Analysis of tetracycline antibiotics in soil: Advances in extraction, clean-up, and quantification

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

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

Green ecofriendly electrochemical sensing platform for the sensitive determination of doxycycline

The detection of pharmaceutical compounds in extremely low concentrations remains a challenge despite recent advancements in electrochemical sensing. In this study, a green hydrothermally synthesized nickel hydroxide-graphene hybrid material was used for the point-of-care determination of the antibiotic doxycycline (DOXY), which is a promising treatment for COVID-19 and other infections. The electrochemical sensor, based on a screen-printed electrode modified with the hybrid material, was able to detect DOXY in the range of 5.1 × 10^-8 to 1.0 × 10^-4 M, with a low detection limit of 9.6 × 10^-9 M. This approach paves the way for eco-friendly and sustainable methods of nanomaterial synthesis for electrochemical analyses, particularly in point-of-care drug monitoring, and has the potential to improve access to testing platforms.

Functional substitutability of native herbivores by livestock for soil carbon stock is mediated by microbial decomposers

Grazing by large mammalian herbivores impacts climate as it can favor the size and stability of a large carbon (C) pool in the soils of grazing ecosystems. As native herbivores in the world's grasslands, steppes, and savannas are progressively being displaced by livestock, it is important to ask whether livestock can emulate the functional roles of their native counterparts. While livestock and native herbivores can have remarkable similarity in their traits, they can differ greatly in their impacts on vegetation composition which can affect soil-C. It is uncertain how these similarities and differences impact soil-C via their influence on microbial decomposers. We test competing alternative hypotheses with a replicated, long-term, landscape-level, grazing-exclusion experiment to ask whether livestock in the Trans-Himalayan ecosystem of northern India can match decadal-scale (2005-2016) soil-C stocks under native herbivores. We evaluate multiple lines of evidence from 17 variables that influence soil-C (quantity and quality of C-input from plants, microbial biomass and metabolism, microbial community composition, eDNA, veterinary antibiotics in soil), and assess their inter-relationships. Livestock and native herbivores differed in their effects on several soil microbial processes. Microbial carbon use efficiency (CUE) was 19% lower in soils under livestock. Compared to native herbivores, areas used by livestock contained 1.5 kg C m^-2 less soil-C. Structural equation models showed that alongside the effects arising from plants, livestock alter soil microbial communities which is detrimental for CUE, and ultimately also for soil-C. Supporting evidence pointed toward a link between veterinary antibiotics used on livestock, microbial communities, and soil-C. Overcoming the challenges of sequestering antibiotics to minimize their potential impacts on climate, alongside microbial rewilding under livestock, may reconcile the conflicting demands from food-security and ecosystem services. Conservation of native herbivores and alternative management of livestock is crucial for soil-C stewardship to envision and achieve natural climate solutions.

Mesocosm experiment to determine the contribution of adsorption, biodegradation, hydrolysis and photodegradation in the attenuation of antibiotics at the water sediment interface

To understand the fate of antibiotics in the aquatic environment, we need to evaluate to which extent the following processes contribute to the overall antibiotic attenuation: adsorption to river sediment, biodegradation, hydrolysis and photodegradation. A laboratory scale mesocosm experiment was conducted in 10 L reactors filled with river sediment and water. The reactors were spiked with four classes of antibiotics (fluoroquinolones, macrolides, sulfonamides, tetracyclines), as well as clindamycin and trimethoprim. The experimental-set-up was designed to study the attenuation processes in parallel in one mesocosm experiment, hence also considering synergetic effects. Our results showed that antibiotics belonging to the same class exhibited similar behavior. Adsorption was the main attenuation process for the fluoroquinolones and tetracyclines (44.4 to 80.0 %). For the sulfonamides, biodegradation was the most frequent process (50.2 to 65.1 %). Hydrolysis appeared to be significant only for tetracyclines (12.6 to 41.8 %). Photodegradation through visible light played a minor role for most of the antibiotics - fluoroquinolones, sulfonamides, and trimethoprim (0.7 to 24.7 %). The macrolides were the only class of antibiotics not affected by the studied processes and they persisted in the water phase. Based on our results, we propose to class the antibiotics in three groups according to their persistence in the water phase. Fluoroquinolones and tetracyclines were non-persistent (half-lives shorter than 11 d). Chlorotetracycline, sulfapyridine and trimethoprim showed a moderate persistence (half-lives between 12 and 35 d). Due to half-lives longer than 36 d sulfonamides and clindamycin were classified as persistent.

Improvement of Carbonyl Groups and Surface Defects in Carbon Nanotubes to Activate Peroxydisulfate for Tetracycline Degradation

Carbon nanotubes (CNTs) were considered a promising activator for persulfates due to their high electrical conductivity, large specific surface area and low toxicity. The functional groups and surface defects of CNTs could significantly affect their activation performance. In this study, CNTs with high C=O ratio and defect density (CNT-O-H) were prepared through a facile treatment of raw CNTs with HNO₃ oxidation followed by calcination at 800 °C under an argon atmosphere. X-ray photoelectron spectroscopy (XPS) and Raman results showed that the C=O proportion and defect degree (I_D/I_G) rose to 75% and 1.53, respectively. The obtained CNT-O-H possessed a superior performance towards peroxydisulfate (PDS) activation, and the degradation efficiency of tetracycline (TC) in the CNT-O-H/PDS system was increased to 75.2% from 56.2% of the raw CNTs/PDS system within 40 min. Moreover, the activity of CNT-O-H after use could be easily recovered with re-calcination. In addition, the CNT-O-H/PDS system exhibited high adaptabilities towards wide solution pH (2-10), common coexisting substances and diverse organic pollutants. Singlet oxygen (¹O₂) was confirmed to be the dominant reactive oxygen species (ROS) generated in the CNT-O-H/PDS system. It was inferred that surface C=O groups and defects of CNTs were the key site to activate PDS for TC degradation.

Source-specific ecological risks and critical source identification of PPCPs in surface water: Comparing urban and rural areas

To control the concentrations of pharmaceutical and personal care products (PPCPs) in the surface water of urban and rural areas, it is important to explore the spatial variation in source-specific ecological risks and identify critical sources. Here, we focused on 22 PPCPs found in the effluent from wastewater treatment plants and surface water in Tianjin, and source-specific risk was quantitatively apportioned combining positive matrix factorization with ecological risk assessment. Results showed that rural areas exhibited a more severe contamination level than urban areas. Medical wastewater (30.1 %) accounted for the highest proportion, while domestic sewage posed the greatest threat to aquatic ecosystems. The incidence of potential risks (RQ > 0.01) caused by domestic sewage in urban areas (88.9 %) was higher than that in rural areas (75.9 %). However, PPCP risks caused by farmland drainage, aquaculture, and livestock discharge were mainly distributed in rural areas. The critical source identified in the entire region was domestic sewage (weight, 0.36), and its weight (0.51) in urban areas was greater than that in rural areas (0.32). The impact of aquaculture (weight, 0.16) in rural areas was noteworthy. These findings may contribute to developing environmental management strategies in key areas to help alleviate PPCP contamination worldwide.

High-Titer Production of the Fungal Anhydrotetracycline, TAN-1612, in Engineered Yeasts

Antibiotic resistance is a growing global health threat, demanding urgent responses. Tetracyclines, a widely used antibiotic class, are increasingly succumbing to antibiotic resistance; generating novel analogues is therefore a top priority for public health. Fungal tetracyclines provide structural and enzymatic diversity for novel tetracycline analogue production in tractable heterologous hosts, like yeasts, to combat antibiotic-resistant pathogens. Here, we successfully engineered Saccharomyces cerevisiae (baker's yeast) and Saccharomyces boulardii (probiotic yeast) to produce the nonantibiotic fungal anhydrotetracycline, TAN-1612, in synthetic defined media─necessary for clean purifications─through heterologously expressing TAN-1612 genes mined from the fungus, Aspergillus niger ATCC 1015. This was accomplished via (i) a promoter library-based combinatorial pathway optimization of the biosynthetic TAN-1612 genes coexpressed with a putative TAN-1612 efflux pump, reducing TAN-1612 toxicity in yeasts while simultaneously increasing supernatant titers and (ii) the development of a medium-throughput UV-visible spectrophotometric assay that facilitates TAN-1612 combinatorial library screening. Through this multipronged approach, we optimized TAN-1612 production, yielding an over 450-fold increase compared to previously reported S. cerevisiae yields. TAN-1612 is an important tetracycline analogue precursor, and we thus present the first step toward generating novel tetracycline analogue therapeutics to combat current and emerging antibiotic resistance. We also report the first heterologous production of a fungal polyketide, like TAN-1612, in the probiotic S. boulardii. This highlights that engineered S. boulardii can biosynthesize complex natural products like tetracyclines, setting the stage to equip probiotic yeasts with synthetic therapeutic functionalities to generate living therapeutics or biocontrol agents for clinical and agricultural applications.

Electrochemical degradation of antibiotics using flow-through graphene sponge electrodes

Graphene sponge electrodes doped with atomic boron and nitrogen were employed for electrochemical degradation of antibiotics sulfamethoxazole, trimethoprim, ofloxacin, and erythromycin. The removal of antibiotics that displayed strong π-π interactions (i.e., ofloxacin) with reduced graphene oxide (RGO) coating was less limited by the mass transfer and removal efficiencies > 80% were observed for the investigated range of electrolyte flowrates. At the highest applied flowrate (700 LMH), increase in the anodic current significantly worsened the removal of trimethoprim and erythromycin due to the detrimental impact of the evolving gas bubbles. Increase in current at 700 LMH led to a stepwise increase in the removal efficiency of sulfamethoxazole due to its enhanced electrosorption. Electrochemical degradation was achieved via ozone, hydrogen peroxide and hydroxyl radical (^•OH). Extraction of the employed graphene sponges confirmed the degradation of the strongly adsorbing antibiotics. Identified electrochemical transformation products of erythromycin confirmed the participation of ^•OH, through N-demethylation of the dimethylamine group. In real tap water, removal efficiencies were lower for all target antibiotics. Lower electric conductivity of tap water and thus increased thickness of the electric double layer likely limited their interaction with the graphene sponge surface, in addition to the presence of low amounts of organic matter.

Determination of antibiotic residues in bovine milk by HPLC-DAD and assessment of human health risks in Northwestern Himalayan region, India

Antibiotic residues in milk affects economics of dairy industry and poses health risks to consumers. This study aimed to assess health risks associated with presence of antibiotics in 173 raw and pasteurized milk sampled from northwestern Himalayan state of India. The oxytetracycline and amoxicillin were quantitatively analyzed using validated HPLC-DAD. Methods were selective and linear (R² > 0.99) with decision limit and detection capability of 1.4 and 0.9 µg/kg and 2.5 and 1.5 µg/kg for oxytetracycline and amoxicillin, respectively. Recoveries ranged from 88-98% with relative standard deviation < 10%. Oxytetracycline and amoxicillin were detected in 8.1% and 1.2% samples, with 1.7% and 1.2% samples exceeding the tolerance limits, respectively. Health risk assessment revealed that estimated daily intakes of antibiotics through milk were lower than acceptable daily intakes (ADI). However, children might receive 9-21% of determined ADI through milk consumption only. Therefore, continuous, sub-therapeutic and long term exposures of antibiotics can pose health risk to consumers. Hence, current findings elucidate the need for vigilant monitoring of antibiotics accompanied by educational programs to farmers for adopting good husbandry practices and adherence to withdrawal periods to meet the expectations of food safety and safeguarding human health.

SUPPLEMENTARY INFORMATION

The online version of this article contains supplementary material available at (10.1007/s13197-021-04988-8).

The development of a wash-free homogeneous immunoassay method for the detection of tetracycline in environmental samples

Antibiotic residues have become the major source of environmental pollutants. In order to monitor tetracycline (TC) in the environment, we have established a highly sensitive and wash-free homogeneous time-resolved immunoassay. This analytical method was based on a rare earth chelate with excellent fluorescence properties. The cryptate organic ligand had good stability and acted as an antenna for Eu3+ excitation. In a homogeneous system, the Eu3+ cryptate complex was used as a label to bind to antibodies. Under the action of immunoaffinity, fluorescent donors and acceptors were close to each other, which induced the FRET effect to produce proportional fluorescence. Under the optimal parameters, the half-inhibitory concentration (IC50) and limit of detection (LOD, IC10) of TC were 0.4188 ng mL-1 and 0.0106 ng mL-1, respectively. The linear range (IC20-IC80) was 0.0273-9.2645 ng mL-1. With the environmental samples, the recovery rate of TC was 84.3-107.2%, and the standard deviation (RSD) was 4.6-12.9%. The results showed the good sensitivity and reliability of the method. Compared with the traditional ELISA, our method has less background interference, only one step was required without the washing procedure, and the detection result can be obtained by 30 min incubation, which improves the detection efficiency. Because of the characteristics of immunoassays, different pollutants can be monitored by changing the antibodies. This method provides an alternative path for detecting environmental pollutants and has the potential to develop into an on-site detection kit.

Insight into the effects of hydroxyl groups on the rates and pathways of tetracycline antibiotics degradation in the carbon black activated peroxydisulfate oxidation process

To investigate the effects of hydroxyl groups on the degradation of tetracycline antibiotics (TCs), three kinds of TCs [tetracycline (TC), oxytetracycline (OTC), and doxycycline (DTC)] were chosen as the target molecules and then degraded in the carbon black (CB)-activated peroxydisulfate (PDS) oxidation process. The degradation ratios of the TC, OTC, and DTC in the CB/PDS oxidation process reached 52%, 60%, and 87% within 40 min, respectively, with the degradation rate following the order of DTC > OTC > TC. According to the density functional theory calculations, these three TCs have different charge distributions, electrostatic potential distributions and average local ionization energy, which are caused by the distinct hydroxyl group position, thus contribute to the different degradation ratios and reaction rate constants. The hydrogenation of TC was slower special degradation pathway relative to those of OTC and DTC, while the decarbonylation of OTC was slower special degradation pathway relative to that of DTC, which adversely resulted in the degradation rate following the order of DTC > OTC > TC. This presentation gives a knowledge that the position and numbers of hydroxyl groups are pivotal to the degradation efficiency toward TCs.

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.

Attenuation of tetracyclines during chicken manure and bagasse co-composting: Degradation, kinetics, and artificial neural network modeling

The main objective of this study was to investigate the feasibility of using a locally abundant bulking material (bagasse) in the composting process to remove tetracycline from chicken manure in Khuzestan Province, Iran. Degradation extent and kinetic of three types of tetracycline (tetracycline hydrochloride (TCH), chlortetracycline (CTC), and oxytetracycline (OTC)) during co-composting of chicken manure and bagasse were investigated. After 56 days of incubation in the dark and room temperature, TCH, CTC, and OTC were removed up to 99.0%, 99.3%, and 99.5%, respectively. Highest Tetracyclines (TCs) removals were observed when chicken manure was composted with 14% bagasse. Both simple and availability-adjusted first-order kinetic models fitted TCH, CTC, and OTC degradation data. Half-lives estimated by both models were close together. TCH, CTC and OTC half-lives were estimated to be 8, 5, and 4 days, respectively. An artificial neural network model was developed to model TCs degradation. Artificial neural network analysis showed the relative importance of time, antibiotic type, bagasse percentage, and initial antibiotics concentration, in TCs degradation to be 80.43%, 7.95%, 6.43%, and 5.17%, respectively.

New Poly(Ionic Liquid) Based Fiber for Determination of Oxytetracycline in Milk Samples by Application of SPME-CE Technique

In this work, a procedure using solid phase microextraction in combination with capillary electrophoresis was developed for the determination of oxytetracycline in milk samples. The method involves the synthesis of poly(1-allyl-3-methyl imidazolium) chloride film on a stainless-steel bar via electropolymerization and its use as an adsorbent for oxytetracycline (OT) by an ionic exchange mechanism. The coated fiber is then immersed in milk samples for retention of oxytetracycline residues, followed by elution, drying, and reconstitution before analysis with capillary electrophoresis. The proposed method achieves a limit of detection of 70 µg L^⁻¹ with adequate precision and uncertainty, making this methodology appropriate for the determination of OT in milk samples. The method was applied to the pre-concentration and quantification of oxytetracycline in ten commercial milk samples. Two tested samples were positive for the presence of oxytetracycline but the concentration was below the maximum residue limit according to the international normative standard. The proposed methodology was evaluated according to the Eco-Scale approach, and the total score of 51 indicated that the methodology proposed is both green and acceptable despite the multi-stage character. SPME-CE methodology allows us to perform the sample pre-treatment and determination of OT in an effective and greener way, decreasing the number of steps during the analysis and the generation of waste.

Determination and distribution of pesticides and antibiotics in agricultural soils from northern China

Different types of soil samples from a typical farmland in northern China were collected and evaluated for the presence of the pesticides and antibiotics. 47 pesticides were extracted with a quick, easy, cheap, effective, rugged, and safe (QuEChERS) preparation method and cleanup with 50 mg C₁₈, while 10 antibiotics were extracted with methanol/EDTA–McIlvaine buffer solution (v/v = 1/1), then both of them were analyzed with high performance liquid chromatography-tandem mass spectrometer (HPLC-MS/MS). Total concentrations of the 47 pesticides in the soil samples ranged from not detectable (ND) to 3.8 mg kg⁻¹. The soil exhibited relatively high ecological risk for atrazine, chlorpyrifos, tebuconazole, difenoconazole, pymetrozine, and thiamethoxam, as over 1.0% of the sample concentrations exceeded 0.1 mg kg⁻¹. The residual levels of the 10 antibiotics were relatively low (ND-951.0 μg kg⁻¹). Tetracyclines exhibited a high detection rate (20.9%), with 2.8% of the soil samples exhibiting tetracyclines concentrations exceeding 100 μg kg⁻¹, implying high ecological risk. The 4 sulfonamides and 2 macrolides analyzed showed detection rates below 0.8%. Spatial changes in the distribution of pesticides and antibiotics appear to be related to land use patterns, particularly orchards and vegetable plots. The over-standard rate of pesticides and antibiotics in orchards was greater than that of vegetable plots, and grain fields had the lowest over-standard rate. These data were helpful to figure out the pollution of these pesticides and antibiotics, and provided valuable information for soil quality assessment and risk assessment.

Different types of soil samples from a typical farmland in northern China were collected and evaluated for the presence of the pesticides and antibiotics.

Pressurized liquid extraction of six tetracyclines from agricultural soils

Veterinary antibiotics used in agriculture can be introduced into the environment through land application of animal manure, accumulating in soils and groundwaters and posing a significant risk to human health and animal well-being. As the analysis of tetracyclines in soil is challenging due to their strong interaction with soil minerals and organic carbon, the objective of this study was to develop a reliable and reproducible method for quantitative analysis of chlortetracycline and oxytetracycline, and their respective metabolites in soils. A method based on pressurized liquid extraction (PLE) with in-cell clean-up was developed for the extraction of chlortetracycline and oxytetracycline and four likely metabolites from a set of four soils. Optimized conditions included a cell size of 22 mL, soil loading of 5 g, pH of 8.0, methanol:water ratio of 3:1, 50 °C, and two cycles. Soil extracts were analysed by high-performance liquid chromatography (HPLC) coupled with ion trap mass spectrometry (MS). Recoveries of seven tetracyclines from soil ranged from 41% to 110%. The limits of detection for tetracyclines were 0.08-0.3 µg g^-1 soil, and intra- and inter-day variation ranged from 0.12-0.34%. The proposed PLE method is suitable for quantification of tetracyclines in agricultural soils at typical concentrations expected in contaminated environments.

Can the pharmaceutically active compounds released in agroecosystems be considered as emerging plant stressors?

Pharmaceutically active compounds (PhACs) entering agroecosystems as a result of various human activities may be taken up by and accumulated within crop plants, with potential human health implications. Despite their extensive metabolism by a sophisticated enzyme-based detoxification system in plant cells, PhACs and their transformation products (TPs) may result in adverse effects on plants' physiology. PhACs-mediated phytotoxic effects, as well as plants' defense responses have been depicted on plants exposed to individual or low number of PhACs under controlled conditions. We highlight the need to consider the cocktails effects and synergistic interactions of PhACs present in mixtures in actual agroecosystems, towards phytotoxicity and agricultural sustainability in general. Considering PhACs as emerging plant stressors will better facilitate the understanding of their phytotoxic effects.

A new approach for the extraction of tetracyclines from soil matrices: application of the microwave-extraction technique

The widespread use of tetracyclines (TCs) in animal husbandry is associated with their constant penetration into the environment and the threat they might pose to living organisms. While the literature data on the analysis of these substances in such matrices as food, tissues, or wastewater are quite extensive, there are still only a few methods presented for the determination of these compounds in soil samples. Moreover, among the literature methods for the extraction of TCs from soil samples, microwave-assisted solvent extraction (MAE) was used only once and in combination with liquid chromatography with spectrophotometric detection (LC-UV). However, according to the EU Commission Decision 2002/657/EC, the use of LC-UV for the determination of compounds, including pharmaceuticals, in environmental samples is not sufficient. Therefore, the development and application of a sensitive and selective method using the MAE-SPE-LC-MS/MS(MRM) technique for the isolation and identification of a mixture of oxytetracycline (OTC), tetracycline (TC), and chlortetracycline (CTC) in soils is presented in our study. The credibility of this method has been confirmed with good parameters of validation. The optimal extraction conditions of three TCs using MAE techniques were to conduct double extraction for 10 min each, at 60 °C, using a mixture of ACN:McIlvaine buffer:0.1 M EDTA (2:1:1, v/v/v) and an additional cleaning of the extracts by SPE. The effectiveness of the extraction of these compounds was assessed based on two different ways (absolute recovery from 46 to 65.1% and relative recovery from 101.1 to 109.5%). Finally, the validated MAE-SPE-LC-MS/MS(MRM) method was used for the analysis of six samples from agricultural areas of northern Poland. OTC and TC, at concentrations of 11.7 and 14.5 μg kg^-1 were determined in two different samples. An assessment of risk quotients was also performed. The presented method was proven to be a useful tool in the analysis of residues of selected TCs in the soil ecosystem. Obtained data on the presence of these drugs in Polish soils is the first report for this country.

The potential implications of reclaimed wastewater reuse for irrigation on the agricultural environment: The knowns and unknowns of the fate of antibiotics and antibiotic resistant bacteria and resistance genes - A review

The use of reclaimed wastewater (RWW) for the irrigation of crops may result in the continuous exposure of the agricultural environment to antibiotics, antibiotic resistant bacteria (ARB) and antibiotic resistance genes (ARGs). In recent years, certain evidence indicate that antibiotics and resistance genes may become disseminated in agricultural soils as a result of the amendment with manure and biosolids and irrigation with RWW. Antibiotic residues and other contaminants may undergo sorption/desorption and transformation processes (both biotic and abiotic), and have the potential to affect the soil microbiota. Antibiotics found in the soil pore water (bioavailable fraction) as a result of RWW irrigation may be taken up by crop plants, bioaccumulate within plant tissues and subsequently enter the food webs; potentially resulting in detrimental public health implications. It can be also hypothesized that ARGs can spread among soil and plant-associated bacteria, a fact that may have serious human health implications. The majority of studies dealing with these environmental and social challenges related with the use of RWW for irrigation were conducted under laboratory or using, somehow, controlled conditions. This critical review discusses the state of the art on the fate of antibiotics, ARB and ARGs in agricultural environment where RWW is applied for irrigation. The implications associated with the uptake of antibiotics by plants (uptake mechanisms) and the potential risks to public health are highlighted. Additionally, knowledge gaps as well as challenges and opportunities are addressed, with the aim of boosting future research towards an enhanced understanding of the fate and implications of these contaminants of emerging concern in the agricultural environment. These are key issues in a world where the increasing water scarcity and the continuous appeal of circular economy demand answers for a long-term safe use of RWW for irrigation.

Instrument-free visual detection of tetracycline on an autocatalytic DNA machine using a caged G-quadruplex as the signal reporter

An instrument-free visual biosensor for the amplified detection of tetracycline has been successfully constructed using an autocatalytic DNA machine as the signal amplifier and a caged G-quadruplex as the signal reporter. The assay is ultrasensitive, enabling the visual detection of trace levels of tetracycline as low as 1 pM without instrumentation.

Procedures of determining organic trace compounds in municipal sewage sludge-a review

Sewage sludge is the largest by-product generated during the wastewater treatment process. Since large amounts of sludge are being produced, different ways of disposal have been introduced. One tempting option is to use it as fertilizer in agricultural fields due to its high contents of inorganic nutrients. This, however, can be limited by the amount of trace contaminants in the sewage sludge, containing a variety of microbiological pollutants and pathogens but also inorganic and organic contaminants. The bioavailability and the effects of trace contaminants on the microorganisms of soil are still largely unknown as well as their mixture effects. Therefore, there is a need to analyze the sludge to test its suitability before further use. In this article, a variety of sampling, pretreatment, extraction, and analysis methods have been reviewed. Additionally, different organic trace compounds often found in the sewage sludge and their methods of analysis have been compiled. In addition to traditional Soxhlet extraction, the most common extraction methods of organic contaminants in sludge include ultrasonic extraction (USE), supercritical fluid extraction (SFE), microwave-assisted extraction (MAE), and pressurized liquid extraction (PLE) followed by instrumental analysis based on gas or liquid chromatography and mass spectrometry.

Tetracyclines metal complexation: Significance and fate of mutual existence in the environment

Concern over tetracyclines (TCs) complexation with metals in the environment is growing as a new class of emerging contaminants. TCs exist as a different net charged species depending on their dissociation constants, pH and the surrounding environment. One of the key concerns about TCs is its strong tendency to interact with various metal ions and form metal complexes. Moreover, co-existence of TCs and metals in the environment and their interactions has shown increased antibiotic resistance. Despite extensive research on TCs complexation, investigations on their antibiotic efficiency and pharmacological profile in bacteria have been limited. In addition, the current knowledge on TCs metal complexation, their fate and risk assessment in the environment are inadequate to obtain a clear understanding of their consequences on living systems. This indicates that vital and comprehensive studies on TCs-metal complexation, especially towards growing antibiotic resistance trends are required. This review summarizes the role of TCs metal complexation on the development of antibiotic resistance. Furthermore, impact of metal complexation on degradation, toxicity and the fate of TCs in the environment are discussed and future recommendations have been made.

Impact of Veterinary Pharmaceuticals on the Agricultural Environment: A Re-inspection

The use of veterinary pharmaceuticals (VPs) is a result of growing animal production. Manure, a great crop fertilizer, contains a significant amount of VPs. The investigation of VPs in manure is prevalent, because of the potential risk for environmental organisms, as well as human health. A re-evaluation of the impact of veterinary pharmaceuticals on the agricultural environment is needed, even though several publications appear every year. The aim of this review was to collate the data from fields investigated for the presence of VPs as an inevitable component of manure. Data on VP concentrations in manure, soils, groundwater and plants were collected from the literature. All of this was connected with biotic and abiotic degradation, leaching and plant uptake. The data showed that the sorption of VPs into soil particles is a process which decreases the negative impact of VPs on the microbial community, the pollution of groundwater, and plant uptake. What was evident was that most of the data came from experiments conducted under conditions different from those in the environment, resulting in an overestimation of data (especially in the case of leaching). The general conclusion is that the application of manure on crop fields leads to a negligible risk for plants, bacteria, and finally humans, but in future every group of compounds needs to be investigated separately, because of the high divergence of properties.

Enantiomeric selectivity in adsorption of chiral β-blockers on sludge

Adsorption of weakly basic compounds by sludge is poorly understood, although it has important implications on the distribution and fate of such micropollutants in wastewater effluent and sludge. Additionally, many of these compounds are chiral, and it is likely that their interactions with sludge is stereoselective and that the process may be further modified by surfactants that coexist in these systems. Adsorption of (R) and (S)-enantiomers of five commonly used β-blockers, i.e., acebutolol, atenolol, metoprolol, pindolol and propranolol, on sludge was characterized through batch experiments. Stereoselectivity in adsorption increased with decreases in hydrophobicity of the β-blockers. The enantiomeric fraction (EF) of the amount of acebutolol, atenolol and metoprolol sorbed on sludge were 0.27, 0.55 and 0.32, respectively. Thus, Kd values of the (S)-enantiomers of acebutolol and metoprolol were approximately twice that of the (R)-enantiomer, that is, 109 ± 11 and 57 ± 8 L/kg compared to 52 ± 13 and 22 ± 8 L/kg, respectively. There was no statistically significant difference in Kd values of the enantiomers of pindolol and propranolol, suggesting stereoselectivity in adsorption was likely driven by specific polar interactions rather than hydrophobic interactions. The EF value of atenolol decreased from 0.55 ± 0.03 to 0.44 ± 0.04 after modifying the sludge with Triton X 100. These results suggested that surfactants altered adsorption of β-blockers to sludge, likely by forming ion pair complexes that promote hydrophobic interactions with the solid surfaces.

Antimicrobial Resistance in Agriculture

In this article, the current knowledge and knowledge gaps in the emergence and spread of antimicrobial resistance (AMR) in livestock and plants and importance in terms of animal and human health are discussed. Some recommendations are provided for generation of the data required in order to develop risk assessments for AMR within agriculture and for risks through the food chain to animals and humans.

Enhancing Extraction and Detection of Veterinary Antibiotics in Solid and Liquid Fractions of Manure

Analysis of veterinary antibiotics in separated liquid and solid fractions of animal manures is vital because of wide variations in the composition of agriculturally applied manure. Differentiation of antibiotic concentrations is important between liquid and solid manures, as their sorption onto the solid fraction depends on physicochemical properties of each antibiotic and manure composition (e.g., organic content, pH) and because each fraction may be treated and reused differently. Here, an efficient and sensitive method for the analysis of 22 veterinary antibiotics in the liquid and solid fractions of manure is reported. Tetracycline (TC), macrolide, and sulfonamide antibiotics were extracted from liquid manure by liquid-liquid extraction (LLE) with methanol following acidification with acetic acid. Extraction from solids was performed by sonication with acetonitrile, methanol, and 0.1 M EDTA-McIlvaine buffer. Cleanup of extracts was achieved by solid-phase extraction with hydrophilic-lipophilic balance (HLB) cartridges or tandem amino (NH2) and HLB cartridges. Quantification of antibiotics was performed by liquid chromatography-tandem mass spectrometry (LC-MS/MS) under wrong-way-round (WWR) ionization for sulfonamides and TCs and right-way-round ionization for macrolides. Recoveries of 58 to 94.7% and 62 to 94.3% were obtained in liquid and solid manure, respectively. Method detection limits range from 1.2 to 12 ng L and 0.5 to 7.9 μg kg dry wt. in liquids and solids, respectively. This method allows for extraction and analysis of both mobile antibiotics in liquid phase and hydrophobic antibiotics adsorbed on the solids. Without separate analysis, antibiotic concentrations may be improperly estimated by analyzing whole manure, as reported in many studies to date.

Fractionation and analysis of veterinary antibiotics and their related degradation products in agricultural soils and drainage waters following swine manure amendment

The fate of antimicrobial active compound residues in the environment, and especially antibiotics used in swine husbandry are of particular interest for their potential toxicity and contribution to antibiotic resistance. The presence of relatively high concentrations of bioactive compounds has been reported in agricultural areas but few information is available on their degradation products. Veterinary antibiotics reach terrestrial environments through many routes, including application of swine manure to soils. The objectives of this project were first, to develop an analytical method able to quantify and identify veterinary antibiotics and their degradation products in manure, soil and water samples; and second, to study the distribution of these target compounds in soils and drainage waters. A brief evaluation of their potential toxicity in the environment was also made. In order to achieve these objectives, liquid chromatography coupled to high-resolution mass spectrometry was used for its ability to quantify contaminants with sensitivity and selectivity, and its capacity to identify degradation products. Samples of manure, soil and water came from a long-term experimental site where swine manure containing veterinary antibiotics has been applied for many years. In this study, tetracycline antibiotics were found at several hundred μg L(-1) in the swine manure slurry used for fertilization, several hundred of ng L(-1) in drainage waters and several ng g(-1) in soils, while degradation products were sometimes found at concentrations higher than the parent compounds.

Effects of soil texture and drought stress on the uptake of antibiotics and the internalization of Salmonella in lettuce following wastewater irrigation

Treated wastewater is expected to be increasingly used as an alternative source of irrigation water in areas facing fresh water scarcity. Understanding the behaviors of contaminants from wastewater in soil and plants following irrigation is critical to assess and manage the risks associated with wastewater irrigation. The objective of this study was to evaluate the effects of soil texture and drought stress on the uptake of antibiotics and the internalization of human pathogens into lettuce through root uptake following wastewater irrigation. Lettuce grown in three soils with variability in soil texture (loam, sandy loam, and sand) and under different levels of water stress (no drought control, mild drought, and severe drought) were irrigated with synthetic wastewater containing three antibiotics (sulfamethoxazole, lincomycin and oxytetracycline) and one Salmonella strain a single time prior to harvest. Antibiotic uptake in lettuce was compound-specific and generally low. Only sulfamethoxazole was detected in lettuce with increasing uptake corresponding to increasing sand content in soil. Increased drought stress resulted in increased uptake of lincomycin and decreased uptake of oxytetracycline and sulfamethoxazole. The internalization of Salmonella was highly dependent on the concentration of the pathogen in irrigation water. Irrigation water containing 5 Log CFU/mL Salmonella resulted in limited incidence of internalization. When irrigation water contained 8 Log CFU/mL Salmonella, the internalization frequency was significantly higher in lettuce grown in sand than in loam (p = 0.009), and was significantly higher in lettuce exposed to severe drought than in unstressed lettuce (p = 0.049). This work demonstrated how environmental factors affected the risk of contaminant uptake by food crops following wastewater irrigation.

Variable Temperature Infrared Spectroscopy Investigations of Benzoic Acid Desorption from Sodium and Calcium Montmorillonite Clays

Processes involved in thermal desorption of benzoic acid from sodium and calcium montmorillonite clays are investigated by using variable temperature diffuse reflection Fourier transform infrared spectroscopy (DRIFTS). By monitoring the temperature dependence of infrared absorbance bands while heating samples, subtle changes in molecular vibrations are detected and employed to characterize specific benzoic acid adsorption sites. Abrupt changes in benzoic acid adsorption site properties occur for both clay samples at about 125 °C. Difference spectra absorbance band frequency variations indicate that adsorbed benzoic acid interacts with interlayer cations through water bridges and that these interactions can be disrupted by the presence of organic anions, in particular, benzoate.

Assessment of oxytetracycline and tetracycline antibiotics in manure samples in different cities of Khuzestan Province, Iran

Tetracyclines (TCs), a class of antibiotics with a broad spectrum, are the most frequently used antibiotics in animal production. The major concern is that the widespread use of the antibiotics may lead to the emergence of new strains of bacteria that are resistant to these antibiotics. The objective of this study was to determine the residual levels of oxytetracycline and tetracycline in 80 animal manure samples that were collected from the livestock and poultry feedlots in Khuzestan Province. The residual levels of the antibiotics in the samples were extracted by using solid-phase extraction (SPE) method and subsequently were measured by liquid chromatography. Recoveries from the spiked poultry manure samples ranged from 65 to 113% for tetracycline and 86 to 132% for oxytetracycline. Relative standard deviations of the recoveries were less than 5.7% within the same day. Method detection limit (MDL) measured for oxytetracycline and tetracycline in the manure were 0.011 and 0.01 mg/kg, respectively. Analysis of the collected 50 chickens and 30 cow manure samples showed that the highest concentration of tetracycline was related to Behbahan City (5.36 mg/kg) and the lowest concentration was detected for Ramhormoz (0.05 mg/kg). The highest and lowest concentrations of oxytetracycline were respectively observed for Behbahan (13.77 mg/kg) and Ramhormoz (0.047 mg/kg). Based on the results, in chicken manure, there was significant statistical difference between the residual TC concentrations among five cities (p(value) < 0.05). However, no significant relationship was observed between oxytetracyclin (OTC) residual concentrations among five cities (p(value) > 0.05).

Assessment of the Impact of Potential Tetracycline Exposure on the Phenotype of Aedes aegypti OX513A: Implications for Field Use

Background

Aedes aegypti is the primary vector of dengue fever, a viral disease which has an estimated incidence of 390 million infections annually. Conventional vector control methods have been unable to curb the transmission of the disease. We have previously reported a novel method of vector control using a tetracycline repressible self-limiting strain of Ae. aegypti OX513A which has achieved >90% suppression of wild populations.

Methodology/Principal Findings

We investigated the impact of tetracycline and its analogues on the phenotype of OX513A from the perspective of possible routes and levels of environmental exposure. We determined the minimum concentration of tetracycline and its analogues that will allow an increased survivorship and found these to be greater than the maximum concentration of tetracyclines found in known Ae. aegypti breeding sites and their surrounding areas. Furthermore, we determined that OX513A parents fed tetracycline are unable to pre-load their progeny with sufficient antidote to increase their survivorship. Finally, we studied the changes in concentration of tetracycline in the mass production rearing water of OX513A and the developing insect.

Conclusion/Significance

Together, these studies demonstrate that potential routes of exposure of OX513A individuals to tetracycline and its analogues in the environment are not expected to increase the survivorship of OX513A.

Dengue fever is spread by the mosquito Aedes aegypti and the most effective method to limit the spread of dengue is to reduce the mosquito population. We have previously reported a transgenic strain of Ae. aegypti which results in >90% population suppression: males, which do not transmit disease, are released into the field carrying a self-limiting gene to mate with wild females, passing on the self-limiting gene which causes >95% progeny to die before becoming vectors of disease. To be able to breed this mosquito in the laboratory an antidote, tetracycline, is used to suppress the effects of the transgene. Given that tetracyclines are commonly used in human and veterinary medicine, it is essential to consider whether sufficient tetracycline could be in the environment to prevent the effective use of this control method by allowing the female’s progeny (from a mating between a released OX513A male and a wild female) to survive. Here we have shown that the concentrations of tetracycline to which the mosquitoes will be exposed in the environment, both in breeding sites and in a blood-meal host are not high enough to influence the effectiveness of this control method.

Speciation and persistence of doxycycline in the aquatic environment: Characterization in terms of steady state kinetics

The aim of the present work was to establish the kinetics for the degradation of doxycycline in the aquatic environment with a view to arriving at a kinetic model that can be used to predict the persistence of antibiotic with confidence. The degradation of doxycycline in both water and sediment phases of aquatic microcosm experiments, as well as in distilled water control experiments, was studied over a period of 90 days. An initial 21% loss due to adsorption by the sediment was observed in the microcosm experiment soon after charging. Biphasic zero-order linear rates of degradation, attributed to microbial degradation of the free and sediment or colloidal particle-adsorbed antibiotic, were observed for both water phase (2.3 × 10(-2) and 4.5 × 10(-3) μgg(-1) day(-1)) and sediment phase (7.9 × 10(-3) and 1.5 × 10(-3) μgg(-1) day(-1)) of the microcosm experiment. The covered distilled water control experiment exhibited a monophasic zero-order linear rate (1.9 × 10(-3) μgg(-1) day(-1)) attributed to hydrolysis, while the distilled water experiment exposed to natural light exhibited biphasic liner rates attributed to a combination of hydrolysis and photolysis (2.9 × 10(-3) μgg(-1) day(-1)) and to microbial degradation (9.8 × 10(-3) μgg(-1) day(-1)). A kinetic model that takes into account hydrolysis, photolysis, microbial degradation as well as sorption/desorption by colloidal and sediment particles is presented to account for the observed zero-order kinetics. The implications of the observed kinetics on the persistence of doxycycline in the aquatic environment are discussed.

Microwave-assisted liquid-liquid microextraction based on solidification of ionic liquid for the determination of sulfonamides in environmental water samples

An easy, quick, and green method, microwave-assisted liquid-liquid microextraction based on solidification of ionic liquid, was first developed and applied to the extraction of sulfonamides in environmental water samples. 1-Ethy-3-methylimidazolium hexafluorophosphate, which is a solid-state ionic liquid at room temperature, was used as extraction solvent in the present method. After microwave irradiation for 90 s, the solid-state ionic liquid was melted into liquid phase and used to finish the extraction of the analytes. The ionic liquid and sample matrix can be separated by freezing and centrifuging. Several experimental parameters, including amount of extraction solvent, microwave power and irradiation time, pH of sample solution, and ionic strength, were investigated and optimized. Under the optimum experimental conditions, good linearity was observed in the range of 2.00-400.00 μg/L with the correlation coefficients ranging from 0.9995 to 0.9999. The limits of detection for sulfathiazole, sulfachlorpyridazine, sulfamethoxazole, and sulfaphenazole were 0.39, 0.33, 0.62, and 0.85 μg/L, respectively. When the present method was applied to the analysis of environmental water samples, the recoveries of the analytes ranged from 75.09 to 115.78% and relative standard deviations were lower than 11.89%.

The effect of aging on sequestration and bioaccessibility of oxytetracycline in soils

Veterinary antibiotics introduced into soil environment may change the composition and functioning of soil microbial communities and promote the spreading of antibiotic resistance. Actual risks depend on the antibiotic's bioaccessibility and sequestration in soils, which may vary with contact time and soil properties. We elucidated changes in the horsebean plant's bioaccessible oxytetracycline with increasing contact time in three different soils (cinnamon, red, and brown soil) and observed discrepancy in oxytetracycline dissipation using sequential extractions with H2O-, 0.01 M CaCl2-, and Mcllvaine- in the same three soils. The results showed lower quantities of oxytetracycline with increasing contact time over 20 days than the level in freshly contaminated soils but hugely discrepant quantities among the three tested soils. In addition, aging largely reduced dissipation of H2O-, 0.01 M CaCl2-, and Mcllvaine- extracted oxytetracycline in soils before planting. However, bioturbation helped increase the H2O-, CaCl2-, and Mcllvaine- extracted oxytetracyline from cinnamon and brown soils with aging. Lastly, correlation analysis indicated that bioaccessibility of oxytetracycline significantly correlates with the total of H2O-, CaCl2-, and Mcllvaine- extracted oxytetracycline (0.676**, p < 0.01) in soils, especially the H2O- (0.789**, p < 0.01) and Mcllvaine- (0.686**, p < 0.01) extracted oxytetracycline with aging. Overall, this study provides some basic understanding of the aging effect on sequestration and bioaccessibility of veterinary antibiotics in soils.