Biotic and abiotic degradation of four cephalosporin antibiotics in a lake surface water and sediment

Aquatic photochemistry for different dissociation forms of cephalosporin antibiotics: Degradation kinetics, products and photo-modified toxicity

Cephalosporin antibiotics (CFs) with ionizable groups (-COOH and -NHn) are widely detected as emerging micropollutants that pose potential environmental risks to aquatic systems, but few studies have revealed their multivariate photochemical transformation behavior in sunlight-irradiated surface waters. In this study, the apparent photodegradation, photo-oxidation towards reactive oxygen species (ROS, •OH and 1O2), and photo-modified toxicity were investigated for the four ionizable CFs: cefoxitin (CFX), cephalothin (CEF), cefoperazone (CFP) and cefazolin (CFZ). Under simulated sunlight irradiation (λ > 290 nm), their multivariate photo-transformation kinetics varied as a function of pHs and the dominant protonated states of the CF in question (H2CFs+, HCFs0 and CFs-). Based on competition kinetics and matrix deconvolution methods, the apparent photolytic rate constants (ki) of different dissociation forms were found to decrease gradually from H2CFs+ to CFs- then to HCFs0, which was dominated by the changing cumulative light absorption (∑(Lλελ,i)) for the different dissociated forms. Interestingly, it was observed that the H2CFs+ or CFs- exhibited higher reactivities towards •OH, while CFs- demonstrated the fastest reaction with 1O2. Using the theoretical derivation, the determined environmental half-lives of the CFs in sunlight-irradiated surface waters were closely dependent on the water pHs and multiple photochemical reaction types. In most cases, apparent photodegradation contributes more than ROS mediated photooxidation to the overall photo-transformation of CFs. The product identification using HPLC-MS/MS indicated that the photodegradation pathways mainly involved photoinduced hydrolysis of the β-lactam ring, cleavage of the side-chain, and decarboxylation. Based on the bioassay to Vibrio fischeri, the most CFs showed photo-enhanced toxicity, which was verified by the ECOSAR assessment, raising concerns about the formation and accumulation of more toxic intermediates. These results are of significance to better assessing the photochemical persistence and risk of the CFs in the aquatic systems and wastewater treatment.

Removal of ceftriaxone and cefotaxime antibiotics from industrial wastewater via complexation with Cu(II)

A high-performance liquid chromatographic method (HPLC) with UV detection is described for determination of ceftriaxone sodium (CFX) and cefotaxime sodium (CFM) content in pharmaceutical industrial wastewater. These methods are based on the detection of these antibiotics via the formation of chelate complexes with Cu(II). The developed Liquid Chromatographic method offers symmetric peak shape, good resolution and reasonable retention time for both drugs. The removal percentage reached about 100 and 92.1% at pH 7.2 for CFX and CFM, respectively. In UV detection, the removal of the chelating antibiotics were based on forming of chelate complexes with Cu(II) which detected at λmax = 253 and 244 nm for CFX and CFM, respectively. Linearity, accuracy and precision were found to be acceptable over the concentration range of 5.99-59.86 µg mL-1 for CFX and 14.33-71.63 µg mL-1 for CFM. The proposed method can be used for the quality control of industrial wastewater containing CFX and CFM.

Dynamic migration and risk of cephalosporin antibiotic resistance genes: Move from pharmaceutical plants through wastewater treatment plants to coastal tidal flats sediments

The migration and dissemination of antibiotics and their corresponding antibiotic resistance genes (ARGs) from pharmaceutical plants through wastewater treatment to the environment introduce exogenous ARGs, increasing the risk of antibiotic resistance. Cephalosporin antibiotics (Ceps) are among the most widely used antibiotics with the largest market scale today, and the issue of resistance is becoming increasingly severe. In this study, a cephalosporin pharmaceutical plant was selected and metagenomic analysis was employed to investigate the dissemination patterns of cephalosporin antibiotics (Ceps) and their ARGs (CepARGs) from the pharmaceutical plant through the wastewater treatment plant to tidal flats sediments. The findings revealed a significant reduction in the total concentration of Ceps by 90.32 % from the pharmaceutical plant's Pioneer Bio Reactor (PBR) to the effluent of the wastewater treatment plant, and a notable surge of 172.13 % in the relative abundance of CepARGs. It was observed that CepARGs originating from the PBR could migrate along the dissemination chain, contributing to 60 % of the CepARGs composition in tidal flats sediments. Microorganisms play a crucial role in the migration of CepARGs, with efflux-mediated CepARGs, as an intrinsic resistance mechanism, exhibiting a higher prospensity for migration due to their presence in multiple hosts. While Class I risk CepARGs are present at the pharmaceutical and wastewater plant stages, Class I ina-CepARGs are completely removed during wastewater treatment and do not migrate to the environment. This study reveals the dynamic migration characteristics and potential risk changes regarding Ceps and CepARGs in real dissemination chains, providing new theoretical evidence for the mitigation, control, and risk prevention of CepARGs.

Migration and transformation behaviors of antibiotics in water-sediment system under simulated light and wind waves

Antibiotics can generally be detected in the water-sediment systems of lakes. However, research on the migration and transformation of antibiotics in water-sediment systems based on the influences of light and wind waves is minimal. To address this research gap, we investigated the specific impacts of light and wind waves on the migration and transformation of three antibiotics, norfloxacin (NOR), trimethoprim (TMP), and sulfamethoxazole (SMX), under simulated light and wind waves disturbance conditions in a water-sediment system from Taihu Lake, China. In the overlying water, NOR was removed the fastest, followed by TMP and SMX. Compared to the no wind waves groups, the disturbance of big wind waves reduced the proportion of antibiotics in the overlying water. The contributions of light and wind waves to TMP and SMX degradation were greater than those of microbial degradation. However, the non-biological and biological contributions of NOR to degradation were almost equal. Wind waves had a significant impact on the microbial community changes in the sediment, especially in Methylophylaceae. These results verified the influence of light and wind waves on the migration and transformation of antibiotics, and provide assistance for the risk of antibiotic occurrence in water and sediments.

Recent advances in the role of dissolved organic matter during antibiotics photodegradation in the aquatic environment

The presence of residual antibiotics in the environment is a prominent issue. Photodegradation behavior is an important way of antibiotics reduction, which is closely related to dissolved organic matter (DOM) in water. The review provides an overview of the latest advancements in the field. Classification, characterization of DOM, and the dominant mechanisms for antibiotic photodegradation were discussed. Furthermore, it summarized and compared the effects of DOM on different antibiotics photodegradation. Moreover, the review comprehensively considered the factors influencing the photodegradation of antibiotics in the aquatic environment, including the characteristics of light, temperature, dosage of DOM, concentration of antibiotics, solution pH, and the presence of coexisting ions. Finally, potential directions were proposed for the development of predictive models for the photodegradation of antibiotics. Based on the review of existing literature, this paper also considered several pathways for the future study of antibiotic photodegradation. This study allows for a better understanding of the DOM's environmental role and provides important new insights into the photochemical fate of antibiotics in the aquatic environment.

Assessment of Directional-Hemispherical Reflectance of Tablets with Cefuroxime during Storage under Elevated Temperature and Ultraviolet Radiation

Environmental conditions can lead to changes in the physical and chemical structures of drug products. In this study, the stability of cefuroxime tablets stored under adverse conditions was evaluated based on total directional-hemispherical reflectance (THR). The THR value was measured before and after the tablets' exposure to stress factors (temperature of 45 °C and UV radiation). Each measurement was performed three times within seven spectral bands at the beginning of the experiment (day 0), and then on days 1, 2, 3, 5, and 7. In addition, hyperspectral profiles (400-1030 nm) were analyzed on days 0 and 7. A significant decrease in THR values in all wavelength ranges was observed when day 7 vs. day 0 were compared, especially for spectral bands of 335-380 nm and 1700-2500 nm (Δ = 0.220, p < 0.001 and Δ = 0.171, p < 0.001, respectively). The hyperspectral analysis confirmed a decrease in the reflectance after the end of stress conditions in the visible light range (400-700 nm) compared to tablets before the experiment. This may indicate that more radiation entered the tablets. In conclusion, the THR of cefuroxime tablets decreases during the exposure to heat and UV radiation, which may result from some physicochemical changes that have occurred during storage.

A state-of-art-review on emerging contaminants: Environmental chemistry, health effect, and modern treatment methods

Pollution problems are increasingly becoming e a priority issue from both scientific and technological points of view. The dispersion and frequency of pollutants in the environment are on the rise, leading to the emergence have been increasing, including of a new class of contaminants that not only impact the environment but also pose risks to people's health. Therefore, developing new methods for identifying and quantifying these pollutants classified as emerging contaminants is imperative. These methods enable regulatory actions that effectively minimize their adverse effects to take steps to regulate and reduce their impact. On the other hand, these new contaminants represent a challenge for current technologies to be adapted to control and remove emerging contaminants and involve innovative, eco-friendly, and sustainable remediation technologies. There is a vast amount of information collected in this review on emerging pollutants, comparing the identification and quantification methods, the technologies applied for their control and remediation, and the policies and regulations necessary for their operation and application. In addition, This review will deal with different aspects of emerging contaminants, their origin, nature, detection, and treatment concerning water and wastewater.

An experimental design study of photocatalytic activity of the Z-scheme silver iodide/tungstate binary nano photocatalyst

A binary AgI/ Ag2WO4 photocatalyst was fabricated and characterized by SEM, XRD, UV-Vis DRS, and FT-IR. It was then used to photodegrade sodium ceftriaxone (CTX) in an aqueous solution. The band gap energies of 2.95, 2.78, and 2.62 eV were obtained by the Kubelka-Munk model for Ag2WO4, AgI, and AgI/Ag2WO4 catalysts. The samples have pHPZC values of 6.9, 4.2, and 6.6, respectively. The synergistic photocatalytic activity of the coupled system depended on the AgI:Ag2WO4 mole ratio and grinding time (optimums:mole ratio of 4:1 and time 30 min). The experimental design was used for optimizing the conditions and a quadratic model well-processed the data based on the model F value of 131.87 > F0.05,14,13 = 2.55 and LOF F value of 0.78 < F0.05,10,3 = 8.78. The optimized RSM run included the irradiation time of 85 min, 3.5 mg/L of CTX sample at pH 9, and a catalyst dose of 1.0 g/L. Under the optimized conditions, about 63% of CTX molecules were photodegraded. In the study of the scavenging agents, the direct Z-scheme mechanism accumulated electrons in the CB-AgI and the holes in the VB-Ag2WO4 level, as stronger reducing and oxidizing centers than the accumulated electrons and holes of the type (II) heterojunction mechanism. Compared to a CTX oxidation potential of about 0.06 V, the direct Z-scheme mechanism is more favorable to reduce or oxidize it.

Bio-inspired sustainable synthesis of novel SnS2/biochar nanocomposite for adsorption coupled photodegradation of amoxicillin and congo red: Effects of reaction parameters, and water matrices

This study aims to fabricate a novel integrated photocatalytic adsorbent (IPA) via a green solvothermal process employing tea (Camellia sinensis var. assamica) leaf extract as a stabilizing and capping agent for the removal of organic pollutants from wastewater. An n-type semiconductor photocatalyst, SnS_2, was chosen as a photocatalyst due to its remarkable photocatalytic activity supported over areca nut (Areca catechu) biochar for the adsorption of pollutants. The adsorption and photocatalytic properties of fabricated IPA were examined by taking amoxicillin (AM) and congo red (CR) as two emerging pollutants found in wastewater. Investigating synergistic adsorption and photocatalytic properties under varying reaction conditions mimicking actual wastewater conditions marks the novelty of the present research. The support of biochar for the SnS₂ thin films induced a reduction in charge recombination rate, which enhanced the photocatalytic activity of the material. The adsorption data were in accordance with the Langmuir nonlinear isotherm model, indicating monolayer chemosorption with the pseudo-second-order rate kinetics. The photodegradation process follows pseudo-first-order kinetics with the highest rate constant of 0.0450 min^-1 for AM and 0.0454 min^-1 for CR. The overall removal efficiency of 93.72 ± 1.19% and 98.43 ± 1.53% could be achieved within 90 min for AM and CR via simultaneous adsorption and photodegradation model. A plausible mechanism of synergistic adsorption and photodegradation of pollutants is also presented. The effect of pH, Humic acid (HA) concentration, inorganic salts and water matrices have also been included.The photodegradation activity of SnS₂ under visible light coupled with the adsorption capability of the biochar results in the excellent removal of the contaminants from the liquid phase.

Utilization of a kinetic isotope effect to decrease decomposition of ceftriaxone in a mixture of D2O/H2O

The discovery of cephalosporin and demonstration of its improved stability in aqueous solution, as well as enhanced in vitro activity against penicillin-resistant organisms, were major breakthroughs in the development of β-lactam antibiotics. Although cephalosporins are more stable with respect to hydrolytic degradation than penicillins, they still experience a variety of chemical transformations. The present study offers an insight into the rates and mechanisms of ceftriaxone degradation at the therapeutic concentration in water, a mixture of water and deuterium oxide, and deuterium oxide itself at the neutral pH. Specific ceftriaxone degradation products were observed in aged samples (including a previously unreported dimer-type species), and by comparing the degradation rates in H₂O and D₂O, the observation of a kinetic isotope effect provided some valuable insight as to the nature of the initial ceftriaxone degradation. The effect of protium to deuterium isotope change on the degradation kinetics of ceftriaxone was evaluated using the method of initial rates based on HPLC analysis as well as by quantitative ¹H NMR spectroscopy. Moreover, computational analysis was utilized to get a molecular insight into chemical processes governing the ceftriaxone degradation and to rationalize the stabilizing effect of replacing H₂O with D₂O.

Antibiotic Pollution of Planktonic Ecosystems: A Review Focused on Community Analysis and the Causal Chain Linking Individual- and Community-Level Responses

Antibiotic pollution has become one of the most challenging environmental issues in aquatic ecosystems, with adverse effects on planktonic organisms that occupy the base of the aquatic food chain. However, research regarding this topic has not been systematically reviewed, especially in terms of community-level responses. In this review, we provide an overview of current antibiotic pollution in aquatic environments worldwide. Then, we summarize recent studies concerning the responses of planktonic communities to antibiotics, ranging from individual- to community-level responses. Studies have shown that extremely high concentrations of antibiotics can directly harm the growth and survival of plankton; however, such concentrations are rarely found in natural freshwater. It is more likely that environmentally relevant concentrations of antibiotics will affect the physiological, morphological, and behavioral characteristics of planktonic organisms; influence interspecific interactions among plankton species via asymmetrical responses in species traits; and thus alter the structure and function of the entire planktonic ecosystem. This review highlights the importance of community analysis in revealing antibiotic toxicity. We also encourage the establishment of the causal relationships between impacts at multiple scales in the future for predicting the community-level consequences of antibiotics based on the currently available individual-level evidence.

Insight on the heterogeneously activated H2O2 with goethite under visible light for cefradine degradation: pH dependence and photoassisted effect

The iron mineral-catalyzed degradation of cephalosporin antibiotics with H₂O₂ occurs ubiquitously in nature. Despite numerous studies, the effects of environmental conditions on reactive species production and degradation processes of cephalosporins remain unclear. Here, we report the iron mineral of goethite as the efficient and heterogenous catalyst for the degradation of cefradine (CRD) via H₂O₂ activation under different conditions involving pH and visible light irradiation. Results show that the CRD removal rate is highly dependent on pH and visible light irradiation. Interestingly, when the pH ranges from 4.0 to 7.0, the degradation intermediates of CRD under dark are the same as under visible light conditions in the goethite/H₂O₂ system. And, the ratio of CRD degradation rate constant (k_Light/k_Dark) reaches a maximum at pH 5.0, suggesting that CRD existing as zwitterion species is preferable for its removal with photoassistance. The mechanism investigation reveals that both •OH and ≡[Fe^IVO]²⁺ oxidants are generated during the reaction process, and •OH is the major oxidant at acidic pH, while ≡[Fe^IVO]²⁺ is more likely to be formed with photoassistance at near-neutral pH. According to UPLC-MS/MS analysis, CRD degradation likely happens via hydrogen atom abstraction from cyclohexadienyl by •OH, thioether and olefin oxidation by ≡[Fe^IVO]²⁺, and Fe^III-catalyzed hydrolytic cleavage of β-lactam ring. These findings highlight the vital roles of pH and photoassistance in the heterogeneously activated H₂O₂ with goethite for CRD degradation.

Boosted photocatalytic effect of binary AgI/Ag2WO4 nanocatalyst: characterization and kinetics study towards ceftriaxone photodegradation

In modern chemistry, great interest has been paid to introducing outstanding photocatalysts for degrading organic pollutants. Herein, a highly efficient binary AgI/Ag₂WO₄ photocatalyst was prepared from AgI and Ag₂WO₄ nanoparticles (NPs) and characterized by scanning electron microscope (SEM), X-ray diffraction (XRD), UV-Vis diffuse reflectance spectroscopy (DRS), electrochemical impedance spectroscopy (EIS), and Fourier transform infrared (FT-IR) techniques. In the Scherrer model, the average crystallite sizes of 34.9, 42.0, and 24.1 nm were estimated for the AgI, Ag₂WO₄, and the binary catalyst, while the values were 91, 13, and 85 nm by the Williamson-Hall model. FTIR confirmed the presence of W-O-W, O-W-O, Ag-I, and O-Ag-O bonds in the coupled material. DRS results showed absorption edge wavelengths of 451, 462, and 495 nm (corresponding to the band gap values of 2.75, 2.68, and 2.51 eV) for Ag₂WO₄, AgI, and AgI/Ag₂WO₄ catalyst, respectively. Synergistic photocatalytic activity of the coupled system was achieved towards ceftriaxone (CTX) in an aqueous solution (about 33% 10 ppm CTX solution was degraded without any optimization in the initial conditions of catal dose 0.3 g/L (Ag₂WO₄:AgI with mole ratio 1:2 and 30 min abrasion time), and irrad. time 45 min, C_CTX). This boosted effect depended on the AgI:Ag₂WO₄ mole ratio and grinding time for the mechanical preparation of the binary catalyst (optimums: mole ratio of 4:1 and time 30 min). The photodegradation kinetics obeyed the Hinshelwood model with the apparent first-order rate constant (k) of 0.013 min^-1 (t_1/2 = 53.30 min). Performing the COD on the photodegraded CTX solutions got a Hinshelwood plot with a slope of 0.019 min^-1 (t_1/2 = 36.5 min).

Impact of Antibiotics as Waste, Physical, Chemical, and Enzymatical Degradation: Use of Laccases

The first traces of Tetracycline (TE) were detected in human skeletons from Sudan and Egypt, finding that it may be related to the diet of the time, the use of some dyes, and the use of soils loaded with microorganisms, such as Streptomyces spp., among other microorganisms capable of producing antibiotics. However, most people only recognise authors dating between 1904 and 1940, such as Ehrlich, Domagk, and Fleming. Antibiotics are the therapeutic option for countless infections treatment; unfortunately, they are the second most common group of drugs in wastewaters worldwide due to failures in industrial waste treatments (pharmaceutics, hospitals, senior residences) and their irrational use in humans and animals. The main antibiotics problem lies in delivered and non-prescribed human use, use in livestock as growth promoters, and crop cultivation as biocides (regulated activities that have not complied in some places). This practice has led to the toxicity of the environment as antibiotics generate eutrophication, water pollution, nutrient imbalance, and press antibiotic resistance. In addition, the removal of antibiotics is not a required process in global wastewater treatment standards. This review aims to raise awareness of the negative impact of antibiotics as residues and physical, chemical, and biological treatments for their degradation. We discuss the high cost of physical and chemical treatments, the risk of using chemicals that worsen the situation, and the fact that each antibiotic class can be transformed differently with each of these treatments and generate new compounds that could be more toxic than the original ones; also, we discuss the use of enzymes for antibiotic degradation, with emphasis on laccases.

Hazard assessment of beta-lactams: Integrating in silico and QSTR approaches with in vivo zebrafish embryo toxicity testing

Antibiotics have emerged as a well-known representative of pharmaceuticals and personal care products (PPCPs) by causing public health and environmental problems due to their potential toxicity. β-lactams are the most commonly used antibiotics in the world. This study used zebrafish embryos to evaluate the toxicity of β-lactams. The results showed that 23 β-lactam compounds induced malformation and death in a concentration-response manner. Moreover, this study established and validated quantitative structure-toxicity relationship (QSTR) models for the toxicity of β-lactams in zebrafish. These models performed well and fast in the prediction of the acute toxicity of β-lactams. Structural interpretation indicated that the β-lactam ring, the thiazolidine/dihydrothiazine rings, the side chains, and spatial configuration are the main factors responsible for the toxicity of β-lactams. The results from our previous studies and this study also revealed that the potential biological risks caused by β-lactams and their degradation products could not be ignored. This study provided important data for further environmental risk assessment of β-lactams and regulatory purposes.

Structure-dependent surface catalytic degradation of cephalosporin antibiotics on the aged polyvinyl chloride microplastics

Microplastics (MPs) have been recognized as a global concern due to their potential health effect, as MPs could adsorb and carry various pollutants in aquatic environment. In the present study, a new environmental behavior related to polyvinyl chloride microplastics (PVC-MPs) and the underlying mechanism were described. Our results showed that the photo-aged PVC-MPs could affect the transformation of cephalosporin antibiotics. For instance, the presence of altered PVC-MPs significantly accelerated the hydrolysis of cefazolin (CFZ), but exhibited negligible effect on the degradation of cephalexin (CFX). As indicated by in situ Fourier transform infrared spectra and theoretical calculations, hydrogen bonds could be formed between β-lactam carbonyl of CFZ and the oxygen-containing moieties on the aged PVC-MP surfaces. The hydrogen-bonding was able to significantly increase the positive atomic Mulliken charge on the β-lactam carbonyl carbon, thus narrowing the energy gap of CFZ hydrolysis and subsequently enhancing the disruption of β-lactam ring. While for CFX, instead of the β-lactam carbonyl, the amide amino group was involved in the hydrogen-bonding due to the structural difference. Therefore, in addition to increasing the adsorption capacity, the aged PVC-MPs could act as the catalyst to mediate the transformation of antibiotics. Our study would help improve the understanding for interactions between contaminants and MPs in natural environments.

Ryegrass (Lolium multiflorum L.) and Indian mustard (Brassica juncea L.) intercropping can improve the phytoremediation of antibiotics and antibiotic resistance genes but not heavy metals

Lolium multiflorum and Brassica juncea display phytoremediation potential for heavy metals and antibiotics pollution. However, there is limited understanding of their function in removing combined pollutants (heavy metals, antibiotics and antibiotic resistance genes (ARGs)) under different cropping patterns. Sole cropping had little effect on heavy metals, but reduced antibiotics by 2.46%-84.88% and increased ARGs by 15.96%-33.82%. Intercropping was more beneficial to soil remediation and plant accumulation of L. multiflorum, and further increased the remediation of antibiotics by 2.38%-54.40%. Members of phyla (Actinobacteria, Bacteroidetes, and Proteobacteria) were mainly responsible for most antibiotics removal. Compared with sole cropping, intercropping reduced more ARGs abundance in rhizosphere soil for L. multiflorum (20.43%) and in bulk soil for B. juncea (23.22%). Mobile genetic elements (MGEs) played a significant role in the variation of ARGs. Further, sample type showed a higher indirect negative impact on ARGs by mainly affecting soil properties and bacterial community, and the co-occurrence between the bacterial community and ARGs in bulk soil was more complex than that in rhizosphere soil. Together these results suggest that phytoremediation of combined soil pollution was positive but limited, and intercropping resulted in enhanced removal efficiency when compared with sole cropping.

Nontronite mineral clay NAu-2 as support for hematite applied as catalyst for heterogeneous photo-Fenton processes

This study describes the characterization of Nontronite, a clay mineral with high content of structural iron, before and after iron incorporation and 600 °C heat treatment. The Nontronite was classified as a mesoporous material, with high absorption in the UV-Vis range and band gap energy of 1.9 eV, indicative of the presence of superficial hematite, also verified in XRD analysis. The heat treatment promoted a structure rearrangement and the conversion of other iron phases to hematite, allowing the formation of surface irregular sites on Nontronite and facilitating the access for the decomposition of H₂O₂ into HO. Its catalytic activity in heterogeneous photo-Fenton process was evaluated during the degradation of the antibiotic sulfathiazole (STZ) and showed high activity achieving undetectable levels of STZ after 20 min under UV-LED irradiation and solar irradiation, and showing no iron leaching under controlled pH = 3. The degradation intermediates identified indicated hydroxylation as the main degradation route.

Experimental and computational study of hydrolysis and photolysis of antibiotic ceftriaxone: Degradation kinetics, pathways, and toxicity

In this work, we have experimentally and computationally investigated the process of hydrolysis and photolysis of cephalosporin antibiotics with ceftriaxone (CEF) as a model compound. The CEF hydrolysis was investigated in ultrapure and natural water, at 25 ± 1 °C and 4 ± 1 °C in the dark. It was found that CEF after 100 and 900 days at 25 ± 1°C and 4 ± 1 °C, respectively practically completely removed from ultrapure water. The CEF hydrolysis in natural water was five and three times slower at 25 ± 1 °C and 4 ± 1 °C, respectively than in ultrapure water. Further, the efficiency of direct photolysis (solar/UVA-B) and solar/H₂O₂ treatment of CEF was investigated. Under UVA-B radiation 95.6% of CEF was removed after 60 min, while for the same time of solar radiation degradation was practically not observed (only 3.2%). Also, the effects of different concentrations of H₂O₂ (0-150 mM) in the presence/absence of solar radiation were studied. The most efficient solar/H₂O₂ treatment was in the presence of 90 mM H₂O₂, whereby 66.8% of CEF was removed after 60 min (41.8% by indirect photolysis, 21.8% by H₂O₂-oxidation, and 3.2% by direct photolysis). Radial distribution functions (RDF) provided information about the distribution of water around the CEF molecule. Aside from the RDF, investigation of intramolecular noncovalent interactions and calculations of bond dissociation energies for hydrogen abstraction enabled understanding of degradation mechanism of CEF. In order to investigate sensitivity of CEF towards the radical attacks, the concept of Fukui functions was used. The structures of intermediates and degradation pathways were suggested by UHPLC-LTQ OrbiTrap MS and density functional theory calculations. Toxicity assessments showed that intermediates formed during hydrolysis exerted only mild cell growth effects in selected cell lines.

β-Lactam antibiotics and antibiotic resistance in Asian lakes and rivers: An overview of contamination, sources and detection methods

Lakes and rivers are sources of livelihood, food and water in many parts of the world. Lakes provide natural resources and valuable ecosystem services. These aquatic ecosystems are also vulnerable to known and new environmental pollutants. Emerging water contaminants are now being studied including antibiotics because of the global phenomenon on antibiotic resistance. β-Lactam antibiotics are widely used in human and animal disease prevention or treatment. The emergence of antibiotic resistance is a public health threat when bacteria become more resistant and infections consequently increase requiring treatment using last resort drugs that are more expensive. This review summarizes the key findings on the occurrence, contamination sources, and determination of β-lactam antibiotics and β-lactam antibiotic resistant bacteria and genes in the Asian lake and river waters. The current methods in the analytical measurements of β-lactam antibiotics in water involving solid-phase extraction and liquid chromatography-mass spectrometry are discussed. Also described is the determination of antibiotic resistance genes which is primarily based on a polymerase chain reaction method. To date, β-lactam antibiotics in the Asian aquatic environments are reported in the ng/L concentrations. Studies on β-lactam resistant bacteria and resistance genes were mostly conducted in China. The occurrence of these emerging contaminants is largely uncharted because many aquatic systems in the Asian region remain to be studied. Comprehensive investigations encompassing the environmental behavior of β-lactam antibiotics, emergence of resistant bacteria, transfer of resistance genes to non-resistant bacteria, multiple antibiotic resistance, and effects on aquatic biota are needed particularly in rivers and lakes that are eventual sinks of these water contaminants.

Improving removal of antibiotics in constructed wetland treatment systems based on key design and operational parameters: A review

While removal of antibiotics in constructed wetland treatment systems (CWTS) has been described previously, few studies examined the synergistic effect of multiple design and operational parameters for improving antibiotic removal. This review describes the removal of 35 widely used antibiotics in CWTS covering the most common design parameters (flow configuration, substrate, plants) and operational parameters (hydraulic retention time/hydraulic loading rates, feeding mode, aeration, influent quality), and discusses how to tailor those parameters for improving antibiotic removal based on complex removal mechanisms. To achieve an overall efficient removal of antibiotics in CWTS, our principal component analysis indicated that optimization of flow configuration, selection of plant species, and compensation for low microbial activity at low temperature is the priority strategy. For instance, a hybrid-CWTS that integrates the advantages of horizontal and vertical subsurface flow CWTS may provide a sufficient removal performance at reasonable cost and footprint. To target removal of specific antibiotics, future research should focus on elucidating key mechanisms for their removal to guide optimization of the design and operational parameters. More efficient experimental designs (e.g., the Box-Behnken design) are recommended to determine the settings of the key parameters. These improvements would promote development of this environmentally friendly and cost-efficient technology for antibiotic removal.

A Model to Investigate the Impact of Farm Practice on Antimicrobial Resistance in UK Dairy Farms

The ecological and human health impact of antibiotic use and the related antimicrobial resistance (AMR) in animal husbandry is poorly understood. In many countries, there has been considerable pressure to reduce overall antibiotic use in agriculture or to cease or minimise use of human critical antibiotics. However, a more nuanced approach would consider the differential impact of use of different antibiotic classes; for example, it is not known whether reduced use of bacteriostatic or bacteriolytic classes of antibiotics would be of greater value. We have developed an ordinary differential equation model to investigate the effects of farm practice on the spread and persistence of AMR in the dairy slurry tank environment. We model the chemical fate of bacteriolytic and bacteriostatic antibiotics within the slurry and their effect on a population of bacteria, which are capable of resistance to both types of antibiotic. Through our analysis, we find that changing the rate at which a slurry tank is emptied may delay the proliferation of multidrug-resistant bacteria by up to five years depending on conditions. This finding has implications for farming practice and the policies that influence waste management practices. We also find that, within our model, the development of multidrug resistance is particularly sensitive to the use of bacteriolytic antibiotics, rather than bacteriostatic antibiotics, and this may be cause for controlling the usage of bacteriolytic antibiotics in agriculture.

A quinine-based quaternized polymer: a potent scaffold with bactericidal properties without resistance

A quinine-based quaternized polymer confers bactericidal efficacy by destroying the membrane structure of bacteria.

Acute Oral Toxicity and Acute Intraperitoneal Studies of Thermally Treated Ceftiofur

Ceftiofur (CEF) is a third-generation and the first animal-specific cephalosporin that is widely used in animal husbandry. As a heat-labile antibiotic, the cytotoxicity of CEF after thermal treatment has been reported. This study seeks to investigate the potential toxicity of thermally treated CEF (TTC) in vivo based on acute oral toxicity studies and acute intraperitoneal studies in mice. Our data indicated that TTC exhibited significant increased toxicity in mice compared with CEF. TTC resulted in weight gain, hypercholesterolemia, hepatocyte steatosis and hepatocyte mitochondrial damage, and downregulated β-oxidation-related genes in mice in acute oral toxicity studies. In addition, TTC caused acute pulmonary congestion, increased levels of reactive oxygen species (ROS), prolonged coagulation time, and even death in mice in acute intraperitoneal toxicity studies. Our data showed that thermal treatment enhanced the toxicity of CEF in vivo. Lung and liver are the main target organs in the pathological damage process mediated by TTC. These findings suggested that residual CEF in animal-derived food may represent a potential food safety risk and pose a potential threat to human health.

Development of a new SLE-SPE-HPLC-MS/MS method for the determination of selected antibiotics and their transformation products in anthropogenically altered solid environmental matrices

The presence of antibiotic residues, their bioactive metabolites and other transformation products in the environment may adversely affect the organisms that live in the environment and may also contribute to increasing the antibiotic resistance of bacteria. It is particularly difficult to determine the types of contaminants in solid samples, in particular, those that are anthropogenically changed, e.g., as a result of controlled biochemical processes. Therefore, the aim of this research was to develop of a new method for the determination of twelve antibiotics belonging to different groups, such as penicillins, sulfonamides, tetracyclines, quinolones, imidazoles and cefalosporins, in digested manure and activated sludge samples, which were used as examples of anthropogenically altered environmental solid samples. The analyses were performed using high performance liquid chromatography coupled with tandem mass spectrometry (HPLC-MS/MS). The solid-liquid extraction (SLE) method to isolate analytes from digested manure and activated sludge was developed and optimized, the same as clean-up procedure followed by solid phase extraction (SPE). The recovery ranged from 45 to 85%. Finally, the validated method was applied to the determination of the selected antibiotics in manure and activated sludge samples after an anaerobic digestion process.. An additional aim of the study was to verify whether the developed method allows simultaneous detection of transformation products of the studied antibiotics in solid samples. The study showed that by optimizing the analysis conditions, it is possible to simultaneously determine the selected antibiotics and their transformation products (including their epimeric forms), which can significantly improve the ability to control the efficiency of the biological processes used in this area. In practice, this means that the developed methodology may be particularly useful in the context of research and other works related to the anaerobic digestion of activated sludge, manure or other solid substrates of environmental origin.

Degradation of aqueous cefotaxime in electro-oxidation - electro-Fenton -persulfate system with Ti/CNT/SnO2-Sb-Er anode and Ni@NCNT cathode

Due to the potential threatening of antibiotics in aqueous environment, a novel electro-oxidation (EO) - electro-Fenton (EF) -persulfate (PS) system with the addition of peroxydisulfate and Fe²⁺ was installed for the degradation of cefotaxime. Ti/CNT/SnO₂-Sb-Er with an ultra-high oxygen evolution potential (2.15 V) and enhanced electrocatalytic surface area was adopted as anode. The OH production and electrode stability test demonstrated great improvement in the electrochemical performances. Ni@NCNT cathode was tested with higher H₂O₂ generation by the presence of nitrogen functionalities due to the acceleration of electron transfer of O₂ reduction. Experiment results indicated CNT and ErO₂ modification increased the molecular and TOC removal of cefotaxime. Coupling processes of EO-EF and EO-PS both resulted in shorter electrolysis time for complete cefotaxime removal, however, the mineralization ability of EO-PS process was lower than EO-EF, which might result from the immediate vanishing of PS. Thus, a further improved treatment EO-EF-PS system achieved an 81.6% TOC removal towards 50 mg L^-1 cefotaxime after 4 h electrolysis, under the optimal working condition Fe²⁺ = PS = 1 mM. The influence of current density and initial concentration on the performance of all processes was assessed. Methanol and tert-butanol were added in the system as OH and SO₄^- scavengers, which illustrating the mechanism of EO-EF-PS oxidizing process was the result of the two free radicals. Major intermediates were deduced and the degradation pathway of cefotaxime was analyzed. This research provides a potential coupling process with high antibiotic removal efficiency and effective materials for practical uses.

Cytotoxicity and degradation product identification of thermally treated ceftiofur

Ceftiofur (CEF) is a cephalosporin antibiotic and is a commonly used drug in animal food production. As a heat-labile compound, the residual CEF toxicity after thermal treatment has rarely been reported. This study was to investigate the potential toxicity of thermally treated CEF and determine the toxic components. By cytotoxicity tests and liquid chromatography-mass spectrometry (LC-MS) assays, the cytotoxicity of the thermally treated CEF (TTC) and the components of TTC was identified, respectively. Our results showed that TTC exhibited significantly increased toxicity compared with CEF towards LO2 cells by inducing apoptosis. Through LC-MS assays, we identified that the toxic compound of TTC was CEF-aldehyde (CEF-1). The IC₅₀ value of CEF-1 on LO2 cells treated for 24 h was 573.1 μg mL⁻¹, approximately 5.3 times lower than CEF (3052.0 μg mL⁻¹) and 3.4 times lower than TTC (1967.0 μg mL⁻¹). Moreover, we found that CEF-1 was also present in thermally treated desfuroylceftiofur (DFC), the primary metabolite of CEF, indicating that residual CEF or DFC could produce CEF-1 during the heating process. These findings suggest that CEF-1 is a newly identified toxic compound, and CEF-1 may pose a potential threat to food safety or public health.

Ceftiofur (CEF) is a cephalosporin antibiotic and is a commonly used drug in animal food production. This study investigated the cytotoxicity of thermally treated CEF.

Zoonosis: An Emerging Link to Antibiotic Resistance Under "One Health Approach"

Current scenario in communicable diseases has generated new era that identifies the "One health" approach to understand the sharing and management of etiological agents with its impact on ecosystem. Under this context the relevance of zoonotic diseases generates major concern. The indiscriminate and higher use of antibiotics in animal husbandry creates substantial pressure on the gut microbiome for development of resistance due to shorter generation time and high density. Thus, gut works as a bioreactor for the breeding of ARBs in this scenario and are continuously released in different niches. These ARBs transfer resistance genes among native flora through horizontal gene transfer events, vectors and quorum sensing. About 60% of infectious diseases in human are caused by zoonotic pathogens have potential to carry ARGs which could be transmitted to humans. The well documented zoonotic diseases are anthrax cause by Bacillus anthracis, bovine tuberculosis by Mycobacterium tuberculosis, brucellosis by Brucella abortus, and hemorrhagic colitis by Escherichia coli. Similarly, most of the antibiotics are not completely metabolized and released in unmetabolized forms which enters the food chain and affect various ecological niches through bioaccumulation. The persistence period of antibiotics ranges from < 1 to 3466 days in environment. The consequences of misusing the antibiotic in livestock and their fate in various ecological niches have been discussed in this review. Further the light sheds on antibiotics persistence and it biodegradation through different abiotic and biotic approaches in environment. The knowledge on personnel hygiene and strong surveillance system for zoonotic disease including ARBs transmission, prevention and control measures should be established to regulate the spread of AMR in the environment and subsequently to the human being through a food web.

Advanced Oxidation Processes for the Removal of Antibiotics from Water. An Overview

In this work, the application of advanced oxidation processes (AOPs) for the removal of antibiotics from water has been reviewed. The present concern about water has been exposed, and the main problems derived from the presence of emerging pollutants have been analyzed. Photolysis processes, ozone-based AOPs including ozonation, O3/UV, O3/H2O2, and O3/H2O2/UV, hydrogen peroxide-based methods (i.e., H2O2/UV, Fenton, Fenton-like, hetero-Fenton, and photo-Fenton), heterogeneous photocatalysis (TiO2/UV and TiO2/H2O2/UV systems), and sonochemical and electrooxidative AOPs have been reviewed. The main challenges and prospects of AOPs, as well as some recommendations for the improvement of AOPs aimed at the removal of antibiotics from wastewaters, are pointed out.

Effective removal of cefazolin from hospital wastewater by the electrocoagulation process

The present study evaluated the treatment of hospital wastewater by the electrocoagulation process using aluminum and iron electrodes. The effects of pH, voltage and reaction time on the removal efficiencies of the antibiotic cefazolin, chemical oxygen demand (COD) and turbidity were investigated. The results showed that by increasing reaction time and input voltage, the removal efficiency of pollutants was increased. The highest removal efficiency of cefazolin, COD, and turbidity occurred at neutral pH, which may have been related to the formation of aluminum hydroxide (Al(OH)₃) flocs through the combination of aluminum released from the surface of the electrode and the hydroxide ions present in the solution. The conductivity of the treated wastewater at neutral to alkaline pH decreased compared to acidic pH, which may have been due to the adsorption of anions and cations from the solution by the Al(OH)₃ flocs. The electrode and energy consumption in the present study was higher than in other studies, which may have been due to the high concentration of COD in and the turbidity of the solution.

An overview of cephalosporin antibiotics as emerging contaminants: a serious environmental concern

Antibiotics have been categorized as emerging pollutants due to their indiscriminate usage, continuous input and persistence in various environmental matrices even at lower concentrations. Cephalosporins are the broad-spectrum antibiotics of β-lactam family. Owing to its enormous production and consumption, it is reported as the second most prescribed antibiotic classes in Europe. The cephalosporin wastewater contains toxic organic compounds, inorganic salts, and active pharmaceutical ingredients (API) which pose a potential threat to the organisms in the environment. Therefore, removal of cephalosporin antibiotics from the environment has become mandatory as it contributes to increase in the level of chemical oxygen demand (COD), causing toxicity of the effluent and production of cephalosporin-resistant microbes. So far, several processes have been reported for degradation/removal of cephalosporins from the environment. A number of individual studies have been published within the last decade covering the various aspects of antibiotics. However, a detailed compilation on cephalosporin antibiotics as an emerging environmental contaminant is still lacking. Hence, the present review intends to highlight the current ecological scenario with respect to distribution, toxicity, degradation, various remediation technologies, and the regulatory aspects concerning cephalosporins. The latest successful technologies for cephalosporin degradation/removal discussed in this review will help researchers for a better understanding of the nature and persistence of cephalosporins in the environment along with the risks associated with their existence. The research thrust discussed in this review will also evoke new technologies to be attempted by the future researchers to develop sustainable options to remediate cephalosporin-contaminated environments.

Veterinary pharmaceutical residues in water resources and tap water in an intensive husbandry area in France

In intensive livestock areas, veterinary pharmaceutical residues (VPRs) can occur in water resources, but also in tap water because treatment processes are not designed to remove these contaminants. The main objective of this study is to assess the occurrence of VPRs in water resources and tap waters in Brittany. As several identical compounds are used in both veterinary and human medicine, a toolbox (stanols and pharmaceuticals) is used to help determine the origin of contamination in the case of mixed-use molecules. Water resources samples were collected from 25 sites (23 surface waters and two groundwaters) used for tap water production and located in watersheds considered as sensitive due to intensive husbandry activities. Samples were also taken at 23 corresponding tap water sites. A list of 38 VPRs of interest was analyzed. In water resources, at least one VPR was quantified in 32% of the samples. 17 different VPRs were quantified, including antibiotics, antiparasitic drugs and anti-inflammatory drugs. Concentration levels ranged between 5 ng/L and 2946 ng/L. Mixed-use pharmaceuticals were quantified in twelve samples of water resources and among these samples nine had a mixed overall fecal contamination. In the context of this large-scale study, it appeared difficult to determine precisely the factors impacting the occurrence of VPRs. VPRs were quantified in 20% of the tap water samples. Twelve VPRs were quantified, including ten compounds exclusively used in veterinary medicine and two mixed-use compounds. Concentration levels are inferior to 40 ng/L for all compounds, with the exception of the antibiotic florfenicol which was quantified at 159 ng/L and 211 ng/L. The population of Brittany may therefore be exposed to these contaminants through tap water. These observations should be put into perspective with the detection frequencies per compound which are all below 10% in both water resources and tap water.

Effect of environmental factors on the oxidative transformation of cephalosporin antibiotics by manganese dioxides

This study aimed to explore the oxidation and transformation of the cephalosporins cefotaxime (CTX), cephalexin (CFX), cephradine (CFD), cephapirin (CFP) and cefazolin (CFZ) by δ-MnO2. The results showed that the MnO2 oxidation rate was promoted by environmental factors such as higher MnO2 loading, lower initial cephalosporin concentration and lower solution pH. The inhibitory effect occurred in the presence of dissolved organic matter and dissolved cations (inhibitory capacity: Mn2+ > Ca2+ > Mg2+ > Fe3+). Total organic carbon analysis indicated that the transformation byproducts of the cephalosporins are less reactive and persistent under MnO2 oxidation. Twelve transformation byproducts (9 CFP byproducts and 3 CTX byproducts) were identified, and two oxidative transformation pathways were proposed: one occurred in the cephem for CFP, and the other occurred at the substituent at the amine position for CTX. The effect of solar light on the oxidation of the five cephalosporin antibiotics by δ-MnO2 was also investigated, and the results indicated that the initial dissolution rate of δ-MnO2 under sunlight was approximately eight times faster than that in the dark in the presence of CFP.

Degradation of cefradine in alga-containing water environment: a mechanism and kinetic study

Large quantities of antibiotics are manufactured, used, and eventually discharged into alga-containing water environment as prototypes, by-products, or transformation products. Different activities of Chlamydomonas reinhardtii toward cefradine (CFD) were studied, and the results indicated that CFD is resistant (removal rate of 5.45-14.72%) in simulated natural water environment. Cefradine was mainly removed by hydrolysis, adsorption, desorption, photodecarboxylation, and photoisomerization. The effects of C. reinhardtii density, initial solution pH, and different light sources on CFD removal efficiency were investigated. The optimum conditions occurred at a density of algae 10 × 10⁴ cells/mL, a solution pH of 9.0, and the ultraviolet (UV) light. Additionally, the removal kinetics under 16 different conditions was explored. The results showed that the removal of CFD fits well with a pseudo-first-order kinetic, and the half-life times are from 0.8 to 261.6 days. This study summarizes the CFD removal mechanisms in alga-containing water environment, highlights the important role played by light irradiation in eliminating CFD, and obtains the important kinetic data on CFD removal.

Veterinary pharmaceutical residues from natural water to tap water: Sales, occurrence and fate

Veterinary pharmaceuticals (VPs) increasingly used in animal husbandry have led to their presence in aquatic environments -surface water (SW) or groundwater (GW) - and even in tap water. This review focuses on studies from 2007 to 2017. Sixty-eight different veterinary pharmaceutical residues (VPRs) have been quantified worldwide in natural waters at concentrations ranging from nanograms per liter (ng L^-1) to several micrograms per liter (μg L^-1). An extensive up-to-date on sales and tonnages of VPs worldwide has been performed. Tetracyclines (TCs) antibiotics are the most sold veterinary pharmaceuticals worldwide. An overview of VPRs degradation pathways in natural waters is provided. VPRs can be degraded or transformed by biodegradation, hydrolysis or photolysis. Photo-degradation appears to be the major degradation pathway in SW. This review then reports occurrences of VPRs found in tap water, and presents data on VPRs removal in drinking water treatment plants (DWTPs) at each step of the process. VPRs have been quantified in tap water at ng L^-1 concentration levels in four studies of the eleven studies dealing with VPRs occurrence in tap water. Overall removals of VPRs in DWTPs generally exceed 90% and advanced treatment processes (oxidation processes, adsorption on activated carbon, membrane filtration) greatly contribute to these removals. However, studies performed on full-scale DWTPs are scarce. A large majority of fate studies in DWTPs have been conducted under laboratory at environmentally irrelevant conditions (high concentration of VPRs (mg L^-1), use of deionized water instead of natural water, high concentration of oxidant, high contact time etc.). Also, studies on VPRs occurrence and fate in tap water focus on antibiotics. There is a scientific gap on the occurrence and fate of antiparatic drugs in tap waters.

Investigating the environmental risks from the use of spray-dried cephalosporin mycelial dreg (CMD) as a soil amendment

Cephalosporin mycelial dreg (CMD) is a by-product of the pharmaceutical industry. Spray-drying is widely used for the dewatering process prior to the application of CMD as a soil amendment. However, the potential environmental behaviors and risks of spray-dried CMD amendment remain unclear. Here, a lab-scale incubation experiment was conducted to investigate the salinity, phytotoxicity, introduced antibiotics, heavy metals and the potential impacts of resistance genes in CMD-amended soil. Spray-dried CMD amendment generally increased soil salinity and only high dosed soils showed phytotoxic effects at the end of the incubation period, implying the physiological damage to plant growth. The introduced antibiotics quickly degraded over time, indicating a relatively low environmental persistence. Heavy metal slightly increased in soil receiving spray-dried CMD, and regulations should be developed to avoid metal accumulation. A decreased diversity and distinct patterns of β-lactam resistance genes as well as a dose-effect of their enrichment were observed in CMD-amended soil, which might be partially explained by the specific metals and introduced antibiotics. Antibiotic resistance genes in soil may be a valuable tool for evaluating the environmental risk associated with use of CMD as a soil amendment.

Cephalosporin antibiotics in the aquatic environment: A critical review of occurrence, fate, ecotoxicity and removal technologies

Due to their widespread occurrence in the aquatic environment, human and veterinary cephalosporin antibiotics have been studied as water pollutants. In order to characterize environmental risks of this compound class, this review evaluates relevant data about physicochemical properties, occurrence, ecotoxicity and degradation of cephalosporins. Although application of cephalosporins is rather low compared to other antibiotics and their environmental life-time is believed to be short (i.e. days), the available data is insufficient to draw conclusions on their environmental relevance. Few studies concerning the fate of cephalosporins in soil are available, while hydrolysis and photo-degradation are suggested as the main attenuation processes in the aquatic environment. Cephalosporins have been detected in different aqueous matrices in concentrations ranging from 0.30 ng L^-1 to 0.03 mg L^-1, with sewage and wastewater being the main matrices with positive findings. For wastewater treatment purposes, several technologies have been tested for the abatement of cephalosporins, including photolysis and adsorption. In most cases, the technology employed led to complete or significant removal (>95%) of parental drugs but few authors reported on cephalosporins' metabolites and transformation products. Furthermore, the present ecotoxicological data are insufficient for comprehensive ecological risk quotient calculations. Considering the total of 53 cephalosporins, effective values (EC, LC, NOAEC, NOAEL, etc.) are only available for around 30% of parental drugs and are very scarce for cyanobacteria, which is considered to be the most sensitive group of organisms to antibiotics. Furthermore, it has been demonstrated that cephalosporins' transformation products can be more toxic and more persistent than the parental drugs. Few investigations considering this possibility are available. Consequently, more effort on ecotoxicological data generation and verification of biological inactivation of cephalosporins-related products is needed. Likewise, the lack of natural depletion rates and knowledge gaps on mixture effects for cephalosporins' degradation and toxicity have to be overcome.

Changes in bacterial community structure and antibiotic resistance genes in soil in the vicinity of a pharmaceutical factory

China is the largest global producer of antibiotics. With the demand for antibiotics increasing every year, it is necessary to assess potential environmental risks and the spread of antibiotic resistance genes (ARGs) associated with antibiotic production. Here, we investigated the occurrence and distribution of ARGs in soil in the vicinity of a pharmaceutical factory. The results showed that antibiotic concentrations were under the detection limit; however, ARGs were present in soil and tended to be enriched near the factory. A significant correlation between the relative abundance of intI-1 and tetracycline ARGs implied that horizontal gene transfer might play an important role in the spread of ARGs. The occurrence of these ARGs could be the results of previous antibiotic contamination. However, the soil bacterial community structure seemed to be more affected by nutrients or other factors than by antibiotics. Overall, this study supports the viewpoint that long-term pharmaceutical activity might have a negative effect on environmental health, thus, underscoring the need to regulate antibiotic production and management.

Substructure Reactivity Affecting the Manganese Dioxide Oxidation of Cephalosporins

Cefotaxime (CTX), cephalexin (CFX), cephradine (CFD), cephapirin (CFP), and cefazolin (CFZ) were selected as target cephalosporin antibiotics to study their oxidative transformation by δ-MnO₂. Although they all have the same core structure (7-aminodesacetoxycephalosporanic acid), very different MnO₂ oxidation rates were observed at pH 4 (the initial reaction rate constant k_init ranged from 0.014 to 2.6 h^-1). An extensive investigation of the substructure compounds and byproduct analysis revealed that the oxidation mainly occurred at the following two sites on the core structure: (1) the sulfur atom in the cephem ring and (2) the carbon-carbon double bond (C═C) and its proximal carboxylic acid group. In the case of (2), when there is an acetyloxymethyl group at the C-3 position of the core structure, the formation of the keto-sulfone byproducts was inhibited. The overall results indicated that a substituent at the C-3 position could stabilize the core structure, which would result in a decrease in the oxidation rate; however, a substituent at the amine position of the core structure might affect the overall degradation rate of the cephalosporin, depending on its reactivity with MnO₂. Thus, the apparent reaction rates varied widely in the trend of CTX > CFP > CFD > core structure ≈ CFX > CFZ. The mechanistic elucidation can also help explain the degradation rates of cephalosporin antibiotics in other oxidation processes.

Use of the PCR-DGGE Method for the Analysis of the Bacterial Community Structure in Soil Treated With the Cephalosporin Antibiotic Cefuroxime and/or Inoculated With a Multidrug-Resistant Pseudomonas putida Strain MC1

The widespread use of cefuroxime (XM) has resulted in the increase in its concentration in hospital and domestic wastewaters. Due to the limited removal of antibiotics and antibiotic-resistant genes in conventional systems, the drugs enter the surface water and soils. Moreover, the introduction of XM and/or XM-resistant bacteria into soil may cause a significant modification of the biodiversity of soil bacterial communities. Therefore, the goal of this research was to assess the genetic diversity of a bacterial community in the cefuroxime (XM1 – 1 mg/kg and XM10 – 10 mg/kg) and/or antibiotic-resistant Pseudomonas putida strain MC1 (Ps – 1.6 × 10⁷ cells/g)-treated soils as determined by the DGGE (denaturing gradient gel electrophoresis) method. The obtained data were also evaluated using a multivariate analysis and the resistance (RS)/resilience (RL) concept. Strain MC1 was isolated from raw sewage in the presence of XM and was resistant not only to this antibiotic but also to vancomycin, clindamycin and erythromycin. The DGGE patterns revealed that the XM10 and XM10+Ps treatments modified the composition of the bacterial community by the alteration of the DGGE profiles as well as a decline in the DGGE indices, in particular on days 30, 60, and 90. In turn, the XM1 and XM1+Ps or Ps treatments did not affect the values of richness and diversity of the soil bacteria members. A principal component analysis (PCA) also indicated that XM markedly changed the diversity of bacterial assemblages in the second part of the experiment. Moreover, there were differences in the RS/RL of the DGGE indices to the disturbances caused by XM and/or Ps. Considering the mean values of the RS index, the resistance was categorized in the following order: diversity (0.997) > evenness (0.993) > richness (0.970). The soil RL index was found to be negative, thus reflecting the progressing detrimental impact of XM on the genetic biodiversity of bacteria within the experiment. These results indicate that the introduction of XM at higher dosages into the soil environment may exert a potential risk for functioning of microorganism.

Base-catalyzed hydrolysis and speciation-dependent photolysis of two cephalosporin antibiotics, ceftiofur and cefapirin

Lately, special attention has been given to veterinary cephalosporin antibiotics due to their broad activity spectrum and significant consumption. Indeed, the determination of hydrolytic and photolytic kinetics provides a better comprehension of the undesired persistence of cephalosporins in aqueous matrices. In this work, the two widely used veterinary antibiotics ceftiofur (CEF) and cefapirin (CEPA) showed high instability under alkaline conditions, degrading in few minutes at pH > 11. In buffered solutions at neutral pH and natural temperature (T = 22 ± 1 °C), both drugs presented moderate stability (t½ = 3 d, CEPA and 1.4 d, CEF). Our study also demonstrated that CEPA and CEF speciation did not significantly influence the direct photolysis rates. Using a simulated water disinfection set-up (λ = 254 nm), all ionic species of CEF and CEPA presented fast and similar pseudo-first order degradation rates, k^app 0.0095 ± 0.0004 and 0.0092 ± 0.001 cm² mJ^-1, respectively. Furthermore, using surface water in hydrolysis experiments, CEF demonstrated significant matrix-dependent stability with a half-life (t½ = 14.7 d) tenfold higher than in buffered solutions. In contrast, CEPA presented a very similar hydrolysis rate in river water (t½ = 4.2 d) and a subtle faster photo-degradation rate in this same matrix (k^app 0.0128 ± 0.001 cm² mJ^-1), highlighting the importance of disinfection radiation for cephalosporin depletion in aqueous environments.

Ecotoxicity of the two veterinarian antibiotics ceftiofur and cefapirin before and after photo-transformation

The release of antibiotics into the environment may lead to deleterious effects in non-target organisms as well as pressure in antimicrobial resistance acquirement. Ceftiofur (CEF) and cefapirin (CEPA) are veterinary cephalosporins used for recurrent and economically relevant infections. Both antibiotics have been detected in aquatic environments and their fate during drinking water processing is still unknown. This work investigated the acute and chronic toxicities of CEF and CEPA towards aquatic organisms including stability tests. Complementary, the effects of water disinfection radiation (UV-C, 254nm) on ecotoxicological responses were studied. CEF and CEPA have significant decay during Daphnia magna tests, portraying half-lives (t_1/2) of 49 and 53h, respectively. During tests with green algae (Scenedesmus spec.), CEPA was more instable (t_1/2 88h) than CEF (t_1/2 267h). CEF and its presumable hydrolysis products induced deleterious effects in Daphnia magna (48h EC₅₀ 139, LC₅₀ 179 in μM), which was not observed with Scenedesmus spec. (72h NOAEC 82.5±2.5μM). In the case of CEPA, no toxic effects were observed in either test (48h EC-LC₅₀>510 and 72h NOAEC 57±6, in μM). Photolysis of CEPA resulted in toxic products, which were effective for the cladoceran but not for the green algae. On the other hand, the different radiation doses studied did not affect CEF ecotoxicity. This investigation illustrates the importance of cephalosporin hydrolysis during standard toxicity tests. Furthermore, the potential formation of species-specific toxic compounds during water processing is demonstrated, highlighting the need of further assessing toxicity of both cephalosporins and their transformation products.

Statistically optimized ceftriaxone sodium biotransformation through Achromobacter xylosoxidans strain Cef6: an unusual insight for bioremediation

The present study underlines a unique promising approach toward efficient biotransformation of ceftriaxone sodium (Ceftx), a highly frequent prescribed cephalosporin antibiotic, by a newly bacterium namely Achromobacter xylosoxidans strain Cef6 isolated from Ceftx contaminated raw materials in pharmaceutical industries. A three step sequential statistical-mathematical approach (Plackett-Burman design [PBD], Central Composite Design [CCD], and ridge-canonical analyses) was anticipated to optimize the biotransformation process. Ceftx concentration and medium volume: bottle volume ratio, two key determinants, significantly (p < 0.05) affected the process outcome deduced by regression analysis of PBD' data. CCD and ridge-canonical analyses localized the optimal levels of Ceftx concentration and medium volume: 250 ml bottle volume ratio to be 0.39 and 7.973 g Ceftx/L modified tryptic soy broth achieving Ceftx biotransformation (100%) after 39 h under aerobic static conditions at 30 °C, irrespectively deduced via HPLC analysis. Impressively, only one of five Ceftx byproducts was detected by the end of the biotransformation process. To the best of authors' knowledge, this is the first report addressing a detailed study regarding efficient biotransformation of Ceftx by single bacterium not bacterial consortium under aerobic conditions. Present data would greatly encourage applying this approach for decontamination of some Ceftx contaminated environmental sites.

Photochemical degradation of the carbapenem antibiotics imipenem and meropenem in aqueous solutions under solar radiation

This paper deals with the photochemical fate of two representative carbapenem antibiotics, namely imipenem and meropenem, in aqueous solutions under solar radiation. The analytical method employed for the determination of the target compounds in various aqueous matrices, such as ultrapure water, municipal wastewater treatment plant effluents, and river water, at environmentally relevant concentrations, was liquid chromatography coupled with hybrid triple quadrupole-linear ion trap-mass spectrometry. The absorption spectra of both compounds were measured in aqueous solutions at pH values from 6 to 8, and both compounds showed a rather strong absorption band centered at about 300 nm, while their molar absorption coefficient was in the order from 9 × 10³-10⁴ L mol^-1 cm^-1. The kinetics of the photochemical degradation of the target compounds was studied in aqueous solutions under natural solar radiation in a solar reactor with compound parabolic collectors. It was found that the photochemical degradation of both compounds at environmentally relevant concentrations follows first order kinetics and the quantum yield was in the order of 10^-3 mol einsten^-1. Several parameters were studied, such as solution pH, the presence of nitrate ions and humic acids, and the effect of water matrix. In all cases, it was found that the presence of various organic and inorganic constituents in the aqueous matrices do not contribute significantly, either positively or negatively, to the photochemical degradation of both compounds under natural solar radiation. In a final set of photolysis experiments, the effect of the level of irradiance was studied under simulated solar radiation and it was found that the quantum yield for the direct photodegradation of both compounds remained practically constant by changing the incident solar irradiance from 28 to 50 W m^-2.

Fe(III)-promoted transformation of β-lactam antibiotics: Hydrolysis vs oxidation

The widely used β-lactam antibiotics are susceptible to oxidative and/or hydrolytic degradation promoted by some metal ions (e.g., Cu(II)). Ferric ions (Fe(III)) are among the most common metal ions, but their role in the environmental transformation and fate of β-lactam antibiotics is still unknown. This study elucidates that Fe(III) can promote degradation of β-lactam antibiotics under environmental aquatic conditions. Degradation rate constants of ampicillin (AMP) linearly increased with increasing Fe(III) concentration, but were independent of AMP concentration when AMP was higher than Fe(III) concentration. Neutral pH was most favorable for Fe(III)-promoted degradation of AMP, and the promoted degradation was also significant in real surface water and wastewater matrix. Among the various β-lactam antibiotics, Fe(III)-promoted degradation of penicillins was faster than that of cephalosporins. Product analysis indicated that only two isomers of hydrolysis products were observed without detection of oxidation products. The Fe(III)-promoted degradation likely occurred via complexation of β-lactam antibiotics with carboxyl group and tertiary nitrogen, and then enhancing the hydrolytic cleavage of β-lactam ring. This study is among the first to identify the role of Fe(III) in the degradation of β-lactam antibiotics and elucidate the mechanism. The new findings indicate iron species are among the factors affecting the environmental fate of β-lactam antibiotics.

Biodegradation of the veterinary antibiotics enrofloxacin and ceftiofur and associated microbial community dynamics

Fluoroquinolones and cephalosporins are two classes of veterinary antibiotics arising as pollutants of emerging concern. In this work, the microbial degradation of two representative antibiotics of both these classes, enrofloxacin (ENR) and ceftiofur (CEF), is reported. Biodegradation of the target antibiotics was investigated by supplementing the culture medium with ENR and CEF, individually and in mixture. Microbial inocula were obtained from rhizosphere sediments of plants derived from experimental constructed wetlands designed for the treatment of livestock wastewaters contaminated with trace amounts of these antibiotics. Selected microbial inocula were acclimated during a period of 5months, where the antibiotics were supplemented every three weeks at the concentration of 1mgL^-1, using acetate as a co-substrate. After this period, the acclimated consortia were investigated for their capacity to biodegrade 2 and 3mgL^-1 of ENR and CEF. Complete removal of CEF from the inoculated culture medium was always observed within 21days, independently of its concentration or the concomitant presence of ENR. Biodegradation of ENR decreased with the increase in its concentration in the culture medium, with defluorination percentages decreasing from ca. 65 to 4%. Ciprofloxacin and norfloxacin were detected as biodegradation intermediates of ENR in the microbial cultures supplemented with this antibiotic, indicating that defluorination of at least part of ENR in these cultures is not an immediate catabolic step. Abiotic mechanisms showed high influence in the removal of CEF, affecting less ENR degradation. The acclimation process with the target antibiotics led to significant shifts in the structure and diversity of the microbial communities, predominantly selecting microorganisms belonging to the phyla Proteobacteria (e.g. Achromobacter, Variovorax and Stenotrophomonas genera) and Bacteroidetes (e.g. Dysgonomonas, Flavobacterium and Chryseobacterium genera). The results presented in this study indicate that biodegradation can be an important mechanism for the environmental removal of the tested compounds.

Occurrence of antibiotics in rural catchments

The transfer of 23 antibiotics from domestic and hospital sources was investigated in two elementary river watersheds receiving wastewater treatment plant (WWTP) discharges, in relation with the hydrological cycle and seasonal conditions. Antibiotic concentrations in the effluent of a WWTP treating wastewaters from both hospital and domestic sources (18-12 850 ng L^-1) were far higher than those from domestic sources exclusively (3-550 ng L^-1). In rivers, upstream of the WWTP discharges, fluoroquinolones only were found at low concentrations (≤10 ng L^-1). Their presence might be explained by transfer from contaminated agricultural fields located on the river banks. Immediately downstream of the WWTP discharge, antibiotic occurrence increased strongly with mean concentrations up to 1210 ng L^-1 for ofloxacin and 100% detection frequencies for vancomycin, sulfamethoxazole, trimethoprim and three fluoroquinolones. Dilution processes during high-flow periods led to concentrations 14 times lower than during low-flow periods. Downstream of the discharge, the antibiotic dissipation rate from the water column was higher for fluoroquinolones, in relation with their high sorption upon suspended matter and sediment. Only five antibiotics (vancomycin and four fluoroquinolones ciprofloxacin, norfloxacin, ofloxacin and enoxacin) were partly distributed (11%-36%) in the particulate phase. Downstream of the discharge, antibiotic contents in sediment ranged from 1700 to 3500 ng g^-1 dry weight, fluoroquinolones accounting for 97% of the total.