Lagoon, Anaerobic Digestion, and Composting of Animal Manure Treatments Impact on Tetracycline Resistance Genes.

Increased demand for animal protein is met by increased food animal production resulting in large quantities of manure. Animal producers, therefore, need sustainable agricultural practices to protect environmental health. Large quantities of antimicrobials are used in commercial food animal production. Consequently, antimicrobial-resistant bacteria and the resistance genes emerge and are excreted through feces. Manure management is essential for the safe disposal of animal waste. Lagoons, with or without covers, and anaerobic digesters, with the primary purpose of methane production, and composting, with the primary purpose of producing organic fertilizer, are widely used methods of manure treatment. We reviewed manure management practices and their impact on tetracycline resistance genes. Lagoons are maintained at ambient temperatures; especially uncovered lagoons are the least effective in removing tetracycline resistance genes. However, some modifications can improve the performance of lagoons: sequential use of uncovered lagoons and the use of covered lagoons resulted in a one-log reduction, while post-treatments such as biofiltration following covered lagoon treatment resulted in 3.4 log reduction. Mesophilic digestion of animal manure did not have any significant effect; only a 0.7 log reduction in tet(A) was observed in one study. While thermophilic anaerobic digesters are effective, if properly operated, they are expensive for animal producers. Aerobic thermophilic composting is a promising technology if optimized with its economic benefits. Composting of raw animal manure can result in up to a 2.5 log reduction, and postdigestion composting can reduce tetracycline resistance gene concentration by >80%. In general, manure management was not designed to mitigate antimicrobial resistance; future research is needed to optimize the economic benefits of biogas or organic fertilizer on the one hand and for the mitigation of foodborne pathogens and antimicrobial resistance on the other.

Anaerobic Digestion of Tetracycline Spiked Livestock Manure and Poultry Litter Increased the Abundances of Antibiotic and Heavy Metal Resistance Genes.

Anaerobic digestion is used for the treatment of animal manure by generating biogas. Heavy metals cause environmental pollutions and co-select for antimicrobial resistance. We evaluated the impact of mesophilic anaerobic digestion of cattle manure (CM), swine manure (SM) and poultry litter (PL) on the concentrations of seven tetracycline [tet(A), tet(B), tet(G), tet(M), tet(O), tet(Q), and tet(W)], macrolide [erm(B)], methicillin (mecA and mecC), copper (copB, pcoA, pcoD, and tcrB) and zinc (czrC) resistance genes, and three bacterial species (E. coli, Enterococcus spp. and Staphylococcus aureus). The total bacterial population and total abundance of the seven tet genes significantly increased in the three manure types after digestion. Concentration of tet(M) was strongly correlated with that of erm(B) and enterococci. As concentration of tetracyclines declined during anaerobic digestion, that of four tet genes (A, B, Q, and W) and 16S rRNA increased, that of tet(M) decreased, and that of tet(G) and tet(O) did not change. Concentrations of copB and pcoA did not change; while that of pcoD did not change in the PL, it increased in the SM and CM. While the concentration of enterococci remained unchanged in CM, it significantly increased in the PL and SM. Concentrations of tcrB significantly increased in the three manure types. While concentrations of S. aureus significantly increased in the CM and PL, that of SM was not affected. Concentrations of mecC significantly increased in all manure types after digestion; while mecA concentrations did not change in the SM, they significantly increased in CM and PL. While concentration of czrC remained low in the CM, it increased in the PL but declined in the SM. In conclusion, while mesophilic anaerobic digestion of animal manure decreased concentration of tetracyclines, it increased the concentrations of total bacteria, tet genes, E. coli, enterococci and S. aureus and methicillin resistance genes. It did not have any effect on concentrations of heavy metals; concentrations of heavy metal resistance genes either increased or remained unaffected depending on the animal species. This study showed the need for post-digestion treatments of animal manure to remove bacteria, antibiotic resistance genes, heavy metals and their resistance genes.

Anaerobic digestion of livestock and poultry manures spiked with tetracycline antibiotics.

We investigated the anaerobic degradation of tetracycline antibiotics (tetracycline [TC], oxytetracycline [OTC] and chlortetracycline [CTC]) in swine, cattle, and poultry manures. The manures were anaerobically digested inside polyvinyl chloride batch reactors for 64 days at room temperature. The degradation rate constants and half-lives of the parent tetracyclines were determined following first-order kinetics. For CTC the fastest degradation rate was observed in swine manure (k = 0.016 ± 0.001 d-1; half-life = 42.8 days), while the slowest degradation rate was observed in poultry litter (k = 0.0043 ± 0.001 d-1; half-life = 161 days). The half-lives of OTC ranged between 88.9 (cattle manure) and 99.0 days (poultry litter), while TC persisted the longest of the tetracycline antibiotics studied with half-lives ranging from 92.4 days (cattle manure) to 330 days (swine manure). In general, the tetracyclines were found to degrade faster in cattle manure, which had the lowest concentrations of organic matter and metals as compared to swine and poultry manures. Our results demonstrate that tetracycline antibiotics persist in the animal manure after anaerobic digestion, which can potentially lead to emergence and persistence of antibiotic resistant bacteria in the environment when anaerobic digestion byproducts are land applied for crop production.

Bis(imino)pyridine iron complexes for catalytic carbene transfer reactions.

The bis(imino)pyridine iron complex, for the first time, is developed as an effective metal carbene catalyst for carbene transfer reactions of donor-acceptor diazo compounds. Its broad catalytic capability is demonstrated by a range of metal carbene reactions, from cyclopropanation, cyclopropenation, epoxidation, and Doyle-Kirmse reaction to O-H insertion, N-H insertion, and C-H insertion reactions. The asymmetric cyclopropanation of styrene and methyl phenyldiazoacetate was successfully achieved by the new chiral bis(imino)pyridine iron catalyst, which delivers a new gateway for the development of chiral iron catalysis for metal carbene reactions.

Abundances of Tetracycline Resistance Genes and Tetracycline Antibiotics during Anaerobic Digestion of Swine Waste.

The impact of anaerobic digestion of animal waste on the persistence of antibiotic resistance genes (ARGs) and antibiotics is not widely studied. Two identical, 800-L digesters seeded with swine slurry were followed up to 100 d in three separate trials. The trials received varying amounts of antibiotic-free corn ( L.) mixed with water to maintain the digestion process. Biogas production, seven tetracycline resistance () genes, and three tetracyclines and their transformation products were measured. Biogas production proportionally increased as the feeding loads increased between trials. In Trial 1, log gene copies showed small but statistically significant ( < 0.01) increases during digestion. In Trial 2, anaerobic digestion did not have a significant ( > 0.05) effect except for significant reductions in B ( < 0.0001) and G ( = 0.0335) log gene copies. In Trial 3, which received the highest amount of corn mix, log copies of the 16S ribosomal RNA and the genes significantly ( < 0.0001) reduced over time during digestion. Up to 36 µg L tetracycline, 112 µg L chlortetracycline, 11.9 mg L isochlortetracycline, and 30 µg L 4-epitetracycline were detected both in the liquid and solid digestates. Results of this study revealed that although anaerobic digestion of swine waste can produce useful biogas, it does not result in complete removal of bacteria, ARGs, and antibiotics regardless of differences in the feeding loads between trials. Further effluent and sludge treatments are required prior to their downstream use in crop production to minimize emergence and environmental dissemination of antimicrobial-resistant bacteria through animal manure.

One-step synthesis of NaLu80-xGdxF4:Yb183+/Er23+(Tm3+) upconversion nanoparticles for in vitro cell imaging.

Upconversion nanoparticles (UCNPs) possess a unique type of photoluminescence (PL) in which lower-energy excitation is converted into higher-energy emission via multi-photon absorption processes. In this work, we have used a facile one-step hydrothermal method promoted water solubility to synthesis NaLuGdF4:Yb3+/Er3+(Tm3+) UCNPs coated with malonic acid (MA). Scanning electron microscopy images and X-ray diffraction patterns reveal sphere-shaped UCNPs with an average size of ~80nm crystallized in the cubic NaLuF4 structure. The characteristic vibrations of cubic UCNPs have been taken into account by using Fourier-transform infrared spectroscopy. Based on PL studies, we have determined an optimal concentration of Gd3+ doping. The dependence of upconversion PL intensity on Gd3+ concentration is discussed via the results of magnetization measurements, which is related to the coupling/uncoupling of Gd3+ ions. Particularly, our study reveals that carboxyl-functionalized NaLuGdF4:Yb3+/Er3+(Tm3+) UCNPs have a relatively high cell viability with HeLa cells.

Dihexadecyldimethylammonium hydroxide admicelles on silica for the preconcentration of selected phenols.

Admicelle based extractions, where sorbents used are prepared by immobilizing charged surfactants in a bilayer arrangement onto a silica or aluminum oxide surface, have been used for preconcentrating a wide variety of analytes. These analytes have a certain degree of hydrophobicity interacting with the alkyl chains of the surfactant or they are counter-charged interacting electrostatically with the charged polar group of the surfactant. Weakly hydrophobic molecules are more challenging to efficiently extract onto this type of medium. Presented is an admicelle extraction procedure for extracting weak acid phenols. An acid-base reaction takes place between modified surfactants containing hydroxide counter ions and weak acid phenols. The result of this reaction is the production of phenolate ions that remain counter to the cationic surfactant. The acid-base reaction together with the fluid nature of the surfactant phase protects the phenolate ions from being removed by counter ions in natural solutions. High extraction efficiencies result.

Investigation of a variety of cationic surfactants attached to cation-exchange silica for hydrophobicity optimization in admicellar solid-phase extraction for high-performance liquid and gas chromatography.

A series of cationic surfactants were attached to cation-exchange silica that included silica modified with sulfopropyl groups and unmodified silica to create hydrophobic solid-phase extraction sorbents. Various chain lengths and chain numbers of amine, ammonium and pyridinium-based cationic surfactants were investigated to reach sufficient sorbent hydrophobicity to capture US Environmental Protection Agency (EPA) priority polycyclic aromatic hydrocarbons (PAHs). Of the tested surfactant/silica combinations, dihexadecyldimethylammonium cations attached to unmodified silica resulted in the sorbent having the greatest hydrophobicity. This sorbent provided strong hydrophobic attraction of PAHs and also efficient elution because the PAHs were removed together with the surfactant using a very mild 5% acetic acid in methanol rinse solution. This admicellar solid-phase extraction procedure was applied for the determination of these PAHs for both high-performance liquid and gas chromatography. The detection limits of these PAHs were below the EPA's maximum contaminant level of 0.2 microg/L.

Determination of polyaromatic hydrocarbons in river water using a sorbent consisting of removable octadecyltrimethylammonium ions attached to cation exchange silica in conjunction with commercial C18 silica.

An application that highlights the usefulness of a solid phase extraction sorbent having a removable surfactant "stationary phase" is introduced. Polyaromatic hydrocarbons (PAHs) efficiently trap on commercially available non-polar sorbents (i.e., C(18) silica). However, solvents that are necessary to break strong hydrophobic interactions between the analyte and sorbent are harmful and incompatible for direct introduction into a reversed phase liquid chromatographic setup. In the presented approach, the entire "stationary phase"-analyte association is removed, resulting in very efficient elutions with a final extract that is mild and reversed phase liquid chromatographic compatible. Commercial C(18) silica was placed adjacent to this sorbent to provide more efficient trapping of less hydrophobic PAHs. PAHs were preconcentrated from river water and were determined using fluorescence detection coupled to HPLC. Detection limits for all PAHs examined were in the sub [micro sign]g L(-1) level.

A solid-phase microextraction device for the analysis of electrochemical reaction products by gas chromatography/mass spectrometry.

Presented is a solid-phase microextraction syringe-electrode assembly that may be used to identify electrode reaction products. After an electrochemical experiment, the electrode within this syringe-electrode assembly can be introduced into the injection port of a gas chromatograph. Electrochemical reaction products can be analyzed, provided they adhere to the electrode surface and are amenable to gas chromatographic/mass spectrometric analysis. We highlight the potential usefulness of this device using well-known electrochemical reaction of quinones.

Voltammetric peak separation of dopamine from uric acid in the presence of ascorbic acid at greater than ambient solution temperatures.

Peak overlap in voltammetry poses challenges for the quantitative analysis of electroactive species. Dopamine and uric acid are typically challenging to determine voltammetrically because of their very similar oxidation peak potentials. We report preliminary results of the use of a screen-printed carbon electrode for the determination of dopamine and uric acid in an electrolyte solution maintained above ambient temperatures. Higher temperatures resulted in dramatic shifting of the dopamine oxidation peak toward lower potentials, while the uric acid peak was essentially stationary. Ascorbic acid, an interference in voltammetric uric acid determinations, is effectively suppressed at higher temperatures. This resulted in a greater peak separation of dopamine from uric acid at higher temperatures, which is desirable for better peak integration. In addition, greater current responses for both species were recorded at higher temperatures. The cause for such an increase in peak current is unraveled using ac impedance measurements. Presented are preliminary results for determining dopamine and uric acid at temperatures higher than ambient. Much improved voltammetric peak separation and sensitivity is obtained at these higher temperatures compared to ambient.

Solid-phase extraction sorbent consisting of alkyltrimethylammonium surfactants immobilized onto strong cation-exchange polystyrene resin.

Presented is a solid-phase extraction sorbent material composed of cationic alkyltrimethylammonium surfactants attached to a strong cation-exchange resin via ion-exchange. The original hydrophilic cation-exchange resin is made hydrophobic by covering the surface with alkyl chains from the hydrophobic portion of the surfactant. The sorbent material now has a better ability to extract hydrophobic molecules from aqueous samples. The entire stationary phase (alkyltrimethylammonium surfactant) is removed along with the analyte during the elution step. The elution step requires a mild elution solvent consisting of 0.25 M Mg2+ in a 50% 2-propanol solution. The main advantage of using a removable stationary phase is that traditionally utilized toxic elution solvents such as methylene chloride, which are necessary to efficiently release strongly hydrophobic species from SPE stationary phases, may now be avoided. Also, the final extract is directly compatible with reversed-phase liquid chromatography. The performance of this procedure is presented using pyrene as a test molecule.