Simultaneous determination of multiclass antibiotics and their metabolites in four types of field-grown vegetables

Multitarget and suspect-screening of antimicrobials in vegetables samples: Uptake experiments and identification of transformation products

This work provided an accurate analytical method to perform a multitarget analysis of a variety of antimicrobials (AMs) including sulfonamides, tetracyclines, macrolides, fluoroquinolones and quinolones, one imidazole and one nitroimidazole, one triazole, one diaminopyridine and one derivative of Penicillium stoloniferum in vegetables. The analysis is performed using liquid-chromatography coupled to a low-resolution triple quadrupole mass spectrometer (UHPLC-MS/MS) to detect the target analytesor coupled to a high-resolution q-Orbitrap (HRMS) to monitor the formed transformation products (TPs). Both instruments were compared in terms of limits of quantification and matrix effect at the detection. The method was applied to determine the presence of AMs in organic and non-organic vegetables, where sulfadiazine and mycophenolic acid were detected. On the other hand, the transference of four AMs (trimethoprim, sulfamethazine, enrofloxacin, and chlortetracycline) from soils to lettuces was evaluated through controlled uptake experiments. The choice of AMs was based on the classification into different families, and on the fact that those AM families are the most frequently detected in the environment. In this case, each of the AMs with which the soils were contaminated were found in the exposed lettuces. Moreover, in both studies, specific TPs of the AMs were identified, posing the necessity of assessing their effects in relation to food and human safety.

A Suitable HPLC-MS/MS Methodology for the Detection of Oxytetracycline, Enrofloxacin, and Sulfachloropyridazine Residues in Lettuce Plants

Oxytetracycline (OTC), enrofloxacin (EFX), and sulfachloropyridazine (SCP) are critically important antimicrobials (AMs) in both human and veterinary medicine, where they are widely used in farm animals. Lettuce has become a matrix of choice for studying the presence of residues of these AMs in plants, as the concentrations of residues detected in lettuce can range from ng to mg. While several analytical methodologies have been developed for the purpose of detecting AMs in lettuce, these currently do not detect both the parent compound and its active metabolites or epimers, such as in the case of ciprofloxacin (CFX) and 4-epi-oxitetracycline (4-epi-OTC), which also pose a risk to public health and the environment due to their AM activity. In light of this situation, this work proposes an analytical method that was developed specifically to allow for the detection of OTC, 4-epi-OTC, EFX, CFX, and SCP in a lettuce matrix. This method uses acetonitrile, methanol, 0.5% formic acid, and McIlvaine-EDTA buffer as extraction solvents, and dispersive solid-phase extraction (dSPE) for the clean-up. The analytes were detected using a liquid chromatography technique coupled to mass spectrometry (HPLC-MS/MS). Parameters such as the specificity, linearity, recovery, precision, limit of detection, and limit (LOD) of quantification (LOQ) were calculated according to the recommendations established in the European Union decision 2021/808/EC and VICH GL2: Validation of analytical procedures. The LOQ for the analytes OTC, 4-epi-OTC, CFX, and SCP was 1 μg·kg-1, whereas for EFX, it was 5 μg·kg-1 dry weight. All calibration curves showed a coefficient of determination (R2) of >0.99. The recovery levels ranged from 93.0 to 110.5% and the precision met the acceptance criteria, with a coefficient of variation of ≤14.02%. Therefore, this methodology allows for the precise and reliable detection and quantification of these analytes. The analysis of commercial samples confirmed the suitability of this method.

Young people exposure to antibiotics: Implication for health risk and the impact from eating habits of takeaway food

Exposure to antibiotics, mainly from animal food ingestion, may have adverse effects on human health. Takeaway food is the preferred choice for the dietary of most Chinese young people nowadays, but the relationship between takeaway eating and antibiotic exposure is not yet adequately understood. In the present study, 297 young people were recruited to collect urine samples and questionnaires with an emphasis on their takeaway eating habits. The internal exposure to 16 antibiotics and three metabolites was measured in urine samples by high-performance liquid chromatography-tandem mass spectrometry, as well as a DNA oxidative damage marker, 8-hydroxydeoxyguanosine (8-OHdG). At least one kind of antibiotic was found in over 90 % of urine samples, with total concentrations from 0.667 to 3.02 × 104 ng/mL. High exposure levels of antibiotics were more likely to be found in individuals with a larger body mass index. The concentrations of six antibiotics were significantly different among people with different overall weekly eating frequencies, usually an upward trend. The estimated daily intakes of antibiotics were on the levels of 0.001-1.0 μg/kg/day, mainly contributed by clarithromycin, ciprofloxacin and oxytetracycline, indicating a potential health risk based on the microbiological effect. A significantly positive correlation was found between DNA oxidative damage and exposure for four categories of antibiotics, conformed by both Spearman correlation and multiple linear regression analysis. The levels of 8-OHdG were 355 %, 239 %, 234 %, and 334 % higher with elevated levels of phenicols, macrolides, tetracyclines and sulfonamides from quartiles 2 to 4. Our results suggest that high-frequency consumption of takeaways may exacerbate oxidative stress trends through human exposure to antibiotics.

Multitarget and suspect screening of antimicrobials in soil and manure by means of QuEChERS - liquid chromatography tandem mass spectrometry

The present work aimed to develop an accurate analytical method for the simultaneous analysis of twenty-four antimicrobials in soil:compost and animal manure samples by means of ultra-high performance liquid chromatography coupled to a triple-quadrupole mass spectrometer (UHPLC-QqQ). For this purpose, the effectiveness of two extraction techniques (i.e. focused ultrasound solid-liquid extraction (FUSLE) and QuEChERS (quick, easy, cheap, effective, rugged and safe)) was evaluated, and the clean-up step using solid-phase extraction (SPE) was also thoroughly studied. The method was successfully validated at 10 μg·kg-1, 25 μg·kg-1, and 50 μg·kg-1 showing adequate trueness (70-130%) and repeatability (RSD < 30%), with few exceptions. Procedural limits of quantification (LOQPRO) were determined for soil:compost (0.45 to 7.50 μg·kg-1) and manure (0.31 to 5.53 μg·kg-1) samples. Pefloxacin could not be validated at the lowest level since LOQPRO ≥ 10 μg·kg-1. Sulfamethazine (7.9 ± 0.8 µg·kg-1), danofloxacin (27.1 ± 1.4 µg·kg-1) and trimethoprim (4.9 ± 0.5 µg·kg-1) were detected in soil samples; and tetracycline (56.8 ± 2.8 µg·kg-1), among other antimicrobials, in the plants grown on the surface of the studied soil samples. Similarly, sulfonamides (SAs), tetracyclines (TCs) and fluoroquinolones (FQs) were detected in sheep manure in a range of 1.7 ± 0.3 to 93.3 ± 6.8 µg·kg-1. Soil and manure samples were also analysed through UHPLC coupled to a high-resolution mass-spectrometer (UHPLC-qOrbitrap) in order to extend the multitarget method to suspect screening of more than 22,281 suspects. A specific transformation product (TP) of sulfamethazine (formyl-sulfamethazine) was annotated at 2a level in manure samples, among others. This work contributes to the efforts that have been made in the last decade to develop analytical methods that allow multitarget analysis of a wide variety of antimicrobials, including TPs, which is a complex task due to the diverse physicochemical properties of the antimicrobials.

Phycobiliprotein recovery coupled to the tertiary treatment of wastewater in semi-continuous photobioreactors. Tracking contaminants of emerging concern

This study evaluated a tertiary wastewater treatment technology using cyanobacteria to recover value-added phycobiliproteins. The presence of contaminants of emerging concern (CECs) in wastewater, cyanobacteria biomass and pigments recovered were also analyzed. For this, a wastewater-borne cyanobacterium (Synechocystis sp. R2020) was used to treat secondary effluent from a municipal wastewater treatment plant, with and without nutrients supplementation. Then, the stability of phycobiliprotein production was assessed by operating the photobioreactor in semi-continuous mode. Results showed similar biomass productivity with and without nutrients supplementation (153.5 and 146.7 mg L^-1 d^-1, respectively). Upon semi-continuous operation, the phycobiliprotein content was stable and reached up to 74.7 mg gDW^-1. The phycocyanin purity ratio ranged from 0.5 to 0.8, corresponding to food grade (> 0.7). Out of 22 CECs detected in secondary effluent, only 3 were present in the phycobiliprotein extract. In order to identify applications, prospective research should focus on CECs removal during pigment purification.

Effects of tetracycline, sulfonamide, fluoroquinolone, and lincosamide load in pig slurry on lettuce: Agricultural and human health implications

The application of pig slurry as fertilizer in agriculture provides nutrients, but it can also contain veterinary medicines, including antibiotic residues (ABs), which can have an ecotoxicological impact on agroecosystems. Furthermore, uptake, translocation, and accumulation of ABs in crops can mobilize them throughout the food chain. This greenhouse study aims to assess AB uptake from soil fertilized with pig slurry and its phenotypical effects on Lactuca sativa L. The plants were cropped in loamy clay soil dosed at 140 kg total N/ha and containing antibiotics (lincomycin, sulfadiazine, oxytetracycline, and enrofloxacin) at different concentration levels (0, 0.05, 0.5, 5, 50, and 500 mg/kg fresh weight, fw). Whereas sulfadiazine (11.8 ng/g fw) was detected in lettuce leaves at the intermediate doses (0.5 mg/kg), lincomycin and its transformation products (hydroxy/sulfate) were only detected at the 50 mg/kg fw dose. In addition, increased AB doses in the pig slurry resulted in decreased lettuce fresh weight and lipid and carbohydrate content and became lethal to lettuce at the highest AB concentrations (500 mg/kg fw). Nevertheless, even at higher doses, the AB content in lettuce following pig-slurry fertilization did not pose any direct significant human health risk (total hazard quotient<0.01). However, the promotion of antimicrobial resistance in humans due to the intake of these vegetables cannot be ruled out.

Impact of organic soil amendments in antibiotic levels, antibiotic resistance gene loads, and microbiome composition in corn fields and crops

The potential spreading of antibiotic resistance genes (ARG) into agricultural fields and crops represent a fundamental limitation on the use of organic fertilization in food production systems. We present here a study of the effect of spreading four types of organic soil amendments (raw pig slurry, liquid and solid fractions, and a digested derivative) on demonstrative plots in two consecutive productive cycles of corn harvest (Zea mays), using a mineral fertilizer as a control, following the application of organic amendments at 32-62 T per ha (150 kg total N/ha) and allowing 5-8 months between fertilization and harvest. A combination of qPCR and high-throughput 16S rDNA sequencing methods showed a small, but significant impact of the fertilizers in both ARG loads and microbiomes in soil samples, particularly after the second harvesting cycle. The slurry solid fraction showed the largest impact on both ARG loads and microbiome variation, whereas its digestion derivatives showed a much smaller impact. Soil samples with the highest ARG loads also presented increased levels of tetracyclines, indicating a potential dual hazard by ARG and antibiotic residues linked to some organic amendments. Unlike soils, no accumulation of ARG or antibiotics was observed in corn leaves (used as fodder) or grains, and no grain sample reached detection limits for neither parameter. These results support the use of organic soil amendments in corn crops, while proposing the reduction of the loads of ARGs and antibiotics from the fertilizers to greatly reduce their potential risk.

Green and Efficient Determination of Fluoroquinolone Residues in Edible Green Fruits and Leafy Vegetables by Ultrasound-Assisted Extraction Followed by HPLC-MS/MS

In this work, a simple, quick and efficient analytical method for determination of human and veterinary fluoroquinolone antimicrobial residues in lettuce, cucumber and spinach is developed. The procedure entails a 6 min ultrasound-assisted extraction (UAE, 3 × 2 min) in an alkaline (2% v/v NH₃) aqueous solution containing Mg²⁺ ions (3 × 6 mL), with no need for organic solvents. The extract is submitted to cleanup on the HLB™ cartridge and the fluoroquinolones are separated and quantified by HPLC-MS/MS in a 10 min chromatographic run, using a small amount of acetonitrile in the mobile phase. The method, entirely developed in real matrices, is validated according to the updated analytical guidelines and provided suitable recoveries in the range of 67–116% and precision (RSD ≤ 20%, n = 3) at different concentrations (15, 70 and 150 ng g⁻¹), with method quantification limits of 2–10 ng g⁻¹. Fluoroquinolones were detected and quantified at concentrations from few to hundreds of nanograms per gram in vegetables from supermarkets, demonstrating the applicability of the method for monitoring residues of these pharmaceuticals.

Occurrence of antibiotics in Lettuce (Lactuca sativa L.) and Radish (Raphanus sativus L.) following organic soil fertilisation under plot-scale conditions: Crop and human health implications

Recent studies have demonstrated the crop uptake of antibiotics (ABs) from soils treated with AB-carrying fertilisers. However, there is a lack of plot-scale studies linking their effects at the agronomic and metabolomic/transcriptomic level to their impact on human health. This paper assesses the plant uptake of 23 ABs following two productive cycles of lettuce and radish cropped with sewage sludge, pig slurry, the organic fraction of municipal solid waste, or chemical fertilisation under plot-scale conditions (32 plots spanning 3-10 m2 each). AB uptake by plants depended on both the vegetable and the AB class and was higher in radish than in lettuce edible parts. Levels ranged from undetectable to up to 76 ng/g (fresh weight). Repetitive organic fertilisation resulted in an increase in the concentration of ABs in lettuce leaves, but not in radish roots. Significant metabolomic and transcriptomic changes were observed following soil fertilisation. Nevertheless, a human health risk assessment indicates that the occurrence of ABs in lettuce or radish edible parts does not pose any risk. To our knowledge, this is the first holistic plot-scale study demonstrating that the use of organic fertilisers containing ABs is safe for crop security and human health.

Implications of the use of organic fertilizers for antibiotic resistance gene distribution in agricultural soils and fresh food products. A plot-scale study

The spread of antibiotic resistance genes (ARG) into agricultural soils, products, and foods severely limits the use of organic fertilizers in agriculture. In order to help designing agricultural practices that minimize the spread of ARG, we fertilized, sown, and harvested lettuces and radish plants in experimental land plots for two consecutive agricultural cycles using four types of fertilizers: mineral fertilization, sewage sludge, pig slurry, or composted organic fraction of municipal solid waste. The analysis of the relative abundances of more than 200,000 ASV (Amplicon Sequence Variants) identified a small, but significant overlap (<10%) between soil's and fertilizer microbiomes. Clinically relevant ARG were found in higher loads (up to 100 fold) in fertilized soils than in the initial soil, particularly in those treated with organic fertilizers, and their loads grossly correlated to the amount of antibiotic residues found in the corresponding fertilizer. Similarly, low, but measurable ARG loads were found in lettuce (tetM, sul1) and radish (sul1), corresponding the lowest values to samples collected from minerally fertilized fields. Comparison of soil samples collected along the total period of the experiment indicated a relatively year-round stability of soil microbiomes in amended soils, whereas ARG loads appeared as unstable and transient. The results indicate that ARG loads in soils and foodstuffs were likely linked to the contribution of bacteria from organic fertilizer to the soil microbiomes, suggesting that an adequate waste management and good pharmacological and veterinarian practices may significantly reduce the presence of these ARGs in agricultural soils and plant products.

Systematic identification of trimethoprim metabolites in lettuce

Antibiotics are some of the most widely used drugs. Their release in the environment is of great concern since their consumption is a major factor for antibiotic resistance, one of the most important threats to human health. Their occurrence and fate in agricultural systems have been extensively investigated in recent years. Yet whilst their biotic and abiotic degradation pathways have been thoroughly researched, their biotransformation pathways in plants are less understood, such as in case of trimethoprim. Although trimethoprim has been reported in the environment, its fate in higher plants still remains unknown. A bench-scale experiment was performed and 30 trimethoprim metabolites were identified in lettuce (Lactuca sativa L.), of which 5 belong to phase I and 25 to phase II. Data mining yielded a list of 1018 ions as possible metabolite candidates, which was filtered to a final list of 87 candidates. Molecular structures were assigned for 19 compounds, including 14 TMP metabolites reported for the first time. Alongside well-known biotransformation pathways in plants, additional novel pathways were suggested, namely, conjugation with sesquiterpene lactones, and abscisic acid as a part of phase II of plant metabolism. The results obtained offer insight into the variety of phase II conjugates and may serve as a guideline for studying the metabolization of other chemicals that share a similar molecular structure or functional groups with trimethoprim. Finally, the toxicity and potential contribution of the identified metabolites to the selective pressure on antibiotic resistance genes and bacterial communities via residual antimicrobial activity were evaluated.

A novel multiscale biophysical model to predict the fate of ionizable compounds in the soil-plant continuum

Soil pollution from emerging contaminants poses a significant threat to water resources management and food production. The development of numerical models to describe the reactive transport of chemicals in both soil and plant is of paramount importance to elaborate mitigation strategies. To this aim, in the present study, a multiscale biophysical model is developed to predict the fate of ionizable compound in the soil-plant continuum. The modeling framework connects a multi-organelles model to describe processes at the cell level with a semi-mechanistic soil-plant model, which includes the widely used Richards-based solver, HYDRUS. A Bayesian probabilistic framework is used to calibrate and assess the capability of the model in reproducing the observations from an experiment on the translocation of five pharmaceuticals in green pea plants. Results show satisfactory fitting performance and limited predictive uncertainty. The subsequent validation with the cell model indicates that the estimated soil-plant parameters preserve a physically realistic meaning, and their calibrated values are comparable with the existing literature values, thus confirming the overall reliability of the analysis. Model results further suggest that pH conditions in both soil and xylem play a crucial role in the uptake and translocation of ionizable compounds.

A review on non-thermal plasma treatment of water contaminated with antibiotics

Large amounts of antibiotics are produced and consumed worldwide, while wastewater treatment is still rather inefficient, leading to considerable water contamination. Concentrations of antibiotics in the environment are often sufficiently high to exert a selective pressure on bacteria of clinical importance that increases the prevalence of resistance. Since the drastic reduction in the use of antibiotics is not envisaged, efforts to reduce their input into the environment by improving treatment of contaminated wastewater is essential to limit uncontrollable spread of antibiotic resistance. This paper reviews recent progress on the use of non-thermal plasma for the degradation of antibiotics in water. The target compounds removal, the energy efficiency and the mineralization are analyzed as a function of discharge configuration and the most important experimental parameters. Various ways to improve the plasma process efficiency are addressed. Based on the identified reaction intermediates, degradation pathways are proposed for various classes of antibiotics and the degradation mechanisms of these chemicals under plasma conditions are discussed.

Development of a QuEChERS-based method for the analysis of pharmaceuticals and personal care products in lettuces grown in field-scale agricultural plots irrigated with reclaimed water

The use of reclaimed water for agricultural irrigation is an increasingly common practice, which recently has found its own European regulatory frame. However, the partial removal of organic contaminants together with other xenobiotic substances in current wastewater treatment plants leads to the occurrence of residues of such pollutants in the treated effluents. Wastewater reclamation techniques are thus required to provide reclaimed water fitting the minimum quality standards set up for irrigation of crops intended for human consumption. This work describes the development and validation of a simple QuEChERS-based extraction and liquid chromatography quadrupole-linear ion trap mass spectrometry (LC-QqLIT-MS/MS) method for the simultaneous quantitative analysis of 55 pharmaceuticals and personal care products (PPCPs) in lettuces irrigated with treated wastewater and reclaimed water. The method showed good recovery rates (80-120%) and low detection limits (0.04-0.8 ng/g dw). In comparison with previous analytical methodologies, this method was simpler, faster and, in most cases, more sensitive. Moreover, is the first one analysing selected personal care products in lettuces. The proposed method was applied to assess the potential transfer of contaminants of urban origin in the use of reclaimed water in agriculture. The case study consisted in the evaluation of the lettuce uptake of the selected contaminants at field scale under two irrigation systems, two soil compositions, and two water types. Benzophenone-2, 4-hydroxybenzophenone, 1H-benzotriazole, 2-(2-Benzotriazol-2-yl)-p-cresol, nalidixic acid, diclofenac, carbamazepine 10,11-epoxy, N-des-methylvenlafaxine, and salicylic acid were transferred to all samples. Highest detected values corresponded to 4-hydroxybenzophenone (84.1 ng/g dw), benzophenone-2 (54.4 ng/g dw), and salicylic acid (53.8 ng/g dw). The best combination to minimize the transfer of the target contaminants from the irrigation water to the lettuces was sprinkling irrigation with water reclaimed by soil infiltration through reactive barriers, and clayey soil.

Uptake, accumulation and impact of antiretroviral and antiviral pharmaceutical compounds in lettuce

While the contamination of agroecosystems with pharmaceutical compounds has been reported, the fate of these compounds, particularly uptake into plants remains unclear. This lack of environmental fate data is evident for a critical class of pharmaceuticals, the antivirals and antiretrovirals (ARVDs). Thus, this study evaluated the root uptake of the antiretroviral compounds nevirapine, lamivudine and efavirenz, and the antiviral compound oseltamivir in lettuce. The lettuce was hydroponically grown in a nutrient solution containing the four ARVD pharmaceutical mixture in the 1-100 μg L-1 concentration range. The measured bioaccumulation showed that efavirenz and lamivudine accumulated to the highest and lowest degree, at concentrations of 3463 ng g-1 and 691 ng g-1 respectively. The translocation factor between the root and leaf for nevirapine was greater than 1. The highest concentration of the pharmaceutical mixture had a physiological impact on the lettuce. Potential toxicity was evidenced by a statistically significant 34% (p = 0.04) mean reduction in root and leaf biomass in the 100 μg L-1 ARVD mix exposed lettuce, compared with the controls. This study advances knowledge of the fate of ARVDs in agroecosystems, in particular, plant root - ARVD interaction and the resulting potentially toxic effects on plants.

Antibiotic and antibiotic-resistant gene loads in swine slurries and their digestates: Implications for their use as fertilizers in agriculture

The spread of antibiotic resistance in bacteria is a matter of global concern, and the identification of possible sources of the associated genetic elements (antibiotic resistance genes -ARGs-, components of the horizontal gene transfer mechanism), is becoming an urgent need. While the transmission of ARGs in medical settings have been adequately characterized, ARG propagation in agroecosystems remains insufficiently studied. Particularly crucial is the determination of potential risks associated to the use of swine slurries and related products as component of organic fertilizers, an increasingly used farming practice. We determined ARGs and antibiotic loads analysed from swine slurries and digestates from eight farms from Catalonia (NE Spain), and compared the results with their microbiome composition. Both ARGs and antibiotic were conspicuous in farm organic wastes, and the levels of some antibiotics exceeded currently accepted minimum inhibitory concentrations. Particularly, the presence of high loads of fluoroquinolones was directly correlated to the prevalence of the related qnrS1 ARG in the slurry. We also found evidence that ARG loads were directly correlated to the prevalence of determined bacterial taxa (Actinobacteria, Proteobacteria, Spirochaeta), a parameter that could be potentially modulated by the processing of the raw slurry prior to their use as fertilizer.

Occurrence and human health risk assessment of antibiotics and their metabolites in vegetables grown in field-scale agricultural systems

The occurrence of antibiotics (ABs) in four types of commercially grown vegetables (lettuce leaves, tomato fruits, cauliflower inflorescences, and broad bean seeds) was analyzed to assess the human exposure and health risks associated with different agronomical practices. Out of 16 targeted AB residues, seven ABs belonging to three groups (i.e., benzyl pyrimidines, fluoroquinolones, and sulfonamides) were above the method detection limit in vegetable samples ranging from 0.09 ng g^-1 to 3.61 ng g^-1 fresh weight. Data analysis (quantile regression models, principal component and hierarchical cluster analysis) showed manure application, irrigation with river water (indirect wastewater reuse), and vegetable type to be the most significant factors for AB occurrence in the targeted crops. Metabolites were detected in 70 of the 80 vegetable samples analyzed, and their occurrence was both plant- and compound-specific. In 73 % of the total samples, the concentration of AB metabolites was higher than the concentration of their parent compound. Finally, the potential human health risk estimated using the hazard quotient approach, based on the acceptable daily intake and the estimated daily intake, showed a negligible risk for human health from vegetable consumption. However, canonical-correspondence analysis showed that detected ABs explained 54 % of the total variation in AB resistance genes abundance in the vegetable samples. Thus, further studies are needed to assess the risks of antibiotic resistance promotion in vegetables and the significance of the occurrence of their metabolites.

Dose effect of Zn and Cu in sludge-amended soils on vegetable uptake of trace elements, antibiotics, and antibiotic resistance genes: Human health implications

The application of sewage sludge to agricultural fields reduces the need for mineral fertilizers by increasing soil organic matter, but may also increase soil pollution. Previous studies indicate that zinc and copper, as the most abundant elements in sewage sludge, affect plant uptake of other contaminants. This paper aims to investigate and compare the effect of increasing amounts of Zn and Cu in sludge-amended soils on the accumulation of trace elements (TEs), antibiotics (ABs), and antibiotic resistance genes (ARGs) in lettuce and radish. The vegetables were grown under controlled conditions, and the influence on plant physiology and human health were also evaluated. The results show that the addition of Zn and Cu significantly increased the concentration of TEs in the edible tissue of both vegetables. According to the hazard quotient (HQ) of the TEs, the human health risk increased 2 to 3 times and was 3-4 times greater in lettuce than in radish. In contrast to the TEs, the occurrence of ABs and most of the ARGs was higher in radish roots than lettuce leaves. ABs were not detected in lettuce leaves, and the amount of all ARGs except bla_TEM was 10 times lower than in radish roots. On the other hand, the addition of Zn and Cu had no significant effect on the occurrence of ABs and ARGs in the edible part of the vegetables, and no damage was found to plant productivity or physiology. The results show that the consumption of lettuce and radish grown in sewage-sludge-amended soils under tested doses of Cu and Zn does not pose an adverse human health effect, as the total HQ value was always less than 1, and the presence of ABs and ARGs was not found to have any potential impact. Nevertheless, further studies are needed to estimate the long-term effect on human health of crops grown under frequent application of biosolids in arable soil.

Occurrence and human health risk assessment of antibiotics and trace elements in Lactuca sativa amended with different organic fertilizers

Soil amendment with organic fertilizers is an effective approach to improve soil fertility. However, organic fertilizers may contain pollutants such as trace elements (TEs) and antibiotics (ABs), which, once deployed in arable soil, can be taken up by vegetables and have adverse effects on crops and human health. This study assesses the presence of 15 TEs and 16 ABs in lettuce grown in a greenhouse facility and amended with 3 different organic fertilizers (sewage sludge (SS), organic fraction of municipal solid waste (OFMSW), and swine manure (SM)) at 3 different fertilization doses. The results show that lettuces amended with SS resulted in the lowest content of TEs. Although 11 ABs were detected in the SM and SS fertilizers, only 3 ABs were detected in lettuce leaves. The concentrations of detected ABs in lettuce ranged from 0.67 ng/g fw (lincomycin) to 14.2 ng/g fw (ciprofloxacin) in SS. The organic fertilization dose did not affect the lettuce uptake of TEs or ABs. Moreover, the use of SS resulted in the highest lettuce yield of the organic amendments. The total hazard quotients (THQs) obtained for TEs and ABs were less than 1 for all the studied fertilization treatments. The highest THQs for TEs were observed in lettuce amended with SM (0.11-0.16), whereas the highest THQs for ABs were observed in SS treatments (0.06-0.09). The results thus suggest that consumption of lettuces amended with organic fertilizers would not pose a risk to human health due to the presence of studied TEs or ABs, but potentially harmful combined effects cannot ruled out.

Stress responses and biological residues of sulfanilamide antibiotics in Arabidopsis thaliana

Sulfonamides (SAs) are antibiotics widely used in clinical practice, livestock and poultry production, and the aquaculture industry. The compounds enter the soil environment largely through livestock and poultry manure application to farmland. SAs not only affect plant growth, but also pose a potential threat to human health through SA residues in plant tissues. In particular, sulfamethoxazole (SMZ) has been classified as a Category 3 carcinogen by the World Health Organization, and thus its soil ecological toxicity and possible health risks are of concern. Using A. thaliana as a model plant, stress responses and biological residues of sulfadiazine (SD), sulfametoxydiazine (SMD), and SMZ were investigated in the present study. Root length and aboveground plant biomass were significantly inhibited by the three types of SA, whereas lateral roots exposed to SMD grew vigorously. The contents of chlorophyll a and chlorophyll b and photosystem II maximum photochemical quantum yield declined with increase in drug concentration, which indicated that exposure to SAs affected photosynthesis and inhibited chlorophyll synthesis in A. thaliana. With increase in drug concentration, reactive oxygen species (ROS) accumulation in the leaves increased significantly. Activities of the antioxidant enzymes superoxide dismutase (SOD) and catalase (CAT) were activated at low SA concentrations, but increased lipid peroxidation occurred with increase in SA concentration. Of the three compounds, SMZ was the most toxic to A. thaliana, followed by SD, and SMD was the least toxic. The results indicated that the risk of SMD entering an organism through the food chain is greater than that for SMZ and SD.

Elucidating biotransformation pathways of ofloxacin in lettuce (Lactuca sativa L)

Antibiotics can be uptaken by plants from soil desorption or directly from irrigation water, but their metabolization pathways in plants are largely unknown. In this paper, an analytical workflow based on high-resolution mass spectrometry was applied for the systematic identification of biotransformation products of ofloxacin in lettuce. The targeted metabolites were selected by comparing the mass chromatograms of exposed with control samples using an advanced spectra-processing method (Fragment Ion Search). The innovative methodology presented allowed us to identify a total of 11 metabolites, including 5 ofloxacin metabolites that are being reported for the first time in plants. Accordingly, major transformation pathways were proposed revealing insight into how ofloxacin and related chemicals are metabolized in lettuce. Furthermore, the influence of biotransformation on potential residual antimicrobial activity of identified compounds was discussed. Human exposure to antibiotics at doses below the minimum inhibitory concentrations is crucial in human risk assessment, including food ingestion; however, in the case of ofloxacin presented results reveal that plant metabolites should also be considered so as not to underestimate their risk.

Enrichment of endophytic Actinobacteria in roots and rhizomes of Miscanthus × giganteus plants exposed to diclofenac and sulfamethoxazole

This study investigates how wastewater containing 2 mg l^-1 of sulfamethoxazole (SMX) and 2 mg l^-1 of diclofenac (DCF) affects the composition of bacterial communities present in the roots and rhizomes of Miscanthus × giganteus plants grown in laboratory-scale constructed wetlands. Bacterial communities in plant roots and rhizomes were identified in treated and control samples by 16S rRNA amplicon sequencing. Moreover, bacterial endophytes were isolated in R2A and 1/10 869 media and screened for their ability to metabolize SMX and DCF in liquid medium by HPLC. Our results show significant changes in the abundance of main genera, namely Sphingobium and Streptomyces between control and treated plants. Around 70% of the strains isolated from exposed plants belonged to the phylum Actinobacteria and were classified as Streptomyces, Microbacterium, and Glycomyces. In non-exposed plants, Proteobacteria represented 43.5% to 63.6% of the total. We identified 17 strains able to remove SMX and DCF in vitro. From those, 76% were isolated from exposed plants. Classified mainly as Streptomyces, they showed the highest SMX (33%) and DCF (41%) removal efficiency. These isolates, alone or in combination, might be used as bio-inoculants in constructed wetlands to enhance the phytoremediation of SMX and DCF during wastewater treatment.

Analysis of Multiclass Antibiotics in Lettuce by Liquid Chromatography-Tandem Mass Spectrometry to Monitor Their Plant Uptake

The main entry routes of antibiotics in the environment are the application of organic wastes to improve soil quality and the irrigation with recycled water. Once in the environment, antibiotics can be introduced in the food chain through their uptake by crops. This paper describes the development of an analytical method based on ultrasound-assisted extraction for the determination of seven antibiotics in lettuce. The developed method was applied to evaluate antibiotic uptake by lettuce grown in pots fertilized with composted poultry litter doped with a mixture of antibiotics to reach a final concentration of 2.5 µg/g in soil. Lettuce were harvested after 21, 36, and 55 days. Five of the seven studied antibiotics were found in all samples. The highest uptake was found for lincomycin (51 ng/g fresh weight) followed by sulfamethoxazole (44 ng/g fresh weight) and sulfamethazine (21 ng/g fresh weight) in lettuce harvested after 21 days. An important decrease of their levels was observed after 36 days, but these levels remained similar after 55 days. Although levels found in lettuce were low, the presence of antibiotics demonstrates the need for further assessing food safety risks related with the use of soil amendments or irrigation water contaminated with antibiotics.