Oxytetracycline as environmental contaminant in arable lands

A perspective of spatial variability and ecological risks of antibiotics in the agricultural-pastoral ecotone soils in eastern Inner Mongolia

Antibiotics have garnered growing attention as pharmaceuticals ubiquitously present in human society. Within the soil environment, antibiotics exhibit a propensity for high environmental persistence, thereby posing a potential threat to the ecosystem. However, research on antibiotics in agricultural-pastoral ecotone soils is scarce. This study investigates the occurrence, distribution and risk of 11 common antibiotics in agricultural soils of the agro-pastoral transition zone in Horqin Left Middle Banner, eastern Inner Mongolia. The total concentration varies from not detectable to 609.62 μg/kg. Tetracyclines are the dominant antibiotic, with a higher detection frequency than Macrolides and Sulfonamides. The detection rates of the three types of antibiotics differ significantly. The study also finds that soil properties (organic matter content, pH, bulk density, clay, cation exchange capacity have no significant correlation with antibiotics in soil. Moreover, spatial regression analysis reveals that population density is the primary factor influencing the spatial distribution of antibiotics in soil. Ecological risk assessment shows that clarithromycin and erythromycin are the two most harmful factors in the ecological risk of agricultural soil.

Accumulation, transportation, and distribution of tetracycline and cadmium in rice

Co-exposure to heavy metal and antibiotic pollution might result in complexation and synergistic interactions, affecting rice growth and further exacerbating pollutant enrichment. Therefore, our study sought to clarify the influence of different Tetracycline (TC) and Cadmium(Cd) concentration ratios (both alone and combined) on rice growth, pollutant accumulation, and transportation during the tillering stage in hydroponic system. Surprisingly, our findings indicated that the interaction between TC and Cd could alleviate the toxic effects of TC/Cd on aerial rice structures and decrease pollutant burdens during root elongation. In contrast, TC and Cd synergistically promoted the accumulation of TC/Cd in rice roots. However, their interaction increased the accumulation of TC in roots while decreasing the accumulation of Cd when the toxicant doses increased. The strong affinity of rice to Cd promoted its upward transport from the roots, whereas the toxic effects of TC reduced TC transport. Therefore, the combined toxicity of the two pollutants inhibited their upward transport. Additionally, a low concentration of TC promoted the accumulation of Cd in rice mainly in the root tip. Furthermore, a certain dose of TC promoted the upward migration of Cd from the root tip. Laser ablation-inductively coupled plasma mass spectrometry demonstrated that Cd mainly accumulated in the epidermis and stele of the root, whereas Fe mainly accumulated in the epidermis, which inhibited the absorption and accumulation of Cd by the rice roots through the generation of a Fe plaque. Our findings thus provide insights into the effects of TC and Cd co-exposure on rice growth.

Isolation, characterization and degradation performance of oxytetracycline degrading bacterium Planococcus sp. strain pw2

Oxytetracycline (OTC), is a widely used veterinary antibiotic for treatment and prophylaxis in aquaculture. As an emerging pollutant, OTC in the environment exerts selective pressure on aquatic organisms causing proliferation of antibiotic resistant genes. In the present study, an OTC tolerant isolate labelled as pw2 was selected among the 11 OTC tolerant isolates, isolated from the aquaculture effluent, for investigating its OTC degrading potential. The cell morphology, biochemical characteristics, and 16S ribosomal RNA (rRNA) gene sequence of the isolated strain indicated that it belonged to the genus Planococcus. The OTC removal percentage was estimated through measuring its residual concentration in the culture medium with high performance liquid chromatography. The strain exhibited maximum removal efficiency of 90.62%, with initial OTC concentration of 10 µg/ml. The optimum degrading conditions were 35 °C and pH 7. The degradation rate of OTC with (biotic) and without strain pw2 (abiotic) was 3.253 and 1.149 mg/l/d, respectively. The half-life was recorded to be 2.13 d in the presence of strain pw2, in contrast to 6.03 days recorded without strain pw2. The total (biotic + abiotic) OTC degradation efficiency was 75.74, 83.93, 90.62, and 86.47% for the initial OTC concentrations of 1 to 25 µg/ml, respectively. Addition of carbon and nitrogen did not influence the OTC removal which indicates Planococcus sp. pw2 use OTC as sole energy source. Thus, Planococcus sp. pw2 plays a vital role in reducing the OTC concentration in the environment, offering a promising method for treatment of aquaculture effluent containing OTC.

A strategy to determine the fate of active chemical compounds in soil; applied to antimicrobially active substances

Data on the fate of chemical substances in the environment after e.g. manure application is mandatory input for risk assessment in perspective of a more circular biobased economy. Such fate studies include a persistence study to determine a half-life value and a mobility study. It is recognized that not only the native substance should be considered, but that also degradation products should be included that might exert a similar effect as the native substance. We report a tiered fate study strategy that starts with a persistence study. For non-persistent substances a study is performed to determine if degradation products have a similar effect as the native compound. If so, a procedure using high resolution mass spectrometry is suggested to identify the potentially active degradation products. Based on the outcomes, substances are divided into three categories: (I) persistent, (II) degradable to inactive products or (III) degradable to active products. Even though the priority is with category I and III, for all substances and possible degradation products a mobility study is proposed. The fate strategy is successfully applied to ten antimicrobially active substances originating from the tetracyclines, sulfonamides, diaminopyrimidines, fluoroquinolones, macrolides and lincosamides. The fluoroquinolones, tetracyclines and trimethoprim were relatively persistent. The sulfonamides, macrolides and lincomycin (the latter also depending on soil type) degraded relatively quickly. Tylosin A proved to degrade to antimicrobially active degradation products which were tentitatively identified as tylosin C, tylosin A acid, tylosin B acid and tylosin C acid.

Antibiotic resistance, antimicrobial residues, and bacterial community diversity in pasture-raised poultry, swine, and beef cattle manures

Animal manure can be a source of antibiotic-resistant genes (ARGs) and pharmaceutical residues; however, few studies have evaluated the presence of ARG in pasture-raised animal production systems. The objective of this study was to examine changes in microbiome diversity and the presence of antibiotic residues (ABRs) on three farms that contained a diverse range of animal species: pasture-raised poultry (broiler and layer), swine, and beef cattle. Total bacterial communities were determined using 16S rRNA microbiome analysis, while specific ARGs (sulfonamide [Sul; Sul1] and tetracycline [Tet; TetA]) were enumerated by qPCR (real-time PCR). Results indicated that the ARG abundances (Sul1 [P < 0.05] and TetA [P < 0.001]) were higher in layer hen manures (16.5 × 10-4 and 1.4 × 10-4 µg kg-1, respectively) followed by broiler chickens (2.9 × 10-4 and 1.7 × 10-4 µg kg-1, respectively), swine (0.22 × 10-4 and 0.20 × 10-4 µg kg-1, respectively) and beef cattle (0.19 × 10-4 and 0.02 × 10-4 µg kg-1, respectively). Average fecal TetA ABR tended to be greater (P = 0.09) for broiler chickens (11.4 µg kg-1) than for other animal species (1.8 to 0.06 µg kg-1), while chlortetracycline, lincomycin, and oxytetracycline ABRs were similar among animal species. Furthermore, fecal microbial richness and abundances differed significantly (P < 0.01) both among farms and specific species of animal. This study indicated that the microbial diversity, ABR, ARG concentrations, and types in feces varied from farm-to-farm and from animal species-to-animal species. Future studies are necessary to perform detailed investigations of the horizontal transfer mechanism of antibiotic-resistant microorganisms (ARMs) and ARG.

Antibiotics in soil and water in China-a systematic review and source analysis

With the high production and consumption of antibiotics in recent years due to increasing economic development and improving population health, China is facing serious antibiotic pollution in the environment, and it is becoming a significant threat to ecology and human health. This study explores the spatial distribution patterns of 65 antibiotics in soil, surface water and coastal water based on a systematic review. Potential emission sources of antibiotics are also analyzed using data extracted from the reviewed literature. The results suggest that China has very high antibiotic detection rates of 100%, 98.0% and 96.4% for soil, surface water and coastal water, respectively. Regions with high antibiotic levels are mainly located in Bohai Bay, including the Beijing‒Tianjin‒Hebei region, Liaoning and Shandong Provinces, and Yangtze River. Tetracyclines (TCs) and quinolones (QNs) are the dominant antibiotics observed in soil and are mainly attributed to the use of manure as fertilizer and the reuse of domestic wastewater. Sulfonamides (SAs), macrolides (MLs), TCs and QNs are the dominant antibiotics observed in surface water and are mainly attributed to aquaculture and the emission of domestic sewage. QNs are the dominant antibiotics observed in coastal water and are mainly attributed to marine cultivation. The detection frequencies and concentrations of TCs, QNs, SAs and MLs in both soil and water are much higher than those in other developed countries. Suggestions including restricting antibiotic usages in livestock farming and aquaculture, innovation of wastewater treatment technology to improve antibiotic removal rate, and establishing guidelines on antibiotic concentration for wastewater discharge and organic fertilizer are provided.

Effect of Oxytetracycline and Chlortetracycline on Bacterial Community Growth in Agricultural Soils

Toxicity on soil bacterial community growth caused by the antibiotics oxytetracycline (OTC) and chlortetracycline (CTC) was studied in 22 agricultural soils after 1, 8 and 42 incubation days. The leucine incorporation method was used with this aim, estimating the concentration of each antibiotic which caused an inhibition of 50% in bacterial community growth (log IC50). For OTC, the mean log IC50 was 2.70, 2.81, 2.84 for each of the three incubation times, while the values were 2.05, 2.22 and 2.47 for CTC, meaning that the magnitude of OTC toxicity was similar over time, whereas it decreased significantly for CTC with incubation time. In addition, results showed that the toxicity on bacterial community growth due to CTC is significantly higher than when due to OTC. Moreover, the toxicity on bacterial community growth due to both antibiotics is dependent on soil properties. Specifically, an increase in soil pH and silt content resulted in higher toxicity of both antibiotics, while increases in total organic carbon and clay contents caused decreases in OTC and CTC toxicities. The results also show that OTC toxicity can be well predicted by means of specific equations, using the values of pH measured in KCl and those of effective cation exchange capacity as input variables. CTC toxicity may be predicted (but with low precision) using pH measured in KCl and total organic carbon. These equations may help to predict the negative effects caused by OTC and CTC on soil bacteria using easily measurable soil parameters.

A new extraction procedure to abate the burden of non-extractable antibiotic residues in manure

Through agricultural soil fertilization using organic manure, antibiotic residues can accumulate in the environment. In order to assess the risks of environmental pollution by veterinary drugs, monitoring of manure for antibiotic residues is necessary. As manure is a complex matrix, extraction of antibiotics proved to be challenging. In this study, 24 extraction solvents were assessed for the extraction of residues from manure representing ten antibiotics from the antibiotic classes tetracyclines, quinolones, macrolides, lincosamides and sulfonamides. Especially for the tetracyclines and quinolones the extraction solvent selection is critical, due to high fractions of non-extractable residues especially when using aqueous solvents (62-77% and 90-95% respectively when using milli-Q water). In contrast, sulfonamides can effectively be extracted with aqueous solvents. Overall, 0.125% trifluoroacetic acid in acetonitrile in combination with McIlvain-EDTA buffer proved to be the most effective extraction solvent. A longitudinal study pointed out that most antibiotics bind to solid manure particles instantaneously after addition. Trimethoprim is an exception, but because by using the optimal extraction solvent, the optimum fraction of bound residues is desorbed, this does not hamper quantitative analysis when using spiked manure quality control samples. Based on these new insights, the current in-house multi-residue LC-MS/MS method for manure analysis, containing 48 antibiotics, was revised, additionally validated and applied to 34 incurred manure samples.

Enhanced Phototransformation of Tetracycline at Smectite Clay Surfaces under Simulated Sunlight via a Lewis-Base Catalyzed Alkalization Mechanism

As an important class of soil minerals and a key constituent of colloidal particles in surface aquifers, smectite clays can strongly retain tetracyclines due to their large surface areas and high cation exchange capacities. However, the research on phototransformation of tetracyclines at smectite clay surfaces is rarely studied. Here, the phototransformation kinetics of tetracycline preadsorbed on two model smectite clays (hectorite and montmorillonite) exchanged with Na⁺, K⁺, or Ca²⁺ suspended in aqueous solution under simulated sunlight was compared with that of tetracycline dissolved in water using batch experiments. Adsorption on clays accelerated tetracycline phototransformation (half-lives shortened by 1.1-5.3 times), with the most significant effects observed for Na⁺-exchanged clays. Regardless of the presence or absence of clay, the phototransformation of tetracycline was facilitated by increasing pH from 4 to 7. Inhibition or enhancement of photolysis-induced reactive species combined with their measurement using scavenger/probe chemicals indicate that the facilitated production of self-photosensitized singlet oxygen (¹O₂) was the key factor contributing to the clay-enhanced phototransformation of tetracycline. As evidenced by the red shifts and the increased molar absorptivity in the UV-vis absorption spectra, the complexation of tetracycline with the negatively charged (Lewis base) sites on clay siloxane surfaces led to formation of the alkalized form, which has larger light absorption rate and is more readily to be oxidized compared to tetracycline in aqueous solution at equivalent pH. Our findings indicate a previously unrecognized, important phototransformation mechanism of tetracyclines catalyzed by smectite clays.

Occurrence and risk assessment of tetracycline antibiotics in soil from organic vegetable farms in a subtropical city, south China

This study investigated the occurrence of tetracycline antibiotics in soils from different organic vegetable farms in Guangzhou, a subtropical city, South China and evaluated their ecological risk. Four tetracycline compounds (oxytetracycline, tetracycline, chlortetracycline, and doxycycline) were extracted ultrasonically from soil samples (n = 69), with a solid-phase extraction cleanup, and were then measured by high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS). The results showed that four compounds were detected in all samples, with the concentrations of the individual compounds ranging from 0.04 to 184.8 μg/kg (dry weight). The concentrations of tetracycline compounds in the soils from different vegetable farms varied greatly, but their patterns of distribution were similar. Doxycycline was the predominant compound with a mean of 21.87 μg/kg, followed by chlortetracycline. The concentrations of doxycycline and chlortetracycline in 7.46 % of the samples were higher than the ecotoxic effect trigger value (100 μg/kg) set by the Steering Committee of Veterinary International Committee on Harmonization. Additionally, the concentrations of tetracyclines in greenhouse soils were significantly lower than those in open-field soils. Risk assessment based on single compound exposure showed that doxycycline could pose medium or high risks. Compared with other studies, the levels of tetracyclines in this study were relatively low. The hypothesis that antibiotic residues in the soil of organic farms fertilized with manure are higher than in the soils of conventional farms was not supported in the area studied due to the high levels of moisture, temperature, and microbial activity.

Occurrence, seasonal variation and removal efficiency of antibiotics and their metabolites in wastewater treatment plants, Jiulongjiang River Basin, South China

Wastewater treatment plants (WWTPs) are regarded as one of the most important sources of antibiotics in the environment. The occurrence, seasonal variation and removal efficiency of 21 antibiotics and 10 metabolites, including five sulfonamides and three of their metabolites, six quinolones, two macrolides, two β-Lactams and five tetracyclines and seven of their metabolites, were investigated in five WWTPs in different seasons in the Jiulongjiang River Region, South China. 16 antibiotics and 6 metabolites in summer and 14 antibiotics and 6 metabolites in winter were found, respectively. The most frequently detected antibiotics were sulfamethazine, sulfamethoxazole, n-acetyl sulfamethazine, n-acetyl sulfamethoxazole, ofloxacin, cephalexin monohydrate and cephradine; of these, the concentration of cephradine was the highest in most of the influent and effluent samples. The highest level of total antibiotics was found in Longyan City WWTPs, where there are more population and swine farms. Seasonal variation of the antibiotics in wastewater samples was also studied. The concentrations of antibiotics in winter were higher than those in summer. The antibiotics could not be removed completely by the WWTPs, and the mean removal efficiency ranged from -71.6 to 56.3%. Of all the antibiotics, the tetracyclines were removed comparatively more efficiently, probably due to their adsorption to sludge. The low removal efficiency of antibiotics in WWTPs could be one of the important reasons for the presence of antibiotics in the environment in Jiulongjiang Region.

A review of plant-pharmaceutical interactions: from uptake and effects in crop plants to phytoremediation in constructed wetlands

Pharmaceuticals are commonly found both in the aquatic and the agricultural environments as a consequence of the human activities and associated discharge of wastewater effluents to the environment. The utilization of treated effluent for crop irrigation, along with land application of manure and biosolids, accelerates the introduction of these compounds into arable lands and crops. Despite the low concentrations of pharmaceuticals usually found, the continuous introduction into the environment from different pathways makes them 'pseudo-persistent'. Several reviews have been published regarding the potential impact of veterinary and human pharmaceuticals on arable land. However, plant uptake as well as phytotoxicity data are scarcely studied. Simultaneously, phytoremediation as a tool for pharmaceutical removal from soils, sediments and water is starting to be researched, with promising results. This review gives an in-depth overview of the phytotoxicity of pharmaceuticals, their uptake and their removal by plants. The aim of the current work was to map the present knowledge concerning pharmaceutical interactions with plants in terms of uptake and the use of plant-based systems for phytoremediation purposes.

Tetracycline accumulates in Iberis sempervirens L. through apoplastic transport inducing oxidative stress and growth inhibition

Environmental antibiotic contamination is due mainly to improper and illegal disposal of these molecules that, yet pharmacologically active, are excreted by humans and animals. These compounds contaminate soil, water and plants. Many studies have reported the bioaccumulation of antibiotics in plants and their negative effects on photosynthesis, cell growth and oxidative balance. Therefore, the principal objective of this paper was the study of antibiotic accumulation sites in plants and its uptake modality. Iberis sempervirens L., grown in soil and in agar in the presence or absence of tetracycline, were used as a model system. Using confocal and transmission electron microscopy, we demonstrated that tetracycline was absorbed and propagated in plants through apoplastic transport and also accumulated in intercellular spaces. Tetracycline was rarely detected inside cells (in cytoplasm and mitochondria where, coherent to its pharmacological activity, it probably affected ribosomes), except in stomata. Moreover, we verified and clarified further the phytotoxic effects of tetracycline on plants. We observed that the antibiotic induced a large reduction in plant growth and development and inhibition of photosynthetic activity. As tetracycline may lead to oxidative stress in plants, plant cells tried to balance this disequilibrium by increasing the amount and activity of some endogenous enzyme antioxidant agents (superoxide dismutase 1 and catalase) and levels of antiradical secondary metabolites.

Occurrence and distribution of heavy metals and tetracyclines in agricultural soils after typical land use change in east China

Land use in east China tends to change from paddy rice to vegetables or other high-value cash crops, resulting in high input rates of organic manures and increased risk of contamination with both heavy metals (HMs) and antibiotics. This investigation was conducted to determine the accumulation, distribution and risks of HMs and tetracyclines (TCs) in surface soils and profiles receiving different amounts of farmyard manure. Soil samples collected from suburbs of Hangzhou city, Zhejiang province were introduced to represent three types of land use change from paddy rice to asparagus production, vineyards and field mustard cultivation, and divided into two portions, one of which was air-dried and sieved through 2-, 0.3- and 0.149-mm nylon mesh for determination of pH and heavy metals. The other portion was frozen at -20 °C, freeze-dried and sieved through a 0.3-mm nylon mesh for tetracyline determination. HM and TC concentrations in surface soils of 14-year-old mustard fields were the highest with total Cu, Zn, Cd and ∑TCs of 50.5, 196, 1.03 mg kg(-1) and 22.9 μg kg(-1), respectively, on average. The total Cu sequence was field mustard>vineyards>asparagus when duration of land use change was considered; oxytetracycline (OTC) and doxycycline were dominant in soils used for asparagus production; OTC was dominant in vineyards and chlortetracycline (CTC) was dominant in mustard soils. There were positive pollution relationships among Cu, Zn and ∑TCs, especially between Cu and Zn or Cu and ∑TCs. Repeated and excessive application of manures from intensive farming systems may produce combined contamination with HMs and TCs which were found in the top 20 cm of the arable soil profiles and also extended to 20-40 cm depth. Increasing manure application rate and cultivation time led to continuing increases in residue concentrations and movement down the soil profile.

Interactive effect of oxytetracycline and lead on soil enzymatic activity and microbial biomass

Interactive effect of oxytetracyline (OTC) and lead on soil enzymatic activity and population of microbes was studied in the paper. The results showed effect of pollutants on bacteria, actinomycetes and enzymatic activity increased in the order: (OTC+Pb)>Pb>OTC, (OTC+Pb)>Pb>OTC and (OTC+Pb)>OTC>Pb, respectively. However, impact of pollutants on fungi decreased in the order: (OTC+Pb)<Pb<OTC. The analysis of X-ray photoelectron spectroscopy (XPS) showed that binding energy and atomic percentage of Al, Fe, C, O, N, Si, Mg and Ca altered after the amended with OTC or Pb. The decrease of oxygen atom density and increase of binding energy can be associated to the charge transfer, resulting from oxygen and carbon atoms coordinated with metal ions, other chemicals or partial decomposition. Thus, the findings of this study can provide a better insight into the interaction of both pollutants and their impacts on soil quality.

Low Doses of Tetracycline Trigger the E. coli Growth: A Case of Hormetic Response

Hormesis is a biphasic dose-response relationship, occurring when low concentrations of toxic agents elicit apparent improvements. In this work, the ability of sub-inhibitory concentrations of Tetracycline to induce hormetic response in a model organism was investigated. To this aim a reference strain of Escherichia coli, MG1655, was exposed to six decreasing doses of Tetracycline (between 0.12 and 0.00375 μg/ml), much lower than the Minimal Inhibitory Concentration (4 μg/ml). An hormetic increase was observed at the intermediate concentrations (0.015-0.03 μg/ml) of the tested range. The Colony Forming Unit number, indeed, rose up to 141% and 121% as compared to the control. At the highest (0.12 μg/ml) and lowest (0.00375 μg/ml) concentrations a slight decrease in CFU number was found. Results demonstrated that, in Escherichia coli, low concentrations of Tetracycline bias the bacterial numerical increase through a hormetic response; the dose-response curve describing this numerical increase is an U-inverted curve. Furthermore, these data confirm that hormesis is common to many - if not all - living systems, including bacteria; they underline the relevance of a deepened knowledge of both the effects and the possible consequences of exposure to low doses of contaminants.

Antibiotic resistance gene abundances associated with antibiotics and heavy metals in animal manures and agricultural soils adjacent to feedlots in Shanghai; China

Eight antibiotic resistance genes (ARGs), 7 heavy metals, and 6 antibiotics were quantified in manures and soils collected from multiple feedlots in Shanghai. The samples were analyzed to determine if ARG abundances were associated with heavy metal concentration and independent of antibiotics. The results revealed the presence of chloramphenicol, sulfonamides and tetracyclines at concentration ranges of 3.27-17.85, 5.85-33.37 and 4.54-24.66 mg kg(-1), respectively. Typical heavy metals, such as Cu, Zn, and As, were detected at concentration ranges of 32.3-730.1, 75.9-4333.8, and 2.6-617.2 mg kg(-1). All ARGs tested were detected in the collected samples except tetB(P), which was absent in animal manures. Overall, sulfonamide ARGs were more abundant than tetracycline ARGs. Except for sulII, only a weak positive correlation was found between ARGs and their corresponding antibiotics. On the contrary, significant positive correlations (p<0.05) were found between some ARGs and typical heavy metals. For example, sulA and sulIII were strongly correlated with levels of Cu, Zn and Hg. The data demonstrated that the presence of ARGs was relatively independent of their respective antibiotic inducer. In addition to antibiotics, toxic heavy metals, such as Hg, Cu, and Zn, exerted a strong selection pressure and acted as complementary factors for ARG abundance.

Biodegradation of oxytetracycline by Pleurotus ostreatus mycelium: a mycoremediation technique

Oxytetracycline (OTC) is administered in high doses to livestocks and enters the environmental compartments as a consequence of animal waste disposal. As a first step in setting up a useful mycoremediation technique, an OTC lab degradation test was performed in liquid medium using the ligninolytic fungus Pleurotus ostreatus. OTC disappearance in culture medium was clearly evident as early as the third day of exposure onwards, with an almost complete removal after 14d. The drug removal was mediated by fungal absorption in the mycelia, where the OTC molecule underwent a degradation step, as demonstrated by mass spectrometry analyses. A putative degradation product, ADOTC (2-acetyl-2-decarboxamido-oxytetracycline) is proposed. Experimental conditions excluded OTC abiotic degradation; the degradation by extracellular laccase was also experimentally discarded.

Characteristics of oxytetracycline sorption and potential bioavailability in soils with various physical-chemical properties

Veterinary antibiotics are widely used for disease treatment, prevention and animal growth promoting. Frequent detection of veterinary antibiotics in environments, caused by land application of untreated or even treated antibiotics-containing animal wastes, has posed the growing concern of their adverse effect on natural ecosystems. Oxytetracycline (OTC) is one of the most widely-used veterinary antibiotics in livestock industry. OTC present as a cation, zwitterions, or net negatively charged ion in soils complicates predicting its sorption characteristics and potential bioavailability and toxicity. This study was to identify soil properties influencing OTC sorption and its subsequent bioavailability in five soils with various physical-chemical properties. A solution used to determine bioavailable analytes in soils and sediments, 1 M MgCl(2) (pH 8.5), was chosen to desorb the potentially bioavailable fraction of OTC sorbed onto soils. Our results demonstrated that soils with higher illite content and permanent cation exchange capacity have higher OTC sorption capacity, but increase the availability of sorbed OTC indicated by higher release of sorbed OTC from soils into aqueous phase in 1 M MgCl(2) (pH 8.5). Reversely, soil organic matter (SOM), clay, kaolinite, variable cation exchange capacity, DCB-Fe and -Al have lower OTC sorption capacity, but decrease the release of sorbed OTC from soils into 1 M MgCl(2). These findings indicate that SOM and clay greatly influence OTC adsorption and potential availability. This study contributes significantly to our understanding of the potential bioavailability of sorbed OTC and the effects of soil properties on OTC sorption behaviors in soils.

Fate of tetracyclines in swine manure of three selected swine farms in China

Veterinary antibiotics can enter the environment due to the common practice of land application of manure from treated animals. The environmental fate of tetracyclines in swine manure after composting and field application remains largely unknown. This study analyzed the concentrations of tetracyclines in manure, manure-based compost and compost amended soil in selected swine farms from Beijing, Jiaxing and Putian, China to determine the dilution effects of antibiotics when released into the soil environment. The results demonstrate that residues of antibiotics were detected in all samples and chlortetracycline as well as its degradation products should be regarded critically concerning their potential ecotoxicity. Application of manure-based compost to soil could reduce the possible risk posed by antibiotic contamination, but the trigger value of 100 microg/kg was still exceeded in soil samples (776.1 microg/kg dw) from Putian City after application of compost. Field studies such as the present one can help to improve the routine administration of antibiotic-containing composted manure.

Investigation of sulfonamide, tetracycline, and quinolone antibiotics in vegetable farmland soil in the Pearl River Delta area, southern China

Thirteen antibiotics in soil from vegetable farmlands of the Pearl River Delta, southern China, were investigated. At least three antibiotics were detected in each sample. Six antibiotics including four quinolones, tetracycline, and sulfamethoxazole were detected in >94% of the samples. The total contents of three tetracyclines, eight sulfonamides, and four quinolones were not detected-242.6, 33.3-321.4, and 27.8-1537.4 μg/kg, respectively. The highest antibiotic concentrations were observed mainly in vegetable farmlands affiliated with livestock farms. Chlortetracycline, sulfameter, and quinolones in some samples exceed the ecotoxic effect trigger value (100 μg/kg) set by the Steering Committee of Veterinary International Committee on Harmonization. The composition and concentration of antibiotics in soil were correlated with vegetable species. This study has revealed an alarming condition of antibiotics in vegetable farmland soil. Further investigation including environmental fate, plant uptake, and human exposure to antibiotics by plant-derived food should be conducted.

Dissipation of carbendazim and chloramphenicol alone and in combination and their effects on soil fungal:bacterial ratios and soil enzyme activities

The dissipation of carbendazim and chloramphenicol alone and in combination and their effects on soil fungal:bacterial ratios and soil enzyme activities were investigated. The results revealed that carbendazim dissipation was little affected by chloramphenicol, whereas chloramphenicol dissipation was found to be retarded significantly by the presence of carbendazim. The inhibitory effect of carbendazim on the fungal:bacterial ratios was increased by the presence of chloramphenicol, and the inhibitory effect of chloramphenicol on neutral phosphatase was increased by the presence of carbendazim. Carbendazim increased soil catalase and urease activities, but this increase was partially diminished by the presence of chloramphenicol. Little interaction was observed between carbendazim and chloramphenicol with regard to their influence on soil invertase. The results obtained in this study suggest that combinations of fungicides and antibiotics may alter the compounds' individual behaviors in soil and their effects on soil enzymes.

Occurrence and source analysis of typical veterinary antibiotics in manure, soil, vegetables and groundwater from organic vegetable bases, northern China

The residue of antibiotics is becoming an intractable environmental problem in many organic vegetable bases. However, their residual levels and distribution are still obscure. This work systematically analyzed the occurrence and migration of typical veterinary antibiotics in organic vegetable bases, northern China. The results showed that there was no obvious geographical difference in antibiotic distribution between soil and manure. A simple migration model can be easy and quick to predict the accumulation of antibiotics in soil. Antibiotics were mainly taken up through water transport and passive absorption in vegetables. The distribution of antibiotics in a plant was in the sequence leaf>stem>root, and performed biological accumulation. The residues of antibiotics in all samples in winter were significantly higher than those in summer. Overall, this work can lay the foundation for understanding ecological risk of antibiotics and their potential adverse effects on human health by food chain.

Phytotoxic antibiotic sulfadimethoxine elicits a complex hormetic response in the weed lythrum salicaria L

In order to evaluate the hormetic response of the weed Lythrum salicaria to drug exposure we investigated the effects of the antibiotic Sulfadimethoxine by growing Lythrum plants for 28 days on culture media containing different drug concentrations (between 0.005 and 50 mg.L(-1)). The antibiotic was absorbed by plants and can be found in plant tissue. The plant response was organ-dependent: roots, cotyledons and cotyledon petioles, were always affected by a toxic effect, whilst internodes and leaves length, showed a variable dose-depending response, with an increased growth at the lower drug concentrations and toxic effects at the higher ones. This variable response was probably dependant on different levels of local contamination resulting from a balance between accumulation rate and drug dilution in the increasing plant biomass. As a consequence, drug toxicity or hormetic response varied according to concentration and were different in each of the examined plant organ/tissue. Thus, even if hormesis can be considered a general plant response, each plant organ/tissue responds differently, depending on the local drug concentration and exposure time.

Hormetic effect(s) of tetracyclines as environmental contaminant on Zea mays

Animal wastes from intensive pig farming as fertilizers may expose crops to antimicrobials. Zea mays cultivations were carried out on a virgin field, subjected to dressing with pig slurries contaminated at 15 mg L(-1) of Oxy- and 5 mg L(-1) of Chlor-tetracycline, and at 8 mg L(-1) of Oxy and 3 mg L(-1) of Chlor, respectively. Pot cultivation was performed outdoor (Oxy in the range 62.5-1000 ng g(-1) dry soil) and plants harvested after 45 days. Tetracyclines analyses on soils and on field plants (roots, stalks, and leaves) did not determine the appreciable presence of tetracyclines. Residues were found in the 45-day pot corn only, in the range of 1-50 ng g(-1) for Oxy in roots, accounting for a 5% carry-over rate, on average. Although no detectable residues in plants from on land cultivations, both experimental batches showed the same biphasic growth form corresponding to a dose/response hormetic curve.

Investigation of the tetracycline, sulfonamide, and fluoroquinolone antimicrobial compounds in animal manure and agricultural soils in Turkey

Occurrence of antimicrobial residuals in the environment is of concern because of the emergence and development of antimicrobial-resistance in pathogen bacteria, and the ecotoxicological behaviour of these compounds. Investigation of antimicrobial pollution in animal manure has special importance since they constitute the major source for the dissemination of these chemicals into the environment. Hence, eight animal manure and nine agricultural soil samples from the North part of Marmara Region (Turkey) were collected and analyzed for two tetracyclines (TCs), four sulfonamides (SAs), and two fluoroquinolones (FQs). At least one antimicrobial compound was detected in all the agricultural soil and animal manure samples. The highest antimicrobial concentrations were in general detected in the fresh poultry manure samples. Mean recoveries from spiked soil and manure samples ranged from 60 to 86% and 62 to 77% for TCs, 69 to 101% and 14 to 82% for SAs, and 46 to 55% and 24 to 42% for FQs, respectively. Relationship between the recovery rates of the antimicrobial compounds and sample characteristics was statistically evaluated by means of hierarchical cluster analysis (HCA), and principal component analysis (PCA) followed by multiple stepwise regression (MSR). HCA showed agricultural soil samples with higher di- and trivalent metal contents resulted in higher TC and lower FQ recoveries. TC recoveries from manure were highest in the samples with lowest K, Mg, and Ca content, while FQs were more efficiently extracted from the manure samples with less % organic carbon (OC) content. The findings of HCA for TCs were supported by those of MSR analysis, giving comparable results. In addition, MSR of SA recoveries revealed that the increasing amounts of manure % OC led to lower recoveries.