A review on the ecotoxicological effect of sulphonamides on aquatic organisms

Biochar-loaded iron oxide as a novel electrode for the electro-Fenton degradation of sulfaquinoxaline: Performance evaluation, mechanistic insights, and toxicity transformation

In this work, carboxymethyl cellulose (CMC)-modified biochar (BC)-supported Fe3O4 was prepared for the degradation of sulfaquinoxaline (SQX) in a heterogeneous electro-Fenton process. The degradation rate of 10 mg/L SQX reached 94.2 % after 180 min of Fe3O4(CMC)/BC treatment, compared to 61.2 % with Fe3O4/BC. CMC allowed Fe3O4 particles to be more evenly distributed on the biochar surface, and its electron transfer capacity effectively activated the in situ generated H2O2 on the electrode with a maximum H2O2 yield of 17.9 mg/L. The produced 1O2 and ⋅O2- are the primary contributors to SQX degradation. The aniline of SQX is susceptible to electrophilic attack, whereas quinoxaline is susceptible to free radical attack, with bis-methylation, heterocyclic oxidation, and amino oxidation being the major reactions in the decomposition of SQX. Toxicity assessment by ECOSAR and T.E.S.T. modeling showed that all the intermediates were considerably less biotoxic than the parent compound. Density functional theory calculations showed that the O2 adsorption and H2O2 decomposition processes are spontaneous reactions, and the intermediates absorbed on the Fe atom have an increased energy potential and a tendency to be less active. The results of material cycling tests and metal ion leaching experiments confirmed the good reusability of the prepared cathode. Additionally, Fe3O4(CMC)/BC achieved excellent performance in livestock wastewater (SQX removal of 93.4 % and COD removal of 79.9 %), demonstrating the possibility of practical application. This study offers a theoretical foundation for the use of novel composite cathode materials to degrade persistent pollutants.

Evaluation of contaminants of emerging concern in surface waters (rivers and lake) from Peru: Occurrence and environmental risk assessment

This study represents one of the first efforts to investigate the presence and environmental risk of contaminants of emerging concern (CECs) in surface water of the main watersheds of the Department of Lima (Rímac River, Chillón River, and Lurin River), Department of Arequipa (Chili-Quilca-Vítor River, Cámana-Majes River, and Tambo River), and Department of Puno (Lake Titicaca) from Peru. Water samples were collected during two sampling campaigns (June and September-October 2023) in Lima and Arequipa, and one sampling campaign (April-May 2023) in Puno. A strategy combining qualitative and quantitative analysis of CECs was applied, based on liquid chromatography coupled to ion mobility-high resolution mass spectrometry (LC-IMS-HRMS) and tandem mass spectrometry (LC-MS/MS), respectively. A total of 16 pharmaceutically active compounds (PhACs) and other compounds (sweeteners, stimulants, UV filters, and preservatives) and 16 metabolites were identified by LC-IMS-HRMS with a high level of confidence, in addition to the 39 target PhACs quantified by LC-MS/MS. The watersheds of Lima showed the highest pollution in terms of the number of pharmaceuticals and concentration levels compared to the watersheds of Arequipa and Lake Titicaca (Puno), with antibiotics persisting from the upper watersheds to the lower watersheds in the rivers and the lake. For the environmental risk assessment, five different scenarios were considered depending on the water uses/destinations, and the multicriteria scoring method allowed to identification of relevant/concerning PhACs. Azithromycin, clarithromycin, erythromycin, ciprofloxacin, flumequine, trimethoprim, diclofenac, acetaminophen, losartan, valsartan, atorvastatin and metabolite O-desmethyl venlafaxine posed a high level of risk/concern. This information will facilitate the design of a Watch List for CECs, with future monitoring programs and environment risk assessments to protect vulnerable areas most affected by anthropogenic pollution.

Effects of oral immunization with Bacillus subtilis displaying Vibrio harveyi FlgE protein on the intestinal structure and gut microbiota of grouper

The development of a novel formulation that combines vaccines and probiotics as a primary strategy to protect fish against pathogenic bacteria and reduce reliance on antibiotics is essential for addressing aquatic diseases in the future. In this study, a novel Bacillus subtilis strain Bs-CotC-FlgE was engineered through genetic modification to express Vibrio harveyi FlgE protein for use in grouper immunization. We orally administered the recombinant Bs-CotC-FlgE spores and the control Bs-CotC spores to groupers and evaluated their effects on the intestinal structure and gut microbiota. To assess the intestinal structure, histological analysis of the hindgut was performed, including measurements of villus length, villus height, and intestinal wall thickness. For gut microbiota analysis, total genomic DNA was extracted from the intestines, and the V3-V4 region of the bacterial 16S rRNA gene was amplified and sequenced using Illumina novaseq6000. The abundance of Vibrio in different groups was evaluated by analyzing the sequencing data at the genus level. The results showed a relative percent survival (RPS) of 63 % for Bs-CotC-FlgE group, significantly higher than the 29.63 % observed in Bs-CotC group (p < 0.01). Both Bs-CotC-FlgE and Bs-CotC spores significantly increased intestinal villus length, villus height, intestinal wall thickness in grouper (p < 0.01). Furthermore, gut microbiota diversity in grouper improved after spore consumption, as indicated by increased Shannon and Shannoneven indices and decreased Simpson index. At the phylum level, compared to the control group, the abundance of Actinobacteria and Firmicutes increased, while that of Ascomycetes decreased in the treatment groups. At the genus level, the abundance of Vibrio was significantly lower in the Bs-CotC-FlgE and Bs-CotC groups than in the control group (p < 0.05), and the abundance of Ralstonia, Halomonas and Bacillus increased. Notably, the abundance of Vibrio in the Bs-CotC-FlgE group was significantly lower than that in the Bs-CotC group (p < 0.05), suggesting Bs-CotC-FlgE immunization stimulates the grouper to produce specific antibodies and inhibits the attachment of Vibrio in the intestine of grouper. However, we observed that the spores can only survive gastric acid exposure and remain viable in the intestine for a limited duration. These findings enhance our understanding of the interaction between Bacillus carrier vaccines and fish gut microbiota and have potential for the development of a live vector vaccine against V. harveyi in grouper, which could contribute to reducing the use of antibiotics in aquaculture. Taken together, our results demonstrate oral immunization with B. subtilis spore expressing FlgE on the surface was a promising, safe and needle-free vaccination strategy against V. harveyi infection in grouper. The Bacillus carrier vaccine strategy can be adapted for different species and environmental conditions, offering a versatile solution to enhance disease resistance and promote sustainable aquaculture development.

Legislative and precautionary approaches to managing pharmaceutical contaminants in Canadian freshwaters

Pharmaceuticals are increasingly recognized as contaminants of emerging concern in aquatic environments due to their potential ecological impacts. In Canada, pharmaceutical pollution remains an under-regulated issue within federal chemical management policy. This study critically examines the extent to which Canada's Chemicals Management Plan (CMP), under the Canadian Environmental Protection Act (CEPA), addresses the risks posed by pharmaceuticals in freshwater systems. Through a review of recent legislation and scientific information, the study identifies regulatory gaps, including limitations in current wastewater treatment practices and ecological risk assessments. The CMP sets out guidelines for assessing and managing chemicals under CEPA to minimize the risks posed by toxic substances. Despite scientific evidence of toxicity to aquatic ecosystems, relatively few pharmaceuticals have been assessed under the CMP. This article explores how Canada's multi-level governments can strengthen pharmaceutical pollution governance, particularly in light of the 2023 legislative amendments to CEPA. Drawing on comparative insights from the European Union, the study emphasizes the need to integrate expanded pharmaceutical screening criteria, enhanced monitoring, and revised persistence and bioaccumulation thresholds into the CMP framework. These improvements would enable Canada to adopt a more adaptive and precautionary approach to managing pharmaceutical pollution in aquatic ecosystems while contributing to global efforts that advance sustainable water management practices.

The Conversion and Degradation of Sulphaguanidine under UV and Electron Beam Irradiation Using Fluorescence

The work presents a spectral-luminescent study of the sulfaguanidine transformation in water under a pulsed e-beam and UV irradiation of an UVb-04 bactericidal mercury lamp (from 180 to 275 nm), KrCl (222 nm), XeBr (282 nm) and XeCl (308 nm) excilamps. Fluorescent decay curves have been used in our analysis of the sulfaguanidine decomposition. The conversion of antibiotic under e-beam irradiation for up to 1 min was more than 80%, compared with UV radiation: UVb-04-26%, XeBr - 20%. KrCl and XeCl - about 10%. At the end of 64 min of irradiation with UVb-04 and XeBr lamps, the conversion was 99%. During irradiation with these lamps, sulfaguanidine almost completely decomposed and passed into the final fluorescent photoproducts. After e-beam irradiated at the end of 13 min the decrease in sulfaguanidine was 93%. At the same time, the formation of sulfaguanidine transformation products was minimal compared to UV irradiation. The effect of UV irradiation and a powerful e-beam on the decomposition mechanisms of sulfaguanidine are significantly different, which is manifested in various changes in the absorption and fluorescence spectra.

Investigating the metabolism of four sulfonamides in grass carp via HPLC-MS for screening candidate materials of matrix reference material

An efficient, sensitive, and precise method for investigating the metabolism of four sulfonamides in grass carp has been established using high-performance liquid chromatography-mass spectrometry. By optimizing the experimental conditions, the method achieved a coefficient of determination above 0.999, with detection and quantification limits set at 0.5 μg/kg and 1.0 μg/kg, respectively. Recovery rates were between 92.90 % and 102.84 %, and relative standard deviations ranged from 1.70 % to 9.83 %, enabling the precise detection of these sulfonamides in grass carp tissue. The factors affecting the metabolic rate during the medicated bath process were investigated, and obtained the optimal parameter conditions for screening the candidate materials. The candidate materials screened through this method exhibit good stability when used to prepare matrix standard substances, this work not only provides a scientific basis for screening sulfonamide candidate materials but also offers insights for developing other matrix reference materials.

Two-stage continuous cultivation of microalgae overexpressing cytochrome P450 improves nitrogen and antibiotics removal from livestock and poultry wastewater

Improper treatment of livestock and poultry wastewater (LPWW) rich in ammonium nitrogen (NH4-N) and antibiotics leads to eutrophication, and contributes to the risk of creating drug-resistant pathogens. The design-build-test-learn strategy was used to engineer a continuous process using Chlorella vulgaris to remove NH4-N and antibiotics. The optimized system removed NH4-N at a rate of 306 mg/L/d, degraded 99 % of lincomycin, and reduced the hydraulic retention time to 4 days. The physiological, metabolic, and genetic mechanisms used by microalgae to tolerate LPWW, remove NH4-N, and degrade antibiotics were elucidated. A new cytochrome P450 enzyme important for NH4-N and antibiotic removal was identified. Finally, application of synthetic biology improved the NH4-N removal rate to 470 mg/L/d, which is the highest removal rate using microalgae reported to date. This research contributes to the mechanistic understanding of wastewater detoxification by microalgae, and the goal of achieving a circular bioeconomy for nutrient and water recycling.

Environmental and toxicological aspects of sulfamethoxazole photodegradation in the presence of oxidizing agents

Sulfamethoxazole (SMX) is a popular active substance, which is extensively applied to treat bacterial infections in humans and animals. Due to its widespread use, SMX enters the natural environment, where it can undergo degradation. Similarly to other emerging contaminants, SMX photodegradation and the use of oxidants in wastewater treatment processes can lead to the formation of potentially adverse transformation products for ecosystems. This study investigated the efficiency of SMX photodegradation in the presence of oxidizing agents (H2O2 and Fenton reagent). The potential environmental consequences of degradation product formation were analyzed based on experimental toxicity characterization. Standardized tests employing diverse organisms were utilized: Alivibrio fischeri (Microtox®), Daphnia magna (Daphtoxkit F®), and Lemna minor (Lemna sp. GIT). The potential environmental impact of the products identified in the reaction mixtures was evaluated using parameters describing aqueous solubility, hydrophobicity, toxicity, bioconcentration, persistence, and mobility. The analysis revealed that photodegradation produces transformation products with higher toxicity than SMX, as confirmed by in vitro tests of the reaction mixtures. Most of the detected compounds were found to have low mobility potential. The formation rates of key environmentally relevant transformation products, such as 1,4-benzoquinone, aniline, and phenol, were also discussed. The changes in total organic carbon (TOC) affected by photodegradation under the influence of the considered oxidizing agents were characterized.

Highlighting antibiotic-free aquaculture by using marine microbes as a sustainable method to suppress Vibrio and enhance the performance of brine shrimp (Artemia franciscana)

Brine shrimp nauplii are widely used as live food in fish and shellfish aquaculture but they may transmit pathogenic Vibrio to the target species causing significant economic loss. Heavy usage of antibiotics is expensive and environmentally damaging. Use of natural microbes as probiotics for disease management is a more sustainable strategy. In this study the abilities of four marine microbes-Debaryomyces hansenii, Ruegeria mobilis, Lactobacillus plantarum and Bacillus subtilis-to suppress Vibrio spp. and promote growth performance and survival of brine shrimp (Artemia franciscana) were investigated. Nauplii (Instar II) were exposed to 108 CFU mL-1 of one of the four microbes; a control without added microbes was included for comparison. The nauplii were fed daily with the microalga Nannochloropsis oculata. Population change, survival, weight gain, length gain, enzyme activity, microbial retention and body biochemical composition of the brine shrimp were measured. The results showed that B. subtilis and L. plantarum significantly decreased the body loading of Vibrio spp. in A. franciscana. Survival rate, weight gain and length gain of (A) franciscana all increased in L. plantarum and (B) subtilis treatments, but the growth performance in the D. hansenii and R. mobilis treatments was less consistent. Higher lipase and protease activities and lower body ash content in the brine shrimp were observed in the B. subtilis and L. plantarum treatments (P < 0.05). The abundance of B. subtilis in the brine shrimp was relatively stable even after 8 days of starvation. These findings demonstrate that B. subtilis was the most promising probiotic among the tested species, especially for long-term application without the need for repeated inoculation.

Degradation pathways of sulfamethoxazole under phototransformation processes: A data base of the major transformation products for their environmental monitoring

Sulfamethoxazole (SMX) is frequently detected in wastewater and aquatic environments worldwide at concentrations from ng L-1 to μg L-1. Unfortunately, SMX is not completely removed in municipal wastewater treatment plants (WWTPs), thus, SMX and their transformation products (TPs) are discharged into aquatic environments, where can be transformed by phototransformation reactions. In this study, the phototransformation of SMX as well as generation of their major TPs under photolysis and photocatalysis processes was reviewed. SMX can be totally removed under photolysis and photocatalysis processes in aqueous solutions using simulated or natural radiation. Degradation pathways such as isomerization, hydroxylation, fragmentation, nitration, and substitution reactions were identified during the generation of the major TPs of SMX. Particularly, 26 TPs were considered for the creation of a data base of the major TPs of SMX generated under phototransformation processes. These 26 compounds could be used as reference during the SMX monitoring both wastewater and water bodies, using analytic methodologies such as target analysis and suspect screening. A data base of the major TPs of pharmaceuticals active compounds (PhACs) as SMX could help to implementation of best environmental monitoring programs for the study of the environmental risks both PhACs and their TPs with highest occurrence in aquatic environments.

The expansion of fungal organisms in environmental biotechnology

Fungal organisms hold vital roles in ecosystem processes. Despite their intricate entanglement with most life on earth and their powerful metabolic capacities, they remain under-represented in environmental biotechnology. The interest in applying fungal biotechnologies to different environments is growing, as light is shed on their versatile potential. A diversity of fungi can be harnessed to promote crop yield, remediate pollutants from terrestrial and aquatic environments, and mitigate climate change impacts. Current technological advancements, such as the increase in high-accuracy 'omics pipelines, provide improvement. However, it is emphasized that there are many knowledge gaps regarding applying fungal biotechnology at scale where other organisms are inherently present. Hence, there is a dire need to increase funding that enables in-depth studies on fungal processes, such as degradation capacities, metabolite production, and cross-kingdom interactions, that promote climate-smart biotechnologies.

Prevalence and molecular characterization of ESBL-producing Escherichia coli isolated from broiler chicken and their respective farms environment in Malaysia

BACKGROUND

Extended spectrum beta-lactamase-producing Escherichia coli (ESBL-EC) is an increasing public health threat. This study aimed to determine the prevalence and characterization of ESBL-producing Escherichia coli (E. coli) isolated from broiler chicken and their farm environment, in Kelantan Malaysia.

METHODS

Escherichia coli was isolated from 453 collected samples, including 210 cloacal swabs and 243 environmental samples. The antimicrobial susceptibility profile of the E. coli isolates was assessed for sixteen antibiotics using the disc diffusion method. The E. coli isolates were evaluated for phenotypic ESBL production using modified double disc synergy. After extraction of genomic DNA, ESBL resistance genes, phylogenetic group, and virulence genes were detected by PCR using appropriate primers. ESBL genes were further confirmed by sequencing. The molecular typing of E. coli strains was determined by Multilocus Sequence Typing (MLST).

RESULTS

A total of 93.8% (425/453) E. coli were isolated from the collected samples. Out of 334 E. coli isolates screened, 14.7% (49/334) were phenotypically ESBL producers. All the ESBL-EC were resistant to tetracycline, ciprofloxacin, and ampicillin. Thus, 100% of the ESBL-EC were multidrug resistant. Of the ESBL-EC 81.6% were positive for at least one ESBL encoding gene. The most prevalent ESBL gene detected was blaTEM (77.6%; 38/49) followed by blaCTX-M (32.7%; 16/49) and blaSHV (18.4%; 9/49). The majority of ESBL-EC belonged to phylogenic groups A followed by B1 accounting for 44.9% and 12.2%, respectively. The most frequently identified sequence types were ST10 (n = 3) and ST206 (n = 3). The most detected virulence genes in the E. coli isolates were astA (33.3%; 22/66) followed by iss (15.2%; 10/66).

CONCLUSIONS

Our results show both broiler chicken and their respective farms environment were reservoirs of multi-drug resistant ESBL-producing E. coli and ESBL resistance genes.

Biodegradation of Photocatalytic Degradation Products of Sulfonamides: Kinetics and Identification of Intermediates

Sulfonamides can be effectively removed from wastewater through a photocatalytic process. However, the mineralization achieved by this method is a long-term and expensive process. The effect of shortening the photocatalytic process is the partial degradation and formation of intermediates. The purpose of this study was to evaluate the sensitivity and transformation of photocatalytic reaction intermediates in aerobic biological processes. Sulfadiazine and sulfamethoxazole solutions were used in the study, which were irradiated in the presence of a TiO2-P25 catalyst. The resulting solutions were then aerated after the addition of river water or activated sludge suspension from a commercial wastewater treatment plant. The reaction kinetics were determined and fifteen products of photocatalytic degradation of sulfonamides were identified. Most of these products were further transformed in the presence of activated sludge suspension or in water taken from the river. They may have been decomposed into other organic and inorganic compounds. The formation of biologically inactive acyl derivatives was observed in the biological process. However, compounds that are more toxic to aquatic organisms than the initial drugs can also be formed. After 28 days, the sulfamethoxazole concentration in the presence of activated sludge was reduced by 66 ± 7%. Sulfadiazine was practically non-biodegradable under the conditions used. The presented results confirm the advisability of using photocatalysis as a process preceding biodegradation.

Enhanced hepatotoxicity in zebrafish due to co-exposure of microplastics and sulfamethoxazole: Insights into ROS-mediated MAPK signaling pathway regulation

The combined pollution of microplastics (MPs) and sulfamethoxazole (SMZ) often occurs in aquatic ecosystems, posing a serious threat to animal and human health. However, little is known about the liver damage caused by the single or co-exposure of MPs and SMZ, and its specific mechanisms are still poorly understood. In this study, we investigated the effects of co-exposure to 20 μm or 80 nm MPs and SMZ in both larval and adult zebrafish models. Firstly, we observed a significant decrease in the number of hepatocytes and the liver damage in larval zebrafish worsened following co-exposure to SMZ and MPs. Additionally, the number of macrophages and neutrophils decreased, while the expression of inflammatory cytokines and antioxidant enzyme activities increased after co-exposure in larval zebrafish. Transcriptome analysis revealed significant changes in gene expression in the co-exposed groups, particularly in processes related to oxidation-reduction, inflammatory response, and the MAPK signaling pathway in the liver of adult zebrafish. Co-exposure of SMZ and MPs also promoted hepatocyte apoptosis and inhibited proliferation levels, which was associated with the translocation of Nrf2 from the cytoplasm to the nucleus and an increase in protein levels of Nrf2 and NF-kB p65 in the adult zebrafish. Furthermore, our pharmacological experiments demonstrated that inhibiting ROS and blocking the MAPK signaling pathway partially rescued the liver injury induced by co-exposure both in larval and adult zebrafish. In conclusion, our findings suggest that co-exposure to SMZ and MPs induces hepatic dysfunction through the ROS-mediated MAPK signaling pathway in zebrafish. This information provides novel insights into the potential environmental risk of MPs and hazardous pollutants co-existence in aquatic ecosystems.

Hidden ecotoxicological dangers: Investigating pathogen circulation and non-toxic risks hazards in a crucial brazilian watershed

Numerous studies evaluate chemical contaminants released by human activities and their effects on biota and aquatic ecosystems. However, few of these studies address non-toxic agents and their potentially harmful effects, which, in a concealed manner, culminate in an increased ecotoxicological risk for aquatic life and public health. This study investigated the presence of toxic and non-toxic pollutants in one of the main watersheds in Northeast Brazil (Rio São Francisco) and proposed a model of dispersion and transfer of resistance among the analyzed bacteria, also assessing the health risks of individuals and aquatic organisms present there. The results are worrying because although most toxic parameters, including physical-chemical and chromatographic aspects, comply with Brazilian environmental standards, non-toxic (microbiological) parameters do not. This research reveals the circulation of pathogens in several points of this hydrographic basin, highlighting the hidden ecotoxicological potential of an aquatic environment considered unaffected by the usual patterns of toxic parameters.

Comparative study on Antibacterial efficacy of a series of chromone sulfonamide derivatives against drug-resistant and MDR-isolates

Sulfonamide derivatives have numerous pharmaceutical applications having antiviral, antibacterial, antifungal, antimalarial, anticancer, and antidepressant activities. The structural flexibility of sulfonamide derivatives makes them an excellent candidate for the development of new multi-target agents, although long-time exposure to sulfonamide drugs results in many toxic impacts on human health. However, sulfonamides may be functionalized for developing less toxic and more competent drugs. In this work, sulfonamides including Sulfapyridine (a), Sulfathiazole (b), Sulfamethoxazole (c), and Sulfamerazine (d) are used to synthesize Schiff bases of 7-hydroxy-4-methyl-2-oxo-2H-chromene-8-carbalde-hyde (1a-1d). The synthesized compounds were spectroscopically characterized and tested against hospital isolates of three Gram-positive (Methicillin-resistant Staphylococcus aureus PH217, Ampicillin-resistant Coagulase-negative Staphylococcus aureus, multidrug-resistant (MDR) Enterococcus faecalis PH007R) and two Gram-negative bacteria (multidrug-resistant Escherichia coli, and Salmonella enterica serovar Typhi), compared to the quality control strains from ATCC (S. aureus 29213, E. faecalis 25922, E. coli 29212) and MTCC (S. Typhi 734). Two of the four Schiff bases 1a and 1b are found to be more active than their counterpart 1c and 1d; while 1a have showed significant activity by inhibiting MRSA PH217 and MDR isolates of E. coli at the minimum inhibitory concentration (MIC) of 150 μg/mL and 128 μg/mL with MBC of 1024 µg/mL, respectively. On the other hand, the MIC of 1b was 150 μg/mL against both S. aureus ATCC 29213 and Salmonella Typhi MTCC 734, compared to the control antibiotics Ampicillin and Gentamycin. Scanning electron microscopy demonstrated the altered surface structure of bacterial cells as a possible mechanism of action, supported by the in-silico molecular docking analysis.

Identification of sulfamethazine degraders in swine farm-impacted river and farmland: A comparative study of aerobic and anaerobic environments

Sulfonamides (SAs) are extensively used antibiotics in the prevention and treatment of animal diseases, leading to significant SAs pollution in surrounding environments. Microbial degradation has been proposed as a crucial mechanism for removing SAs, but the taxonomic identification of microbial functional guilds responsible for SAs degradation in nature remain largely unexplored. Here, we employed 13C-sulfamethazine (SMZ)-based DNA-stable isotope probing (SIP) and metagenomic sequencing to investigate SMZ degraders in three distinct swine farm wastewater-receiving environments within an agricultural ecosystem. These environments include the aerobic riparian wetland soil, agricultural soil, and anaerobic river sediment. SMZ mineralization activities exhibited significant variation, with the highest rate observed in aerobic riparian wetland soil. SMZ had a substantial impact on the microbial community compositions across all samples. DNA-SIP analysis demonstrated that Thiobacillus, Auicella, Sphingomonas, and Rhodobacter were dominant active SMZ degraders in the wetland soil, whereas Ellin6067, Ilumatobacter, Dongia, and Steroidobacter predominated in the agricultural soil. The genus MND1 and family Vicinamibacteraceae were identified as SMZ degrader in both soils. In contrast, anaerobic SMZ degradation in the river sediment was mainly performed by genera Microvirga, Flavobacterium, Dechlorobacter, Atopostipes, and families Nocardioidaceae, Micrococcaceae, Anaerolineaceae. Metagenomic analysis of 13C-DNA identified key SAs degradation genes (sadA and sadC), and various of dioxygenases, and aromatic hydrocarbon degradation-related functional genes, indicating their involvement in degradation of SMZ and its intermediate products. These findings highlight the variations of indigenous SAs oxidizers in complex natural habitats and emphasize the consideration of applying these naturally active degraders in future antibiotic bioremediation.

Difference of Microbial Community in the Stream Adjacent to the Mixed Antibiotic Effluent Source

Released antibiotics from source to stream can influence bacterial communities and potentially alter the ecosystem. This research provides a comprehensive examination of the sources, distribution, and bacterial community dynamics associated with varied antibiotic release sources adjacent to the stream. The residual of antibiotics from different sources was determined, and the bacterial community structure was examined to reveal the differences in the bacteria community in the stream. The residual of antibiotics was quantified with liquid chromatography-tandem mass spectrometry (LC-MS/MS), and the Illumina MiSeq platform was utilized to sequence bacterial 16S rRNA genes, providing comprehensive insights into the bacterial community structure in the sediment across five different sites. Results indicated that the presence and distribution of antibiotics were significantly influenced by released sources. In the case of the bacterial community, the Proteobacteria and Firmicutes were the most dominant phyla in the sediment, and especially, the Firmicutes showed higher abundance in sites mostly affected by livestock sources. Additionally, livestock gut bacteria such as Clostridium saudiense, Proteiniclasticum ruminis, and Turicibacter sanguinis were prevalent in antibiotic-contaminated sites adjacent to livestock facilities. Overall, this study provides critical insights into the effect of antibiotic contamination by verifying the relationship between the occurrence of antibiotic residuals and the alteration in the bacterial community in the stream.

Functionalities of electrochemical fluoroquinolone sensors and biosensors

Fluoroquinolones (FQs) are a class of broad-spectrum antimicrobial agents that are used to treat variety of infectious diseases. This class of antibiotics was being used for patients exhibiting early symptoms of a human respiratory disease known as the COVID-19 virus. As a result, this outbreak causes an increase in drug-resistant strains and environmental pollution, both of which pose serious threats to biota and human health. Thus, to ensure public health and prevent antimicrobial resistance, it is crucial to develop effective detection methods for FQs determination in water bodies even at trace levels. Due to their characteristics like specificity, selectivity, sensitivity, and low detection limits, electrochemical biosensors are promising future platforms for quick and on-site monitoring of FQs residues in a variety of samples when compared to conventional detection techniques. Despite their excellent properties, biosensor stability continues to be a problem even today. However, the integration of nanomaterials (NMs) could improve biocompatibility, stability, sensitivity, and speed of response in biosensors. This review concentrated on recent developments and contemporary methods in FQs biosensors. Furthermore, a variety of modification materials on the electrode surface are discussed. We also pay more attention to the practical applications of electrochemical biosensors for FQs detection. In addition, the existing challenges, outlook, and promising future perspectives in this field have been proposed. We hope that this review can serve as a bedrock for future researchers and provide new ideas for the development of electrochemical biosensors for antibiotics detection in the future.

Developing a Slow-Release Permanganate Composite for Degrading Aquaculture Antibiotics

Copious use of antibiotics in aquaculture farming systems has resulted in surface water contamination in some countries. Our objective was to develop a slow-release oxidant that could be used in situ to reduce antibiotic concentrations in discharges from aquaculture lagoons. We accomplished this by generating a slow-release permanganate (SR-MnO₄^-) that was composed of a biodegradable wax and a phosphate-based dispersing agent. Sulfadimethoxine (SDM) and its synergistic antibiotics were used as representative surrogates. Kinetic experiments verified that the antibiotic-MnO₄^- reactions were first-order with respect to MnO₄^- and initial antibiotic concentration (second-order rates: 0.056-0.128 s^-1 M^-1). A series of batch experiments showed that solution pH, water matrices, and humic acids impacted SDM degradation efficiency. Degradation plateaus were observed in the presence of humic acids (>20 mgL^-1), which caused greater MnO₂ production. A mixture of KMnO₄/beeswax/paraffin (SRB) at a ratio of 11.5:4:1 (w/w) was better for biodegradability and the continual release of MnO₄^-, but MnO₂ formation altered release patterns. Adding tetrapotassium pyrophosphate (TKPP) into the composite resulted in delaying MnO₂ aggregation and increased SDM removal efficiency to 90% due to the increased oxidative sites on the MnO₂ particle surface. The MnO₄^- release data fit the Siepmann-Peppas model over the long term (t < 48 d) while a Higuchi model provided a better fit for shorter timeframes (t < 8 d). Our flow-through discharge tank system using SRB with TKPP continually reduced the SDM concentration in both DI water and lagoon wastewater. These results support SRB with TKPP as an effective composite for treating antibiotic residues in aquaculture discharge water.

Microplastic biofilm, associated pathogen and antimicrobial resistance dynamics through a wastewater treatment process incorporating a constructed wetland

Microplastics in wastewater are colonized by biofilms containing pathogens and antimicrobial resistance (AMR) genes that can be exported into receiving water bodies. This study investigated establishment and changes in microplastic-associated biofilm and AMR during a conventional full-scale 2100 population equivalent wastewater treatment process combined with a free water surface polishing constructed wetland. Sequential microplastic colonization experiments were conducted at different stages of the wastewater treatment process, including in raw sewage, treated effluent and the constructed wetland. Two scenarios were tested in which the constructed wetland served as either (i) a polishing step or (ii) as primary recipient of sewage inoculated microplastics. Bacterial 16S rRNA gene sequencing was carried out for qualitative bacterial community analysis. qPCR was applied for quantitative analysis of AMR genes (sul1, ermB, tetW, intiI1), bacterial biomass (16S rRNA) and a human fecal marker (HF183). Microbial diversity on microplastics increased with incubation time. The initial sewage-derived biofilm composition changed more significantly in the wastewater effluent compared to the constructed wetland. Pathogen and AMR load decreased by up to two orders of magnitude after coupled conventional and constructed wetland treatment, while less impact was observed when sewage-inoculated microplastic material was directly transferred into the constructed wetland. Aeromonas, Klebsiella, and Streptococcus were key pathogenic genera correlated with AMR in microplastic-associated biofilms. Despite decreasing trends on human pathogens and AMR load along the treatment process, microplastic-associated biofilms were a considerable potential hotspot for AMR (intI1 gene) and accommodated Cyanobacteria and fish pathogens.

Development of a synthesis strategy for sulfamethoxazole derivatives and their coupling with hydrogel microparticles

Sulfonamides were the first synthetic antibiotics broadly applied in veterinary and human medicine. Their increased use over the last few decades and limited technology to degrade them after entering the sewage system have led to their accumulation in the environment. A new hydrogel microparticle based biosensing application for sulfonamides is developed to overcome existing labour-intensive, and expensive detection methods to analyse and quantify their environmental distribution. This biosensing assay is based on the soft colloidal probe principle and requires microparticle functionalization strategies with target molecules. In this study, we developed a step-wise synthesis approach for sulfamethoxazole (SMX) derivatives in high yield, with SMX being one of the most ubiquitous sulfonamide antibiotics. After de novo synthesis of the SMX derivative, two coupling schemes to poly(ethylene glycol) (PEG) hydrogel microparticles bearing maleimide and thiol groups were investigated. In one approach, we coupled a cysteamine linker to a carboxyl group at the SMX derivative allowing for subsequent binding via the thiol-functionality to the maleimide groups of the microparticles in a mild, high-yielding thiol-ene "click" reaction. In a second approach, an additional 1,11-bis(maleimido)-3,6,9-trioxaundecane linker was coupled to the cysteamine to target the hydrolytically more stable thiol-groups of the microparticles. Successful PEG microparticle functionalization with the SMX derivatives was proven by IR spectroscopy and fluorescence microscopy. SMX-functionalized microparticles will be used in future applications for sulfonamide detection as well as for pull-down assays and screenings for new sulfomethoxazole binding targets.

Preparation of bifunctional monomer molecularly imprinted polymer filled solid-phase extraction for sensitivity improvement of quantitative analysis of sulfonamide in milk

To solve the problems of unstable adsorption performance and high organic solvent consumption of traditional molecular imprinting materials, we developed a water-resistant and highly adsorptive molecularly imprinted sulfamethazine polymer (MIP) through a novel synthetic strategy consisting of the application of mixed functional monomers combined with hydrophobic crosslinkers. The results showed that the imprinting factor of the prepared MIP was increased from 0.93 to 4.38, and that the relative selection coefficient k' was 5.59. With the application of the material to be developed as a solid-phase extraction (SPE) filler for sulfonamides (SAs) in milk combined with UPLC-MS/MS, the validated method showed a sensitive quantification limit (0.89 µg/kg), a steady recovery (95.55%-97.97%) and an excellent precision (0.08%-2.92% RSD). Moreover, after 5 times usage, the recovery rate of MIP-SPE was still above 90%. Therefore, the prepared materials showed high performance of molecular adsorption and were water-resistant, which was also considered an excellent filler of SPE for SAs extraction in food or other fields.

Investigating the Effect of Bi2MoO6/g-C3N4 Ratio on Photocatalytic Degradation of Sulfadiazine under Visible Light

In this study, a series of Bi2MoO6/g-C3N4 composites were prepared through a wet-impregnation method, and their photocatalytic properties were investigated for the degradation of sulfadiazine (SDZ) under visible light irradiation. Physical and chemical characterizations were carried out using X-ray diffraction (XRD), scanning electron microscope (SEM), Fourier transform infrared spectroscopy (FT-IR), photoluminescence spectroscopy (PL), UV-vis diffuse reflectance spectra (UV-vis), and electrochemical impedance spectra (EIS). Compared to pure g-C3N4, the introduction of Bi2MoO6 significantly enhanced the visible light responsive photocatalytic activity, with the 1:32 Bi2MoO6/g-C3N4 composite exhibiting the highest photodegradation efficiency towards SDZ under visible light irradiation with a photocatalytic efficiency of 93.88% after 120 min of visible light irradiation. The improved photocatalytic activity can be attributed to the formation of a heterojunction between Bi2MoO6 and g-C3N4, which promotes the transfer of photogenerated electron-hole pairs, thereby elevating its photocatalytic activity. The results suggest that Bi2MoO6/g-C3N4 composites have potential application for the degradation of sulfonamides in aquatic environments.

Improving the sensitivity and selectivity of sulfonamides electrochemical detection with double-system imprinted polymers

The extensive use of antibiotics leading to the rapid spread of antibiotic resistance poses high health risks to humans, but to date there is still lack of an on-site detection method of SA residues. In this study, we integrated radical polymerization using sodium p-styrenesulfonate as a functional monomer and the self-polymerization of dopamine to prepare double-system imprinted polymers (DIPs) using sulfonamide antibiotics as templates. We found that the DIPs were semi-interpenetrating polymer networks and introduction of poly(dopamine) improved the selectivity of the imprinted cavities as well as the conductivity. The selectivity and sensitivity of the sensor using DIPs were much higher than those using single-system MIPs. This sensor could determine sulfonamides in complex samples in the presence of structural analogues. The linear range was from 0.01 to 10.00 μmol L^-1 with a detection limit of 4.00 nmol L^-1. Furthermore, based on the highly selective DIPs and statistics analysis, this method could be used for simultaneous analysis of 4 sulfonamide types in real samples with an accuracy of 94.87 %. This work provides a strategy to improve the selectivity and sensitivity of MIPs based-sensor that can serve as tool for the simultaneous analysis of antibiotic residues in environment samples.

Sulfamethoxazole (SMX) Alters Immune and Apoptotic Endpoints in Developing Zebrafish (Danio rerio)

Sulfamethoxazole (SMX) is a broad-range bacteriostatic antibiotic widely used in animal and fish farming and is also employed in human medicine. These antibiotics can ultimately end up in the aquatic ecosystem and affect non-target organisms such as fish. To discern the effect of SMX on developing zebrafish embryos and larvae, we investigated a broad range of sub-lethal toxicity endpoints. Higher concentrations of SMX affected survivability, caused hatch delay, and induced malformations including edema of the yolk sac, pericardial effusion, bent tail, and curved spine in developing embryos. Lower levels of SMX provoked an inflammatory response in larvae at seven days post fertilization (dpf), as noted by up-regulation of interferon (ifn-γ) and interleukin 1β (il-1β). SMX also increased the expression of genes related to apoptosis, including BCL2-Associated Agonist of Cell Death (bad) and BCL2 Associated X, Apoptosis Regulator (bax) at 50 µg/L and decreased caspase 3 (casp3) expression in a dose-dependent manner. SMX induced hyperactivity in larval fish at 500 and 2500 µg/L based upon the light/dark preference test. Collectively, this study revealed that exposure to SMX can disrupt the immune system by altering host defense mechanisms as well as transcripts related to apoptosis. These data improve understanding of antibiotic chemical toxicity in aquatic organisms and serves as a baseline for in-depth environmental risk assessment of SMX and antibiotics.

Aptamer-based NanoBioSensors for seafood safety

Chemical and biological contaminants are of primary concern in ensuring seafood safety. Rapid detection of such contaminants is needed to keep us safe from being affected. For over three decades, immunoassay (IA) technology has been used for the detection of contaminants in seafood products. However, limitations inherent to antibody generation against small molecular targets that cannot elicit an immune response, along with the instability of antibodies under ambient conditions greatly limit their wider application for developing robust detection and monitoring tools, particularly for non-biomedical applications. As an alternative, aptamer-based biosensors (aptasensors) have emerged as a powerful yet robust analytical tool for the detection of a wide range of analytes. Due to the high specificity of aptamers in recognising targets ranging from small molecules to large proteins and even whole cells, these have been suggested to be viable molecular recognition elements (MREs) in the development of new diagnostic and biosensing tools for detecting a wide range of contaminants including heavy metals, antibiotics, pesticides, pathogens and biotoxins. In this review, we discuss the recent progress made in the field of aptasensors for detection of contaminants in seafood products with a view of effectively managing their potential human health hazards. A critical outlook is also provided to facilitate translation of aptasensors from academic laboratories to the mainstream seafood industry and consumer applications.

The distinct resistance mechanisms of cyanobacteria and green algae to sulfamethoxazole and its implications for environmental risk assessment

Cyanobacteria and green algae are the OECD recommended test organisms for environmental toxicity assessments of chemicals. Whether the differences in these two species' responses to the identical chemical affect the assessment outcomes is a question worth investigating. Firstly, we investigated the distinct resistance mechanisms of Synechococcus sp. (cyanobacteria) and R. subcapitata (green algae) to sulfamethoxazole (SMX). The antioxidant system analysis demonstrated that R. subcapitata mainly relies on enhancing the activity of first line defense antioxidants, including superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPx), which is the most powerful and efficient response to get rid of ROS, whereas Synechococcus sp. depends upon increasing the activity of glutathione-S-transferase (GST) and GPx to resist oxidative stress. Besides, a total 7 transformation products (TPs) of SMX were identified in R. subcapitata culture medium. The analysis of conjectural transformation pathways and the predicted toxicity indicates that R. subcapitata could relieve SMX toxicity by degrading it to low eco-toxic TPs. Additionally, we summarized numerous exposure data and assessed the environmental risk of various antibiotics, revealing an inconsistent result for the same type of antibiotic by using cyanobacteria and green algae, which is most likely due to the different resistance mechanisms. In the future, modified indicators or comprehensive assessment methods should be considered to improve the rationality of environmental toxicity assessments.

A Low-Cost Electrochemical Method for the Determination of Sulfadiazine in Aquaculture Wastewater

As the concept of green development spreads worldwide, environmental protection awareness for production and life has been continuously strengthened. Antibiotic residues in aquaculture wastewaters aggravate environmental pollution and threaten human health. Therefore, the detection of residual antibiotics in wastewater is crucial. In this paper, a new, simple, and low-cost method based on the glassy carbon electrode electrochemical sensor for the detection of sulfadiazine in aquaculture wastewater was developed without using complex materials to modify the electrode surface, to detect sulfadiazine which electrochemically oxidizes directly. The electrochemical performance of the sensor was studied and optimized with differential pulse voltammetry and cyclic voltammetry in the three-electrode system. The optimal electrolyte was acetic acid-sodium acetate buffer, and the optimal pH was 4.0. Finally, based on the optimized conditions, the newly established method showed satisfactory results for detecting sulfadiazine in aquaculture wastewater. The concentration of sulfadiazine and the peak current intensity showed a linear relationship in the range of 20 to 300 μmol/L, and the limit of detection was 6.14 μmol/L, the recovery rate of standard addition was 87-95%, with satisfactory reproducibility and low interference.

Adaptation responses of microalgal-bacterial granular sludge to sulfamethoxazole

The presence of widely used sulfamethoxazole (SMX) in wastewater poses a threat to aquatic organisms and humans. Here, the responses of the emerging microalgal-bacterial granular sludge (MBGS) process in treating SMX-containing wastewater were investigated. The results indicated that 1, 5 and 10 mg/L SMX had little effect on the removals of organics and nutrients after an acclimation period of three to five days. SMX reduced intracellular glycogen content of MBGS, while the production of chlorophyll and extracellular polymeric substances tended to be promoted. Furthermore, the potential mechanisms on how MBGS adapted to SMX were deciphered to be the alterations of microbial community structure and function of MBGS. SMX might be degraded intracellularly into a carbon source for microbial metabolism and the SMX degraders were suspected to be Scenedesmaceae, Rhodocyclaceae and Burkholderiaceae. This study suggests that the MBGS process can handle SMX-containing wastewater, advancing knowledge on MBGS for antibiotics degradation.

A Review of Current Bacterial Resistance to Antibiotics in Food Animals

The overuse of antibiotics in food animals has led to the development of bacterial resistance and the widespread of resistant bacteria in the world. Antibiotic-resistant bacteria (ARB) and antibiotic-resistant genes (ARGs) in food animals are currently considered emerging contaminants, which are a serious threat to public health globally. The current situation of ARB and ARGs from food animal farms, manure, and the wastewater was firstly covered in this review. Potential risks to public health were also highlighted, as well as strategies (including novel technologies, alternatives, and administration) to fight against bacterial resistance. This review can provide an avenue for further research, development, and application of novel antibacterial agents to reduce the adverse effects of antibiotic resistance in food animal farms.