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Purpose: As irrigation with untreated wastewater often leads to an accumulation of contaminants in soils, nowadays, treated wastewater is increasingly used for irrigation. Here, we investigated whether and to which degree irrigation with treated wastewater might cause desorption of antibiotics from three soils (Leptosol, Phaeozem, Vertisol) and a sediment (Endhó reservoir) of the Mezquital Valley, Mexico, that were exposed to untreated wastewater in the past. Materials and methods: We performed sequential batch desorption experiments with treated wastewater, artificial wastewater with anionic surfactants, and artificial wastewater without surfactants. Results and discussion: We observed no desorption, but net sorption of ciprofloxacin in contact with treated wastewater containing 3.475 μg L of ciprofloxacin. Sulfamethoxazole was desorbed from the Leptosol, the Phaeozem, and the Vertisol in a similar degree with and without surfactant, but not from sediment, where no sulfamethoxazole was detected. In contact with treated wastewater containing 1.045 μg L of sulfamethoxazole, it was desorbed from the Leptosol and the Phaeozem with low clay, Fe oxide, and organic matter contents, whereas the Vertisol and sediment showed a net sulfamethoxazole sorption. Desorption could be described with a bi-phasic kinetic desorption model, with most sulfamethoxazole being desorbed via a rate-limited process from poorly accessible binding sites, where it had been accumulated during the long-term irrigation in the past. Conclusions: We conclude that a potential release of pharmaceuticals as a result from changes in wastewater irrigation is soil specific: Leptosols and Phaeozems of the Mezquital Valley might act as long-term sources of the sulfonamide sulfamethoxazole, though not of the fluoroquinolone ciprofloxacin. [ABSTRACT FROM AUTHOR]

In regions with high livestock densities, the usage of antibiotics and metals for veterinary purposes or as growth promoters poses a risk in manured soils. We investigated to which degree the concentrations and depth distributions of Cu, Zn, Cr and As could be used as a tracer to discover contaminations with sulfonamides, tetracyclines and fluoroquinolones. Besides, we estimated the potential vertical translocation of antibiotics and compared the results to measured data. In the peri-urban region of Beijing, China, soil was sampled from agricultural fields and a dry riverbed contaminated by organic waste disposal. The antibiotic concentrations reached 110 μg kg sulfamethazine, 111 μg kg chlortetracycline and 62 μg kg enrofloxacin in the topsoil of agricultural fields. Intriguingly, total concentrations of Cu, Zn, Cr and As were smaller than 65, 130, 36 and 10 mg kg in surface soil, respectively, therewith fulfilling Chinese quality standards. Correlations between sulfamethazine concentrations and Cu or Zn suggest that in regions with high manure applications, one might use the frequently existing monitoring data for metals to identify potential pollution hotspots for antibiotics in topsoils. In the subsoils, we found sulfamethazine down to ≥2 m depth on agricultural sites and down to ≥4 m depth in the riverbed. As no translocation of metals was observed, subsoil antibiotic contamination could not be predicted from metal data. Nevertheless, sulfonamide stocks in the subsoil could be estimated with an accuracy of 35-200 % from fertilisation data and potential leaching rates. While this may not be sufficient for precise prediction of antibiotic exposure, it may very well be useful for the pre-identification of risk hotspots for subsequent in-depth assessment studies. [ABSTRACT FROM AUTHOR]

Difloxacin ( DIF) belongs to the class of fluoroquinolone antibiotics that have been intensively used for the treatment of bacterial infections in veterinary and human medicine. The aim of this field study was to compare the effect of manure from DIF-treated pigs and untreated pigs on the bacterial community structure and resistance gene abundance in bulk soil and rhizosphere of maize. A significant effect of DIF manure on the bacterial community composition in bulk soil was revealed by denaturing gradient gel electrophoresis ( DGGE) of bacterial 16 S r RNA gene fragments amplified from total community DNA. In few samples, quinolone resistance genes qnrB and qnrS1/qnrS2 were detected by PCR and subsequent hybridization, while qnrA was not detected. Quantitative PCR revealed an increased abundance of the integrase gene intI1 of class I integrons and sulfonamide resistance genes sul1 and sul2 in DIF manure-treated bulk soil and rhizosphere, relative to 16 S r RNA genes, while traN genes specific for Low GC-type plasmids were increased only in bulk soil. Principal component analysis of DGGE profiles suggested a manure effect in soil until day 28, but samples of days 71 and 140 were found close to untreated soil, indicating resilience of soil community compositions from disturbances by manure. [ABSTRACT FROM AUTHOR]

Abstract: Veterinary antibiotics reach the soil environment by manure application, where they accumulate or are prone to vertical translocation. We assumed that a high pH value at slightly calcareous soil properties should retain tetracyclines and fluoroquinolones even at high manure loads, whereas it should facilitate leaching of sulfonamides. Hence, we investigated the transport of manure-added antibiotics in a soil developed from calcareous parent material on a farm in peri-urban Beijing, China. Leachate was collected from zero-tension samplers, installed at 40cm depth under undisturbed soil, which was treated according to (i) routine farm practice and (ii) worst-case conditions (high antibiotic concentrations, irrigation imitating heavy rainfall). Additionally, the soil depth distribution of pharmaceuticals at the end of the leaching experiment was analysed. Under routine farm practice, sulfamethazine was repeatedly detected in the leachate with a maximum concentration of 0.12μgL−1. All applied substances were still detected in soil after 53days, suggesting that there was no overall rapid and complete dissipation. Worst-case conditions enhanced vertical translocation; all leachate samples contained sulfonamides (up to 653μgL−1 sulfamethazine), and even tetracyclines were found in the leachate once, with doxycycline reaching the highest concentration (0.19μgL−1). The concentrated simultaneous occurrence of sulfonamides with the bromide tracer in leachate samples pointed to preferential flow as underlying transport process. The high pH values did not prevent the single leaching event for tetracyclines and hardly affected overall leaching behaviour. The applied fluoroquinolones were not significantly translocated below 4cm depth, irrespective of irrigation and high manure addition. [Copyright &y& Elsevier]

The long-term environmental fate of the veterinary antibiotic sulfadiazine (SDZ) in soils is determined by a reversible sequestration into a residual fraction and an irreversible formation of non-extractable residues (NER), which can be described as first-order rate processes. However, the concentration dynamics of the resulting fractions of SDZ in soil show an unexplained rapid reduction of extractability during the first 24 h. We therefore investigated the short-term extractability of SDZ in two different soils under different SDZ application procedures over 24 h: with and without manure, for air-dried and for moist soils. In all batches, we observed an instantaneous loss of extractability on a time scale of minutes as well as kinetically determined sequestration and NER formation over 24 h. Data evaluation with a simple kinetic model led to the conclusion that application with manure accelerated the short-term formation of NER, whereas sequestration was very similar for all batches. [Copyright &y& Elsevier]

Veterinary antibiotics entering agricultural land with manure pose the risk of spreading antibiotic resistance. The fate of sulfadiazine ( SDZ) introduced via manure and its effect on resistance gene levels in the rhizosphere were compared with that in bulk soil. Maize plants were grown for 9 weeks in soil fertilized with manure either from SDZ-treated pigs ( SDZ treatment) or from untreated pigs (control). CaCl2-extractable concentrations of SDZ dissipated faster in the rhizosphere than in bulk soil, but SDZ remained detectable over the whole time. For bulk soil, the abundance of sul1 and sul2 relative to 16S r RNA gene copies was higher in the SDZ treatment than in the control, as revealed by quantitative PCR on days 14 and 63. In the rhizosphere, sampled on day 63, the relative sul gene abundances were also significantly increased in the SDZ treatment. The accumulated SDZ exposure (until day 63) of the bacteria significantly correlated with the log relative abundance of sul1 and sul2, so that these resistance genes were less abundant in the rhizosphere than in bulk soil. Plasmids conferring SDZ resistance, which were exogenously captured in Escherichia coli, mainly belonged to the Low GC group and carried a heterogeneous load of resistances to different classes of antibiotics. [ABSTRACT FROM AUTHOR]

Veterinary antibiotics introduced into the 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 persistence and (bio)accessibility, which may differ between laboratory and field conditions. We examined the dissipation and sequestration of sulfadiazine (SDZ) and its main metabolites in soil under field conditions and how it was influenced by temperature, soil moisture, plant roots, and soil aggregation compared to controlled laboratory experiments. A sequential extraction accounted for easily extractable (CaCl2-extractable) and sequestered (microwave-extractable, residual) SDZ fractions. Dissipation from both fractions was largely temperature-dependent and could be well predicted from laboratory data recorded at different temperatures. Soil moisture additionally seemed to control sequestration, being accelerated in dry soil. Sequestration, as indicated by increasing apparent distribution coefficients and decreasing rates of kinetic release into CaCl2, governed the antibiotic's long-term fate in soil. Besides, we observed spatial gradients of antibiotic concentrations across soil aggregates and in the vicinity of roots. The former were short-lived and equilibrated due to aggregate reorganization, while dissipation of the easily extractable fraction was accelerated near roots throughout the growth period. There was little if any impact of the plants on residual SDZ concentrations. [ABSTRACT FROM AUTHOR]

Large amounts of veterinary antibiotics are applied worldwide to farm animals and reach agricultural fields by manure fertilization, where they might lead to an increased abundance and transferability of antibiotic-resistance determinants. In this review we discuss recent advances, limitations, and research needs in determining the fate of veterinary antibiotics and resistant bacteria applied with manure to soil, and their effects on the structure and function of soil microbial communities in bulk soils and the rhizosphere. The increased abundance and mobilization of antibiotic-resistance genes (ARGs) might contribute to the emergence of multi-resistant human pathogens that increasingly threaten the successful antibiotic treatment of bacterial infections. [ABSTRACT FROM AUTHOR]

Abstract: Antibiotics of inorganic and organic origin in pig manure can inhibit the anaerobic process in biogas plants. The influence of three frequently used antibiotics, copper dosed as CuSO4, sulfadiazine (SDZ), and difloxacin (DIF), on the anaerobic digestion process of pig manure was studied in semi-continuous experiments. Biogas production recovered after every Cu dosage up to a sum of 12.94g Cukg−1 organic dry matter (ODM), probably due to Cu precipitation following the formation of sulphide from sulphate. Complete inhibition was found at the very high Cu concentration of 19.40g Cukg−1 ODM. Inhibitory effect of SDZ and DIF was observed at concentrations as high as 2.70gkg−1 ODM and 0.54gkg−1 ODM, respectively. It seems very unlikely that the antibiotics tested would inhibit the anaerobic process in a full-scale biogas plant. [Copyright &y& Elsevier]