Global review of macrolide antibiotics in the aquatic environment: Sources, occurrence, fate, ecotoxicity, and risk assessment

Occurrence and risks of pharmaceuticals, personal care products, and endocrine-disrupting compounds in Chinese surface waters

The continuous and rapid increase of chemical pollution in surface waters has become a pressing and widely recognized global concern. As emerging contaminants (ECs) in surface waters, pharmaceutical and personal care products (PPCPs), and endocrine-disrupting compounds (EDCs) have attracted considerable attention due to their wide occurrence and potential threat to human health. Therefore, a comprehensive understanding of the occurrence and risks of ECs in Chinese surface waters is urgently required. This study summarizes and assesses the environmental occurrence concentrations and ecological risks of 42 pharmaceuticals, 15 personal care products (PCPs), and 20 EDCs frequently detected in Chinese surface waters. The ECs were primarily detected in China's densely populated and highly industrialized regions. Most detected PPCPs and EDCs had concentrations between ng/L to µg/L, whereas norfloxacin, caffeine, and erythromycin had relatively high contamination levels, even exceeding 2000 ng/L. Risk evaluation based on the risk quotient method revealed that 34 PPCPs and EDCs in Chinese surface waters did not pose a significant risk, whereas 4-nonylphenol, 4-tert-octylphenol, 17α-ethinyl estradiol, 17β-estradiol, and triclocarban did. This review provides a comprehensive summary of the occurrence and associated hazards of typical PPCPs and EDCs in Chinese surface waters over the past decade, and will aid in the regulation and control of these ECs in Chinese surface waters.

Three-birds-with-one-stone: An eco-friendly and renewable humic acid-derived material application strategy for macrolide antibiotic detection and multifunctional composite film preparation

This research proposes a simple and novel strategy for the green detection of antibiotics along with the reduction of microplastic and humic acid (HA) hazards. The entire process is based on a single-step solvent-sieving method to separate HA into insoluble (IHA) and soluble (SHA) components, subsequently recombining and designing the application according to the original characteristics of selected fractions in accordance with the zero-waste principle. IHA was applied as a dispersive solid phase extraction (DSPE) sorbent without chemical modification for the enrichment of trace MACs in complex biological matrices. The recovery of MACs was 74.06-100.84 % in the range of 2.5-1000 μg∙kg-1. Furthermore, SHA could be combined with biodegradable polyvinyl alcohol (PVA) to prepare multifunctional composite films. SHA endows the PVA film with favorable mechanical properties, excellent UV shielding as well as oxidation resistance performance. Compared with pure PVA, the tensile strength, toughness, antioxidant and UV-protection properties were increased to 157.3 Mpa, 258.6 MJ·m-3, 78.6 % and 60 % respectively. This study achieved a green and economically valuable utilization of all components of waste HA, introduced a novel approach for monitoring and controlling harmful substances and reducing white pollution. This has significant implications for promoting sustainable development and recovering valuable resources.

Nature-based solutions for antibiotics and antimicrobial resistance removal in tertiary wastewater treatment: Microbiological composition and risk assessment

This field-scale study evaluates the seasonal effectiveness of employing nature-based solutions (NBSs), particularly surface flow and horizontal subsurface flow constructed wetland configurations, as tertiary treatment technologies for the removal of antibiotics (ABs) and antibiotic resistance genes (ARGs) compared to a conventional treatment involving UV and chlorination. Out of the 21 monitored ABs, 13 were detected in the influent of three tertiary wastewater treatments, with concentrations ranging from 2 to 1218 ng·L-1. The ARGs sul1 and dfrA1 exhibited concentrations ranging from 1 × 105 to 9 × 106 copies/100 mL. NBSs were better at reducing ABs (average 69 to 88 %) and ARGs (2-3 log units) compared to the conventional tertiary system (average 36 to 39 % and no removal to 2 log units) in both seasons. Taxonomic compositions in influent water samples shifted from wastewater-impacted communities (Actinomycetota and Firmicutes) to a combination of plant rhizosphere-associated and river communities in NBS effluents (Alphaproteobacteria). In contrast, the conventional technology showed no substantial differences in community composition. Moreover, NBSs substantially reduced the ecotoxicological risk assessment (cumulative RQs). Furthermore, NBSs reduced the ecotoxicological risk (cumulative RQs) by an average of over 70 % across seasons, whereas the benchmark technology only achieved a 6 % reduction. In conclusion, NBSs present a robust alternative for minimizing the discharge of ABs and ARGs into surface water bodies.

Spatiotemporal distribution of the planktonic microbiome and antibiotic resistance genes in a typical urban river contaminated by macrolide antibiotics

The widespread application of macrolide antibiotics has caused antibiotic resistance pollution, threatening the river ecological health. In this study, five macrolide antibiotics (azithromycin, clarithromycin, roxithromycin, erythromycin, and anhydro erythromycin A) were monitored in the Zao River across three hydrological periods (April, July, and December). Simultaneously, the changes in antibiotic resistance genes (ARGs), mobile genetic elements (MGEs), and planktonic bacterial communities were determined using metagenomic sequencing. A clear pollution gradient was observed for azithromycin and roxithromycin, with the concentrations in the dry season surpassing those in other seasons. The highest concentration was observed for azithromycin (1.36 μg/L). The abundance of MLS resistance genes increased along the Zao River during the dry season, whereas the opposite trend was obtained during the wet season. A significant correlation between the levels of MLS resistance genes and macrolide antibiotics was identified during the dry season. Notably, compared with the reference site, the abundance of transposase in the effluent from wastewater treatment plants (WWTPs) was significantly elevated in both dry and wet seasons, whereas the abundance of insertion sequences (IS) and plasmids declined during the dry season. The exposure to wastewater containing macrolide antibiotics altered the diversity of planktonic bacterial communities. The bacterial host for ARGs appeared to be Pseudomonas, primarily associated with multidrug subtypes. Moreover, the ARG subtypes were highly correlated with MGEs (transposase and istA). The partial least-squares path model (PLS-PM) demonstrated a positive correlation between the abundance of MGEs and ARGs, indicating the significance of horizontal gene transfer (HGT) in the dissemination of ARGs within the Zao River. Environmental variables, such as TN and NO3--N, were significantly correlated with the abundance of MGEs, ARGs, and bacteria. Collectively, our findings could provide insights into the shift patterns of the microbiome and ARGs across the contamination gradient of AZI and ROX in the river.

When antibiotics encounter microplastics in aquatic environments: Interaction, combined toxicity, and risk assessments

Antibiotics and microplastics (MPs), known as emerging pollutants, are bound to coexist in aquatic environments due to their widespread distribution and prolonged persistence. To date, few systematic summaries are available for the interaction between MPs and antibiotics in aquatic ecosystems, and a comprehensive reanalysis of their combined toxicity is also needed. Based on the collected published data, we have analyzed the source and distribution of MPs and antibiotics in global aquatic environments, finding their coexistence occurs in a lot of study sites. Accordingly, the presence of MPs can directly alter the environmental behavior of antibiotics. The main influencing factors of interaction between antibiotics and MPs have been summarized in terms of the characteristics of MPs and antibiotics, as well as the environmental factors. Then, we have conducted a meta-analysis to evaluate the combined toxicity of antibiotics and MPs on aquatic organisms and the related toxicity indicators, suggesting a significant adverse effect on algae, and inapparent on fish and daphnia. Finally, the environmental risk assessments for antibiotics and MPs were discussed, but unfortunately the standardized methodology for the risk assessment of MPs is still challenging, let alone assessment for their combined toxicity. This review provides insights into the interactions and environment risks of antibiotics and MPs in the aquatic environment, and suggests perspectives for future research.

Antibiotics in the rice-crayfish rotation pattern: Occurrence, prioritization, and resistance risk

Antibiotics are extensively utilized in aquaculture to mitigate diseases and augment the productivity of aquatic commodities. However, to date, there have been no reports on the presence and associated risks of antibiotics in the emergent rice-crayfish rotation (RCR) system. This study investigated the occurrence, temporal dynamics, prioritization, sources, and potential for resistance development of 15 antibiotics within the RCR ecosystem. The findings revealed that during the crayfish breeding and rice planting periods, florfenicol (FFC) predominated in the RCR's surface water, with peak and average concentrations of 1219.70 ng/L and 57.43 ng/L, and 1280.70 ng/L and 52.60 ng/L, respectively. Meanwhile, enrofloxacin (ENX) was the primary antibiotic detected in RCR soil and its maximum and average concentrations were 624.73 ng/L and 69.02 ng/L in the crayfish breeding period, and 871.27 ng/L and 45.89 ng/L in the rice planting period. Throughout the adjustment period, antibiotic concentrations remained relatively stable in both phases. Notably, antibiotic levels in surface water and soil escalated during the crayfish breeding period and subsided during the rice planting period, with these fluctuations predominantly influenced by FFC and ENX. Source analysis indicated that the antibiotics in RCR predominantly originated from aquaculture activities, supplemented by water exchange processes. Utilizing the entropy utility function and a resistance development model, FFC, clarithromycin (CLR), and roxithromycin (ROX) in surface water, along with ENX, CLR, and ROX in soil, were identified as priority antibiotics. FFC, ENX, and ROX exhibited a medium risk for resistance development. Consequently, this study underscores the necessity to intensify antibiotic usage control during the crayfish breeding period in the RCR system to mitigate environmental risks.

Impact of environmental factors changes induced by marine heatwaves and heavy precipitation on antibiotic toxicity to Isochrysis galbana: Implications for climate change adaptation

Isochrysis galbana, a crucial primary producer and food source in aquatic ecosystems, faces increasing challenges from climate change and emerging contaminants like antibiotics. This study investigates the combined effects of sudden temperature increase (representing marine heatwaves) and rapid salinity change (representing extreme precipitation events) on the toxicity of tetracycline (TC) and oxytetracycline (OTC) to I. galbana. Short-term experiments reveal heightened antibiotic toxicity at 31 °C or salinities of 18 PSU, surpassing algal tolerance limits. Long-term tests show decreased inhibition of algal growth on day 9, indicating algal adaptation to the environment. Analyses of photosynthesis II efficiency, pigment content, and macromolecular composition support this, suggesting adaptation mechanism activation. While algae acclimate to the environment during long-term antibiotic exposure, extreme weather conditions may compromise this adaptation. These findings have implications for managing antibiotics in aquatic environments under climate change.

Effects of erythromycin on biofilm formation and resistance mutation of Escherichia coli on pristine and UV-aged polystyrene microplastics

Microplastics (MPs) and antibiotics co-occur widely in the environment and pose combined risk to microbial communities. The present study investigated the effects of erythromycin on biofilm formation and resistance mutation of a model bacterium, E. coli, on the surface of pristine and UV-aged polystyrene (PS) MPs sized 1-2 mm. The properties of UV-aged PS were significantly altered compared to pristine PS, with notable increases in specific surface area, carbonyl index, hydrophilicity, and hydroxyl radical content. Importantly, the adsorption capacity of UV-aged PS towards erythromycin was approximately 8-fold higher than that of pristine PS. Biofilms colonizing on UV-aged PS had a greater cell count (5.6 × 108 CFU mg-1) and a higher frequency of resistance mutation (1.0 × 10-7) than those on pristine PS (1.4 × 108 CFU mg-1 and 1.4 × 10-8, respectively). Moreover, erythromycin at 0.1 and 1.0 mg L-1 significantly (p < 0.05) promoted the formation and resistance mutation of biofilm on both pristine and UV-aged PS. DNA sequencing results confirmed that the biofilm resistance was attributed to point mutations in rpoB segment of the bacterial genome. qPCR results demonstrated that both UV aging and erythromycin repressed the expression levels of a global regulator rpoS in biofilm bacteria, as well as two DNA mismatch repair genes mutS and uvrD, which was likely to contribute to increased resistance mutation frequency.

Chronic toxic effects of erythromycin and its photodegradation products on microalgae Chlorella pyrenoidosa

The photodegradation products (PDPs) of antibiotics in the aquatic environment received increasing concern, but their chronic effects on microalgae remain unclear. This study initially focused on examining the acute effects of erythromycin (ERY), then explored the chronic impacts of ERY PDPs on Chlorella pyrenoidosa. ERY of 4.0 - 32 mg/L ERY notably inhibited the cell growth and chlorophyll synthesis. The determined 96 h median effective concentration of ERY to C. pyrenoidosa was 11.78 mg/L. Higher concentrations of ERY induced more serious oxidative damage, antioxidant enzymes alleviated the oxidative stress. 6 PDPs (PDP749, PDP747, PDP719, PDP715, PDP701 and PDP557) were identified in the photodegradation process of ERY. The predicted combined toxicity of PDPs increased in the first 3 h, then decreased. Chronic exposure showed a gradual decreasing inhibition on microalgae growth and chlorophyll content. The acute effect of ERY PDPs manifested as growth stimulation, but the chronic effect manifested as growth inhibition. The malonaldehyde contents decreased with the degradation time of ERY at 7, 14 and 21 d. However, the malonaldehyde contents of ERY PDPs treatments were elevated compared to those in the control group after 21 d. Risk assessment still need to consider the potential toxicity of degradation products under long-term exposure.

Adsorption of Macrolide Antibiotics and a Metabolite onto Polyethylene Terephthalate and Polyethylene Microplastics in Aquatic Environments

Microplastics (MPs) and antibiotics are emerging pollutants widely found in aquatic environments, potentially causing environmental harm. MPs may act as carriers for antibiotics, affecting their environmental distribution. This study investigates the adsorption of four macrolide antibiotics and a metabolite onto two types of MPs: polyethylene terephthalate (PET) and polyethylene (PE). Results revealed a linear isotherm adsorption model, with higher adsorption to PET than to PE (R2 > 0.936 for PE and R2 > 0.910 for PET). Hydrophobic interactions and hydrogen bonding could be the main adsorption mechanisms, with pore filling potentially involved. Reduced particle size enhances adsorption due to the increase of active adsorption sites. This increasement is more pronounced in PE than in PET, leading to an 11.6% increase in the average adsorption of all macrolides to PE, compared to only 5.1% to PET. Dissolved organic matter inhibits adsorption (azithromycin adsorption to PE was reduced from 12% to 5.1%), while salinity enhances it just until 1% salinity. pH slightly influences adsorption, with maximal adsorption at neutral pH. Results in real samples showed that complexity of the matrix decreased adsorption. Overall, these findings indicate that PE and PET MPs can be a vector of macrolides in aquatic environments.

Contaminants of Emerging Concern: Antibiotics Research in Mussels from the Coasts of the Tyrrhenian Sea (Sardinia, Italy)

Contaminants of emerging concern (CECs) are compounds found in several environmental compartments whose ubiquitous presence can cause toxicity for the entire ecosystem. Several personal care products, including antibiotics, have entered this group of compounds, constituting a major global threat. It is essential to develop simple and reliable methods by which to quantify these contaminants in several matrices. In this work, mussels were chosen as sentinel organisms to assess environmental pollution and the safety of bivalve mollusk consumption according to the "One Health perspective". A liquid chromatographic tandem mass spectrometry method (LC-MS/MS) was developed for the quantification of two macrolides, erythromycin (ERY) and azithromycin (AZI), in mussels. This new method was validated according to international guidelines, showing high selectivity, good recoveries (>60% for both of them), sensitivity, and precision. The method was successfully applied for ERY and AZI research in mussels farmed along the Sardinian coasts (Italy), demonstrating itself to be useful for routine analysis by competent authorities. The tested macrolides were not determined in the analyzed sites at concentrations above the limits of detection (LODs). These results demonstrate the food safety of mussels (as concerns the studied antibiotics) and a negligible amount of pollution derived from these drugs in the studied area.

Characterization of heavy metal, antibiotic pollution, and their resistance genes in paddy with secondary municipal-treated wastewater irrigation

Secondary municipal-treated wastewater irrigation may introduce residual antibiotics into the agricultural systems contaminated with certain heavy metals, ultimately leading to the coexistence of antibiotics and heavy metals. The coexistence may induce synergistic resistance to both in the microbial community. Here, we investigated the effects of long-term municipal-treated irrigation for rice on the microbiome and resistome. The results showed that the target antibiotics were undetectable in edible grains, and the heavy metal concentrations did not exceed the standard in edible rice grains. Heavy metal resistance genes (MRGs) ruvB and acn antibiotic resistance genes (ARGs) sul1 and sul2 were the dominating resistant genes. The coexistence of antibiotics and heavy metals affected the microbial community and promoted metal and antibiotic resistance. Network analysis revealed that Proteobacteria were the most influential hosts for MRGs, ARGs, and integrons, and co-selection may serve as a potential mechanism for resistance maintenance. MRG czcA and ARG sul1 can be recommended as model genes to study the co-selection of ARGs and MRGs in environments. The obtained results highlight the importance of considering the co-occurrence of heavy metals and antibiotics while developing effective methods to prevent the transmission of ARGs. These findings are critical for assessing the possible human health concerns associated with secondary municipal-treated wastewater irrigation for agriculture and improving the understanding of the coexistence of heavy metals and antibiotics.

Source apportionment and predictable driving factors contribute to antibiotics profiles in Changshou Lake of the Three Gorges Reservoir area, China

Lakes, crucial antibiotic reservoirs, lack thorough exploration of quantitative relationships between antibiotics and influencing factors. Here, we conducted a comprehensive year-long investigation in Changshou Lake within the Three Gorges Reservoir area, China. The concentrations of 21 antibiotics spanned 35.6-200 ng/L, 50.3-348 ng/L and 0.57-57.9 ng/g in surface water, overlying water and sediment, respectively. Compared with abundant water period, surface water and overlying water displayed significantly high antibiotic concentrations in flat and low water periods, while sediment remained unchanged. Moreover, tetracyclines, fluoroquinolones and erythromycin posed notable risks to algae. Six primary sources were identified using positive matrix factorization model, with aquaculture contributing 21.2%, 22.7% and 25.4% in surface water, overlying water and sediment, respectively. The crucial predictors were screened through machine learning, redundancy analysis and Mantel test. Our findings emphasized the pivotal roles of water quality parameters, including water temperature (WT), pH, dissolved oxygen, electrical conductivity, inorganic anions (NO3⁻, Cl⁻ and F⁻) and metal cations (Ca, Mg, Fe, K and Cr), with WT influencing greatest. Total nitrogen (TN), cation exchange capacity, K, Al and Cd significantly impacted sediment antibiotics, with TN having the most pronounced effect. This study can promise valuable insights for environmental planning and policies addressing antibiotic pollution.

Developing a novel magnetic organic polymer for selective extraction and determination of 16 macrolides in water and honey samples

A novel magnetic organic polymer Fe3O4@SiO2@Tb-PDAN was designed and synthesized, which was used as an adsorbent for magnetic solid-phase extraction (MSPE) of 16 macrolides (MALs) in water and honey. The synthesized adsorbent was characterized using techniques including scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR) and X-ray diffraction (XRD). Then several parameters of the extraction process were further optimized. Under the optimized conditions, an MSPE-LC-MS/MS method was established for extraction and determination of 16 MALs, which showed good linearity (r ≥ 0.999), low limits of detection (0.001-0.012 μg L-1 for water and 0.001-0.367 μg kg-1 for honey) and satisfactory recoveries (70.02-118.91%) with the relative standard deviations (RSDs) lower than 10.0%. This established method was then successfully applied to detect MALs in real samples, which suggested that Fe3O4@SiO2@Tb-PDAN was a potential magnetic adsorbent for efficient extraction and analysis of MALs.

Repeated Exposure Enhanced Toxicity of Clarithromycin on Microcystis aeruginosa Versus Single Exposure through Photosynthesis, Oxidative Stress, and Energy Metabolism Shift

Antibiotics are being increasingly detected in aquatic environments, and their potential ecological risk is of great concern. However, most antibiotic toxicity studies involve single-exposure experiments. Herein, we studied the effects and mechanisms of repeated versus single clarithromycin (CLA) exposure on Microcystis aeruginosa. The 96 h effective concentration of CLA was 13.37 μg/L upon single exposure but it reduced to 6.90 μg/L upon repeated exposure. Single-exposure CLA inhibited algal photosynthesis by disrupting energy absorption, dissipation and trapping, reaction center activation, and electron transport, thereby inducing oxidative stress and ultrastructural damage. In addition, CLA upregulated glycolysis, pyruvate metabolism, and the tricarboxylic acid cycle. Repeated exposure caused stronger inhibition of algal growth via altering photosynthetic pigments, reaction center subunits biosynthesis, and electron transport, thereby inducing more substantial oxidative damage. Furthermore, repeated exposure reduced carbohydrate utilization by blocking the pentose phosphate pathway, consequently altering the characteristics of extracellular polymeric substances and eventually impairing the defense mechanisms of M. aeruginosa. Risk quotients calculated from repeated exposure were higher than 1, indicating significant ecological risks. This study elucidated the strong influence of repeated antibiotic exposure on algae, providing new insight into antibiotic risk assessment.

Assessing the ecotoxicity of florfenicol exposure at environmental levels: A case study of histology, apoptosis and microbiota in hepatopancreas of Eriocheir sinensis

The intensification of production practices in the aquaculture industry has led to the indiscriminate use of antibiotics to combat diseases and reduce costs, which has resulted in environmental pollution, posing serious threats to aquaculture sustainability and food safety. However, the toxic effect of florfenicol (FF) exposure on the hepatopancreas of crustaceans remains unclear. Herein, by employing Chinese mitten crab (Eriocheir sinensis) as subjects to investigate the toxic effects on histopathology, oxidative stress, apoptosis and microbiota of hepatopancreas under environment-relevant (0.5 and 5 μg/L), and extreme concentrations (50 μg/L) of FF. Our results revealed that the damage of hepatopancreas tissue structure caused by FF exposure in a dose-and time-dependent manner. Combined with the increased expression of apoptosis-related genes (Caspase 3, Caspase 8, p53, Bax and Bcl-2) at mRNA and protein levels, activation of catalase (CAT) and superoxide dismutase (SOD), and malondialdehyde (MDA) accumulation, FF exposure also induced oxidative stress, and apoptosis in hepatopancreas. Interestingly, 7 days exposure triggered more pronounced toxic effect in crabs than 14 days under environment-relevant FF concentration. Integrated biomarker response version 2 (IBRv2) index indicated that 14 days FF exposure under extreme concentration has serious toxicity effect on crabs. Furthermore, 14 days exposure to FF changed the diversity and composition of hepatopancreas microbiota leading remarkable increase of pathogenic microorganism Spirochaetes following exposure to 50 μg/L of FF. Taken together, our study explained potential mechanism of FF toxicity on hepatopancreas of crustaceans, and provided a reference for the concentration of FF to be used in culture of Chinese mitten crab.

Competitive adsorption and bioaccumulation of sulfamethoxazole and roxithromycin by sediment and zebrafish (Danio rerio) during individual and combined exposure in water

Antibiotics are extensively used for health protection and food production, causing antibiotic pollution in the aquatic environment. This study aims to determine the bioavailability and bioaccumulation of typical antibiotics sulfamethoxazole (SMX) and roxithromycin (RTM) in zebrafish under environmentally realistic conditions. Four different microcosms, i.e. water, water-sediment, water-zebrafish, and water-sediment-zebrafish were constructed, with three replicates in parallel. The concentrations of SMX and RTM in water, sediment and zebrafish were extracted and analyzed by ultra-high performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) to assess their kinetic behavior and bioavailability. In the water-sediment system, the dissolved concentration of both SMX and RTM decreased with time following the first-order kinetic while their adsorption by sediment increased with time. In the water-zebrafish system, SMX and RTM bioaccumulation was increasing with time following the pseudo second-order kinetics. RTM bioaccumulation in zebrafish (up to 16.4 ng/g) was an order of magnitude higher than SMX (up to 5.2 ng/g), likely due to RTM being more hydrophobic than SMX. In addition, the bioaccumulation factor (BAF) value of SMX in zebrafish was greater than its sediment partition coefficient, while the opposite trend was observed for RTM, demonstrating the importance of antibiotics properties in affecting their bioavailability. Furthermore, increasing dissolved organic carbon concentration in water reduced SMX bioaccumulation, but increased RTM bioaccumulation at the same time. The findings are important in future studies of environmental fate and bioavailability of toxic chemicals with different pollution sources and physicochemical properties.

Antibiotic occurrence, environmental risks, and their removal from aquatic environments using microalgae: Advances and future perspectives

Antibiotic pollution has caused a continuous increase in the development of antibiotic-resistant bacteria and antibiotic-resistant genes (ARGs) in aquatic environments worldwide. Algae-based bioremediation technology is a promising eco-friendly means to remove antibiotics and highly resistant ARGs, and the generated biomass can be utilized to produce value-added products of industrial significance. This review discussed the prevalence of antibiotics and ARGs in aquatic environments and their environmental risks to non-target organisms. The potential of various microalgal species for antibiotic and ARG removal, their mechanisms, strategies for enhanced removal, and future directions were reviewed. Antibiotics can be degraded into non-toxic compounds in microalgal cells through the action of extracellular polymeric substances, glutathione-S-transferase, and cytochrome P450; however, antibiotic stress can alter microalgal gene expression and growth. This review also deciphered the effect of antibiotic stress on microalgal physiology, biomass production, and biochemical composition that can impact their commercial applications.

Metabolomic Response of Thalassiosira weissflogii to Erythromycin Stress: Detoxification Systems, Steroidal Metabolites, and Energy Metabolism

Erythromycin, a macrolide antibiotic, is a prioritized pollutant that poses a high risk to environmental health. It has been detected in different environmental matrices and can cause undesired effects in aquatic organisms, particularly freshwater algae, which are primary producers. However, the impact of erythromycin on marine algae remains largely unexplored. Erythromycin has been reported to induce hormetic effects in the marine diatom Thalassiosira weissflogii (T. weissflogii). These effects are associated with the molecular pathways and biological processes of ribosome assembly, protein translation, photosynthesis, and oxidative stress. However, the alterations in the global gene expression have yet to be validated at the metabolic level. The present study used non-targeted metabolomic analysis to reveal the altered metabolic profiles of T. weissflogii under erythromycin stress. The results showed that the increased cell density was possibly attributed to the accumulation of steroidal compounds with potential hormonic action at the metabolic level. Additionally, slight increases in the mitochondrial membrane potential (MMP) and viable cells were observed in the treatment of 0.001 mg/L of erythromycin (an environmentally realistic level). Contrarily, the 0.75 and 2.5 mg/L erythromycin treatments (corresponding to EC20 and EC50, respectively) showed decreases in the MMP, cell density, and viable algal cells, which were associated with modified metabolic pathways involving ATP-binding cassette (ABC) transporters, the metabolism of hydrocarbons and lipids, thiamine metabolism, and the metabolism of porphyrin and chlorophyll. These findings suggest that metabolomic analysis, as a complement to the measurement of apical endpoints, could provide novel insights into the molecular mechanisms of hormesis induced by antibiotic agents in algae.

Transformation products of antibacterial drugs in environmental water: Identification approaches based on liquid chromatography-high resolution mass spectrometry

In recent years, the presence of antibiotics in the aquatic environment has caused increasing concern for the possible consequences on human health and ecosystems, including the development of antibiotic-resistant bacteria. However, once antibiotics enter the environment, mainly through hospital and municipal discharges and the effluents of wastewater treatment plants, they can be subject to transformation reactions, driven by both biotic (e.g. microorganism and mammalian metabolisms) and abiotic factors (e.g. oxidation, photodegradation, and hydrolysis). The resulting transformation products (TPs) can be less or more active than their parent compounds, therefore the inclusion of TPs in monitoring programs should be mandatory. However, only the reference standards of a few known TPs are available, whereas many other TPs are still unknown, due to the high diversity of possible transformation reactions in the environment. Modern high-resolution mass spectrometry (HRMS) instrumentation is now ready to tackle this problem through suspect and untargeted screening approaches. However, for handling the large amount of data typically encountered in the analysis of environmental samples, these approaches also require suitable processing workflows and accurate tandem mass spectra interpretation. The compilation of a suspect list containing the possible monoisotopic masses of TPs retrieved from the literature and/or from laboratory simulated degradation experiments showed unique advantages. However, the employment of in silico prediction tools could improve the identification reliability. In this review, the most recent strategies relying on liquid chromatography-HRMS for the analysis of environmental TPs of the main antibiotic classes were examined, whereas TPs formed during water treatments or disinfection were not included.

Mechanism of the toxic effects of tetracycline on blood meal digestion in Haemaphysalis longicornis

The extensive utilization of antibiotics in the field of animal husbandry gives rise to various concerns pertaining to the environment and human health. Here, we demonstrate that the administration of tetracycline impedes blood meal digestion in the tick Haemaphysalis longicornis. Tissue sectioning, 16S rRNA high-throughput sequencing, and transcriptome sequencing of the midgut were employed to elucidate the mechanism underlying tetracycline toxicity. The treatment group consisted of engorged female ticks that were subjected to tetracycline microinjections (75 µg per tick), whereas the control group received sterile water injections. On days 2 and 4 following the injections, the tick body weight changes were assessed and the midguts were dissected and processed. Change in tick body weight in tetracycline-treated group was less than in the control group. In tetracycline-treated ticks, midgut epithelial cells were loosely connected and blood meal digestion was impaired compared to the control group. There was no significant change in midgut bacterial diversity after tetracycline treatment. On day 2 following treatment, the relative abundance of Escherichia-Shigella was significantly decreased, whereas the relative abundance of Allorhizobium was significantly increased compared to the control group. On day 4 following treatment, the relative abundance of Escherichia-Shigella, Allorhizobium, Ochrobactrum, and Acidibacter decreased significantly, whereas the relative abundance of Paraburkholderia and Pelomonas increased significantly. Tetracycline treatment also affected midgut gene expression, producing a cumulative effect wherein the differentially expressed genes (DEGs) were mostly down-regulated. KEGG enrichment pathway analysis revealed that on day 2 the up-regulated DEGs were significantly enriched in 21 pathways, including apoptosis and phagosome. Comparatively, the down-regulated DEGs were significantly enriched in 26 pathways, including N-glycan biosynthesis, lysosome, and autophagy. In contrast, on day 4 the up-regulated DEGs were significantly enriched in 10 pathways including aminoacyl-tRNA biosynthesis, ribosome biogenesis, RNA transport, and DNA replication, whereas the down-regulated differential genes were significantly enriched in 11 pathways including lysosome, peroxisome, N-glycan biosynthesis, and fatty acid synthesis. This indicates that tetracycline injection inhibited blood meal digestion by affecting midgut digestive cells, gut flora diversity, and gene expression. These findings could contribute to tick control by inhibiting blood meal digestion.

Photocatalytic degradation of tetracycline antibiotics by RGO-CdTe composite with enhanced apparent quantum efficiency

RGO-CdTe composite was synthesized using a straightforward, easy-to-realize, one-pot solvothermal technique. The synthesized composite was characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), Brunauer-Emmett-Teller method (BET), Raman spectra, UV-Vis absorption, and photoluminescence measurement. The RGO-CdTe composite exhibited 83.6% photocatalytic degradation efficiency for the aqueous tetracycline (TC) antibiotic solution and the apparent quantum yield (AQY) for the same was as high as 22.29% which is 2.63 times higher than that of CdTe. The scavenger investigation demonstrated that although hole acts as the leading active species, despite that, superoxide and hydroxyl radicals have also played crucial roles. The initial pH-dependent photocatalytic performance was measured. The zeta potential of the composite at different pH values was evaluated to establish the photocatalytic performance of the RGO-CdTe towards TC degradation at different pH. The recycling experiment depicts that only a 10% degradation performance declines after 5 times recycle use of the RGO-CdTe photocatalyst. An efficient photocurrent generation in RGO-CdTe thin film device has also been observed. Our study establishes as-synthesized composite of RGO-CdTe as a highly potential, and stable photocatalyst for the degradation of antibiotics from the polluted aqueous environment with a very good photoinduced charge generation efficiency in its solid phase.

Immunotechniques for the Group Determination of Macrolide Antibiotics Traces in the Environment Using a Volume-Mediated Sensitivity Enhancement Strategy

Macrolide antibiotics, which are effective antimicrobial agents, are intensively used in human and veterinary medicine, as well as in agriculture. Consequently, they are found all over the world as environmental pollutants, causing harm to sensitive ecological communities and provoking a selection of resistant forms. A novel azithromycin derivative, which was used as hapten conjugate, ensured the group immunorecognition of six major macrolide representatives (105-41%), namely erythromycin, erythromycin ethylsuccinate, clarithromycin, roxithromycin, azithromycin, and dirithromycin in a competitive immunoassay based on anti-clarithromycin antibodies. The heterologous hapten-based ELISA format resulted in a 5-fold increase in sensitivity, with an IC50 value of 0.04 ng/mL for erythromycin. In this study, we proposed an underexploited strategy in an immunoassay field to significantly improve the detectability of analytes in environmental samples. Unlike most approaches, it does not require special enhancers/amplifiers or additional concentration/extraction procedures; instead, it involves analyzing a larger volume of test samples. A gradual volume increase in the samples (from 0.025 to 10 mL) analyzed using a direct competitive ELISA, immunobeads, and immunofiltration assay formats based on the same reagents resulted in a significant improvement (more than 50-fold) in assay sensitivity and detection limit up to 5 and 1 pg/mL, respectively. The suitability of the test for detecting the macrolide contamination of natural water was confirmed by the recovery of macrolides from spiked blank samples (71.7-141.3%). During 2022-2023, a series of natural water samples from Lake Onega and its influents near Petrozavodsk were analyzed, using both the developed immunoassay and HPLC-MS/MS. The results revealed no contamination of macrolide antibiotic.

In five wastewater treatment plants in Xinjiang, China: Removal processes for illicit drugs, their occurrence in receiving river waters, and ecological risk assessment

Residues of illicit drugs are frequently detected in wastewater, but data on their removal efficiency by wastewater treatment plants (WWTPs) and the ecological risks to the aquatic environment are lacking in this study. The research evaluates the residues, mass load, drug removal efficiency, and risk assessment of illicit drugs in WWTPs and aquatic environments (lakes) in Xinjiang, China. Initially, the concentration (incidence) and mass load of 10 selected illicit drugs were analyzed through wastewater analysis. The detected substances included methamphetamine (METH), morphine (MOR), 3,4-methylenedioxy methamphetamine (MDMA), methadone (MTD), cocaine (COC), benzoylecgonine (BE), ketamine (KET), and codeine (COD), with concentrations ranging from 0.11 ± 0.01 ng/L (methadone) to 48.26 ± 25.05 ng/L (morphine). Notably, morphine (59.74 ± 5.82 g/day) and methamphetamine (41.81 ± 4.91 g/day) contributed significantly to the WWTPs. Next, the drug removal efficiency by different sewage treatment processes was ranked as follows: Anaerobic-Oxic (A/O) combined Membrane Bio-Reactor (MBR) treatment process > Oxidation ditch treatment process > Anaerobic-Anoxic-Oxic (A2/O) treatment process > Anaerobic-Anoxic-Oxic combined Membrane Bio-Reactor treatment process. Finally, the research reviewed the concentration and toxicity assessments of these substances in the aquatic environment (lakes). The results indicated that Lake1 presented a medium risk level concerning the impact of illicit drugs on the aquatic environment, whereas the other lakes exhibited a low risk level. As a result, it is recommended to conduct long-term monitoring and source analysis of illicit drugs, specifically in Lake1, for further investigation. In conclusion, to enhance the understanding of the effects of illicit drugs on the environment, future research should expand the list of target analytes.

Antibiotics and their associations with antibiotic resistance genes and microbial communities in estuarine and coastal sediment of Quanzhou Bay, Southeast China

The antibiotic concentrations spanned from 11.2 to 173.8 ng/g, with quinolones and tetracyclines being observed to be prevalent. The amount of microbial biomass as determined by Phospholipid fatty acid (PLFA) ranged from 2.92 to 10.99 mg kg-1, with G- bacteria dominating. A total of 254 distinct ARGs and 10 MEGs were identified, with multidrug ARGs having the highest relative abundance (1.18 × 10-2 to 3.00 × 10-1 copies/16S rRNA gene copies), while vancomycin and sulfonamide resistance genes were the least abundant. Results from canonical-correlation analyses combined with redundancy analysis indicated that macrolides were significantly related to the shifts of microbial community structure in sediments, particularly in G+ bacteria that were more sensitive to antibiotic residues. It was observed that sulfonamide ARGs had a greater correlation with residual antibiotics than other ARGs. This study provided a field evidence that multiple residual antibiotics from coastal sites could cause fundamental shifts in microbial community and their associated ARGs.

Antibiotic and Heavy Metal Co-Resistant Strain Isolated from Enrichment Culture of Marine Sediments, with Potential for Environmental Bioremediation Applications

Antibiotics and heavy metals have caused serious contamination of the environment and even resulted in public health concerns. It has therefore become even more urgent to adopt a sustainable approach to combating these polluted environments. In this paper, we investigated the microbial community of marine sediment samples after 255 days of enrichment culture under Cu (II) and lincomycin stress and ZC255 was the most resistant strain obtained. The 16S rRNA gene sequence confirmed that it belonged to the genus Rossellomorea. Strain ZC255 was resistant to 12 kinds of antibiotics, and had a superior tolerance to Cu (II), Pb (II), Ni (II), Zn (II), Cr (III), and Cd (II). Moreover, it exhibits strong bioremoval ability of Cu and lincomycin. The removal efficiency of Cu (II) and lincomycin can achieve 651 mg/g biomass and 32.5 mg/g biomass, respectively. Strain ZC255 was a promising isolate for pollution bioremediation applications.

The Challenge of Overcoming Antibiotic Resistance in Carbapenem-Resistant Gram-Negative Bacteria: "Attack on Titan"

The global burden of bacterial resistance remains one of the most serious public health concerns. Infections caused by multidrug-resistant (MDR) bacteria in critically ill patients require immediate empirical treatment, which may not only be ineffective due to the resistance of MDR bacteria to multiple classes of antibiotics, but may also contribute to the selection and spread of antimicrobial resistance. Both the WHO and the ECDC consider carbapenem-resistant Enterobacteriaceae (CRE), carbapenem-resistant Pseudomonas aeruginosa (CRPA), and carbapenem-resistant Acinetobacter baumannii (CRAB) to be the highest priority. The ability to form biofilm and the acquisition of multiple drug resistance genes, in particular to carbapenems, have made these pathogens particularly difficult to treat. They are a growing cause of healthcare-associated infections and a significant threat to public health, associated with a high mortality rate. Moreover, co-colonization with these pathogens in critically ill patients was found to be a significant predictor for in-hospital mortality. Importantly, they have the potential to spread resistance using mobile genetic elements. Given the current situation, it is clear that finding new ways to combat antimicrobial resistance can no longer be delayed. The aim of this review was to evaluate the literature on how these pathogens contribute to the global burden of AMR. The review also highlights the importance of the rational use of antibiotics and the need to implement antimicrobial stewardship principles to prevent the transmission of drug-resistant organisms in healthcare settings. Finally, the review discusses the advantages and limitations of alternative therapies for the treatment of infections caused by these "titans" of antibiotic resistance.

Current Trends in Nanomaterials-Based Electrochemiluminescence Aptasensors for the Determination of Antibiotic Residues in Foodstuffs: A Comprehensive Review

Veterinary pharmaceuticals have been recently recognized as newly emerging environmental contaminants. Indeed, because of their uncontrolled or overused disposal, we are now facing undesirable amounts of these constituents in foodstuff and its related human health concerns. In this context, developing a well-organized environmental and foodstuff screening toward antibiotic levels is of paramount importance to ensure the safety of food products as well as human health. In this case, with the development and progress of electric/photo detecting, nanomaterials, and nucleic acid aptamer technology, their incorporation-driven evolving electrochemiluminescence aptasensing strategy has presented the hopeful potentials in identifying the residual amounts of different antibiotics toward sensitivity, economy, and practicality. In this context, we reviewed the up-to-date development of ECL aptasensors with aptamers as recognition elements and nanomaterials as the active elements for quantitative sensing the residual antibiotics in foodstuff and agriculture-related matrices, dissected the unavoidable challenges, and debated the upcoming prospects.

Evaluating the Combined Effects of Erythromycin and Levofloxacin on the Growth of Navicula sp. and Understanding the Underlying Mechanisms

Navicula sp., a type of benthic diatom, plays a crucial role in the carbon cycle as a widely distributed algae in water bodies, making it an essential primary producer in the context of global carbon neutrality. However, using erythromycin (ERY) and levofloxacin (LEV) in medicine, livestock, and aquaculture has introduced a new class of pollutants known as antibiotic pollutants, which pose potential threats to human and animal health. This study aimed to investigate the toxic effects of ERY and LEV, individually or in combination, on the growth, antioxidant system, chlorophyll synthesis, and various cell osmotic pressure indexes (such as soluble protein, proline, and betaine) of Navicula sp. The results indicated that ERY (1 mg/L), LEV (320 mg/L), and their combined effects could inhibit the growth of Navicula sp. Interestingly, the combination of these two drugs exhibited a time-dependent effect on the chlorophyll synthesis of Navicula sp., with ERY inhibiting the process while LEV promoted it. Furthermore, after 96 h of exposure to the drugs, the activities of GSH-Px, POD, CAT, and the contents of MDA, proline, and betaine increased. Conversely, the actions of GST and the contents of GSH and soluble protein decreased in the ERY group. In the LEV group, the activities of POD and CAT and the contents of GSH, MDA, proline, and betaine increased, while the contents of soluble protein decreased. Conversely, the mixed group exhibited increased POD activity and contents of GSH, MDA, proline, betaine, and soluble protein. These findings suggest that antibiotics found in pharmaceutical and personal care products (PPCPs) can harm primary marine benthic eukaryotes. The findings from the research on the possible hazards linked to antibiotic medications in aquatic ecosystems offer valuable knowledge for ensuring the safe application of these drugs in environmental contexts.

A mega study of antibiotics contamination in Eastern aquatic ecosystems of China: occurrence, interphase transfer processes, ecotoxicological risks, and source modeling

Understanding the occurrence, sources, transfer mechanisms, fugacity, and ecotoxicological risks of antibiotics play a pivotal role in improving the sustainability and ecological health of freshwater ecosystems. Therefore, in order to determine the levels of antibiotics, water and sediment samples were collected from multiple Eastern freshwater ecosystems (EFEs) of China, including Luoma Lake (LML), Yuqiao Reservoir (YQR), Songhua Lake (SHL), Dahuofang Reservoir (DHR), and Xiaoxingkai Lake (XKL), and were analyzed using Ultra Performance Liquid Chromatography/Tandem Mass Spectrometry (UPLC-MS/MS). EFEs regions are particularly interesting due to higher urban density, industrialization, and diverse land use in China. The findings revealed that a collective total of 15 antibiotics categorized into four families, which included sulfonamides (SAs), fluoroquinolones (FQs), tetracyclines (TCs), and macrolides (MLs), exhibited high detection frequencies, indicating widespread antibiotic contamination. The pollution levels in the water phase were in the order of LML > DHR > XKL > SHL > YQR. The sum concentration of individual antibiotics for each water body ranged from not detected (ND) to 57.48 ng/L (LML), ND to 12.25 ng/L (YQR), ND to 57.7 ng/L (SHL), ND to 40.50 ng/L (DHR), and ND to 26.30 ng/L (XKL) in the water phase. Similarly, in the sediment phase, the sum concentration of individual antibiotics ranged from ND to 15.35 ng/g, ND to 198.75 ng/g, ND to 1233.34 ng/g, ND to 388.44 ng/g, and ND to 862.19 ng/g, for LML, YQR, SHL, DHR, and XKL, respectively. Interphase fugacity (ff_sw) and partition coefficient (K_d) indicated dominant resuspension of antibiotics from sediment to water, causing secondary pollution in EFEs. Two groups of antibiotics, namely MLs (erythromycin, azithromycin, and roxithromycin) and FQs (ofloxacin and enrofloxacin), showed a medium-high level of adsorption tendency on sediment. Source modeling (PMF5.0) identified wastewater treatment plants, sewage, hospitals, aquaculture, and agriculture as the major antibiotic pollution sources in EFEs, contributing between 6% and 80% to different aquatic bodies. Finally, the ecological risk posed by antibiotics ranged from medium to high in EFEs. This study offers valuable insights into the levels, transfer mechanisms, and risks associated with antibiotics in EFEs, enabling the formulation of large-scale policies for pollution control.

Ecotoxicity and resistance genes induction changing of antibiotic tetracycline degradation products dominated by differential free radicals

Studying the ecological risks of antibiotics and their degradation products is of great importance to water environment security and advanced oxidation processes (AOPs) development. This work studied the changes and internal influencing mechanisms of ecotoxicity and the capacity for inducing antibiotic resistance genes (ARGs) shown by the tetracycline (TC) degradation products generated in AOPs with differential free radicals. Under the action of superoxide radicals and singlet oxygen in the ozone system, and sulfate and hydroxyl radicals in the thermally activated potassium persulfate system, TC exhibited differential degradation pathways and resulted in the differential growth inhibition trends on the determined strains. Microcosm experiments combined with metagenomics were also performed to analyze the remarkable changes in the TC resistance genes tetA (60), tetT, and otr(B) induced by the degradation products and ARG hosts in the natural water environment. Microcosm experiments exhibited that the microbial community in actual water have changed significantly with the addition of TC and degradation intermediates. Furthermore, the richness of genes related to oxidative stress was investigated to discuss the effect on reactive oxygen species production and SOS response caused by TC and its intermediates.

Efficient adsorption and photocatalytic degradation of water emerging contaminants through nanoarchitectonics of pore sizes and optical properties of zirconium-based MOFs

Over the past decades, the presence of pharmaceutical emerging contaminants in water bodies is receiving increasing attention due to the high concentration detected from wastewater effluent. Water systems contain a wide range of components coexisting together, which increases the difficulty of removing pollutants from the water. In order to achieve selective photodegradation and to enhance the photocatalytic activity of the photocatalyst on emerging contaminants, a Zr-based metal-organic framework (MOF), termed VNU-1 (VNU represents Vietnam National University) constructed with ditopic linker 1,4-bis(2-[4-carboxyphenyl]ethynyl)benzene (H₂CPEB), with enlarged pore size and ameliorated optical properties, was synthesized and applied in this study. When compared to UiO-66 MOFs, which only had 30% photodegradation of sulfamethoxazole, VNU-1 had 7.5 times higher adsorption and reached 100% photodegradation in 10 min. The tailored pore size of VNU-1 resulted in size-selective properties between small-molecule antibiotics and big-molecule humic acid, and VNU-1 maintained high photodegradation performance after 5 cycles. Based on the toxicity test and the scavenger test, the products after photodegradation had no toxic effect on V. fischeri bacteria, and the superoxide radical (·O₂^-) and holes (h⁺) generated from VNU-1 dominated the photodegradation reaction. These results demonstrate that VNU-1 is a promising photocatalyst and provide a new insight for developing MOF photocatalyst to remove emerging contaminants in the wastewater systems.

Performance of a Pilot-Scale Continuous Flow Ozone-Based Hospital Wastewater Treatment System

Antimicrobial resistance (AMR) is becoming a global concern. Recently, research has emerged to evaluate the human and environmental health implications of wastewater from medical facilities and to identify acceptable wastewater treatment methods. In this study, a disinfection wastewater treatment system using an ozone-based continuous flow system was installed in a general hospital located in Japan. The effectiveness of antimicrobial-resistant bacteria (ARB) and antimicrobials in mitigating the environmental impact of hospital wastewater was evaluated. Metagenomic analysis was conducted to characterize the microorganisms in the wastewater before and after treatment. The results demonstrated that ozone treatment enables effective inactivation of general gut bacteria, including Bacteroides, Prevotella, Escherichia coli, Klebsiella, DNA molecules, and ARGs, as well as antimicrobials. Azithromycin and doxycycline removal rates were >99% immediately after treatment, and levofloxacin and vancomycin removal rates remained between 90% and 97% for approximately one month. Clarithromycin was more readily removed than the other antimicrobials (81-91%), and no clear removal trend was observed for ampicillin. Our findings provide a better understanding of the environmental management of hospital wastewater and enhance the effectiveness of disinfection wastewater treatment systems at medical facilities for mitigating the discharge of pollutants into aquatic environments.

Occurrence and risk levels of antibiotic pollution in the coastal waters of eastern China

In order to preliminarily explore the distribution of antibiotic pollution in the coastal waters of eastern China, the concentrations of 13 antibiotics in 5 representative coastal rivers in Jiangsu and 21 sampling sites in the coastal waters of Jiangsu were analyzed. The total antibiotic concentrations in the 5 rivers ranged from 33.14 to 417.78 ng L^-1, and the total antibiotic concentrations in the 21 sampling sites ranged from 0.90 to 86.33 ng L^-1. Macrolides exhibited the highest total concentration and the maximum detection frequency in both coastal rivers and the coastal waters. The concentrations of antibiotics in a sampling site decreased as the distance of the sampling site from the coastline increased, indicating that river inputs are important sources of antibiotic pollution in the coastal waters of Jiangsu. The detection frequencies of roxithromycin, lincomycin, azithromycin, and sulfamethoxazole in the rivers and sampling sites were above 70%. Correlation analysis showed that the concentrations of antibiotics were positively correlated with the levels of chemical oxygen demand, total phosphorus, and total nitrogen. Risk assessments revealed that roxithromycin and ofloxacin posed medium ecological and resistance risks, respectively, to the most sensitive aquatic organisms in the coastal waters of Jiangsu. The results of this study highlight the significance of monitoring and controlling the concentrations of antibiotic contaminants in the coastal waters of Jiangsu.

Impact of antibiotics on microbial community in aquatic environment and biodegradation mechanism: a review and bibliometric analysis

Antibiotic residues in aquatic environments pose a potential hazard, and microbes, which play important roles in aquatic ecosystems, are vulnerable to the impacts of antibiotics. This study aimed to analyze the research progress, trends, and hot topics of the impact of antibiotics on microbial community and biodegradation mechanism using bibliometric analysis. An in-depth analysis of the publication characteristics of 6143 articles published between 1990 and 2021 revealed that the number of articles published increased exponentially. The research sites have been mainly concentrated in the Yamuna River, Pearl River, Lake Taihu, Lake Michigan, Danjiangkou Reservoir, etc., illustrating that research around the world is not even. Antibiotics could change the diversity, structure, and ecological functions of bacterial communities, stimulate a widespread abundance of antibiotic-resistant bacteria and antibiotic-resistant genes, and increase the diversity of eukaryotes, thus triggering the shift of food web structure to predatory and pathogenic. Latent Dirichlet allocation theme model analysis showed three clusters, and the research hotspots mainly included the effect of antibiotics on the denitrification process, microplastics combined with antibiotics, and methods for removing antibiotics. Furthermore, the mechanisms of microbe-mediated antibiotic degradation were unraveled, and importantly, we provided bottlenecks and future research perspectives on antibiotics and microbial diversity research.

Microwave-Assisted Synthesis of MoS2/BiVO4 Heterojunction for Photocatalytic Degradation of Tetracycline Hydrochloride

Compared with traditional hydrothermal synthesis, microwave-assisted synthesis has the advantages of being faster and more energy efficient. In this work, the MoS₂/BiVO₄ heterojunction photocatalyst was synthesized by the microwave-assisted hydrothermal method within 30 min. The morphology, structure and chemical composition were characterized by X-ray diffraction (XRD), Raman, X-ray photoelectron spectroscopy (XPS), scanning electron microscope (SEM), and high-resolution transmission electron microscopy (HRTEM). The results of characterizations demonstrated that the synthesized MoS₂/BiVO₄ heterojunction was a spherical structure with dimensions in the nanorange. In addition, the photocatalytic activity of the samples was investigated by degrading tetracycline hydrochloride (TC) under visible light irradiation. Results indicated that the MoS₂/BiVO₄ heterojunction significantly improved the photocatalytic performance compared with BiVO₄ and MoS₂, in which the degradation rate of TC (5 mg L^-1) by compound where the mass ratio of MoS₂/BiVO₄ was 5 wt% (MB5) was 93.7% in 90 min, which was 2.36 times of BiVO₄. The active species capture experiments indicated that •OH, •O₂^- and h⁺ active species play a major role in the degradation of TC. The degradation mechanism and pathway of the photocatalysts were proposed through the analysis of the band structure and element valence state. Therefore, microwave technology provided a quick and efficient way to prepare MoS₂/BiVO₄ heterojunction photocatalytic efficiently.

Evaluating the spatial and temporal distribution of emerging contaminants in the Pearl River Basin for regulating purposes

Little information is available on how the types, concentrations, and distribution of chemicals have evolved over the years. The objective of the present study is therefore to review the spatial and temporal distribution profile of emerging contaminants with limited toxicology data in the pearl river basin over the years to build up the emerging contaminants database in this region for risk assessment and regulatory purposes. The result revealed that seven groups of emerging contaminants were abundant in this region, and many emerging contaminants had been detected at much higher concentrations before 2011. Specifically, antibiotics, phenolic compounds, and acidic pharmaceuticals were the most abundant emerging contaminants detected in the aquatic compartment, while phenolic compounds were of the most profound concern in soil. Flame retardants and plastics were the most frequently studied chemicals in organisms. The abundance of the field concentrations and frequencies varied considerably over the years, and currently available data can hardly be used for regulation purposes. It is suggested that watershed management should establish a regular monitoring scheme and comprehensive database to monitor the distribution of emerging contaminants considering the highly condensed population in this region. The priority monitoring list should be formed in consideration of historical abundance, potential toxic effects of emerging contaminants as well as the distribution of heavily polluting industries in the region.

Occurrence, distribution, and ecological risks of antibiotics in Honghu Lake and surrounding aquaculture ponds, China

Antibiotics are largely applied in aquaculture to increase production and control diseases, while how the antibiotics used in pond farming influence the distribution of antibiotics in receiving water seasonally is still not well understood. In this study, the variations of 15 frequently used antibiotics in Honghu Lake and surrounding ponds were investigated seasonally to figure out the impact of pond farming on antibiotics distributions in Honghu Lake. Results showed that the antibiotic concentrations in fish ponds ranged from 11.76 to 389.8 ng/L, while in crab and crayfish ponds were lower than 30.49 ng/L. The predominant antibiotic in fish ponds was florfenicol, followed by sulfonamides and quinolones, with generally low concentrations. Sulfonamides and florfenicol were the main antibiotics in Honghu Lake, affected by the surrounding aquaculture water partially. The antibiotics residue in aquaculture ponds showed obvious seasonal characteristics, with the lowest in spring. From summer, the concentrations of antibiotics in aquaculture ponds gradually increased and reached a peak in autumn, and the seasonal variation of antibiotics in the receiving lake was also related to the antibiotics in the aquaculture ponds. Risk assessment analysis showed that antibiotics such as enrofloxacin and florfenicol in fish ponds posed a medium and low risk to algae, and Honghu Lake acted as a natural reservoir of antibiotics and poses increased risks to algae. In general, our study demonstrated that aquaculture represented by pond farming brought significant risks of antibiotic pollution to natural water bodies. Therefore, reasonable control of the fish antibiotics usage in autumn and winter, as well as the rational use of antibiotics in aquaculture and the use of antibiotics before pond cleaning, is required to reduce the migration of antibiotics from aquaculture surface water to the receiving lake.

Effects of erythromycin and roxithromycin on river periphyton: Structure, functions and metabolic pathways

Macrolides have been frequently detected in the surface waters worldwide, posing a threat to the aquatic microbes. Several studies have evaluated the ecotoxicological effects of macrolides on single algal and bacterial strains. However, without considering the species interaction in the aquatic microbial community, these results cannot be extrapolated to the field. Thus, the present study aimed to evaluate the effects of two macrolides (erythromycin and roxithromycin) on the structure, photosynthetic process, carbon utilization capacity, and the antibiotic metabolic pathways in river periphyton. The colonized periphyton was exposed to the graded concentration (0 μg/L (control), 0.5 μg/L (low), 5 μg/L (medium), 50 μg/L (high)) of ERY and ROX, respectively, for 7 days. Herein, high levels of ERY and ROX altered the community composition by reducing the relative abundance of Chlorophyta in the eukaryotic community. Also, the Shannon and Simpson diversity indexes of prokaryotes were reduced, although similar effects were seldomly detected in the low and medium groups. In contrast to the unchanged carbon utilization capacity, the PSII reaction center involved in the periphytic photosynthesis was significantly inhibited by macrolides at high levels. In addition, both antibiotics had been degraded by periphyton, with the removal rate of 51.63-66.87% and 41.85-48.27% for ERY and ROX, respectively, wherein the side chain and ring cleavage were the main degradation pathways. Overall, this study provides an insight into the structural and functional toxicity and degradation processes of macrolides in river periphyton.

A Minireview for Recent Development of Nanomaterial-Based Detection of Antibiotics

Antibiotics are considered a new type of organic pollutant. Antibiotic residues have become a global issue due to their harm to human health. As the use of antibiotics is increasing in human life, such as in medicine, crops, livestock, and even drinking water, the accurate analysis of antibiotics is very vital. In order to develop rapid and on-site approaches for the detection of antibiotics and the analysis of trace-level residual antibiotics, a high-sensitivity, simple, and portable solution is required. Meanwhile, the rapid nanotechnology development of a variety of nanomaterials has been achieved. In this review, nanomaterial-based techniques for antibiotic detection are discussed, and some reports that have employed combined nanomaterials with optical techniques or electrochemical techniques are highlighted.

Response Surface Methodology (RSM) Approach to Optimization of Coagulation-Flocculation of Aquaculture Wastewater Treatment Using Chitosan from Carapace of Giant Freshwater Prawn Macrobrachium rosenbergii

The major sources of waste from aquaculture operations emanates from fish or shellfish processing and wastewater generation. A simple technique called coagulation/flocculation utilizes biowaste from aquaculture to produce chitosan coagulant for wastewater treatment. A chemical method was applied in the present study for chitin and chitosan extraction from carapace of Macrobrachium rosenbergii and subsequent application for removal of turbidity and salinity from shrimp aquaculture wastewater. Box-Behnken in RSM was used to determine the optimum operating conditions of chitosan dosage, pH, and settling time, after which quadratic models were developed and validated. Results show that 80 g of raw powder carapace yielded chitin and chitosan of 23.79% and 20.21%, respectively. The low moisture (0.38%) and ash (12.58%) content were an indication of good quality chitosan, while other properties such as water-binding capacity (WBC), fat-binding capacity (FBC), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and scanning electron microscope (SEM) confirmed the structure and the α-group, as well as the rough morphology of chitosan. In addition, the high solubility (71.23%) and DDA (85.20%) suggested good coagulant potentials. It was recorded in this study that 87.67% turbidity was successfully removed at 20 mg/L of chitosan dosage and 6.25 pH after 30 min settling time, while 21.43% salinity was removed at 5 mg/L of chitosan dosage, 7.5 pH, and 30 min settling time. Therefore, the process conditions adopted in this study yielded chitosan of good quality, suitable as biopolymer coagulant for aquaculture wastewater treatment.

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.

Antibiotic Toxicity Isolated and as Binary Mixture to Freshwater Algae Raphidocelis subcapitata: Growth Inhibition, Prediction Model, and Environmental Risk Assessment

Antibiotics in aqueous environments can have extremely adverse effects on non-targeted organisms. However, many research projects have only focused on the toxicological evaluation of individual antibiotics in various environments. In the present work, individual and binary mixture toxicity experiments have been conducted with the model organism Raphidocelis subcapitata (R. subcapitata), and a mixture concentration-response curve was established and contrasted with the estimated effects on the basis of both the concentration addition (CA) and the independent action (IA) models. In addition, different risk assessment methods were used and compared to evaluate the environmental risk of binary mixtures. The toxic ranking of the selected antibiotics to R. subcapitata was erythromycin (ERY) > sulfamethoxazole (SMX) > sulfamethazine (SMZ). In general, the conclusion of this study is that the adverse effects of binary mixtures are higher than the individual antibiotics. The CA model and RQSTU are more suitable for toxicity prediction and risk assessment of binary mixtures. This study reveals the potential ecological risks that antibiotics and their mixtures may pose to water ecosystems, thus providing scientific information for environmental quality regulation.