Degradation and transformation of fluoroquinolones by microorganisms with special emphasis on ciprofloxacin

High-carbon-content biochar from chemical manufacturing plant sludge for effective removal of ciprofloxacin from aqueous media

Biochar is considered a promising biosorbent for harmful organic pollutants in aqueous media. However, only a limited number of biochars derived from industrial sludges have been utilized due to their problematic high ash content and heavy metal leaching. In this study, a highly effective biochar was prepared as a superabsorbent for ciprofloxacin (CIP) from chemical manufacturing plant sludge via K2CO3-activated pyrolysis, and its CIP removal behavior was evaluated. Unlike sewage sludge, chemical manufacturing plant sludge contains low SiO2, resulting in an ultra-pure carbon (95.4%) based biochar with almost negligible ash content. As the pyrolysis temperature increased from 400 to 800 °C, the ordered graphitic carbon structure transformed into an amorphous carbon phase, and most oxygen-containing groups disappeared. However, the pore size significantly decreased to ∼4.5 nm due to the corrosive carbon volatilization caused by K2CO3, resulting in an extremely large surface area of 2331.8 m2/g. Based on its large surface area and porous carbon structure, the activated biochar at 800 °C (CAB-800) exhibited an outstanding CIP adsorption capacity of 555.56 mg/g. The CIP adsorption isotherm, kinetic, and thermodynamic studies were systematically investigated. The CIP adsorption on CAB-800 was mainly attributed to π-π interactions and hydrogen bond formation, with electrostatic interactions partially contributing to the adsorption reaction. From pH 2 to 12, CAB-800 showed an excellent CIP adsorption capacity of over 316.7 mg/g, with adsorption favored under acidic conditions. Except for HCO3- and CO32-, the presence of anions and humic acids did not significantly affect CIP adsorption capacity. These results demonstrate that biochar produced from chemical manufacturing industry sludge via K2CO3 activation is a highly feasible material for the removal of CIP from aqueous media.

Mechanistic insights into the potential application of Scenedesmus strains towards the elimination of antibiotics from wastewater

Scenedesmus strains have been reported to have the potential to tolerate and bioremediate antibiotic pollutants through bioadsorption, bioaccumulation, and biodegradation mechanism from the wastewater medium. Hormesis effects have been observed in the Scenedesmus strains when exposed to different concentrations of antibiotic pollutants. Lower concentrations of antibiotic pollutants are known to trigger growth-stimulating effects by triggering adaptive responses such as increased metabolic activity and activating detoxifying mechanisms leading to the biotransformation pathway. The present review examines the existing body of information pertaining to biotransformation pathways tolerance, hormesis effects, and efficiency of Scenedesmus strains in removing various antibiotic pollutants. This review provides critical information on using Scenedesmus species to treat antibiotic-polluted wastewater by boosting growth and resilience tolerant doses and avoiding toxicity at higher doses.

Fate of emerging antibiotics in soil-plant systems: A case on fluoroquinolones

Fluoroquinolones (FQs), a class of broad-spectrum antibiotics widely used to treat human and animal diseases globally, have limited adsorption and are often excreted unchanged or as metabolites. These compounds enter the soil environment through feces, urban wastewater, or discharge of biological solids. The fluorine atoms in FQs impart high electronegativity, chemical stability, and resistance to microbial degradation, allowing them to potentially enter food chains. The persistence of FQs in soils raises questions about their impacts on plant growth, an aspect not yet conclusively determined. We reviewed whether, like other organic compounds, FQs are actively absorbed by plants, resulting in bioaccumulation and posing threats to human health. The influx of FQs has led to antibiotic resistance in soil microbes by exerting selective pressure and contributing to multidrug-resistant bacteria. Therefore, the environmental risks of FQs warrant further attention. This work provides a comprehensive review of the fate and behavior of FQs at the plant-environment interface, their migration and transport from the environment into plants, and associated toxicity. Current limitations in research are discussed and prospects for future investigations outlined. Thus, understanding antibiotic behavior in plants and translocation within tissues is not only crucial for ecosystem health (plant health), but also assessing potential human health risks. In addition, it can offer insights into the fate of emerging soil pollutants in plant-soil systems.

Quantitative assessment, molecular docking and novel metabolic pathways reveal the interaction mechanisms between norfloxacin biodegradation and environmental implications

Norfloxacin (NOR) is widely used in medicine and animal husbandry, but its accumulation in the environment poses a substantial threat to ecological and human health. Traditional physical, chemical, and rudimentary biological methods often fall short in mitigating NOR contamination, necessitating innovative biological approaches. This study proposes an engineered bacterial consortium found in marine sediment as a strategy to enhance NOR degradation through inter-strain co-metabolism of diverse substrates. Strategically supplementing the engineered bacterial consortium with exogenous carbon sources and metal ions boosted the activity of key degradation enzymes like laccase, manganese peroxidase, and dehydrogenase. Iron and amino acids demonstrated synergistic effects, resulting in a remarkable 70.8% reduction in NOR levels. The innovative application of molecular docking elucidated enzyme interactions with NOR, uncovering potential biodegradation mechanisms. Quantitative assessment reinforced the efficiency of NOR degradation within the engineered bacterial consortium. Four metabolic routes are herein proposed: acetylation, defluorination, ring scission, and hydroxylation. Notably, this study discloses distinctive, co-operative metabolic pathways for NOR degradation within the specific microbial community. These findings provide new ways of understanding and investigating the bioremediation potential of NOR contaminants, which may lead to the development of more sustainable and effective environmental management strategies.

A Review on Fluoroquinolones' Toxicity to Freshwater Organisms and a Risk Assessment

Fluoroquinolones (FQs) have achieved significant success in both human and veterinary medicine. However, regulatory authorities have recommended limiting their use, firstly because they can have disabling side effects; secondly, because of the need to limit the spread of antibiotic resistance. This review addresses another concerning consequence of the excessive use of FQs: the freshwater environments contamination and the impact on non-target organisms. Here, an overview of the highest concentrations found in Europe, Asia, and the USA is provided, the sensitivity of various taxa is presented through a comparison of the lowest EC50s from about a hundred acute toxicity tests, and primary mechanisms of FQ toxicity are described. A risk assessment is conducted based on the estimation of the Predicted No Effect Concentration (PNEC). This is calculated traditionally and, in a more contemporary manner, by constructing a normalized Species Sensitivity Distribution curve. The lowest individual HC5 (6.52 µg L-1) was obtained for levofloxacin, followed by ciprofloxacin (7.51 µg L-1), sarafloxacin and clinafloxacin (12.23 µg L-1), and ofloxacin (17.12 µg L-1). By comparing the calculated PNEC with detected concentrations, it is evident that the risk cannot be denied: the potential impact of FQs on freshwater ecosystems is a further reason to minimize their use.

Efficiency of phytoremediation and identification of biotransformation pathways of fluoroquinolones in the aquatic environment

Phytoremediation is a low-cost and sustainable green technology that uses plants to remove organic and inorganic pollutants from aquatic environments. The aim of this study was to investigate the phytoextraction, phytoaccumulation, and phytotransformation of three fluoroquinolones (FQs) (ciprofloxacin [CIP], enrofloxacin [ENF], and levofloxacin [LVF]) by Japanese radish (Raphanus sativus var. longipinnatus) and duckweed (Lemma minor). Determination of FQs and identification of their transformation products (TPs) were performed using ultra-high-performance liquid chromatography coupled with tandem mass spectrometry (UHPLC-MS/MS). Inter-tissue translocation of FQs in Japanese radish tissues depended on their initial concentration in the medium. CIP (IT = 14.4) and ENF (IT = 17.0) accumulated mainly in radish roots, while LVF in leaves (IT = 230.8) at an initial concentration of 10 µg g-1. CIP (2,104 ng g-1) was detected in the highest concentration, followed by ENF (426.3 ng g-1) and LVF (273.3 ng g-1) in the tissues of both plants. FQs' bioaccumulation factors were significantly higher for duckweed (1.490-18.240) than Japanese radish (0.027-0.103). The removal of FQs from water using duckweed was mainly due to their photolysis and hydrolysis than plant sorption. In the screening, analysis detected 29 FQ TPs. The biotransformation pathways of FQs are described in detail, and the factors that influence their formation are indicated.

Study on mechanism of removal of sudden Tetracycline by compound modified biological sand filtration process

The removal of tetracycline from the sewage plant effluents through advanced treatment methods is key to controlling tetracycline levels in the water environment. In this study, modified quartz sands (QS) were used in a biological sand filter to remove tetracycline. The modified QS, with different surface characteristics, were prepared using glass etching technology combined with subsequent chemical modification methods, including hydroxylation treatment, metal ion modification, and amino modification. The adsorption efficiency of hydroxylated QS was higher than that of metal ion modified and amino modified QS, with adsorption efficiencies of 20.4331 mg/kg, 12.8736 mg/kg, and 10.1737 mg/kg, respectively. Results indicated that QS primarily reduce tetracycline through adsorption. Adsorption on ordinary QS fit the pseudo-first-order kinetic model, while adsorption on other modified QS and biofilm-coated QS fit the pseudo-second-order kinetics model. Biodegradation was identified as another mechanism for tetracycline reduction, which fit the zero-order kinetic model. Pseudomonas alcaligenes and unclassified Pseudomonas accounted for 96.6% of the total tetracycline-degrading bacteria. This study elucidates the effectiveness and mechanisms of five types of QS in treating tetracycline from sewage plant effluents. It provides a novel method for tetracycline reduction in real-world wastewater scenarios.

Long-term exposure of Allonais inaequalis to a mixture of antibiotics in freshwater and synthetic wastewater matrices: Reproduction, recovery, and swimming responses

Antibiotics from sulfonamide, fluoroquinolone, and diaminopyrimidine classes are widely used in human and veterinary medicine, and their combined occurrence in the aquatic environment is increasing around the world. In parallel, the understanding of how mixtures of these compounds affect non-target species from tropical freshwaters is scarce. Thus, this work aimed to study the long-term reproductive, recovery, and swimming effects of mixtures of 12 antibiotics from three different classes (up to 10 μg L-1 ) added to freshwater (FWM) and synthetic wastewater (SWM) matrices on freshwater worm Allonais inaequalis. Results revealed that at the reproduction level, the exposure to antibiotics in the SWM matrix does not cause a significant toxic effect on species after 10 days. On the other hand, exposures to initial dose mixtures (10 μg L-1 each) in FWM caused a significant reduction of offspring by 19.2%. In addition, recovery bioassays (10 days in an antibiotic-free environment) suggested that A. inaequalis has reduced offspring production due to previous exposure to antibiotic mixtures in both matrices. Furthermore, despite slight variation in swimming speed over treatments, no significant differences were pointed out. Regarding antibiotics in the water matrices after 10-day exposures, the highest concentrations were up to 2.7, 7.8, and 4.2 μg L-1 for antibiotics from sulfonamide, fluoroquinolone, and diaminopyrimidine classes, respectively. These findings suggest that a species positioned between primary producers and secondary consumers may experience late reproductive damage even in an antibiotic-free zone, after previous 10-day exposure to antibiotic mixtures. PRACTITIONER POINTS: A mixture of sulfonamide, fluoroquinolone, and diaminopyrimidine antibiotics in freshwater affects the offspring production of A. inaequalis after 10 days. After the 10-day antibiotic exposure, the reproduction of A. inaequalis remains affected in an antibiotic-free environment over the recovery period. The swimming speed of the worms does not change after 10 days of exposure to the antibiotic mixture. The concentration of dissolved solids can limit the natural degradation of sulfonamide, fluoroquinolone, and diaminopyrimidine antibiotics in the aquatic environment.

Insights into the molecular network underlying phytotoxicity and phytoaccumulation of ciprofloxacin

Ciprofloxacin (CIP) is frequently detected in agricultural soils and can be accumulated by crops, causing phytotoxicities and food safety concerns. However, the molecular basis of its phytotoxicity and phytoaccumulation is hardly known. Here, we analyzed physiological and molecular responses of choysum (Brassica parachinensis) to CIP stress by comparing low CIP accumulation variety (LAV) and high accumulation variety (HAV). Results showed that the LAV suffered more severe inhibition of growth and photosynthesis than the HAV, exhibiting a lower tolerance to CIP toxicity. Integrated transcriptome and proteome analyses suggested that more differentially expressed genes/proteins (DEGs/DEPs) involved in basic metabolic processes were downregulated to a larger extent in the LAV, explaining its lower CIP tolerance at molecular level. By contrast, more DEGs/DEPs involved in defense responses were upregulated to a larger extent in the HAV, showing the molecular basis of its stronger CIP tolerance. Further, a CIP phytotoxicity-responsive molecular network was constructed for the two varieties to better understand the molecular mechanisms underlying the variety-specific CIP tolerance and accumulation. The results present the first comprehensive molecular profile of plant response to CIP stress for molecular-assisted breeding to improve CIP tolerance and minimize CIP accumulation in crops.

Predictive binary mixture toxicity modeling of fluoroquinolones (FQs) and the projection of toxicity of hypothetical binary FQ mixtures: a combination of 2D-QSAR and machine-learning approaches

All sorts of chemicals get degraded under various environmental stresses, and the degradates coexist with the parent compounds as mixtures in the environment. Antibiotics emerge as an additional concern due to the bioactive nature of both the parent compound and degradation products and their combined exposure to the environment. Therefore, environmental risk assessment of antibiotics and their degradation products is very much necessary. In this direction, we made use of in silico new approach methodologies (NAMs) and machine-learning algorithms. In this study, we have developed a robust and predictive mixture-quantitative structure-activity relationship (QSAR) model with promising quality and predictability (internal: MAETrain = 0.085, QLOO2 = 0.849, external: MAETest = 0.090, and QF12 = 0.859) for predicting the toxicity of the mixtures of a class of antibiotics and their degradation products. To obtain the predictive model, toxicity data of 78 binary fluoroquinolone mixtures in E. coli (endpoint: log 1/IC50 in molar) have been utilized. We have used only 0D-2D descriptors to efficiently encode the structural features of mixture components without any additional complexities. The optimization of the class of mixture descriptors has been performed in this study by using three different mixing rules (linear combination of molecular contributions, the squared molecular contributions, and the norm of molecular contributions). Different machine-learning approaches namely, random forest (RF), ada boost, gradient boost (GB), extreme gradient boost (XGB), support vector machine (SVM), linear support vector machine (LSVM), and ridge regression (RR) have been employed here apart from the conventional partial least squares (PLS) regression to optimize the modeling approach. A rigorous validation protocol has been used for assessing the goodness-of-fit, robustness, and external predictability of the models. Finally, the toxicity of possible untested mixtures of different photodegradation products of fluoroquinolones has been predicted using the best model reported in this study.

Deciphering Campylobacter jejuni DsbA1 protein dynamics in the presence of anti-virulent compounds: a multi-pronged computer-aided approach

The current study aims to evaluate Asinex library compounds against Campylobacter jejuni DsbA1 protein, a thiol disulfide oxidoreductase enzyme that plays a major role in the oxidative folding of bacterial virulence proteins, making it a promising anti-viral drug target. By employing several techniques of computer-aided drug design, BDC25697459, BDD33601083, and BDC30129064 were identified with binding energy scores of -8.8 kcal/mol, -8.8 kcal/mol, and -8.3 kcal/mol, respectively. However, the control molecule, tetraethylene glycol, exhibited a binding energy score of -7.0 kcal/mol. The control, BDD33601083, and BDC30129064 were unveiled to bind the same co-crystallized binding site (pocket 1), while BDC25697459 interacted with a new binding pocket (pocket 2) adjacent to the control binding region. The molecular dynamics simulation showed that complexes exhibit stable dynamics without significant global or residue-level fluctuations. The average RMSD values were in the range of 2.07 Å-2.45 Å. Similarly, mean RMSF was recorded between 1.30 and 1.42 Å. The C. jejuni DsbA1 was also observed as compact in the presence of the compounds, showing a mean RoG value in the range of 16.42 Å-16.55 Å. In terms of MM/PBSA binding energy, the BDC30129064 complex was ranked top with -44.88 ± 4.14 kcal/mol, whereas the positive control molecule exhibited -22.22 ± 3.33 kcal/mol. From a pharmacokinetic perspective, the compounds are suitable candidates for clinical trial investigation. Preliminary computational analysis of these virtual hits indicates that these compounds have a low potential for ADME and toxicity-associated liabilities. In summary, the compounds displayed a high affinity for the C. jejuni DsbA1 protein, indicating potential efficacy that requires further investigation.Communicated by Ramaswamy H. Sarma.

Antimicrobial Resistance: Two-Component Regulatory Systems and Multidrug Efflux Pumps

The number of multidrug-resistant bacteria is rapidly spreading worldwide. Among the various mechanisms determining resistance to antimicrobial agents, multidrug efflux pumps play a noteworthy role because they export extraneous and noxious substrates from the inside to the outside environment of the bacterial cell contributing to multidrug resistance (MDR) and, consequently, to the failure of anti-infective therapies. The expression of multidrug efflux pumps can be under the control of transcriptional regulators and two-component systems (TCS). TCS are a major mechanism by which microorganisms sense and reply to external and/or intramembrane stimuli by coordinating the expression of genes involved not only in pathogenic pathways but also in antibiotic resistance. In this review, we describe the influence of TCS on multidrug efflux pump expression and activity in some Gram-negative and Gram-positive bacteria. Taking into account the strict correlation between TCS and multidrug efflux pumps, the development of drugs targeting TCS, alone or together with already discovered efflux pump inhibitors, may represent a beneficial strategy to contribute to the fight against growing antibiotic resistance.

Mechanistic insight into the degradation of ciprofloxacin in water by hydroxyl radicals

Ciprofloxacin (CIP), an effective antibacterial drug, is widely used to treat bacterial infections in humans and animals. However, drug pollution from residues and the development of resistant genes may pose serious ecological risks. Among the known methods of CIP degradation, advanced oxidation technology initiated by hydroxyl radicals exhibits great potential. However, an in-depth study of the degradation mechanism is difficult because of the limitations of the testing methods. In this study, CIP oxidation by hydroxyl radicals was evaluated using density functional theory (DFT), and the thermodynamics, kinetics, and toxicity were investigated. The results show that CIP oxidation occurs mainly through the piperazine ring, benzene ring, and CC. High reactivity is achieved in the initial reactions, where only five reactions are not thermodynamically spontaneous. Reactions involving direct hydrogen abstraction by oxygen in this system are superior to the indirect reactions. Some theoretically predicted products, such as P6 and P11, are consistent with those reported in previous experiments, indicating that the theoretical study can provide supplementary information about the oxidation paths. The branching ratios for the hydrogen atom abstraction and addition reactions were 37. 45% and 62.55%, respectively. Finally, this reaction system is completely nontoxic based on toxicity assessment.

Bacterial genome sequencing tracks the housefly-associated dispersal of fluoroquinolone- and cephalosporin-resistant Escherichia coli from a pig farm

The regular use of antimicrobials in livestock production selects for antimicrobial resistance. The potential impact of this practice on human health needs to be studied in more detail, including the role of the environment for the persistence and transmission of antimicrobial-resistant bacteria. During an investigation of a pig farm and its surroundings in Brandenburg, Germany, we detected abundant cephalosporin- and fluoroquinolone-resistant Escherichia coli in pig faeces, sedimented dust, and house flies (Musca domestica). Genome sequencing of E. coli isolates revealed large phylogenetic diversity and plasmid-borne extended-spectrum beta lactamase (ESBL) genes CTX-M-1 in multiple strains. [Correction added on 28 February 2023, after first online publication: In the preceding sentence, 'and TEM-1' was previously included but has been deleted in this version.] Close genomic relationships indicated frequent transmission of antimicrobial-resistant E. coli between pigs from different herds and across buildings of the farm and suggested dust and flies as vectors for dissemination of faecal pathogens. Strikingly, we repeatedly recovered E. coli from flies collected up to 2 km away from the source, whose genome sequences were identical or closely related to those from pig faeces isolates, indicating the fly-associated transport of diverse ESBL-producing E. coli from the pig farm into urban habitation areas. The observed proximity of contaminated flies to human households poses a risk of transmission of antimicrobial-resistant enteric pathogens from livestock to man.

Evaluation of rice straw and its transformation products on norfloxacin degradation and antibiotic resistome attenuation during soil incorporation

Straw incorporation into reclaimed soils has been demonstrated to increase soil nutrients and has the potential to efficiently increase crop production. However, which incorporation mode is more helpful in the control of antibiotic resistance genes (ARGs) remains unknown. In this study, we systematically compared the occurrence of antibiotic resistome in norfloxacin contaminated soils amended with rice straw (RS) and the transformation products, biochar (RSB) and ash (RSA). RS significantly promoted the degradation of norfloxacin (0.0648 d^-1, 3 times faster than control), whereas RSB had little effect and RSA hindered the degradation. Based on metagenomic analysis, RS and RSB significantly reduced the ARGs relative abundance (0.1421 and 0.1991 compared to 0.2540 in control) at the end of soil incubation. Adonis test indicated that all of amendment treatments significantly affect the microbial communities in soils, whereas only RS and RSB significantly affect the variation of antibiotic resistome. Procrustes analysis confirmed the association of microbial communities and ARGs. Network analysis further revealed that the reduction in Actinobacteria was the main reason for the general decrease of ARGs relative abundance during soil incorporation, whereas Proteobacteria and Bacteroidetes were responsible for temporary promotion of ARGs in RS and RSB at the early stage. Finally, scientifically setting up the usage of rice straw and optimizing the preparation process of biochar are suggested for the synchronous control of the risk of antibiotics and ARGs during soil incorporation.

Fate and transport of tetracycline and ciprofloxacin and impact on nitrate reduction activity in coastal sediments from the Seine Estuary, France

Fluoroquinolones and tetracyclines are frequently detected antibiotics in aquatic sediments. In this study, the transport of ciprofloxacin (CIP) and tetracycline (TET) was investigated in sediments from the Seine Estuary (France), under nitrate reducing conditions. Dynamic flow experiments showed that although TET and CIP strongly interacted with the sediment components through adsorption and (bio)-chemical transformation, they kept their antimicrobial activities. Less nitrate reduction was observed during the first period of breakthrough, while TET and CIP were absent in the column effluent. Batch experiments with freeze-dried vs fresh sediments showed that adsorption and abiotic degradation are the major removal processes, while microbe-driven transformation is of less importance. Whereas TET is to a large extent chemically transformed and little adsorbed in the sediment, CIP was less transformed and more adsorbed, most likely due to the great reactivity of TET with redox-active mineral surfaces. Our findings show the strong capacity of natural sediment to retain and transform antibiotics, while still maintaining their antimicrobial activity or inhibitory effect of nitrate reducing activity.

Determination of antimicrobial agents and their transformation products in an agricultural water-soil system modified with manure

Manure fertilization is the primary source of veterinary antimicrobials in the water-soil system. The research gap is the fate of antimicrobials after their release into the environment. This study aimed to provide a detailed and multi-faceted examination of fertilized cultivated fields using two types of manure (poultry and bovine) enriched with selected antimicrobials. The research focused on assessing the mobility and stability of antimicrobials in the water-soil system. Additionally, transformation products of antimicrobials in the environment were identified. The extraction (solid-phase extraction and/or solid-liquid extraction) and LC-MS/MS analysis procedures were developed to determine 14 antimicrobials in the soil and pore water samples. Ten out of fourteen antimicrobials were detected in manure-amended soil and pore water samples. The highest concentration in the soil was 109.1 ng g^-1 (doxycycline), while in pore water, it was 186.6 ng L^-1 (ciprofloxacin). Sixteen transformation products of antimicrobials were identified in the soil and soil-related pore water. The same transformation products were detected in both soil and soil pore water extracts, with significantly higher signal intensities observed in soil extracts than in water. Transformation products were formed in oxidation, carbonylation, and ring-opening reactions.

Efficient Activation of Peroxymonosulfate by Biochar-Loaded Zero-Valent Copper for Enrofloxacin Degradation: Singlet Oxygen-Dominated Oxidation Process

The removal of contaminants of emerging concern (CECs) has become a hot research topic in the field of environmental engineering in recent years. In this work, a simple pyrolysis method was designed to prepare a high-performance biochar-loaded zero-valent copper (CuC) material for the catalytic degradation of antibiotics ENR by PMS. The results showed that 10 mg/L of ENR was completely removed within 30 min at an initial pH of 3, CuC 0.3 g/L, and PMS 2 mmol/L. Further studies confirmed that the reactive oxygen species (ROS) involved in ENR degradation are ·OH, SO4-·, ¹O₂, and O2-. Among them, ¹O₂ played a major role in degradation, whereas O2-· played a key role in the indirect generation of ¹O₂. On the one hand, CuC adsorbed and activated PMS to generate ·OH, SO4-· and O2-·. O2-· was unstable and reacted rapidly with H₂O and ·OH to generate large amounts of ¹O₂. On the other hand, both the self-decomposition of PMS and direct activation of PMS by C=O on biochar also generated ¹O₂. Five byproducts were generated during degradation and eventually mineralized to CO₂, H₂O, NO3-, and F^-. This study provides a facile strategy and new insights into the biochar-loaded zero-valent transition-metal-catalyzed PMS degradation of CECs.

Effects of Ciprofloxacin Alone or in Mixture with Sulfamethoxazole on the Efficiency of Anaerobic Digestion and Its Microbial Community

Some livestock farms rely on anaerobic digestion (AD) technology for manure disposal, thus obtaining energy (biogas) and fertilizer (digestate). Mixtures of antibiotics used for animal health often occur in organic waste and their possible synergistic/antagonistic effects on microorganisms involved in AD are still poorly studied. This work focuses on the effects of adding ciprofloxacin, alone (5 mg L-1) and in combination with sulfamethoxazole (2.5-5-10 mg L-1), on AD efficiency and microbial community structure. The experiment consisted of 90-day cattle manure batch tests and antibiotic removal percentages were assessed. Adding antibiotics always promoted CH4 and H2 production compared to untreated controls; however, CH4 production was lowered with the highest ciprofloxacin (CIP) concentrations. The overall results show antibiotic degradation caused by acidogenic Bacteria, and CH4 was mainly produced through the hydrogenotrophic-pathway by methanogenic Archaea. Shifts in microbial community abundance (DAPI counts) and composition (Illumina-MiSeq and FISH analyses) were observed.

Acinetobacter baumannii, Klebsiella pneumoniae and Elizabethkingia miricola isolated from wastewater have biodegradable activity against fluoroquinolone

Ciprofloxacin (CIP) and levofloxacin (LEV), widely used fluoroquinolone antibiotics, are often found in sewage from the sewage treatment plants and marine environment. In this study, CIP and LEV biodegrading bacterial consortia were obtained from industrial wastewater. Microorganisms in these consortia were identified as Acinetobacter baumannii (A. baumannii), Klebsiella pneumoniae (K. pneumoniae) and Elizabethkingia miricola (E. miricola). The impacts of the critical operating parameters on the elimination of CIP and LEV by bacterial consortia have been investigated and optimized to achieve the maximum levels of CIP and LEV biodegradation. Using liquid chromatography with tandem mass spectrometry (LC-MS-MS), possible degradation pathways for CIP and LEV were suggested by analyzing the intermediate degradation products. The role of the enzymes fluoroquinolone-acetylating aminoglycoside (6'-N-acetyltransferase) and cytochrome P450 (CYP450) in the breakdown of fluoroquinolones (FQs) was investigated as well. According to our findings, various biodegradation mechanisms have been suggested, including cleavage of piperazine ring, substitution of F atom, hydroxylation, decarboxylation, and acetylation, as the main biotransformation reactions. This study discovers the ability of non-reported bacterial strains to biodegrade both CIP and LEV as a sole carbon source, providing new insights into the biodegradation of CIP and LEV.

Response Surface Methodology for Optimization of Operational Parameters To Remove Ciprofloxacin from Contaminated Water in the Presence of a Bacterial Consortium

Ciprofloxacin (CFX) is a broad-spectrum fluoroquinolone antibiotic that is widely used to treat bacterial infections in humans and other animals. However, its unwanted occurrence in any (eco)system can affect nontarget bacterial communities, which may also impair the performance of the natural or artificially established bioremediation system. The problem could be minimized by optimization of operational parameters via modeling of multifactorial tests. To this end, we used a Box-Behnken design in response surface methodology (RSM) to generate the experimental layout for testing the effect of the CFX biodegradation for four important parameters, that is, temperature (°C), pH, inoculum size (v/v %), and CFX concentration (mg L^-1). For inoculation, a consortium of three bacterial strains, namely, Acenitobacter lwofii ACRH76, Bacillus pumilus C2A1, and Mesorihizobium sp. HN3 was used to degrade 26 mg L^-1 of CFX. We found maximum degradation of CFX (98.97%; initial concentration of 25 mg L^-1) at 2% inoculum size, 7 pH, and 35 °C of temperature in 16 days. However, minimum degradation of CFX (48%; initial concentration of 50 mg L^-1) was found at pH 6, temperature 30 °C, and inoculum size 1%. Among different tested parameters, pH appears to be the main limiting factor for CFX degradation. Independent factors attributed 89.37% of variation toward CFX degradation as revealed by the value of the determination coefficient, that is, R ² = 0.8937. These results were used to formulate a mathematical model in which the computational data strongly correlated with the experimental results. This study showcases the importance of parameter optimization via RSM for any bioremediation studies particularly for antibiotics in an economical, harmless, and eco-friendly manner.

Uptake of Pharmaceutical Pollutants and Their Metabolites from Soil Fertilized with Manure to Parsley Tissues

Manure is a major source of soil and plant contamination with veterinary drugs residues. The aim of this study was to evaluate the uptake of 14 veterinary pharmaceuticals by parsley from soil fertilized with manure. Pharmaceutical content was determined in roots and leaves. Liquid chromatography coupled with tandem mass spectrometry was used for targeted analysis. Screening analysis was performed to identify transformation products in the parsley tissues. A solid-liquid extraction procedure was developed combined with solid-phase extraction, providing recoveries of 61.9–97.1% for leaves and 51.7–95.6% for roots. Four analytes were detected in parsley: enrofloxacin, tylosin, sulfamethoxazole, and doxycycline. Enrofloxacin was detected at the highest concentrations (13.4–26.3 ng g⁻¹). Doxycycline accumulated mainly in the roots, tylosin in the leaves, and sulfamethoxazole was found in both tissues. 14 transformation products were identified and their distribution were determined. This study provides important data on the uptake and transformation of pharmaceuticals in plant tissues.

Role of the Two-Component System CiaRH in the Regulation of Efflux Pump SatAB and Its Correlation with Fluoroquinolone Susceptibility

Streptococcus suis is an important pathogen in both pigs and humans. Although the diseases associated with S. suis can typically be treated with antibiotics, such use has resulted in a sustained increase in drug resistance. Bacteria can sense and respond to antibiotics via two-component systems (TCSs). In this study, the TCS CiaRH was identified as playing an important role in the susceptibility of S. suis to fluoroquinolones (FQs). We found that a ΔciaRH mutant possessed lower susceptibility to FQs than the wild-type strain, with no observed growth defects at the tested concentrations and lower levels of intracellular drugs and dye. Proteomic data revealed that the levels of SatA and SatB expression were upregulated in the ΔciaRH mutant compared with their levels in the wild-type strain. The satA and satB genes encode a narrow-spectrum FQ efflux pump. The phenomena associated with combined ciaRH-and-satAB deletion mutations almost returned the ΔciaRH ΔsatAB mutant to the phenotype of the wild-type strain compared to the phenotype of the ΔciaRH mutant, suggesting that the resistance of the ΔciaRH strain to FQs could be attributed to satAB overexpression. Moreover, SatAB expression was regulated by CiaR (a response regulator of CiaRH) and SatR (a regulator of the MarR family). The ciaRH genes were consistently downregulated in response to antibiotic stress. The results of electrophoretic mobility shift assays (EMSAs) and affinity assays revealed that both regulator proteins directly controlled the ABC transporter proteins SatAB. Together, the results show that cascade-mediated regulation of antibiotic export by CiaRH is crucial for the ability of S. suis to adapt to conditions of antibiotic pressure. Our study may provide a new target for future antibiotic research and development. IMPORTANCE Streptococcus suis is a zoonotic pathogen with high incidence and mortality rates in both swine and humans. Following antibiotic treatment, the organism has evolved many resistance mechanisms, among which efflux pump overexpression can promote drug extrusion from the cell. This study clarified the role of CiaRH in fluoroquinolone resistance. A mutant with the ciaRH genes deleted showed decreased susceptibility to the antibiotics tested, an invariant growth rate, and reduced intracellular efflux pump substrates. This research also demonstrated that overexpression of the efflux pump SatAB was the main cause of ΔciaRH resistance. In addition, CiaR could combine with the promoter region of satAB to further directly suppress target gene transcription. Simultaneously, satAB was also directly regulated by SatR. Our findings may provide novel insights for the development of drug targets and help to exploit corresponding inhibitors to combat bacterial multidrug resistance.

Efficient with low-cost removal and adsorption mechanisms of norfloxacin, ciprofloxacin and ofloxacin on modified thermal kaolin: experimental and theoretical studies

Quinolone antibiotics (QNs) can be potential hazard to environment and human. Combination of experimental and theoretical studies was used to analyze the adsorption properties of norfloxacin, ciprofloxacin and ofloxacin on modified thermally activated kaolin (KL). Main factors (calcination temperature, dose, pH, cations and regeneration) affecting the adsorption were discussed. Adsorption processes fit the pseudo-second order kinetic and Langmuir model well. The adsorption removal of norfloxacin, ciprofloxacin and ofloxacin can reach 88.53%, 89.43% and 91.46%, respectively. Cations inhibited adsorption, and AlS-KLB can maintain 80% efficiency in five cycles under optimal conditions. Simulations showed that the materials had good adsorption capacity for QNs, and the "①" of KL had the best capacity. Simulations explain the adsorption mechanism: F, H, O atoms of QNs are covalently bonded to O atoms from KL, Al₂O₃ and Al (OH)₃, C atoms from amorphous carbon and H atoms from C-H and Al (OH)₃. The Al atoms of Al₂O₃ and Al, Si atoms of KL are ionically bonded to F, H, O atoms of QNs. This study shed new light on the removal of QNs by providing low-cost and efficient modified KL and elucidating the adsorption mechanism in conjunction with DFT simulations.

Occurrence, detection and ecotoxicity studies of selected pharmaceuticals in aqueous ecosystems- a systematic appraisal

Pharmaceutical compounds (PCs) have globally emerged as a significant group of environmental contaminants due to the constant detection of their residues in the environment. The main scope of this review is to fill the void of information on the knowledge on the African occurrence of selected PCs in environmental matrices in comparison with those outside Africa and their respective toxic actions on both aquatic and non-aquatic biota through ecotoxicity bioassays. To achieve this objective, the study focused on commonly used and detected pharmaceutical drugs (residues). Based on the conducted literature survey, Africa has the highest levels of ciprofloxacin, sulfamethoxazole, lamivudine, acetaminophen, and diclofenac while Europe has the lowest of all these PC residues in her physical environments. For ecotoxicity bioassays, the few data available are mostly on individual groups of pharmaceuticals whereas there is sparsely available data on their combined forms.

Biotransformation of Tetracyclines by Fungi: Challenges and Future Research Perspectives

Tetracycline antibiotics are used worldwide in human and veterinary medicine. On the basis of low metabolization and through organic fertilizers, tetracyclines enter the environment in a biologically active form. This can have toxic effects on microbial communities and promote the selection of resistant strains. The use of fungi could be a promising approach to deactivate tetracyclines by degradation or derivatization as a result of their particular enzyme endowment. Here, we highlight the current analytical and biotechnological challenges associated with the bioconversion of tetracyclines by fungi and propose research approaches to advance the technology for wastewater and manure treatment.

Potential of agro-industrial produced laccase to remove ciprofloxacin

Ciprofloxacin (CIP), a widely used antibiotic, is frequently detected in the environment due to insufficient wastewater and water treatment. Hence, novel, green and cost-effective technologies are required to enhance the removal of these pollutants. The potency of crude enzymes, especially laccases, produced by white-rot fungi was tested to assess their effectiveness to degrade CIP from water. Crude laccase alone could not oxidize CIP. The addition of syringaldehyde, a redox mediator, resulted in a decrease in antibiotic concentration up to 68.09±0.12% in 24 h, which was the highest removal efficiency achieved with 0.15 mg/mL syringaldehyde and 2 mg/mL of crude laccase (0.1 U/ml). Crude laccase oxidation of CIP was inhibited after 6 h of treatment. To compare, a pure enzyme with the same activity as the crude one removed 86% of CIP in 24 h. No inhibitory effect during the treatment was observed. The estimation of antimicrobial efficiency revealed that after 6 h of treatment, the toxicity towards Escherichia coli decreased by 30%. The wastewater treatment by the crude laccase-mediated system was estimated to significantly reduce the cost of enzymatic treatment.

Antibiotic degradation dominates the removal of antibiotic resistance genes during composting

To identify the key hosts involved in horizontal gene transfer (HGT) and vertical gene transfer (VGT) of antibiotic resistance genes (ARGs) and to determine the extent to and ways in which environmental properties contribute to ARG removal, the changes in ARG profile and key hosts during biogas residue and pig manure composting were investigated using metagenomic sequencing coupled with network analysis. Composting significantly reduced the abundances of ARGs other than bacA. Seventy and 41 hosts from Firmicutes, Actinobacteria, Proteobacteria and Bacteroidetes were associated with HGT and VGT, respectively. The key environmental properties were determined using structural equation modelling. Antibiotics directly affected HGT and determined ARG removal. Temperature indirectly affected HGT, mainly by influencing the degradation of antibiotics. BacA was associated only with hosts involved in VGT, which may lead to its low removal rate. These findings specify the priority and pathway of antibiotics and temperature affecting ARG profile.

Treatment technologies to mitigate the harmful effects of recalcitrant fluoroquinolone antibiotics on the environ- ment and human health

Antibiotic proliferation in the environment and their persistent nature is an issue of global concern as they induce antibiotic resistance threatening both human health and the ecosystem. Antibiotics have therefore been categorized as emerging pollutants. Fluoroquinolone (FQs) antibiotics are an emerging class of contaminants that are used extensively in human and veterinary medicine. The recalcitrant nature of fluoroquinolones has led to their presence in wastewater, effluents and water bodies. Even at a low concentration, FQs can stimulate antibacterial resistance. The main sources of FQ contamination include waste from pharmaceutical manufacturing industries, hospitals and households that ultimately reaches the wastewater treatment plants (WWTPs). The conventional WWTPs are unable to completely remove FQs due to their chemical stability. Therefore, the development and implementation of more efficient, economical, convenient treatment and removal technologies are needed to adequately address the issue. This review provides an overview of the technologies available for the removal of fluoroquinolone antibiotics from wastewater including adsorptive removal, advanced oxidation processes, removal using non-carbon based nanomaterials, microbial degradation and enzymatic degradation. Each treatment technology is discussed on its merits and limitations and a comparative view is presented on the choice of an advanced treatment process for future studies and implementation. A discussion on the commercialization potential and eco-friendliness of each technology is also included in the review. The importance of metabolite identification and their residual toxicity determination has been emphasized. The last section of the review provides an overview of the policy interventions and regulatory frameworks that aid in retrofitting antibiotics as a central key focus contaminant and thereby defining the discharge limits for antibiotics and establishing safe manufacturing practices.

Doxofylline Protects Gram-Negative Pathogens against Antibiotic-Mediated Killing

Given the growing rate of Gram-negative bacterial infections, antibiotics are now frequently prescribed for various respiratory diseases. Doxofylline is a newer generation xanthine with both bronchodilating and anti-inflammatory activities, but its influence on antibiotics remains poorly understood. Here, we first report the discovery of doxofylline-induced high minimum inhibitory concentrations of antibiotics. We also showed that doxofylline blocked antimicrobial-mediated killing for Gram-negative pathogens in vitro and in murine lung infection models in vivo. By combining efflux pump inhibition tests, gene expression analyses, and using the gene tolC knockout strain, we found that doxofylline positively regulated gene expression of the AcrAB-TolC efflux pump and attenuated the effect of doxofylline on antibacterial activities in ΔtolC mutants. Notably, doxofylline-mediated protection correlated with decreased reactive oxygen species (ROS) production. Collectively, our study indicates that doxofylline protects Gram-negative bacteria from antimicrobial lethality by regulating the AcrAB-TolC efflux pump in a TolC-dependent manner and suppressing antibiotic-induced ROS accumulation. These results suggest caution when using antibiotics alongside doxofylline in clinical treatment.

Biological Effects of Quinolones: A Family of Broad-Spectrum Antimicrobial Agents

Broad antibacterial spectrum, high oral bioavailability and excellent tissue penetration combined with safety and few, yet rare, unwanted effects, have made the quinolones class of antimicrobials one of the most used in inpatients and outpatients. Initially discovered during the search for improved chloroquine-derivative molecules with increased anti-malarial activity, today the quinolones, intended as antimicrobials, comprehend four generations that progressively have been extending antimicrobial spectrum and clinical use. The quinolone class of antimicrobials exerts its antimicrobial actions through inhibiting DNA gyrase and Topoisomerase IV that in turn inhibits synthesis of DNA and RNA. Good distribution through different tissues and organs to treat Gram-positive and Gram-negative bacteria have made quinolones a good choice to treat disease in both humans and animals. The extensive use of quinolones, in both human health and in the veterinary field, has induced a rise of resistance and menace with leaving the quinolones family ineffective to treat infections. This review revises the evolution of quinolones structures, biological activity, and the clinical importance of this evolving family. Next, updated information regarding the mechanism of antimicrobial activity is revised. The veterinary use of quinolones in animal productions is also considered for its environmental role in spreading resistance. Finally, considerations for the use of quinolones in human and veterinary medicine are discussed.

Insights into the removal of pharmaceutically active compounds from sewage sludge by two-stage mesophilic anaerobic digestion

The removal efficiencies (REs) of twenty-seven pharmaceutically active compounds (PhACs) (eight analgesic/anti-inflammatories, six antibiotics, four β-blockers, two antihypertensives/diuretics, three lipid regulators and four psychiatric drugs) were evaluated in a pilot-scale two-stage mesophilic anaerobic digestion (MAD) system treating thickened sewage sludge from a pilot-scale A²O™ wastewater treatment plant (WWTP) which was fed with wastewater from the pre-treatment of the full-scale WWTP Murcia Este (Murcia, Spain). The MAD system was long-term operated using two different sets of sludge retention times (SRTs) for the acidogenic (AcD) and methanogenic (MD) digesters (phase I, 2 and 12 days; and phase II, 5 and 24 days, in AcD and MD, respectively). Quantitative PCR (qPCR) and Illumina MiSeq sequencing were used to estimate the absolute abundance of Bacteria, Archaea, and Fungi and investigate the structure, diversity and population dynamics of their communities in the AcD and MD effluents. The extension of the SRT from 12 (phase I) to 24 days (phase II) in the MD was significantly linked with an improved removal of carbamazepine, clarithromycin, codeine, gemfibrozil, ibuprofen, lorazepam, and propranolol. The absolute abundances of total Bacteria and Archaea were higher in the MD regardless of the phase, while the diversity of bacterial and archaeal communities was lower in phase II, in both digesters. Non-metric multidimensional scaling (MDS) plots showed strong negative correlations among phyla Proteobacteria and Firmicutes and between genera Methanosaeta and Methanosarcina throughout the full experimental period. Strong positive correlations were revealed between the relative abundances of Methanospirillum and Methanoculleus and the methanogenesis performance parameters (volatile solids removal, CH₄ recovery rate and %CH₄ in the biogas), which were also related to longer SRT. The REs of several PhACs (naproxen, ketoprofen, ofloxacin, fenofibrate, trimethoprim, and atenolol) correlated positively (r > 0.75) with the relative abundances of specific bacterial and archaeal groups, suggesting their participation in biodegradation/biotransformation pathways.

Potential biotransformation pathways and efficiencies of ciprofloxacin and norfloxacin by an activated sludge consortium

Fluoroquinolones (FQs), such as ciprofloxacin (CIP) and norfloxacin (NOR), are types of emerging trace pollutants that have attracted great attention. In this study, an activated sludge (AS) consortium with high bio-removal capability to CIP and NOR was obtained by acclimating with CIP and NOR for 10 d. Meanwhile, a CIP- and NOR- transforming bacterial strain (S5), which is highly homologous to the 16S rRNA gene sequence of Enterobacter sp., was isolated from the acclimated AS. The bio-removal efficiency of CIP under the acclimated AS consortium was better than that under the pure culture of Enterobacter sp. S5 (93.1% vs. 89.3%), while the bio-removal efficiency of NOR under the acclimated AS consortium was lower than that under the pure culture of Enterobacter sp. S5 (83.9% vs. 89.8%). The biotransformation and bio-adsorption were two main ways to bio-remove CIP and NOR. However, the CIP and NOR biotransformation efficiencies of the acclimated AS were higher than under the pure culture of Enterobacter sp. S5, while the CIP and NOR adsorption of acclimated AS were lower than that under the pure culture of Enterobacter sp. S5. The N-acetylciprofloxacin and N-acetylnorfloxacin were the main biotransformation products of CIP and NOR. It is possible that acetyltransferase may be involved in the biotransformation process. Whether under the pure culture or AS consortium, the cytotoxicity of CIP and NOR transformation products to gram-negative bacteria was alleviated. Therefore, the acclimated AS and Enterobacter sp. S5 might provide a new strategy for removing contaminants and alleviating of FQs resistance.

Chemical speciation of ciprofloxacin in aqueous solution regulates its phytotoxicity and uptake by rice (Oryza sativa L.)

Ciprofloxacin (CIP), a widely used fluoroquinolone antibiotic, is frequently detected in aqueous environments, and could be assimilated by vegetable plants to possess potential threats to human and animal health through food chains. However, plant uptake of CIP in different chemical speciation has still far from clear now. Thus, the toxicity and uptake of CIP by rice plants were investigated under different solution pH, owing to its contribution to different chemical speciation of CIP. Results display that high pH-driven changes of CIP from cation (CIP⁺) to anion (CIP^-) decreased its adsorption and uptake by excised roots and intact plants, respectively. However, CIP concentrations in roots, stems and leaves all exhibited no significant differences with increasing solution pH. Moreover, six intermediates of CIP were detected and two possible transformation pathways were proposed in rice plants, including firstly oxidation and following consecutive cleavage of piperazine ring. After accumulated in plant tissues, CIP significantly inhibited the plant growth, decreased the photosynthetic pigments contents and enhanced the antioxidant enzyme activities in a concentration-dependent manner. Besides, high pH exacerbated the growth inhibition and changed the oxidative damage responses of rice plants to CIP. These findings indicate that the uptake and toxicity of CIP in rice plants were influenced by solution pH-driven changes of its chemical speciation.

Biotransformation of lincomycin and fluoroquinolone antibiotics by the ammonia oxidizers AOA, AOB and comammox: A comparison of removal, pathways, and mechanisms

In this study, we evaluated the biotransformation mechanisms of lincomycin (LIN) and three fluoroquinolone antibiotics (FQs), ciprofloxacin (CFX), norfloxacin (NFX), and ofloxacin (OFX), which regularly enter aquatic environments through human activities, by different ammonia-oxidizing microorganisms (AOM). The organisms included a pure culture of the complete ammonia oxidizer (comammox) Nitrospira inopinata, an ammonia oxidizing archaeon (AOA) Nitrososphaera gargensis, and an ammonia-oxidizing bacterium (AOB) Nitrosomonas nitrosa Nm90. The removal of these antibiotics by the pure microbial cultures and the protein-normalized biotransformation rate constants indicated that LIN was significantly co-metabolically biotransformed by AOA and comammox, but not by AOB. CFX and NFX were significantly co-metabolized by AOA and AOB, but not by comammox. None of the tested cultures transformed OFX effectively. Generally, AOA showed the best biotransformation capability for LIN and FQs, followed by comammox and AOB. The transformation products and their related biotransformation mechanisms were also elucidated. i) The AOA performed hydroxylation, S-oxidation, and demethylation of LIN, as well as nitrosation and cleavage of the piperazine moiety of CFX and NFX; ii) the AOB utilized nitrosation to biotransform CFX and NFX; and iii) the comammox carried out hydroxylation, demethylation, and demethylthioation of LIN. Hydroxylamine, an intermediate of ammonia oxidation, chemically reacted with LIN and the selected FQs, with removals exceeding 90%. Collectively, these findings provide important fundamental insights into the roles of different ammonia oxidizers and their intermediates on LIN and FQ biotransformation in nitrifying environments including wastewater treatment systems.

Fate of emerging and priority micropollutants during the sewage sludge treatment - Part 2: Mass balances of organic contaminants on sludge treatments are challenging

This paper analyzes the fate of 71 priority and emerging organic contaminants all along the treatment trains of sewage sludge treatment facilities in Paris including dewatering by centrifugation, thermal drying and anaerobic digestion. It aimed at proposing and applying a mass balances calculation methodology to each process and pollutant. This data validation strategy demonstrated the complexity to perform representative inlet/outlet sampling and analysis campaigns at industrial scales regarding organic compounds and to propose options to overcome this issue. Centrifugation and drying processes only implied physical mechanisms as phase separation and water elimination. Hence, correct mass balance were expected observed for organic contaminants if sampling and analysis campaigns were representative. This was the case for hydrophobic and neutral compounds. For the other more hydrophilic and charged compounds, the mass balances were scarcely correct. Thus, the conventional sampling and analytical practices used with sludge should be questioned and adapted to better take into account the high heterogeneity of sludge and the evolution of matrix effect within sludge treatment processes on micropollutant determination. For the biological anaerobic digestion process where degradations can occur and removals can be observed, the mass balances were deeply interpreted for 60 contaminants. This process contributed to the elimination above 70% of 21 detected compounds including 16 pharmaceuticals, 2 phthalates, 2 hormones and 1 perfluorinated compound. Removals of domperidone, propranolol, escitalopram, lidocaine, verapamil and cefoperazone under this condition were reported for the first time.

Crop irrigation (soybean, bean, and corn) with enrofloxacin-contaminated water leads to yield reductions and antibiotic accumulation

The increasing use of antibiotics in animal production has become an emergent environmental problem. The large percentages of applied antibiotic doses eliminated in animal excrement often end up contaminating water resources, which are then used for irrigation - compromising agricultural production and/or food security. Here, we evaluated the effects of crop irrigation with water artificially contaminated by enrofloxacin (10 μg l-1) and its accumulation in soybean, bean, and corn tissues. Grain production was evaluated on the basis of grain dry weight plant-1, while enrofloxacin and ciprofloxacin (its breakdown metabolite) concentrations in plant tissues were evaluated by HPLC after harvesting. Diminished production was observed only in soybean plants irrigated with antibiotic-contaminated water. Enrofloxacin [1.68 ng g fresh weight (FW)-1 to 26.17 µg g FW-1] and ciprofloxacin (8.23 ng g FW-1 to 51.05 ng g FW-1), were found in all of the plant tissues (roots, leaves, and seeds) of the three species. Regardless of the species, the highest enrofloxacin concentrations were observed in their roots, followed by the leaves and seeds, while ciprofloxacin concentrations varied among the different plant tissues of the different species. The presence of enrofloxacin in the water used for irrigating soybeans can result in productivity losses and, as that antibiotic was encountered in plant tissues (leaves and seeds) of all of the three species analyzed that are consumed in the diets of both humans and animals, it can interfere with food security.

An adjusted 3D-QSAR model for the combined activity of fluoroquinolones photodegradation and microbial degradation assisted by dynamic simulation and its application in molecular modification

This study developed a comprehensive characterization method for the combined degradation effect of modified fluoroquinolones (FQs) photodegradation and microbial degradation. A combination of revised 3D-QSAR model, molecular docking, path simulation inference, pharmacokinetics, molecular dynamics (MD) simulation and toxicokinetics simulation was used to construct a systematic environment-friendly drug screening system. Five derivatives were screened with significantly improved combined degradation effect (over 20%) and functional characteristics and human health parameters through combined model verification, functional and human health risk assessment. The simulation path of photo- and microbial-degradation of gatifloxacin and new gatifloxacin molecules was derived, and the reaction energy barrier was also calculated. The ratio of the total rate-determining steps change rate of the decreased energy barrier (14.10%:26.30%) was consistent with the ratio of the increased degradation performance predicted by the model (22.87%:19.77%), demonstrating the reliability of revised 3D-QSAR model and it could be applied in molecular modification. MD and toxicokinetics simulation were used to predict the binding energy and aquatic toxicity between photo- and microbial-degradation products and the degradation enzymes, which further to screen the degradation pathways with low potential environmental risks. The findings will be helpful to screen environment-friendly drug and develop appropriate strategies for its risk management.

Occurrence, Distribution, and Ecological Risk Assessment of Antibiotics in Selected Urban Lakes of Hanoi, Vietnam

Residue concentrations of fifteen antibiotics including sulfonamides, quinolones, macrolides, β-lactams, and trimethoprim in lakes from Hanoi metropolitan area, Vietnam, were analyzed using ultra-performance liquid chromatography coupled with tandem mass spectrometry (UPLC/MS-MS) to elucidate their occurrence and behavior in urban environment. For surface water, the average concentrations of five antibiotic classes decreased in the order: sulfonamides (117.9 ng/L) > β-lactams (31.28 ng/L) > quinolones (20.19 ng/L) > macrolides (17.74 ng/L) > trimethoprim (8.93 ng/L). While the highest concentration of SMX was detected at 806.5 ng/L in surface water, those obtained in sediment were only at 1.35 ng/g because of their high solubility in water. Quinolones were found at a maximal concentration of 158.7 ng/L for OFL in water phase whereas those in sediment phase were 4,017 ng/g due to their great affinity in sediment. These findings revealed the different fate and release mechanisms of each antibiotic group in the environment. The ecological risk assessment implied some targeted compounds, and in particular, OFL and AZM could pose high risks to algae in the aquatic ecosystem.

Interaction between tetracycline and microorganisms during wastewater treatment: A review

Tetracycline (TC) is a commonly used human and veterinary antibiotic that is mostly discharged into wastewater in the form of the parent compounds. At present, wastewater treatment plants (WWTPs) use activated sludge processes that are not specifically designed to remove such pollutants. Considering the biological toxicity of TC in aquatic environment, the migration and fate of TC in the process of wastewater treatment deserve attention. This paper reviews the influence of TC on the functional bacteria in the sludge matrix and the development of tetracycline-resistant genes, and also discusses their adsorption removal rates, their adsorption kinetics and adsorption isotherm models, and infers their adsorption mechanism. In addition, the biodegradation of TC in the process of biological treatment is reviewed. Co-metabolism and the role of dominant bacteria in the degradation process are described, along with the formation of degradation byproducts and their toxicity. Furthermore, the current popular integrated coupling-system for TC degradation is also introduced. This paper systematically introduces the interaction between TC and activated sludge in WWTPs. The review concludes by providing directions to address research and knowledge gaps in TC removal from wastewater.

Antimicrobials and Antibiotic-Resistant Bacteria: A Risk to the Environment and to Public Health

The release of antibiotics to the environment, and the consequences of the presence of persistent antimicrobial residues in ecosystems, have been the subject of numerous studies in all parts of the world. The overuse and misuse of antibiotics is a common global phenomenon, which substantially increases the levels of antibiotics in the environment and the rates of their spread. Today, it can be said with certainty that the mass production and use of antibiotics for purposes other than medical treatment has an impact on both the environment and human health. This review aims to track the pathways of the environmental distribution of antimicrobials and identify the biological effects of their subinhibitory concentration in different environmental compartments; it also assesses the associated public health risk and government policy interventions needed to ensure the effectiveness of existing antimicrobials. The recent surge in interest in this issue has been driven by the dramatic increase in the number of infections caused by drug-resistant bacteria worldwide. Our study is in line with the global One Health approach.

Co-occurrence characteristics of antibiotics and estrogens and their relationships in a lake system affected by wastewater

Antibiotics and estrogens are recognized as emerging contaminants in the water environment because of their potentially adverse effects on aquatic ecosystems. The concentrations of four steroid estrogens (17α-estradiol, 17β-estradiol, estrone, and estriol) and eight antibiotics (norfloxacin, levofloxacin, ciprofloxacin, enrofloxacin, metronidazole, sulfapyridine, doxycycline, and sulfamethoxazole) in the Chaohu Lake basin in Anhui province, China, were analyzed along with adjacent wastewater. The levels of the target antibiotics and estrogens were below detection limits (not detected [nd])-89.86 and nd-118.09 ng L^-1 , respectively, in the lake water. All of the target antibiotics and estrogens were detected in sediment, and the concentrations ranged widely (nd-35,544 and nd-16,344 ng kg^-1 , respectively). Antibiotics and estrogens varied spatially in the study area and mostly came from untreated wastewater. Antibiotics and estrogens were associated with water parameters such as pH and total nitrogen. A significant positive correlation was observed between estriol and levofloxacin concentrations (r = .65; p < .01), indicating that levofloxacin from the same source might have inhibited the microbiological degradation of estriol in the surface water. Overall, the estrogens pose a more severe risk than antibiotics to the Chaohu Lake system. However, co-occurrence of antibiotics may affect the fate of estrogens in the same lake media. More attention should be given to estrogens than to antibiotics in wastewater-affected lake systems.

Simple, fast and environmentally friendly method to determine ciprofloxacin in wastewater samples based on an impedimetric immunosensor

In this study an impedimetric immunosensor was developed in order to determine ciprofloxacin (CIP) in wastewater samples, an emergent contaminant widely found in wastewater. To achieve this, an anti-ciprofloxacin antibody was immobilized on the surface of a printed carbon electrode. Then, the developed immunosensor was applied in wastewater samples from Université Laval residences (Québec, Canada) through the load transfer resistance (R_ct) using [Fe(CN)₆]^3−/4− as a redox probe, and the average CIP concentration was found to be 2.90 × 10⁻⁴ μg mL⁻¹. The observed R_ct changes presented a linear relationship from CIP concentrations of 10⁻⁵ to 1.0 μg mL⁻¹, with detection and quantification limits of 2.50 × 10⁻⁶ and 7.90 × 10⁻⁶ μg mL⁻¹, respectively. The immunosensor presented high selectivity and repeatability, as well as a good recovery rate in wastewater samples (97%). Significant interference with other compounds was not observed. The proposed method requires only 30 μL of sample without the use of organic solvents or preceding sample preparation and/or extraction techniques. Moreover, the method is fast: only 20 min of incubation followed by 2 min of analysis time was sufficient to obtain the CIP concentration. The method's estimated cost is U$ 2.00 per sample.

In this study an impedimetric immunosensor was developed in order to determine ciprofloxacin (CIP) in wastewater samples, an emergent contaminant widely found in wastewater samples.

Enhanced reductive removal of ciprofloxacin in pharmaceutical wastewater using biogenic palladium nanoparticles by bubbling H2

To treat waste with waste and efficiently remove the organic pollutant, waste palladiums(ii) were adsorbed and reduced on microorganism surface to catalyze the reductive removal of ciprofloxacin in pharmaceutical wastewater. By optimizing conditions such as pH and temperature, the amount of biogenic palladium adsorbed and reduced on E. coli reached 139.48 mg g⁻¹ (Pd/microorganisms). Moreover, most of the Pd(ii) was reduced to nanometer-sized Pd(0) as characterized by TEM and SEM with EDXA. Using the obtained biogenic palladium, the reductive removal of ciprofloxacin is up to 87.70% at 25 °C, 3.03 folds of that achieved in the absence of H₂. The results show that waste E. coli microorganisms can efficiently adsorb and remove waste Pd(ii) and produce Bio-Pd nanoparticle catalysts in the presence of H₂. This biogenic palladium presents high catalytic activity and great advantages in the reductive degradation of ciprofloxacin. Our method can also be applied to other waste metal ions to prepare the biogenic metals, facilitate their recovery and reuse in degrading organic pollutants in wastewater to achieve “treating waste using waste”.

A solution has been successfully introduced to three key challenges from the wastewater containing waste microorganisms, metal and ciprofloxacin, respectively.