leading to the increasing presence of BAC in aquatic ecosystems. However, the potential environmental health impacts of BAC on fish remain poorly explored. In this study, we show that BAC and TCS can induce the gut dysbiosis in zebrafish (Danio rerio), with substantial effects on health. Breeding pairs of adult zebrafish were exposed to environmentally relevant concentrations of BAC and TCS (0.4-40 μg/L) for 42 days. Both BAC and TCS exposure perturbed the gut microbiota, triggering the classical NF-κB signaling pathway and resulting in downstream pathological toxicity associated with inflammatory responses, histological damage, inhibited ingestion, and decreased survival. These effects were dose-dependent and sex-specific, as female zebrafish were more susceptible than male zebrafish. Furthermore, we found that BAC induced toxicity to a greater extent than the restricted TCS at environmentally relevant concentrations, which is particularly concerning. Our results suggest that environmental exposure to antimicrobial chemicals can have ecological consequences by perturbing the gut microbiota, a previously underappreciated target of such chemicals. Rigorous ecological analysis should be conducted before widely introducing replacement antimicrobial compounds into disinfecting products.

Wastewater surveillance for antibiotic resistance genes during the late 2020 SARS-CoV-2 peak in two different populations

The United States Centers for Disease Control and Prevention reported a rise in resistant infections after the coronavirus disease 2019 (COVID-19) pandemic started. How and if the pandemic contributed to antibiotic resistance in the larger population is not well understood. Wastewater treatment plants are good locations for environmental surveillance because they can sample entire populations. This study aimed to validate methods used for COVID-19 wastewater surveillance for bacterial targets and to understand how rising COVID-19 cases from October 2020 to February 2021 in Portugal (PT) and King County, Washington contributed to antibiotic resistance genes in wastewater. Primary influent wastewater was collected from two treatment plants in King County and five treatment plants in PT, and hospital effluent was collected from three hospitals in PT. Genomic extracts were tested with the quantitative polymerase chain reaction for antibiotic resistance genes conferring resistance against antibiotics under threat. Random-effect models were fit for log-transformed gene abundances to assess temporal trends. All samples collected tested positive for multiple resistance genes. During the sampling period, mecA statistically significantly increased in King County and PT. No statistical evidence exists of correlation between samples collected in the same Portuguese metro area.