An Ultrasensitive Label-Free Fluorescent Aptasensor Platform for Detection of Sulfamethazine

Purpose

Sulfamethazine (SMZ) exposed in the environment can enter the human body through the food chain and pose a serious threat to human health. Therefore, it is important to develop a rapid and sensitive method for detecting SMZ in environmental samples. In order to fastly and quantitatively detect SMZ in environmental samples, we developed a label-free fluorescent aptasensor based on specific aptamer (SMZ1S) and fluorescence resonance energy transfer (FRET) between gold nanoparticles (AuNPs) and rhodamine B (RhoB).

Methods

In the absence of SMZ, SMZ1S was adsorbed on the surface of AuNPs, which led to dispersion of the AuNPs in high concentration saline solution, thus effectively quenching the fluorescence of RhoB. With the increase of the SMZ concentration, the specific binding of SMZ1S and SMZ led to the aggregation of AuNPs in the presence of NaCl, which reduced the quenching of RhoB fluorescence and increased the fluorescence intensity. The sensitivity and linearity curve of the label-free fluorescent aptasensor were determined with different concentrations of sulfamethazine standard solutions. The specificity of this fluorescent aptasensor was determined by replacing sulfamethazine with different antibiotics. In addition, the actual water and soil samples were spiked and recovered.

Results

Under optimized conditions, the proposed fluorescent aptasensor demonstrated a good linear detection of SMZ in binding buffer from 1.25 ng mL^-1 to 40 ng mL^-1 and the limit of detection was 0.82 ng mL^-1. The spiked recoveries for SMZ were 94.4% to 108.8% with a relative standard deviation of 1.8-10.3% in water and soil samples, respectively.

Conclusion

The label-free fluorescent aptasensor investigated in the current study is a promising tool to detect and quantify SMZ in water and soil samples.

Functional Characterization of the Effects of N-acetyltransferase 2 Alleles on N-acetylation of Eight Drugs and Worldwide Distribution of Substrate-Specific Diversity

Variability in the enzymatic activity of N-acetyltransferase 2 (NAT2) is an important contributor to interindividual differences in drug responses. However, there is little information on functional differences in N-acetylation activities according to NAT2 phenotypes, i.e., rapid, intermediate, slow, and ultra-slow acetylators, between different substrate drugs. Here, we estimated NAT2 genotypes in 990 Japanese individuals and compared the frequencies of different genotypes with those of different populations. We then calculated in vitro kinetic parameters of four NAT2 alleles (NAT2^∗4, ^∗5, ^∗6, and ^∗7) for N-acetylation of aminoglutethimide, diaminodiphenyl sulfone, hydralazine, isoniazid, phenelzine, procaineamide, sulfamethazine (SMZ), and sulfapyrizine. NAT2^∗5, ^∗6, and ^∗7 exhibited significantly reduced N-acetylation activities with lower Vmax and CLint values of all drugs when compared with NAT2^∗4. Hierarchical clustering analysis revealed that 10 NAT2 genotypes were categorized into three or four clusters. According to the results of in vitro metabolic experiments using SMZ as a substrate, the frequencies of ultra-slow acetylators were calculated to be 29.05–54.27% in Europeans, Africans, and South East Asians, whereas Japanese and East Asian populations showed lower frequencies (4.75 and 11.11%, respectively). Our findings will be helpful for prediction of responses to drugs primarily metabolized by NAT2.

Synthesis and Characterization of Nano-Sized 4-Aminosalicylic Acid-Sulfamethazine Cocrystals

Drug–drug cocrystals are formulated to produce combined medication, not just to modulate active pharmaceutical ingredient (API) properties. Nano-crystals adjust the pharmacokinetic properties and enhance the dissolution of APIs. Nano-cocrystals seem to enhance API properties by combining the benefits of both technologies. Despite the promising opportunities of nano-sized cocrystals, the research at the interface of nano-technology and cocrystals has, however, been described to be in its infancy. In this study, high-pressure homogenization (HPH) and high-power ultrasound were used to prepare nano-sized cocrystals of 4-aminosalysilic acid and sulfamethazine in order to establish differences between the two methods in terms of cocrystal size, morphology, polymorphic form, and dissolution rate enhancement. It was found that both methods resulted in the formation of form I cocrystals with a high degree of crystallinity. HPH yielded nano-sized cocrystals, while those prepared by high-power ultrasound were in the micro-size range. Furthermore, HPH produced smaller-size cocrystals with a narrow size distribution when a higher pressure was used. Cocrystals appeared to be needle-like when prepared by HPH compared to those prepared by high-power ultrasound, which had a different morphology. The highest dissolution enhancement was observed in cocrystals prepared by HPH; however, both micro- and nano-sized cocrystals enhanced the dissolution of sulfamethazine.

Immunochromatographic assay based on time-resolved fluorescent nanobeads for the rapid detection of sulfamethazine in egg, honey, and pork

BACKGROUND

Sulfamethazine (SMZ), a veterinary drug widely used in animal husbandry, is harmful to human health when excess residues are present in food. In this study, a fast, reliable, and sensitive immunochromatographic assay (ICA) was developed on the basis of the competitive format by using time-resolved fluorescent nanobeads (TRFN) as label for the detection of SMZ in egg, honey, and pork samples.

RESULTS

Under optimized working conditions, this method had limits of detection of 0.016, 0.049, and 0.029 ng mL^-1 and corresponding linear ranges of 0.05 to 1.00, 0.05 to 5.00, and 0.05 to 1.00 ng mL^-1 in egg, honey, and pork samples, respectively. The recovery experiments showed that the average recoveries ranged from 90.5% to 113.9%, 82.4% to 112.0%, and 79.8% to 93.4% with corresponding coefficients of variation of 4.1% to 11.7%, 7.5% to 11.5%, and 4.8% to 8.7% for egg, honey, and pork samples, respectively. The developed TRFN-ICA was also systematically compared with high-performance liquid chromatography coupled with tandem mass spectrometry (HPLC-MS/MS) by analyzing 45 actual samples from egg, honey, and pork.

CONCLUSION

Overall, the developed TRFN-ICA had high reliability and excellent potential for the ultrasensitive detection of SMZ for food safety monitoring, also providing a universal platform for the on-site detection of other targets. © 2020 Society of Chemical Industry.

Removal of Pharmaceutical Micropollutants with Integrated Biochar and Marine Microalgae

Using microalgae to remove pharmaceuticals and personal care products (PPCPs) micropollutants (MPs) have attracted considerable interest. However, high concentrations of persistent PPCPs can reduce the performance of microalgae in remediating PPCPs. Three persistent PPCPs, namely, carbamazepine (CBZ), sulfamethazine (SMT) and tramadol (TRA), were treated with a combination of Chaetoceros muelleri and biochar in a photobioreactor during this study. Two reactors were run. The first reactor comprised Chaetoceros muelleri, as the control, and the second reactor comprised Chaetoceros muelleri and biochar. The second reactor showed a better performance in removing PPCPs. Through the response surface methodology, 68.9% (0.330 mg L-1) of CBZ, 64.8% (0.311 mg L-1) of SMT and 69.3% (0.332 mg L-1) of TRA were removed at the initial concentrations of MPs (0.48 mg L-1) and contact time of 8.1 days. An artificial neural network was used in optimising elimination efficiency for each MP. The rational mean squared errors and high R2 values showed that the removal of PPCPs was optimised. Moreover, the effects of PPCPs concentration (0-100 mg L-1) on Chaetoceros muelleri were studied. Low PPCP concentrations (<40 mg L-1) increased the amounts of chlorophyll and proteins in the microalgae. However, cell viability, chlorophyll and protein contents dramatically decreased with increasing PPCPs concentrations (>40 mg L-1).

Synthesis and assessment of schwertmannite/few-layer graphene composite for the degradation of sulfamethazine in heterogeneous Fenton-like reaction

Schwertmannite (sch), an iron oxyhydrosulfate mineral, can catalyse a Fenton-like reaction to degrade organic contaminants, but the reduction of Fe(III) to Fe(II) on the surface of schwertmannite is a limiting step for the Fenton-like process. In the present study, the sch/few-layer graphene (sch-FLG) composite was synthesized to promote the catalytic activity of sch in a Fenton-like reaction. It was found that sch can be successfully carried by FLG in sch-FLG composite, mainly via the chemical bond of Fe-O-C on the surface of sch-FLG. The sch-FLG exhibited a much higher catalytic activity than sch or FLG for the degradation of sulfamethazine (SMT) in the heterogeneous Fenton-like reaction, which resulted from the fact that the FLG can pass electrons efficiently. The degradation efficiency of SMT was around 100% under the reaction conditions of H2O2 200-500 mg l-1, sch-FLG dosage 1-2 g l-1, temperature 28-38°C, and initial solution pH 1-9. During the repeated uses of sch-FLG in the Fenton-like reaction, it maintained a certain catalytic activity for the degradation of SMT and the mineral structure was not changed. In addition, SMT may be finally mineralized in the Fenton-like reaction catalysed by sch-FLG, and the possible degradation pathways were proposed. Therefore, the sch-FLG is an excellent catalyst for SMT degradation in a heterogeneous Fenton-like reaction.

Adsorption of Sulfamethazine Drug onto the Modified Derivatives of Carbon Nanotubes at Different pH

The sulfamethazine drug interaction with carbon nanotubes was investigated with the aim of improving the adsorption capacity of the adsorptive materials. Experiments were performed to clarify how the molecular environment affects the adsorption process. Single-walled carbon nanotubes have a higher removal efficiency of sulfamethazine than pristine or functionalized multi-walled carbon nanotubes. Although the presence of cyclodextrin molecules improves the solubility of sulfamethazine, it reduces the adsorption capacity of the carbon nanotube towards the sulfamethazine drug and, therefore, inhibits the removal of these antibiotic pollutants from waters by carbon nanotubes.

[Adsorption Characteristics of Sulfamethazine on Three Typical Porous High-temperature Modified Solid Waste Materials]

Three typical porous solid wastes, including livestock manure, crop straw, and coal mining waste, were used as raw materials to prepare cattle manure charcoal, straw charcoal, and coal gangue charcoal by low-oxygen controlling temperature carbonization and calcination. Batch adsorption experiments of sulfamethazine (SMZ) in water were carried out. Adsorption kinetics and isothermal adsorption equilibrium were used to investigate the adsorption characteristics of SMZ on cattle dung charcoal, straw charcoal, and coal gangue charcoal, and the adsorption mechanism was discussed by means of field-electron scanning electron microscope, Fourier transform infrared spectroscopy, Boehm titration, Brunauer-Emmett-Teller measurement, and zeta potentiometric titration. The results showed that the adsorption of SMZ on the three carbon materials reached equilibrium at 24 h. The adsorption kinetics of SMZ on three kinds of carbon materials agreed with the quasi-second-order kinetics equation. R² ranged from 0.9968 to 0.9999, and the adsorption rate decreased with the decrease in effective adsorption sites on the surface of carbon materials. The adsorption process mainly consists of three steps:membrane diffusion, intraparticle diffusion, and the equilibrium stage. Both intraparticle diffusion and membrane diffusion control the adsorption rate. Isothermal adsorption is more consistent with the Freundlich model. R² is between 0.9874 and 0.9997. It is mainly physical adsorption and spontaneous exothermic reaction. The maximum adsorption capacity of the three kinds of carbon materials was cattle dung carbon (19.64 mg·g^-1) > coal gangue carbon (12.06 mg·g^-1) > straw carbon (9.16 mg·g^-1). The adsorption mechanism of SMZ on the three kinds of carbon materials mainly includes hydrogen bonding between molecules, surface electrostatic adsorption of multi-molecular layers, and pore filling. Of these, electrostatic adsorption is the main adsorption mechanism. The best adsorption performance of cattle manure charcoal may be due to its rich oxygen-containing functional groups, more negative charges, and larger specific surface area and pore volume.

Thermodynamic Characterization of the Interaction between the Antimicrobial Drug Sulfamethazine and Two Selected Cyclodextrins

Sulfamethazine is a representative member of the sulfonamide antibiotic drugs; it is still used in human and veterinary therapy. The protonation state of this drug affects its aqueous solubility, which can be controlled by its inclusion complexes with native or chemically-modified cyclodextrins. In this work, the temperature-dependent (298–313 K) interaction of sulfamethazine with native and randomly methylated β-cyclodextrins have been investigated at acidic and neutral pH. Surprisingly, the interaction between the neutral and anionic forms of the guest molecule and cyclodextrins with electron rich cavity are thermodynamically more favorable compared to the cationic guest. This property probably due to the enhanced formation of zwitterionic form of sulfamethazine in the hydrophobic cavities of cyclodextrins. Spectroscopic measurements and molecular modeling studies indicated the possible driving forces (hydrophobic interaction, hydrogen bonding, and electrostatic interaction) of the complex formation, and highlighted the importance of the reorganization of the solvent molecules during the entering of the guest molecule into the host’s cavity.

Sulfamethazine contamination level and exposure assessment in domestic and imported poultry meats in Jordan

BACKGROUND AND AIM

Sulfamethazine (SMZ) is an important and widely used antibiotic in poultry industry due to its high efficacy in fighting diseases and promoting growth. In addition, SMZ is a possible human carcinogen and has been found in many food types including poultry meat. Accordingly, this study aimed to survey the contamination level and estimated daily intake (EDI) of SMZ in domestic and imported poultry meat samples in Jordan.

MATERIALS AND METHODS

A total of 120 samples; 60, 30, and 30 of fresh and frozen domestic and frozen imported poultry samples, respectively, were collected from different cities in Jordan. Poultry samples were analyzed for SMZ incidence rate and contamination level using a competitive enzyme-linked immunosorbent assay technique. EDI values were calculated from the SMZ concentration, average poultry daily consumption rate, and adult body weight (b.w.).

RESULTS

Of the 120 surveyed samples, 20 samples (16.7%) were SMZ violative positive and exceeded the European Union maximum limit (100 µg/kg) and accordingly were unfit for human consumption. Whereas, 51 samples (42.5%) were with SMZ concentrations of 10-100 µg/kg. The average SMZ concentration was 235.58 µg/kg, with a range of 11.47-800 µg/kg poultry meat. It is also noteworthy the high EDI of SMZ by Jordanian adults, 0.286 µg SMZ/kg b.w./day. Moreover, results prevailed that the highest SMZ incidence rate and contamination level were for imported poultry samples followed by domestic poultry samples, which may indicate that SMZ contamination in poultry meat is an international issue.

CONCLUSION

The current study prevailed high SMZ incidence rate, contamination level, and EDI values, which is likely due to indiscriminate use of SMZ in poultry production. Results also prevailed the high risk that consumers in Jordan may expose due to SMZ residues. Therefore, more strict program and good agricultural practices should be applied to monitor antibiotic withdrawal periods in animals used for human consumption to ensure the legal residue requirements of these antibiotics.

Multiresidue Determination of 27 Sulfonamides in Poultry Feathers and Its Application to a Sulfamethazine Pharmacokinetics Study on Laying Hen Feathers and Sulfonamide Residue Monitoring on Poultry Feathers

A method for the simultaneous determination of 27 sulfonamides in poultry feathers using ultra performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) was established in this study. The samples were extracted using 0.1 mol/L HCl solutions in a 60 °C water bath for 2 h, purified using hydrophilic-lipophilic balance solid-phase extraction, nitrogen-dried, and then reconstituted for UPLC-MS/MS analysis, which was performed with a CSH-C18 column. Linearity, limit of detection, limit of quantification, recovery, and precision were calculated in accordance with Commission Decision 2002/657/EC. For linearity, all standard curves showed a standard coefficient greater than 0.99, and the recoveries and coefficient of variation were 89-115% and <20%, respectively. The limit of detection and limit of quantification were 0.2-5 and 0.5-20 ng/g, respectively. The method was successfully applied to sulfamethazine (SMZ) residue accumulation monitoring in laying hen feathers and sulfonamide residue monitoring on poultry feathers. SMZ residue accumulation in the laying hen feathers was studied after administration with 100 mg/kg of SMZ for 21 consecutive days. SMZ residues were still detected in feathers 14 days after drug administration and persisted for up to 85 days. Results from 42 poultry feather samples showed that the feather is a suitable medium to monitor the illegal use of sulfonamides in poultry production.

Uptake, translocation, and metabolism of sulfamethazine by Arabidopsis thaliana: distinguishing between phytometabolites and abiotic transformation products in the media

Plant accumulation of antibiotic residues presents potential risks to human and ecosystem health. However, the phytometabolic pathways of antibiotics following plant uptake are still largely uncharacterized. This study investigated the phytometabolism of sulfamethazine (SMT) by Arabidopsis thaliana, using ¹⁴C-labeled and unlabeled SMT. SMT was accumulated in both roots and shoots of axenic A. thaliana plants (123.7 ± 12.3 and 22.7 ± 1.0 µg/kg fw, respectively) after 21 days of exposure. However, the parent ¹⁴C-SMT accounted for only 1.7 ± 0.01% of the total ¹⁴C-radioactivity in plant tissues. The majority of ¹⁴C-radioactivity taken up by plants was present as bound residues (42.0-68.2% of initially applied ¹⁴C-SMT), while extractable ¹⁴C-residues accounted for only 7.7-12.6%. A. thaliana metabolized SMT primarily through glycosylation at the N⁴-nitrogen atom. Additionally, other products, including pterin-SMT, methylsalicylate-SMT, N⁴-formyl-SMT, desulfo-SMT, hydroxyl-SMT, N⁴-acetyl-SMT, desamino-SMT, and 2-amino-4,6-dimethylpyrimidine, were also identified. Notably, a portion of the extractable metabolites was excreted into the culture media, requiring characterization of these metabolites as either excreted phytometabolites or abiotic transformation products of SMT based on comparisons between experimental and control reactors.

Assessment of veterinary drugs present in pork kidney from a Midwest US retail market

A total of 1040 pork kidneys were purchased from 4 retail stores located in a Midwestern US town and screened for antibiotics with the Charm-KIS™ screening test. Six samples (0.6%) tested positive with the Charm-KIS™. Sixty-five samples from each retail location and the 18 Charm-KIS™ positive or 'caution' samples were also subjected to ELISA to determine the presence of commonly used veterinary drugs including flunixin, ractopamine, sulfamethazine, and/or tetracycline of the 278 samples assessed by ELISA, flunixin, ractopamine, sulfamethazine, and tetracycline residues were found to be 0%, 22%, 4%, and 10% ELISA positive respectively, and had greater than limit of quantitation concentrations as measured by LC-MS/MS.  All residue levels determined by LC-MS/MS were well below US tolerances, regardless of analyte.  These findings suggest that veterinary drugs are being used in accordance with US regulations and that veterinary drug residues in pork do not pose a health concern to US consumers.

Rapid Detection of the Antibiotic Sulfamethazine in Pig Body Fluids by Paper Spray Mass Spectrometry

We report herein a practical method for nonlethal detection of the antibiotic sulfamethazine in pig body fluids via the combination of simple extraction and paper spray mass spectrometry (PS-MS). This method requires minimal sample preparation while still providing high sensitivities and accuracies in complex matrices including pig whole blood (LOD = 7.9 μg/L; recovery = 95.4-103.7%), pig serum (LOD = 11.5 μg/L; recovery = 103.2-106.2%), and synthetic urine (LOD = 11.2 μg/L; recovery = 99.1-103.2%). Given a known correlation between the level of sulfamethazine in body fluids and edible tissues, this method shows great promise as a practical and nonlethal solution for rapid testing of the drug, which can substantially aid managerial decision in the livestock industry.

Evaluation of sulfamethazine removal kinetics using fixed structured bed bioreactor

The use of anaerobic biomass attached to a support has been recently presented as a good prospect in the treatment of wastewater containing recalcitrant compounds, such as sulfamethazine (SMZ). SMZ has been found in swine wastewater and sewage treatment plants, which motivates assessing their degradation by new wastewater treatment technologies. Thus, this paper describes the use of a continuous fixed structured bed bioreactor for the purpose of evaluating SMZ removal kinetics present in lab-made wastewater. The analysis of SMZ used online solid-phase extraction coupled to liquid chromatography/tandem mass spectrometry (SPE online-LC-MS/MS). Chemical oxygen demand (COD) was also monitored to evaluate the organic matter removal. The bioreactor was operated under mesophilic conditions (30 ∘ C), with a hydraulic retention time of 24 h. In order to evaluate SMZ removal, four different concentration levels were studied: 200, 400, 600, and 800 ng L^-1. COD removal efficiency obtained for filtered effluent kept at 91.01% and there was no interference due to the increase of SMZ concentration. For SMZ, the removal efficiencies were of 52.8±12.1% for 200 ng L^-1 concentration level; 55.0±8.15% for 400 ng L^-1; 53.0±6.14% for 600 ng L^-1, and 48.8±5.44% for 800 ng L^-1. COD removal kinetics presented a first-order apparent removal rate constant ( kapp ) of 0.281±0.0295  h^-1. SMZ also showed a first-order apparent removal rate constant of 0.158±0.0093  h^-1 for the following concentrations levels: 200, 400, 600, and 800 ng L^-1.

[Photo-assisted Degradation of Sulfamethazine by Ferrocene-catalyzed Heterogeneous Fenton-like System]

Antibiotics are acknowledged micropollutants in wastewaters and surface waters. They are of particular concern because they can trigger an increase in resistant bacteria. Therefore, novel and efficient technology for the removal of antibiotics is urgently needed. In this study, heterogeneous Fenton-like reaction based on ferrocene (Fc) had been constructed, sulfamethazine (SMZ) was selected as target compound due to its abundance in water. The degradation kinetics, transformation pathway, and degradation products of SMZ in this system were investigated. The results showed that Fc+H₂O₂+UV had better degradation efficiency for SMZ than did Fc, Fc+UV, H₂O₂, and H₂O₂+UV, Fc+H₂O₂ systems. Radical scavenger experiments confirmed that the photogenerated OH was largely responsible for the photolytic enhancement of SMZ in the Fc+H₂O₂+UV system. Additionally, the electron spin resonance technique revealed that photogenerated O₂^- was found in the system, indicating that Fc can generate electrons under light conditions. H₂O₂ underwent electron disproportionation to produce OH, which promoted the degradation of SMZ. The degradation products of SMZ in the Fc+H₂O₂+UV system were identified by LC/LTQ-Orbitrap MS. The hydroxylation of SMZ, the removal of SO₂, and the products of breaking C-S, S-N, and N-C bonds were observed. Common soluble components (such as DOM, Cl^-, and Br^-) in water can quench OH, thus inhibiting the photodegradation of SMZ. However, the ionic strength had no significant effect on the degradation of SMZ in the Fc+H₂O₂+UV system, which showed that this technique positively affected the treatment of wastewater containing high-salinity antibiotics.

Novel Thermosensitive Core⁻Shell Surface Molecularly Imprinted Polymers Based on SiO₂ for the Selective Adsorption of Sulfamethazine

In this research, a novel, sulfamethazine, thermosensitive, molecularly-imprinted polymer (MIP) with an obvious core–shell structure for the enrichment of sulfamethazine (SMZ), which involved temperature sensitive monomer N-Isopropylacrylamide, functional monomer methacrylic acid and cross-linking agents ethyleneglycol dimethacrylate (EGDMA) and N,N′-methylenebisacrylamide, was successfully compounded using the surface polymerization method. To ensure the best experimental group, we designed and compared three groups of controlled experiments of MIPs with different crosslinking agents. When the adsorption temperature was almost the lower critical solution temperature (LCST) of Poly(N-Isopropylacrylamide), the preparative MIPs showed outstanding adsorption capacity and specific identification to sulfamethazine. Moreover, this allowed the MIPs to better facilitate by combining the template molecules, as well as optimizing the imprinting factor. In addition, after 80 min, the adsorption of the MIPs leveled off and remained constant, and the adsorption quantity reached (a maximum of) at 8.1 mg·g⁻¹.

[Effects of the Veterinary Antibiotic Sulfamethazine on Ammonia Volatilization from a Paddy Field Treated with Conventional Synthetic Fertilizer and Manure]

Veterinary antibiotics have been widely detected in croplands due to the application of animal excrements as fertilizer. However, their effects on ammonia (NH₃) volatilization remain unclear. A field experiment was conducted to evaluate the effect of sulfamethazine on NH₃ volatilization from a paddy field when conventional synthetic fertilizer or manure was applied as basal fertilizer. Five different treatments were conducted in this study: without application of fertilizers and antibiotics (CK), compound fertilizer used as basal fertilizer with and without the addition of sulfamethazine (CF+SD and CF respectively), and pig manure used as base fertilizer with and without the addition of sulfamethazine (CM+SD and CM respectively). Urea was used for topdressing in the CF, CF+SD, CM, and CM+SD treatments. The results showed that regardless of the fertilizer type applied, sulfamethazine did not affect the seasonal pattern of NH₃volatilization. However, it promoted the NH₃ volatilization rate in the topdressing stage significantly (P<0.01). During the observation period, the proportions of applied N lost as NH₃-N in the CF+SD and CM+SD treatments were 1.65 and 2.78 times higher than those in the CF and CM treatments, respectively. The promoting effect of sulfamethazine was more obvious in the pig manure treatment than in the compound fertilizer treatment. Sulfamethazine significantly increased the soil urease activity (P<0.05). Furthermore, the NH₃ volatilization rate was positively correlated with urease activity and soil ammonia nitrogen content (P<0.05). This indicates that sulfamethazine can increase the NH₃ volatilization rate by changing the soil urease activity and inorganic nitrogen content. Controlling the misuse of veterinary antibiotics and environmental and ecological risks posed by the antibiotic residues in farmland excrements are urgent problems in China that need to be solved.

Aqueous chlorination of sulfamethazine and sulfamethoxypyridazine: Kinetics and transformation products identification

Sulfonamides (SNs) are synthetic antimicrobial agents. These substances are continually introduced into the environment, and they may spread and maintain bacterial resistance in the different compartments. The chlorination of 2 SNs, namely, sulfamethazine (SMT) and sulfamethoxypyridazine (SMP), was investigated to study their reactivity with chlorine at typical concentrations for water treatment conditions. Experiments conducted in purified water show an acceleration of SMT and SMP degradation of a factor 1.5 by comparison to drinking water matrix. This difference is due to pH variation and competitive reactions between SNs and mineral and organic compounds, with chlorine in drinking water. In the presence of an excess of chlorine (6.7 μmol·L^-1 ) in ultrapure water at pH 7.2, second-order degradation rate constants were equal to 4.5 × 10² M^-1 ·s^-1 and 5.2 × 10² M^-1 ·s^-1 for SMT and SMP, respectively. The structures of transformation products were investigated by liquid chromatography tandem mass spectrometry analyses with equimolar concentrations between chlorine and SNs. SO₂ elimination, cyclization, and electrophilic substitutions were the main pathways of by-products formation. Moreover, the toxicity of the proposed structures was predicted by using toxicity estimation software tool program. The results indicated that most by-products may present developmental toxicity.

Metabolomic analysis of short-term sulfamethazine exposure on marine medaka (Oryzias melastigma) by comprehensive two-dimensional gas chromatography-time-of-flight mass spectrometry

Toxicological effects of sulfamethazine (SM₂) have garnered increasing concern due to its wide applications in aquaculture and persistence in the aquatic environment. Most studies have main focused on freshwater fish (i.e. zebrafish), while information regarding effects of SM₂ on marine species is still scarce. Here, the hepatotoxicities in marine medaka (Oryzias melastigma) with an increasing SM2 concentration exposures (0.01 mg/L, 0.1 mg/L and 1 mg/L) were assessed by comprehensive two-dimensional gas chromatography-time-of-flight mass spectrometry (GC × GC-TOF/MS) based metabolomics. Significant metabolites belonging to different metabolites classes were identified by multivariate statistical analysis. The increases levels of amino acids including alanine, asparagine, ornithine, proline, threonine, glutamic acid, lysine, tyrosine and phenylalanine were found in at least two exposure levels. Pathway analysis revealed that amino acids played important biological roles during SM₂ exposure: up-regulation of high energy-related amino acids for energy alteration; immune function disorder, oxidative stress and corresponding toxicities defenses. The down regulations of sugar and fatty acid metabolism were observed with an increasing level of SM2 exposure, suggesting that extra energy for cellular defense and detoxification was demanded in terms of different stress request. This study provided an innovative perspective to explore possible SM2 induced hepatic damages at three exposure levels on a nontarget aquatic specie.

Photocatalytic degradation of sulfamethazine in aqueous solution using ZnO with different morphologies

In this study, photocatalytic experiments of 20 mg l-1 sulfamethazine (SMN) in aqueous solution containing ZnO with different morphologies, tetra-needle-like ZnO (T-ZnO), flower-like ZnO (F-ZnO) and nanoparticles ZnO (P-ZnO), were performed. The results indicated that photocatalytic degradation of SMN was effective and followed the pseudo-first-order reaction, but the degree of SMN mineralization showed obvious differences using ZnO with different shapes. After 12 h irradiation, 86%, 71% and 50% of the initial total organic carbon was eliminated in SMN suspension containing T-ZnO, F-ZnO and P-ZnO, respectively. The release ratio of sulfur was close to 100% in the presence of T-ZnO, but reached to 86% and 67% in the presence of F-ZnO and P-ZnO, respectively. The release ratio of nitrogen was about 76%, 63% and 40% using T-ZnO, F-ZnO and P-ZnO as photocatalyst, respectively. The morphology of ZnO played an important role in determining its catalytic activity. Seven intermediates were observed and identified in the UV/T-ZnO reaction system by LC-MS/MS analysis, and a possible degradation pathway was proposed.

Dissipation of antimicrobial resistance genes in compost originating from cattle manure after direct oral administration or post-excretion fortification of antimicrobials

Dissipation of antimicrobial resistance genes (ARG) during composting of cattle manure generated through fortification versus administration of antimicrobials in feed was compared. Manure was collected from cattle fed diets containing (kg^-1) dry matter (DM): (1) 44 mg chlortetracycline (CTC), (2) a mixture of 44 mg each of chlortetracycline and sulfamethazine (CTCSMZ), (3) 11 mg tylosin (TYL) or (4) Control, no antimicrobials. Manures were composted for 30 d with a single mixing after 16 d to generate the second heating cycle. Quantitative PCR (qPCR) was used to measure 16S rDNA and tetracycline (tet), erythromycin (erm) and sulfamethazine (sul) genes. Temperature peaks ranged from 48 to 68°C across treatments in the first composting cycle, but except for the control, did not exceed 55°C in the second cycle. Copy numbers of 16S rDNA decreased (P < 0.05) during composting, but were not altered by antimcrobials. Except tet(L), all ARG decreased by 0.1-1.6 log₁₀ g DM^-1 in the first cycle, but some genes (tet[B], tet[L], erm[F], erm[X]) increased (P < 0.05) by 1.0-3.1 log₁₀ g DM^-1 in the second. During composting, levels of tet(M) and tet(W) in CTC, erm(A), erm(B) and erm(X) in TYL, and sul(1) in CTCSMZ remained higher (P < 0.05) in fed than fortified treatments. The dissipation of ARG during composting of manure fortified with antimicrobials differs from manure generated by cattle that are administered antimicrobials in feed, and does not always align with the dissipation of antimicrobial residues.

Pyridine and 3-methylpyridine solvates of the triple sulfa drug constitutent sulfamethazine

Sulfonamides display a wide variety of pharmacological activities. Sulfamethazine [abbreviated as SMZ; systematic name 4-amino-N-(4,6-dimethylpyrimidin-2-yl)benzenesulfonamide], one of the constitutents of the triple sulfa drugs, has wide clinical use. Pharmaceutical solvates are crystalline solids of active pharmaceutical ingredients (APIs) incorporating one or more solvent molecules in the crystal lattice, and these have received special attention, as the solvent molecule can impart characteristic physicochemical properties to APIs and solvates, therefore playing a significant role in drug development. The ability of SMZ to form solvates has been investigated. Both pyridine and 3-methylpyridine form solvates with SMZ in 1:1 molar ratios. The pyridine monosolvate, C₁₂H₁₄N₄O₂S·C₅H₅N, crystallizes in the orthorhombic space group Pna2₁, with Z = 8 and two molecules per assymetric unit, whereas the 3-methylpyridine monosolvate, C₁₂H₁₄N₄O₂S·C₆H₇N, crystallizes in the orthorhombic space group P2₁2₁2₁, with Z = 4. Crystal structure analysis reveals intramolecular N-H...N hydrogen bonds between the molecules of SMZ and the pyridine solvent molecules. The solvent molecules in both structures play an active part in strong intermolecular interactions, thereby contributing significantly to the stability of both structures. Three-dimensional hydrogen-bonding networks exist in both structures involving at least one sulfonyl O atom and the amine N atom. In the pyridine solvate, there is a short π-π interaction [centroid-centroid distance = 3.926 (3) Å] involving the centroids of the pyridine rings of two solvent molecules and a weak intermolecular C-H...π interaction also contributes to the stability of the crystal packing.

Monitoring of Antibiotic Residues in Aquatic Products in Urban and Rural Areas of Vietnam

Antibiotic residues in aquatic products in Vietnam were investigated. A total of 511 fish and shrimp samples were collected from markets in Ho Chi Minh City (HCMC), Thai Binh (TB), and Nha Trang (NT) from July 2013 to October 2015. The samples were extracted with 2% formic acid in acetonitrile and washed with dispersive C18 sorbent. Thirty-two antibiotics were analyzed by LC-MS/MS. Of the 362 samples from HCMC, antibiotic residues were found in 53 samples. Enrofloxacin was commonly detected, at a rate of 10.8%. In contrast, samples from TB and NT were less contaminated: only 1 of 118 analyzed samples showed residues in TB and only 1 of 31 showed residues in NT. These differences were attributed to the local manufacturing/distribution systems. To understand the current status of antibiotic use and prevent adverse effects that may be caused by their overuse, continual monitoring is required.

Antibiotics versus no treatment for toxoplasma retinochoroiditis

BACKGROUND

Acute toxoplasma retinochoroiditis causes transient symptoms of ocular discomfort and may lead to permanent visual loss. Antibiotic treatment aims primarily to reduce the risk of permanent visual loss, recurrent retinochoroiditis, and the severity and duration of acute symptoms. There is uncertainty about the effectiveness of antibiotic treatment.

OBJECTIVES

To compare the effects of antibiotic treatment versus placebo or no treatment for toxoplasma retinochoroiditis.

SEARCH METHODS

We searched CENTRAL (which contains the Cochrane Eyes and Vision group Trials Register) (2016, Issue 1), Ovid MEDLINE, Ovid MEDLINE In-Process and Other Non-Indexed Citations, Ovid MEDLINE Daily, Ovid OLDMEDLINE (January 1946 to February 2016), EMBASE (January 1980 to February 2016), Latin American and Caribbean Health Sciences Literature Database (LILACS) (January 1982 to February 2016), the ISRCTN registry (www.isrctn.com/editAdvancedSearch), ClinicalTrials.gov (www.clinicaltrials.gov), and the World Health Organization (WHO) International Clinical Trials Registry Platform (ICTRP) (www.who.int/ictrp/search/en). We did not use any date or language restrictions in the electronic searches for trials. We last searched the electronic databases on 22 February 2016. We searched the reference lists of identified articles and contacted pharmaceutical companies for unpublished trials.

SELECTION CRITERIA

We included randomised controlled trials that compared any antibiotic treatment against placebo or no treatment. We excluded trials that included immunocompromised participants. We considered any antibiotic treatment known to be active against Toxoplasma gondii. Antibiotic treatment could be given in any dose orally, by intramuscular injection, by intravenous infusion, or by intravitreal injection.

DATA COLLECTION AND ANALYSIS

The primary outcomes for this review were visual acuity at least three months after treatment and risk of recurrent retinochoroiditis. Secondary outcomes were improvement in symptoms and signs of intraocular inflammation, size of lesion, and adverse events. We used standard methodological procedures expected by Cochrane.

MAIN RESULTS

Four trials that randomised a total of 268 participants met the inclusion criteria. In all four studies antibiotic was administered orally.One study conducted in Brazil in both adults and children compared trimethoprim-sulfamexacocol over 20 months to no treatment and was judged to be at high risk of performance, detection, and attrition bias. The other three studies compared antibiotic treatment to placebo. We judged these three studies to be at a mixture of low or unclear risk of bias due to poor reporting. One study conducted in the US in adults studied pyrimethamine-trisulfapyrimidine for eight weeks; one study conducted in the UK in children and adults evaluated pyrimethamine for four weeks; and one study conducted in Brazil in adults investigated trimethoprim-sulfamethoxazole for 12 months. In the last study, all participants had active retinochoroiditis and were treated with antibiotics for 45 days prior to randomisation to trimethoprim-sulfamethoxazole versus placebo.Only the study in Brazil of trimethoprim-sulfamethoxazole over 12 months, in participants with healed lesions, reported the effect of treatment on visual acuity. People treated with antibiotics may have a similar change in visual acuity compared with people treated with placebo at one year (mean difference -1.00 letters, 95% confidence interval (CI) -7.93 to 5.93 letters; 93 participants; low-quality evidence).Treatment with antibiotics probably reduces the risk of recurrent retinochoroiditis compared with placebo (risk ratio (RR) 0.26, 95% CI 0.11 to 0.63; 227 participants; 3 studies; I(2) = 0%; moderate-quality evidence); similar results were seen for acute and chronic retinochoroiditis.The UK study of pyrimethamine for four weeks reported an improvement in intraocular inflammation in treated compared with control participants (RR 1.76, 95% CI 0.98 to 3.19; 29 participants; low-quality evidence). The study in Brazil of trimethoprim-sulfamethoxazole for 12 months stated that the severity of inflammation was higher in the comparator group when compared to the antibiotic-treated group but did not provide further details. In the US study of pyrimethamine-trisulfapyrimidine for eight weeks intraocular inflammation had almost completely resolved by eight weeks in all participants, however in this study all participants received steroid treatment.Two studies (UK and US studies) reported an increased risk of adverse events in treated participants. These were a fall in haemoglobin, leucocyte, and platelet count, nausea, loss of appetite, rash, and arthralgia.

AUTHORS' CONCLUSIONS

Treatment with antibiotics probably reduces the risk of recurrent toxoplasma retinochoroiditis, but there is currently no good evidence that this leads to better visual outcomes. However, absence of evidence of effect is not the same as evidence of no effect. Further trials of people with acute and chronic toxoplasma retinochoroiditis affecting any part of the retina are required to determine the effects of antibiotic treatment on visual outcomes.