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A new ternary coordination polymer (CP), {[Cd(L)(nip)(H2O)]·H2O}n (1) (L = 1,6-bis(benzimidazol-2-yl)hexane, H2nip = 5-nitroisophthalic acid), was hydrothermally synthesized and characterized. 1 is a two-dimensional sheet and extends into three-dimensional supramolecular networks through O-H···O hydrogen bonding interactions, which displays high thermal and pH stabilities. 1 demonstrated notable selectivity, sensitivity, and reusability for the luminescent sensing of chlortetracycline (CTC) and Fe3+ ions. Density functional theory calculations and UV−Vis absorption spectroscopy were employed to investigate the possible sensing mechanisms. A new Cd(II) metal coordination polymer, namely {[Cd(L)(nip)(H2O)]·H2O}n can act as a sensitive luminescent probe for chlortetracycline (CTC) and Fe3+ ions in water with excellent selectivity and recyclability. [ABSTRACT FROM AUTHOR]

Antimicrobial Resistance (AMR) in bacteria is a growing public health concern in the US and around the world threatening the continual use of antimicrobials. In pigs, the oral route, either in-feed or in-water, is by far the most common route of administration of antimicrobials. Because the distribution of the antibiotic in the gut and the dosages are different, the impact of in-feed vs. in-water administration of antibiotics on the prevalence of pathogens, such as Salmonella, and the development of AMR are likely to be different. Therefore, a study was conducted to compare in-feed vs. in-water administrations of chlortetracycline (CTC) and/or tiamulin on the fecal prevalence and AMR profiles of Salmonella in nursery piglets. A total of 1296 weaned piglets, housed in 48 pens (27 piglets per pen), were assigned randomly to six treatment groups: Control (no antibiotic), in-feed CTC, in-water CTC, in-feed tiamulin, in-water tiamulin, or in-feed CTC and tiamulin. Fecal samples (n = 1440) were collected randomly from five piglets from each pen during the pre-treatment (days 7, 0), treatment (days 7, 14), and post-treatment (days 21, 28) phases. Salmonella enterica isolation and identification were completed by culture and PCR methods. The microbroth dilution method with SensititreTM (ThermoFisher Scientific, Lenexa, KS, USA) plates was used to determine the antimicrobial susceptibility and resistance of Salmonella strains. The susceptibility and resistance were interpreted based on the Clinical and Laboratory Standards Institute guidelines. The overall prevalence of Salmonella was 3.0% (43/1440). All isolates belonged to Salmonella enterica subsp. enterica serovar Typhimurium. Salmonella isolates were susceptible to azithromycin and resistant (100%) to ampicillin, streptomycin, sulfisoxazole, tiamulin, and tetracycline. Neither antibiotic, CTC or tiamulin, nor the route of administration, in-feed or in-water, had an effect (p > 0.05) on the occurrence of resistant Salmonella in the feces of piglets. [ABSTRACT FROM AUTHOR]

The work deals with the development of an approach to the determination of chlortetracycline, which combines the preconcentration of the analyte with its subsequent determination by capillary zone electrophoresis. The conditions that ensure the lowest value of the limit of determination for chlortetracycline in aqueous solutions using a Kapel-105M capillary electrophoresis system (Lumex, Russia) are determined, i.e., temperature, time and pressure of sample injection, background electrolyte composition, and detection wavelength. It is shown that the stability of a chlortetracycline solution is maximum at a storage temperature of 0.5°С in the absence of buffer systems or in using a dilute ammonium acetate buffer solution. It is found that the recovery of chlortetracycline by strongly acidic cation exchangers KU-1, KU-2 is higher compared to that by KB-4 and KB-4P2, bearing weakly acidic functional groups. The conditions under which the recovery of the analyte by KU-1 from a phosphate buffer solution is about 90% are determined. [ABSTRACT FROM AUTHOR]

In view of the serious side effects of chlortetracycline (CTC) on the human body, it is particularly important to develop rapid, sensitive, and selective technologies for the detection of CTC in food. In this work, a molecularly imprinted electrochemical sensor with [Fe(CN)6]3−/4− as signal probe was proposed for the highly sensitive and selective detection of CTC. For this purpose, TiO2, which acts as an interlayer scaffold, was uniformly grown on the surface of Ti3C2Tx sheets through a simple two-step calcination process using Ti3C2Tx as the precursor to effectively avoid the stacking of Ti3C2Tx layers due to hydrogen bonding and van der Waals forces. This endowed TiO2@Ti3C2Tx with large specific surface, abundant functional sites, and rapid mass transfer. Then, polypyrrole molecularly imprinted polymers (MIPs) with outstanding electrical conductivity were modified on the surface of TiO2@Ti3C2Tx via simple electro-polymerization, where the pyrrole was employed as a polymeric monomer and the CTC provided a source of template molecules. This will not only provide specific recognition sites for CTC, but also facilitate electron transport on the electrode surface. The synergistic effects between TiO2@Ti3C2Tx and polypyrrole MIPs afforded the TiO2@Ti3C2Tx/MIP-based electrochemical sensor excellent detection properties toward CTC, including ultra-low limits of detection (LOD) (0.027 nM), a wide linear range (0.06–1000 nM), and outstanding stability, reproducibility, selectivity, and feasibility in real samples. The results indicate that this strategy is feasible and will broaden the horizon for highly sensitive and selective detection of CTC. [ABSTRACT FROM AUTHOR]

Deposition of calcium-containing minerals such as hydroxyapatite and whitlockite in the subretinal pigment epithelial (sub-RPE) space of the retina is linked to the development of and progression to the end-stage of age-related macular degeneration (AMD). AMD is the most common eye disease causing blindness amongst the elderly in developed countries; early diagnosis is desirable, particularly to begin treatment where available. Calcification in the sub-RPE space is also directly linked to other diseases such as Pseudoxanthoma elasticum (PXE). We found that these mineral deposits could be imaged by fluorescence using tetracycline antibiotics as specific stains. Binding of tetracyclines to the minerals was accompanied by increases in fluorescence intensity and fluorescence lifetime. The lifetimes for tetracyclines differed substantially from the known background lifetime of the existing natural retinal fluorophores, suggesting that calcification could be visualized by lifetime imaging. However, the excitation wavelengths used to excite these lifetime changes were generally shorter than those approved for retinal imaging. Here, we show that tetracycline-stained drusen in post mortem human retinas may be imaged by fluorescence lifetime contrast using multiphoton (infrared) excitation. For this pilot study, ten eyes from six anonymous deceased donors (3 female, 3 male, mean age 83.7 years, range 79–97 years) were obtained with informed consent from the Maryland State Anatomy Board with ethical oversight and approval by the Institutional Review Board. [ABSTRACT FROM AUTHOR]

Probes such as carbon dots (C-dots) have extensive and important applications in the quantitative analysis of complex biological and environmental systems. However, the development of probes is often hindered by incomplete selectivity, i.e., a probe that responds to one substance is also prone to respond to coexisting structurally similar substances. Therefore, the above dilemma often leads to be developed as semi-selective probes, so that the development of probes is abandoned halfway. This work shows how a semi-selective probe can enhance selectivity by combining a proper multivariate calibration model. Primarily, we developed a semi-selective fluorescent probe that responded to tetracyclines (TCs) with discarded tobacco leaves. Then, we introduced the multivariate quantitative fluorescence model (QFM) to enhance its selectivity and solve the problem of fluorescence spectral shift. For the determination of chlortetracycline (CTC) with this semi-selective C-dots probe in mineral and lake water samples and compared to the traditional quantitative model, the introduced QFM resulted in an average relative predictive error (ARPE) in mineral water spiked samples decreased from 57.1 to 5.6%, which reduced the ARPE in the lake water spiked samples from 18.1 to 4.7%. The above results show that the QFM-assisted semi-selective probe C-dots strategy (QFMC−dots) can enhance selectivity, and QFMC−dots achieved high-selective and accurate determination of CTC in interfering mineral and lake water samples, with the limit of detection and limit of quantitation of 0.55 and 1.66 μM, respectively. The proposed strategy of enhancing selectivity by introducing a proper multivariate calibration model can reduce the difficulty and increase success rate of developing probes, which can be expected to provide an interesting alternative for the development of probes, especially when encountering semi-selective problems. Graphical Abstract This is a visual representation of the abstract. [ABSTRACT FROM AUTHOR]

We have shown that all sub-retinal pigment epithelial (sub-RPE) deposits examined contain calcium phosphate minerals: hydroxyapatite (HAP), whitlockite (Wht), or both. These typically take the form of ca. 1 μm diameter spherules or >10 μm nodules and appear to be involved in the development and progression of age-related macular degeneration (AMD). Thus, these minerals may serve as useful biomarkers the for early detection and monitoring of sub-RPE changes in AMD. We demonstrated that HAP deposits could be imaged in vitro by fluorescence lifetime imaging microscopy (FLIM) in flat-mounted retinas using legacy tetracycline antibiotics as selective sensors for HAP. As the contrast on a FLIM image is based on the difference in fluorescence lifetime and not intensity of the tetracycline-stained HAP, distinguishing tissue autofluorescence from the background is significantly improved. The focus of the present pilot study was to assess whether vascular perfusion of the well tolerated and characterized chlortetracycline (widely used as an orally bioavailable antibiotic) can fluorescently label retinal HAP using human cadavers. We found that the tetracycline delivered through the peripheral circulation can indeed selectively label sub-RPE deposits opening the possibility for its use for ophthalmic monitoring of a range of diseases in which deposit formation is reported, such as AMD and Alzheimer disease (AD). [ABSTRACT FROM AUTHOR]

The modification of biochar is essential for the development of multifunctional biochar materials with enhanced remediation effects on contaminated water. In this work, a biochar-based microcatalyst with sunlight sensitivity was synthesized by a creative modification method that involved the rapid fabrication of MnO2 microspheres by high-energy electron beam (HEEB) irradiation, and loading them into corn straw-derived honeycomb-like KOH-modified biochar (MBC) to obtain a sunlight-sensitive microcatalyst (SSM). The honeycomb-like structure of MBC facilitated the improvement in MnO2 dispersion and photocatalytic property through confinement effect. The effects of photocatalyst dosage, initial chlortetracycline (CTC) concentration, solution pH, temperature and coexisting ions on the photocatalytic performance of SSM were systemically investigated. The results indicated that SSM could efficiently degrade CTC in water and swine urine under sunlight, and exhibited high stability against coexistence of urea, Cl− and SO42−. Moreover, SSM showed good reusability in regeneration studies. This work provides a novel method for degrading CTC with potential application prospect. [ABSTRACT FROM AUTHOR]

In this study, degradation of oxytetracycline (OTC) and chlortetracycline (CTC) was investigated by Fenton process. In experimental studies conducted for this purpose, different values of pH, Fe2+ concentration, H2O2 concentration and reaction time were tested as important parameters for the Fenton process and optimum conditions for OTC and CTC removal were determined. For both antibiotics, the optimum values of the parameters in the Fenton process were the same, and these values were found to be 3 for pH, 20 mg/L for Fe2+ concentration, 25 mg/L for H2O2 concentration, 5 min for reaction time. Under these optimum conditions, OTC degradation was 100%, CTC degradation was 99.68%, chemical oxygen demand (COD) removal efficiency for oxytetracycline (O-COD) was 89.6%, COD removal efficiency for chlortetracycline (C-COD) was 88.5%. These results show that the Fenton process is an effective method that can be used for OTC and CTC degradation. [ABSTRACT FROM AUTHOR]

In the recent years, the issue of antibiotic residues in food has become an important topic. Most current methods of detecting antibiotics are time-consuming, laborious, and cannot meet the requirements of field testing. In this study, electro-filter paper spray ionization was coupled with a portable linear ion trap mass spectrometer for the rapid determination of four antibiotics (norfloxacin, tetracycline, oxytetracycline, and chlortetracycline) in pork and milk samples. The experimental setup is not only structurally simple but enables analysis of both solid and liquid samples. The samples require only a simple pretreatment and the complete analysis of a sample requires less than 1 min. The linear range for the determination of the four antibiotic standards was from 1 to 100 mg/L (R2≥0.960). The limits of detection (LOD) for the analytes were 0.100 mg/L, with recoveries from 72.4% to 11%. The relative standard deviations (RSDs) were between 2.70% and 16.5%. This study expands the capability for rapid field testing of antibiotics in meat using portable mass spectrometers, which is important for food safety, environmental protection, and criminal investigations. [ABSTRACT FROM AUTHOR]

Melanoma is still one of the most dangerous cancers. New methods of treatment are sought due to its high aggressiveness and the relatively low effectiveness of therapies. Tetracyclines are drugs exhibiting anticancer activity. Previous studies have also shown their activity against melanoma cells. The possibility of tetracycline accumulation in pigmented tissues and the increase in their toxicity under the influence of UVA radiation creates the possibility of developing a new anti-melanoma therapy. This study aimed to analyze the phototoxic effect of doxycycline and chlortetracycline on melanotic melanoma cells COLO 829 and G-361. The results indicated that tetracycline-induced phototoxicity significantly decreased the number of live cells by cell cycle arrest as well as a decrease in cell viability. The simultaneous exposure of cells to drugs and UVA caused the depolarization of mitochondria as well as inducing oxidative stress and apoptosis. It was found that the combined treatment activated initiator and effector caspases, caused DNA fragmentation and elevated p53 level. Finally, it was concluded that doxycycline demonstrated a stronger cytotoxic and phototoxic effect. UVA irradiation of melanoma cells treated with doxycycline and chlortetracycline allows for the reduction of therapeutic drug concentrations and increases the effectiveness of tested tetracyclines. [ABSTRACT FROM AUTHOR]

CeO2/ZnO-based photocatalytic materials were synthesized by the sol-gel method in order to establish heterojunctions that increase the degradation efficiency of some types of antibiotics by preventing the recombination of electron–hole pairs. The synthesized materials were analysed by XRD, SEM, EDAX, FTIR, and UV-Vis. After several tests, the optimal concentration of the catalyst was determined to be 0.05 g‧L−1 and 0.025 g‧L−1 for chlortetracycline and 0.05 g‧L−1 for ceftriaxone. CeO2/ZnO assemblies showed much better degradation efficiency compared to ZnO or CeO2 tested individually. Sample S3 shows good photocatalytic properties for the elimination of ceftriaxone and tetracycline both from single solutions and from the binary solution. This work provides a different perspective to identify other powerful and inexpensive photocatalysts for wastewater treatment. [ABSTRACT FROM AUTHOR]

Concerns about environmental and food contamination caused by chlortetracycline (CTC) residues have prompted people to explore efficient and convenient CTC monitoring platforms. However, the reported fluorescent probes generally fail to selectively detect CTC due to the structural similarity of tetracycline antibiotics. Herein, an intrinsic dual-emission carbon dots (D-CDs) ratiometric fluorescence sensor was prepared for highly sensitive and selective determination of CTC over other tetracyclines by one-step synthesis. The sensor exhibited a significant fluorescence enhancement at 425 nm after introducing CTC. The fluorescence "turn on" of the sensing system is due to aggregation-induced emission (AIE) phenomenon formed by hydrogen bonds and π conjugation promoting the specific recognition of CTC by D-CDs. The linear detection varied from 0.98 to 143.67 ng mL−1 with a low limit of detection (LOD) of 1.29 ng mL−1 (R2 = 0.998), which was lower than most reported in the literature. The D-CDs sensor was applied to detect CTC in spiked milk, blocked normal human serum, and fish samples with recoveries of 95.5–104.2% and relative standard deviations (RSDs) of 2.6%. Particularly, D-CDs based test papers with a smartphone were prepared for portable and visual detection of CTC by analyzing the various color changes of RGB of fluorescence color, with an LOD of 7.18 ng mL−1 (R2 = 0.9909). The fluorescence sensor designed in this work could be used as a rapid tool with high performance and selectivity for monitoring control in foods. [ABSTRACT FROM AUTHOR]

Concerns about environmental and food contamination caused by chlortetracycline (CTC) residues have prompted people to explore efficient and convenient CTC monitoring platforms. However, the reported fluorescent probes generally fail to selectively detect CTC due to the structural similarity of tetracycline antibiotics. Herein, an intrinsic dual-emission carbon dots (D-CDs) ratiometric fluorescence sensor was prepared for highly sensitive and selective determination of CTC over other tetracyclines by one-step synthesis. The sensor exhibited a significant fluorescence enhancement at 425 nm after introducing CTC. The fluorescence "turn on" of the sensing system is due to aggregation-induced emission (AIE) phenomenon formed by hydrogen bonds and π conjugation promoting the specific recognition of CTC by D-CDs. The linear detection varied from 0.98 to 143.67 ng mL−1 with a low limit of detection (LOD) of 1.29 ng mL−1 (R2 = 0.998), which was lower than most reported in the literature. The D-CDs sensor was applied to detect CTC in spiked milk, blocked normal human serum, and fish samples with recoveries of 95.5–104.2% and relative standard deviations (RSDs) of 2.6%. Particularly, D-CDs based test papers with a smartphone were prepared for portable and visual detection of CTC by analyzing the various color changes of RGB of fluorescence color, with an LOD of 7.18 ng mL−1 (R2 = 0.9909). The fluorescence sensor designed in this work could be used as a rapid tool with high performance and selectivity for monitoring control in foods. [ABSTRACT FROM AUTHOR]

Chlortetracycline (CTC) and paracetamol (PCT), which are among the most widely used drugs today, have started to be detected in groundwater and surface waters. For this reason, water resources are exposed to more and more drug pollution every day. For this purpose, it is important to remove these pollutants from the environments where they are located. In this study, CTC and PCT drugs together with ammonium (NH4‐N) and nitrate (NO3‐N) pollutants were simultaneously removed in a single reactor. At the end of the study, PCT and CTC were removed at maximum 99.8 % and 66 % under the same conditions, respectively. At the same time, nitrification and denitrification efficiency were obtained as 99 %. In terms of volumetric removal flux, chlortetracycline and equivalent O2 flux of chlortetracycline maximum were calculated as 2.05 and 3.56 mg/L.d. Likewise, the maximum removal volumetric flux of paracetamol and its O2 equivalent flux were determined as 136 and 301.5 mg/L.d. The results showed that, aerobic nitrified bacteria preferred paracetamol rather than chlortetracycline. In other words, nitrified bacteria preferred paracetamol/chlortetracycline as the second electron acceptor after O2. As a result, chlortetracycline and paracetamol were successfully eliminated in the SBR system. In addition, simultaneous biological removal of these drugs with nitrogenous pollutants has been successfully achieved. [ABSTRACT FROM AUTHOR]

Pharmaceutical pollution has pervaded many water resources all over the globe. The propagation of this health threat drew the researchers' concern in seeking an efficient solution. This study introduced toilet paper waste as a precursor for carbon nanoparticles (CRNPs). The TEM results showed a particle size range of 30.2 nm to 48.1 nm, the BET surface area was 283 m2 g−1, and the XRD pattern indicated cubical-graphite crystals. The synthesized CRNPs were tested for removing tigecycline (TGCN), chlortetracycline (CTCN), oxytetracycline (OTCN), and doxycycline (DXCN) via the batch process. The adsorption equilibrium time for TGCN, DXCN, CTCN, and OTCN was 60 min, and the concentration influence revealed an adsorption capacity of 172.5, 200.1, 202.4, and 200.0 mg g−1, respectively. The sorption of the four drugs followed the PSFO, and the LFDM models indicated their high sorption affinity to the CRNPs. The adsorption of the four drugs fitted the multilayer FIM that supported the high-affinity claim. The removals of the four drugs were exothermic and spontaneous physisorption. The fabricated CRNPs possessed an excellent remediation efficiency for contaminated SW and GW; therefore, CRNPs are suggested for water remediation as low-cost sorbent. [ABSTRACT FROM AUTHOR]

Abstract Water-in-oil-in-water (W/O/W) crystallizable double emulsions stabilized with a mixture of octenyl succinic anhydride starch (OSA starch) and xanthan gum (XG) were formulated. These systems were proposed as modules for the release of chlortetracycline (CTC). The characterization results indicated that the stability, the average diameter of the globules, and the apparent viscosity of the double emulsions formulated depend on OSA starch and XG concentrations, and on their ratio in the outer water phase. In addition, emulsions exhibited good creaming stability during 40 days of rest at 25 °C and 40 °C. However, samples prepared with 0.25%/0.5% and 0.5%/0.5% of OSA starch/XG mixture were found more stable. Also, it was noticed that the encapsulation efficiency (EE) and the release rate of CTC incorporated in the inner water phase strongly depend on the polymer concentrations in the outer water phase. Furthermore, the increase in the concentration of biopolymer results in a slowing down of the drug encapsulation and an improvement in the EE. Moreover, the Korsmeyer-Peppas model was tested to represent the kinetics of CTC release; the release mechanism was found as a simple diffusion type. [ABSTRACT FROM AUTHOR]

Chlortetracycline (CTC), a derivative of tetracycline (TC), is a broadly used antibiotic that inhibits the synthesis of bacterial proteins by competing with the A‐site tRNA on ribosomes. A recent study showed that during the biosynthesis of CTC in Streptomyces aureofaciens, the halogenase CtcP catalyzes the final chlorination reaction and transforms TC into CTC. However, the structure of this fundamental enzyme is still lacking. Here, selenomethionine‐derivatized CtcP from S. aureofaciens was overexpressed and purified and its structure was determined at 2.7 Å resolution. The structure of CtcP reveals the conserved monooxygenase domain shared by all flavin‐dependent halogenases and a unique C‐terminal domain. Although FAD was not observed in the structure, the monooxygenase domain has a conserved FAD‐binding pocket and active center. The C‐terminal domain displays an α‐helical bundle fold, which could contribute to substrate specificity. This work provides a molecular basis for enzyme engineering to improve the industrial production of CTC. [ABSTRACT FROM AUTHOR]

Riemerella anatipestifer can cause septicemia and death in ducks and geese, leading to significant economic losses to animal farms. The emergence of resistance of R. anatipestifer to commonly used antibiotics increases the difficulty of treating R. anatipestifer infection. The aim of this study was to evaluate the utility of antibiotic combination to restrict mutant selection of multidrug-resistant (MDR) R. anatipestifer isolates. Pharmacokinetics of florfenicol and chlortetracycline in Pekin ducks were evaluated using both noncompartmental analysis and population pharmacokinetic models. The areas under the curve of florfenicol and chlortetracycline after single 20 and 10 mg/kg oral administration were 49.3 and 6.84 mg*h/L, respectively. Chlortetracycline exhibited high apparent clearance and low systemic exposure. Minimum inhibitory concentration (MIC) and mutant prevention concentration (MPC) values of the two antibiotics were determined in 10 and 2 MDR R. anatipestifer isolates, respectively, to derive fTMSW (the fraction of time over 24 hours wherein the free drug concentration was within the mutant selection window [MSW]) and fT>MPC (the fraction of time that the free drug concentration was above the MPC). Both fTMSW and fT>MPC were estimated from simulated concentration-time profiles relative to MIC and MPC. Florfenicol and chlortetracycline combination have additive activities against R. anatipestifer in majority of isolates and could significantly decrease monotherapy MPC of florfenicol and chlortetracycline, as well as optimize both fTMSW and fT>MPC parameters, provided that the bioavailability of chlortetracycline is improved. The application of pharmacokinetic/pharmacodynamic analyses to MPC concepts to restrict selection of mutant bacterial strains can help improve short- and long-term outcomes of antibiotic treatment in animal farms. [ABSTRACT FROM AUTHOR]

[Display omitted] • Novel graphitic carbon nitride (g-C 3 N 4) nanodots (CCNDs) were synthesized. • CCNDs applied to the selective and sensitive detection of CTC by AIE-based fluorescence-enhanced effect. • CCNDs were successfully applied to the actual detection of CTC in chicken and feed samples as well as living cells. • The bonding mechanism of CCNDs towards CTC was investigated in detail. In this study, the novel graphitic carbon nitride (g-C 3 N 4) nanodots etched with citrate (CCNDs) were synthesized successfully. And the result CCNDs exhibited an obvious aggregation emission effect (AIE) by forming a fluorescence complex with chlortetracycline (CTC) and significantly enhanced the fluorescence intensity of CCNDs. On the strength of this, the synthesized CCNDs demonstrated remarkable sensitivity and selectivity to CTC, which has been effectively studied and utilized for selectively and sensitively detecting CTC by AIE-based fluorescence-enhanced effect with a detection range spanning from 0 to 15 μM and a limit of detection (LOD) as low as 13 nM. The CCNDs were viably used for actually detecting CTC in real samples including chicken and feed, and further extended to detecting CTC in living cells. Finally, the bonding mechanism of CCNDs towards CTC was investigated in detail by dynamic light scattering (DLS), zeta(ζ) potential, TEM, ultraviolet-visible absorption spectrometry (UV-Vis), resonance light scattering (RLS) and fluorescence lifetime. It is due to the combination of a special fluorescent complex between CCNDs and CTC, which distinguishes CTC from other TCs. [ABSTRACT FROM AUTHOR]

The accumulation and distribution of oxytetracycline (OTC) and chlortetracycline (CTC) in tobacco seedlings, and their effects on tobacco seedling growth, were studied using the floating seedling method in greenhouse conditions. Results showed that both OTC and CTC could inhibit the growth of tobacco seedlings, and inhibition effects were greater at higher concentrations. Compared with controlling tobacco seedlings treated with the highest concentration T4 (100 mg/L), the root length and root fresh weight in OTC treatment group decreased by 39% and 53%. The length and fresh weight of stem decreased by 34% and 39%. The maximum leaf area and fresh leaf weight decreased by 34% and 46%. The root length and fresh weight in CTC treatment group decreased by 37% and 54%. The length and fresh weight of stem decreased by 53% and 62%. The maximum leaf area and fresh leaf weight were reduced by 59% and 70%. The higher the concentration of antibiotics in the nutrient solution, the higher the accumulation of antibiotics in each tissue of the tobacco seedlings, and accumulation increased significantly from 2 to 80 μg/g over time (7-20 days). And accumulation in leaves (5 to 60, 5 to 80 μg/g respectively) was greater than that in roots (3 to 30, 3 to 15 μg/g respectively) and stems (2 to 25, 2 to 25 μg/g respectively), and CTC inhibited tobacco seedlings more than OTC. The above mentioned two kinds of antibiotic have an effect on tobacco seedling. [ABSTRACT FROM AUTHOR]

Extensive beef cattle production systems depend on forage as the predominant nutrient source. However, mineral requirements are not always met solely through forage consumption. To maintain optimum animal productivity, beef cattle producers must provide mineral supplementation and free-choice supplements are most common. Free-choice supplement intake by grazing cattle is highly variable and is dictated by season, individual animal preference, supplement palatability and other factors. Variation in supplement intake is problematic for delivering medication such as chlortetracycline (CTC), which is aimed to mitigate the risk of bovine anaplasmosis in beef herds. Research investigating the relationship between individual animal attributes and supplement consumption in extensive settings is limited. Recently, adoption of technology such as a portable, self-contained individual feeding unit (SmartFeed; C-Lock Inc.) into supplementation programs has facilitated unprecedented data collection in grazing cattle. The study objectives were to describe the consumption patterns of a granular CTC-containing supplement and to evaluate the factors contributing to consumption variability by gestating cows on pasture. A total of 103 nonlactating, pregnant, crossbred cows were assigned to this experiment on d -28 and allocated to 1 of 3 pastures equipped with a SmartFeed unit to record individual supplement intake. Cows were offered dried distillers grains for 27 d of acclimation to the units (mean intake of 0.29 kg of supplement/cow daily; 74% of cows) before transition to a commercially available granular mineral supplement containing CTC for 46 d. Supplement was formulated such that a 630 kg cow must consume 113 g/d to receive the label CTC dose (1.1 mg/kg). Cow intake and unit visit frequency data were analyzed using a general linear model (PROC GLM) and differences evaluated using Least Squared Means. The runs test for serial randomness was used to evaluate clustering of feeding and non-feeding events. Feeding and non-feeding events during the 46-d observation period were not randomly distributed (P < 0.01), and the mean number of consecutive days a cow did or did not consume mineral supplement were 1.8 and 5.6 days, respectively. As cow age increased, visits to the feeding unit decreased and total supplement consumption also decreased (P < 0.01). According to supplement label instructions, each cow was expected to consume 5.2 kg of supplement in total over 46 d to receive the total recommended 32.2 g CTC dose. Mean supplement consumption was 40.5 g· cow-1· d-1, providing 0.25 g CTC· cow-1· d-1, and only 1.9% (2/103 cows) consumed enough supplement to receive the recommended dose. Collectively, results indicate that providing a granular free-choice supplement containing CTC is not an effective method of ensuring cows consume an adequate amount of supplement to receive CTC at the label-directed dose and frequency. [ABSTRACT FROM AUTHOR]

Aim: Weaning stress can cause serious damage to piglet's health. Chlortetracycline (CTC) is widely used to ameliorate weaning stress and prevent infectious diseases in weaned piglets. However, antibiotics as growth promoters have to be limited because of increased antimicrobial resistance. In this study, we evaluated the effects of CTC on growth performance and intestinal functions in order to provide evidence for seeking antibiotic substitutes in weaned piglets. Methods and results: A total of 20 weaned piglets were fed a basal diet or a diet supplemented with 75 mg/kg CTC. CTC decreased the crypt depth and increased the ratio of villus height to crypt depth, whilst failing to affect growth performance and serum biochemical parameters and cytokines. 16S rRNA sequencing suggested that CTC supplementation had no effect on the diversity and composition of colonic microbiota. Conclusion: We speculated that gut microbiota is no longer sensitive to a low concentration of CTC due to the long‐term use and low bioavailability of CTC in weaned piglets. [ABSTRACT FROM AUTHOR]

The aggregation-induced emission (AIE) characteristic of copper nanoclusters (CuNC) was for the first time used to construct a ratiometric fluorescence probe (CuNC-Al3+) for detection of chlortetracycline (CTC). Aluminum ion (Al3+) can aggregate free CuNC and make it emit a bright and stable red fluorescence. A slight excess of Al3+ in CuNC-Al3+ solution can form a CTC-Al3+ complex to limit the conformational rotation of CTC molecule and enhance CTC fluorescence. So, the red fluorescence of CuNC-Al3+ probe and the enhanced CTC fluorescence are used as a reference signal and a response signal to detect CTC, respectively. The method developed shows a good linear relationship between the CTC concentration and the fluorescence intensity ratio (I495/I575) in the range 0.1-3.0 µM, and the detection limit is 25.3 nM (S/N = 3). In addition, the fluorescent color of CuNC-Al3+ probe changes from red to yellow-green as the concentration of CTC increases. Based on this observation, a fluorescent test paper has also been fabricated. Schematic illustration of Al3+ inducing CuNC to produce AIE performance and detecting CTC. [ABSTRACT FROM AUTHOR]

The chlortetracycline (CTC) residue in food poses a threat to human health. Therefore, developing sensitive, convenient and selective analytical methods for CTC detection is crucial. This study innovatively uses tin disulfide/bimetallic organic framework (SnS 2 /ZnCo-MOF) nanocomposites in conjunction with gold nanoparticles (AuNPs) to co-modify a glassy carbon electrode (GCE). Further, a molecularly imprinted polymer (MIP)-based electrochemical sensing platform Au-MIP/SnS 2 /ZnCo-MOF/Au/GCE (AZG) was fabricated for selective CTC detection. SnS 2 /ZnCo-MOF enhanced the stability and surface area of the AZG sensor. The presence of AuNPs facilitated electron transport between the probe and the electrode across the insulating MIP layer. The fixation of AuNPs and MIP via electropolymerization enhanced the selective recognition of this sensor and amplified its output signal. The AZG sensor demonstrated a wide linear detection range (0.1–100 μM), low detection limit (0.072 nM), and high sensitivity (0.830 μA μM−1). It has been used for detecting CTC in animal-origin food with good recovery (96.08%–104.60%). [Display omitted] • Ultrasensitive sensor was successfully developed for selective determination of CTC. • SnS 2 /ZnCo-MOF provided more uptake sites for the loading of CTC template. • AuNPs act as "electron wires" to facilitate electron transfer. • The low LOD and good recovery as well as stability were achieved. • The sensor showed great potential for CTC detection in animal-origin food. [ABSTRACT FROM AUTHOR]

Antibiotics are widely used in clinical medicine due to their excellent antibacterial abilities. As typical emerging pollutants, their misuse can lead to excess antibiotics entering the environment, causing antimicrobial resistance and leading to serious health problems via food chain. Herein, a nano-fluorescent probe based on nitrogen-doped carbon dots (N-CDs) was constructed for the sensitive detection of chlortetracycline (CTC). N-CDs with stable fluorescence were synthesized by hydrothermal method using alizarin red and melamine as raw materials. The N-CDs exhibited significant independence to excitation wavelength. The fluorescence of N-CDs was significantly quenched by CTC ascribing to the fluorescence resonance energy transfer mechanism. The concentration of N-CDs, solution pH and incubation time were optimized to obtain the optimal detection parameters. Under optimal conditions, CTC exhibited excellent linearity over the range of 20–1200 μg/L, and the detection limit was 8.74 μg/L. The method was validated with actual water samples and achieved satisfied spiked recoveries of 97.6–102.6%. Therefore, the proposed method has significant application value in the detection of CTC in waters. [Display omitted] • N-CDs were obtained by hydrothermal method with alizarin red and melamine. • N-CDs based probes exhibited high selectivity for chlortetracycline. • Quenching of CTC fluorescence was contributed to resonance energy transfer. • The constructed probe was sensitive, rapid, robust for detecting CTC. [ABSTRACT FROM AUTHOR]

[Display omitted] • NiZnCo-N-C heterojunction structures composed of bimetallic oxides were prepared. • The catalytic system enabled efficient degradation of tetracycline antibiotics. • All components of the material provided the environment for electron transfer. • NiZnCo-N-C had great d-orbital hybridization used to adsorb CTC and PDS. • NiZnCo-N-C had more oxygen vacancies used to create ·O 2 – and 1O 2. The bimetallic oxides heterojunction structure from new 3D-ZIF was prepared to degrade the chlortetracycline by PDS activation. The system achieved more than 95 % degradation of chlortetracycline within 40 min. Theoretical calculations and physicochemical characterization of the NiZnCo-N-C proved that the material had better electron transfer properties and multi-site reactivity, and the presence of Zn provided an effective intermediate medium for the reaction of Co and Ni, while the non-metallic N-C component also constituted good electron reaction sites. Meanwhile, the existence of abundant oxygen vacancies established the good foundation for the formation of oxygen radicals in the material, and the rapid electron transfer processes speeded up non-radical processes such as electron transfer and 1O 2.The combination of two degradation pathways reduced the impact of environmental factors, the PDS + NiZnCo-N-C system exhibited relatively stable or even better performance in the existence of inorganic anions. Furthermore, the structure of the NiZnCo-N-C had the smallest d-band center, which efficiently adsorbed PDS molecules and broke the O-O bond in PDS. DFT Conclusion and LC-MS of CTC suggested the various reaction processes in the system. Our study provided new solutions and insights for the organic pollutions in the aquatic environment. [ABSTRACT FROM AUTHOR]

A GSH-Se nanozyme, which simultaneously possesses fluorescent and glutathione peroxidase-like activities, was prepared using a one-pot hydrothermal method. This nanozyme can be used for fluorescence-enhanced detection or imaging of CTC in food and cells. [Display omitted] • Novel GSH-Se nanozyme shows dual fluorescence and peroxidase-like activities. • Enhanced GSH-Se fluorescence detects chlortetracycline (CTC) sensitively and selectivity. • Low toxicity, GSH-Se enables real-time CTC monitoring in cells. Developing rapid monitoring methods to detect antibiotic residues in food plays an important role in safeguarding human health. This study presents the development of a novel fluorescence-enhanced detection method for chlortetracycline (CTC) using a GSH-Se nanozyme. A GSH-Se nanozyme prepared using a one-pot hydrothermal method not only possesses excellent fluorescent properties but also exhibits good glutathione peroxidase-like activity. The results show that the addition of CTC leads to a significant enhancement in the fluorescence intensity of GSH-Se, and this increase exhibits a good linear relationship with the concentration of CTC. The linear range of this method is 0.02–1 µM, and the limit of detection (LOD) for CTC was 0.02 µM. Moreover, the cell toxicity of GSH-Se is low and can be used for monitoring and imaging of CTC in cells, and satisfactory results have been obtained in the analysis of actual food samples. [ABSTRACT FROM AUTHOR]

[Display omitted] • The spontaneous binding behavior of CTC to casein was revealed for the first time. • Binding sites engaged in the formation of the casein-CTC complex were deciphered. • The complexation between casein and CTC inhibited the thermal degradation of CTC. Bovine casein was selected as a model protein to evaluate the impact of food matrix on the thermal degradation of antibiotics. Fluorescence quenching and isothermal titration calorimetry experiments revealed that chlortetracycline (CTC) could spontaneously bind to casein via hydrogen bonding and hydrophobic interactions. The amino acid residues forming the binding pocket were further identified using molecular docking, while saturation transfer difference NMR deciphered that the binding of CTC engages its -N(CH 3) 2 group. Moreover, the degradation behavior of free CTC versus that bound in casein-CTC complex was compared during thermal treatment. Compared with free CTC, a lower first-order rate constant was observed in the presence of casein. Removal of casein shortened the half-life of CTC by at least 48.1% at low concentrations. Elucidating that the formation of protein-antibiotic complexes alters the amenability of antibiotics to degradative reactions, which could help eliminate residual antibiotics and guarantee the safety of dairy products. [ABSTRACT FROM AUTHOR]

In this study, a monoclonal antibody (mAb) against chlortetracycline was prepared by immunisation using chlortetracycline conjugated to bovine serum albumin (CTC-BSA) and cell fusion. One monoclonal antibody (1-2B) against chlortetracycline was obtained with an IC50 of 0.33 ng/ml and a detection limit of 0.1 ng/ml. The cross reactivity of this antibody with structurally related and non-related compounds was less than 0.1%, demonstrating that the obtained mAb provided high specificity. Under optimal conditions for ic-ELISA, a linearity was obtained between 0.06 and 3.9 ng/ml of chlortetracycline. The quantification of CTC-spiked milk and honey samples was also performed, demonstrating recovery rates ranging from 95.2% to 105.6% and the coefficient of variation below 10% for both intra- and inter-variation assays. Based on the sensitivity and specificity measurement, mAb 1-2B could feasibility be used as a screening tool for CTC residue detection in milk and honey samples. [ABSTRACT FROM AUTHOR]

Background and Aim: Digital dermatitis (DD) is one of the most common causes of lameness in dairy cattle. It is seen in nearly all dairy herds across the world and has substantial welfare and economic implications. In this study, we aimed to investigate the efficacy of phenytoin sodium topical treatment on painful ulcerative stage of bovine digital dermatitis (BDD). Materials and Methods: In total, 45 Holstein-Friesian dairy cows with DD were randomly assigned to one of the three topical treatment trials (15 each): Saline solution (first treatment, negative control), chlortetracycline spray (second treatment, positive control), or phenytoin sodium powder (third treatment, positive control) (third treatment). On day 0 (pre-treatment) and on days 7, 14, 21, and 28 post-treatment, the response of DD-affected cows to the medications used was evaluated by measuring lesion depth and size, as well as the total clinical score (lameness, pain, and discomfort). Results: The cure rate in cows treated with phenytoin (86.66%) on day 28 was significantly improved compared to cows treated with either chlortetracycline (60%) or normal saline (6.66 %). Conclusion: Our findings highlight the superiority of phenytoin over the commonly used antibacterial agent, chlortetracycline, in the topical treatment of BDD, and subsequently suggest that phenytoin should be considered a suitable alternative treatment option for the treatment of BDD. [ABSTRACT FROM AUTHOR]

Degradation of antimicrobial resistance genes (ARG) in manure from beef cattle administered (kg−1 feed) 44 mg of chlortetracycline (CTC), 44 mg of chlortetracycline plus sulfamethazine (CTCSMZ), 11 mg of tylosin (TYL), or no antimicrobials (Control) was examined. Manure was stockpiled and quantitative PCR (qPCR) was used to assess tetracycline [tet(C), (L), (M), (W)], erythromycin [erm(A), (B), (F), (X)], and sulfamethazine [sul(1), (2)] ARG and 16S rDNA. After 102 d, copies of all ARG decreased by 0.3 to 1.5 log10 copies (g dry matter)−1. Temperature in the interior of piles averaged ≥ 55 °C for 10 d, except for CTCSMZ, but did not reach 55 °C at pile exteriors. Compared to Control, CTCSMZ increased (P < 0.05) tet(C), tet(M), tet(W), sul(1), and sul(2) in stockpiled manure. Copies of 16S rDNA remained higher (P < 0.05) in CTCSMZ than Control for the first 26 d. Levels of most ARG did not differ between the interior and exterior of stockpiles. Our results suggest that stockpiled manure would still introduce ARG to land upon manure application, but at levels lower than if manure was applied fresh. [ABSTRACT FROM AUTHOR]

The specific concentrations of tetracycline, chlortetracycline, oxytetracycline and doxycycline in non‐target feed for food‐producing animals, below which there would not be an effect on the emergence of, and/or selection for, resistance in bacteria relevant for human and animal health, as well as the specific antimicrobial concentrations in feed which have an effect in terms of growth promotion/increased yield were assessed by EFSA in collaboration with EMA. Details of the methodology used for this assessment, associated data gaps and uncertainties are presented in a separate document. To address antimicrobial resistance, the Feed Antimicrobial Resistance Selection Concentration (FARSC) model developed specifically for the assessment was applied. The FARSC for these four tetracyclines was estimated. To address growth promotion, data from scientific publications obtained from an extensive literature review were used. Levels in feed that showed to have an effect on growth promotion/increased yield were reported for tetracycline, chlortetracycline, oxytetracycline, whilst for doxycycline no suitable data for the assessment were available. Uncertainties and data gaps associated with the levels reported were addressed. It was recommended to perform further studies to supply more diverse and complete data related to the requirements for calculation of the FARSC for these antimicrobials. [ABSTRACT FROM AUTHOR]

The article used high performance liquid chromatography to determine and analyze the content of chlortetracycline in feed, and analyzes the source of uncertainty in the detection process, and calculates the uncertainty of the detection result. The results showed that when the content of chlortetracycline was 69.567 mg/kg, the extended uncertainty of the results was 1.792 mg/kg at the 95% confidence interval (k=2). Among the components affecting the test results, the purity of the standard product and the uncertainty introduced by the standard solution preparation process has a greater impact on the results. [ABSTRACT FROM AUTHOR]

In this study, electrochemical behavior of tetracycline (TC), chlortetracycline (CTC) and oxytetracycline (OTC) were investigated in 20; 30 and 40% acetonitrile-water mixture at the pH of 1.5; 2; 2.5; 3; 4 prepared Britton- Robinson (BR) buffers, by the differential pulse voltammetric method. Voltammetric determinations of TC, CTC and OTC were carried out using molecularly imprinted (MIP) and non-imprinted polypyrrole (NIP) modified graphite electrodes. Both types of electrode were prepared by the cyclic voltammetric method. The effect of the asetonitrile--water ratio and pH, on the performance of the modified graphite electrode (MIP) was investigated and optimized. The highest anodic signals of TC, CTC and OTC with modified graphite electrode were obtained in BR buffer solution were prepared in 20% asetonitrile-water at pH 2. [ABSTRACT FROM AUTHOR]

Among the tetracycline antibiotics, chlortetracycline (CTC) is the most frequently used antibiotic except for tetracycline (TC) for enhancing the ability of the organism to fight bacterial infections. The poor metabolism and degradability of CTC can cause serious health effects. Most studies have focused on the detection and analysis of TC, and research on CTC is relatively scarce. This is because the structures of CTC and TC and oxytetracycline (OTC) are extremely similar, and even indistinguishable. In this study, CTC was used as a template molecule and a molecularly imprinted layer was coated on the surface of highly fluorescent N-CDs using a reversed-phase microemulsion method to form N-CDs@MIPs. It was possible to specifically identify CTC without the influence of TC and OTC, which are extremely similar in structure. By comparing with the non-imprinted polymer (N-CDs@NIPs), it exhibited high sensitivity and selectivity with an imprinting factor of 2.02. And it was used in the determination of CTC in milk with recoveries and relative standard deviations of 96.7%–109.8% and 0.64%–3.27%, respectively, with high accuracy and precision. The specificity of the measurement is excellent compared with other assays, and it is a valid and reliable assay. [Display omitted] • Identify CTC specifically from the extremely similar structures of CTC, TC and OTC. • N-CDs@MIPs accurately detect CTC by a test signal and a validation signal. • The MIT was introduced, which is a source of high selectivity. • The synthesized N-CDs@MIPs retain the highly fluorescent properties of N-CDs. [ABSTRACT FROM AUTHOR]

Fluoroquinolones (FQs), as the most commonly used antibiotics, are ubiquitous in the aquatic environment. The FQs' self-sensitization process could generate reactive oxygen species (ROS), which could react with other coexisting organic pollutants, impacting their transformation behaviors. However, the FQs' influences and mechanisms on the photochemical transformation of coexisting antibiotics are not yet revealed. In this study, we found ofloxacin (OFL) and norfloxacin (NOR), the two common FQs, can obviously accelerate chlortetracycline (CTC) photodegradation. In the presence of OFL and NOR (i.e., 10 μM), CTC photodegradation rate constants increased by 181.1% and 82.9%, respectively. With the help of electron paramagnetic resonance (EPR) and quenching experiments, this enhancement was attributed to aromatic ketone structure in FQs, which absorbed photons to generate ROS (i.e., 3OFL*, 3NOR*,1O 2 , and •OH). Notably, 3OFL* or 3NOR* was dominantly contributed to the enhanced CTC photodegradation, with the contribution ratios of 79.9% and 77.3% in CTC indirect photodegradation, respectively. Compared to CTC direct photodegradation, some new photodegradation products were detected in FQs solution, suggesting that 3OFL* or 3NOR* may oxide CTC through electron transfer. Moreover, the higher triple-excited state energy of OFL and NOR over DFT calculation implied that energy transfer from 3OFL* or 3NOR* to CTC was also theoretically feasible. Therefore, the presence of FQs could significantly accelerate the photodegradation of coexisting antibiotics mainly via electron or energy transfer of 3FQs*. The present study provided a new insight for accurately evaluating environmental behaviors and risks when multiple antibiotics coexist. [Display omitted] • Fluoroquinolones enhanced the CTC photodegradation upon simulated solar irradiation. • 3FQs*, generated from FQs self-sensitization, dominated to accelerate CTC photodegradation. • The calculated energy of 3FQs* is obviously higher than that of 3CTC*. • More photodegradation products of CTC were detected in the presence of FQs. • 3FQs* induced CTC indirect photodegradation through energy transfer and energy transfer. [ABSTRACT FROM AUTHOR]

Chlortetracycline (CTC), a widely used typical tetracycline antibiotic, has raised increasing concerns due to its potential health and environmental risks. Biodegradation is considered an effective method to reduce CTC in environment. In this study, a strain Aspergillus sp. LS-1, which can efficiently degrade CTC, was isolated from CTC-rich activated sludge. Under optimal conditions, the maximum removal efficiency of CTC could reach 95.41%. Temperature was the most significant factor affecting the degradation efficiency of LS-1. The 19 products were identified in the CTC degradation by strain LS-1, and three degradation pathways were proposed. All the degradation pathways for CTC exhibited ring-cleaving, which may accelerate the mineralization of CTC. To gain more comprehensive insights into this strain, we obtained the genome of LS-1, which had high GC content (50.1%) and completeness (99.3%). The gene annotation revealed that LS-1 contains some vital enzymes and resistance genes that may carry functional genes involved in the CTC degradation. In addition, other antibiotic resistance genes were found in the genome of LS-1, indicating that LS-1 has the potential to degrade other antibiotics. This study provides a more theoretical basis for the investigation of CTC degradation by fungi and new insights into the biodegradation of CTC. [Display omitted] • Aspergillus sp. LS-1 can degrade chlortetracycline 95.41% within 72h. • Temperature was the most significant factor affecting the degradation efficiency. • LS-1 contains enzymes and resistance genes involved in CTC degradation. • Three potential biodegradation pathways of chlortetracycline were proposed. [ABSTRACT FROM AUTHOR]

Four robust Cd(II)-CPs can be acted as sensitive dual-responsive sensors for Co2+/Hg2+ and chlortetracycline in water with excellent selectivity and recyclability. The quenching mechanism of four CPs were investigated in detail. [Display omitted] • Four new ternary Cd(II)-CPs were synthesized and characterized. • 1 and 3 exhibited selective sensing for chlortetracycline and Hg2+. • 2 and 4 exhibited selective sensing for chlortetracycline and Co2+. Four new ternary Cd(II) coordination polymers (CPs) based on rarely-used 2-(pyridin-2-yl)-1-(pyridin-3-ylmethyl)-1 H -benzo[ d ]imidazole (L) were synthesized via hydrothermal method, namely {[Cd(L)(H 2 DOBDC)]·H 2 O} n (1), {[Cd(L)(TP)]·2H 2 O} n (2), [Cd 2 (L)(DCTP) 2 (H 2 O)] n (3) and {[Cd 2 (L)(NDA) 2 ]·H 2 O} n (4) (H 4 DOBDC = 2,5-dihydroxy terephthalic acids, H 2 TP = terephthalic acid, H 2 DCTP = 2,5-dichloroterephthalic acid and H 2 NDA = 1, 4-naphthalenedicarboxylic acid). 1 and 2 are 4-connected 2D sql layers, in which 2 is further expanded into a 3D supramolecular network by π − π stacking interaction, while 3 and 4 exhibit three-dimensional frameworks with unusual topology. 1 and 3/2 and 4 can act as dual-functional fluorescent sensors for the sensing of Hg2+ / Co2+and chlortetracycline (CTC) with response times of 30 s for Hg2+ / Co2+ and 20 s for CTC, respectively, in which 2 and 3 as promising fluorescence probes for analytes with detection limits of 1.44 and 0.91 μmoL/L, 3.34 and 0.66 μmoL/L, respectively. The fluorescence sensing mechanism was discussed in detail. [ABSTRACT FROM AUTHOR]

Here we demonstrated that the Co doped anatase titanium dioxide (Co@TiO 2) prepared by a facile wet chemical method could activate peroxymonosulfate (PMS) for efficiently degrading a wide range of refractory organic pollutants. The characterization results demonstrated that the doped Co replaced partial Ti while did not bring obvious structural change. The Co@TiO 2 /PMS system can efficiently remove about 100 % chlortetracycline (CTC) within 40 min and 100 % Rhodamine B (RhB) within 15 min. The Co@TiO 2 /PMS/CTC system maintained a good catalytic performance over a wide pH range from 3 to 11 and the removal efficiency of CTC improved with increasing pH. The Co@TiO 2 /PMS system had a good anti-interference ability, which was free from interference by inorganic ions (such as H 2 PO 4 2-, NO 3 - and SO 4 2-, etc.) and HA, and also in the different real water matrixes and refractory organic pollutants. Quenching experiments and electron spin resonance (EPR) measurements confirmed that the system had a typical radical process as hydroxyl radical (•OH), sulfate radical (SO 4 •−) and superoxide radical (O 2 •−) were the main reactive species for the degradation of CTC. Furthermore, the Co@TiO 2 also showed excellent stability and low metal leaching during long-term use because of the excellent chemical and physical stability of TiO 2. A Co-doped anatase TiO 2 catalyst was synthesized by a facile wet chemical strategy and used for degrading various organic contaminants via peroxymonosulfate activation. [Display omitted] • Co doped anatase TiO 2 was prepared by a facile wet chemical method. • Effects of doping amount and annealing temperature were studied. • Co@TiO 2 /PMS system noticeably removed 100 % CTC under a broad conditions within 40 min • The system had a typical radical process as •OH, SO 4 •− and O 2 •− were the main reactive species. • The fantastic adaptability of the Co@TiO 2 /PMS system was also demonstrated. [ABSTRACT FROM AUTHOR]

Antibiotic-resistant microorganisms are drawing a lot of attention due to their severe and irreversible consequences on human health. The animal industry is considered responsible in part because of the enormous volume of antibiotics used annually. In the current research, veterinary antibiotic (VA) degradation, finding the threshold of removal and recognizing the joint effects of chlortetracycline (CTC) and Tylosin combination on the digestion process were studied. Laboratory scale anaerobic digesters were utilized to investigate potential mitigation of VA in swine manure. The digesters had a working volume of 1.38 L (in 1.89-L glass jar), with a hydraulic retention time (HRT) of 21 days and a loading rate of 1.0 g-VS L−1 d −1 . Digesters were kept at 39 ± 2 ◦C in incubators and loaded every two days, produced biogas every 4 days and digester pH were measured weekly. The anaerobic digestion (AD) process was allowed 1.5 to 2 HRT to stabilize before adding the VAs. Tests were conducted to compare the effects of VAs onto manure nutrients, volatile solid removal, VA degradation, and biogas production. Concentrations of VA added to the manure samples were 263 to 298 mg/L of CTC, and 88 to 263 mg/L of Tylosin, respectively. Analysis of VA concentrations before and after the AD process was conducted to determine the VA degradation. Additional tests were also conducted to confirm the degradation of both VAs dissolved in water under room temperature and digester temperature. Some fluctuations of biogas production and operating variables were observed because of the VA addition. All CTC was found degraded even only after 6 days of storage in water solution; thus, there was no baseline to estimate the effects of AD. As for Tylosin, 100% degradation was observed due to the AD (removal was 100%, compared with 24–40% degradation observed in the 12-day water solution storage). Besides, complete Tylosin degradation was also observed in the digestate samples treated with a mixture of the two VAs. Lastly, amplicon sequencing was performed on each group by using the 50 most variable operational taxonomic units (OTUs)s and perfect discriminations were detected between groups. The effect of administration period and dosage of VAs on Phyla Firmicutes Proteobacteria, Synergistetes and Phylum Bacteroides was investigated. These biomarkers’ abundance can be employed to predict the sample’s treatment group. [ABSTRACT FROM AUTHOR]

Tetracyclines continue to be important antimicrobials in veterinary medicine. However, the pharmacokinetics (PK) of tigecycline (TIG) and minocycline (MIN) in broiler chickens has not been investigated to date, and the PK of chlortetracycline (CTC) and tetracycline (TET) remains insufficiently researched, especially in terms of absorption. These antimicrobials have never been compared in a single setting in a single species; therefore, the aim of the present study was to compare the PK of TIG, MIN, CTC, and TET in broiler chickens. Each drug (10 mg/kg) was administered intravenously (IV) and orally (PO). The plasma concentrations of each drug were determined by liquid chromatography-tandem mass spectrometry, and the results were analyzed using compartmental and noncompartmental PK models. Despite the fact that all of the studied antimicrobials were administered at an identical IV dose, the area under the concentration-timecurve between zero and the last sampling point (AUC0/t) for MIN (35,014 6 3,274 mg ! hour/mL) and CTC (41,851 6 10,965 mg ! hour/mL) differed significantly fromthat determined forTIG(18,86664,326 mg!hour/ mL) and TET (17,817 6 4,469 mg!hour/mL). After IV administration, the values of AUC0/t were also directly related to total body clearance values which were significantly higher forTIG(0.5660.14 L/hour!kg) andTET (0.60 6 0.14 L/hour!kg) than for CTC (0.256 0.05 L/ hour!kg) and MIN (0.2960.03 L/hour!kg). In turn, after PO administration, TIG was absorbed in only 1.55% 6 0.82, and CTC in 30.54% 6 6.99, whereas the bioavailability of MIN and TET was relatively high at 52.33% 6 3.92 and 56.45% 6 9.71, respectively. The differences in PK parameters between these drugs, despite their structural similarities, suggest that active transport mechanisms may play a role in their absorption and distribution. [ABSTRACT FROM AUTHOR]

In this study, the performance of chitin for removing chlortetracycline (CTC) from aqueous solutions was assessed. The effects of pH, chitin dose, CTC concentration and contact time on CTC adsorption by chitin were investigated. The maximum CTC removal efficiency of 82.9% was determined at pH 7, chitin dose of 5 g/L, CTC concentration of 8.8 mg/L and contact time of 120 min. The highest CTC adsorption capacity was found as 12.01 mg/g for CTC of 82.2 mg/L concentration at pH 7. The results demonstrated that CTC removal efficiency decreased from 82.9% to 73.0% with increasing CTC concentration from 8.8 to 82.2 mg/L. The equilibrium data for CTC adsorption indicated a good fit to the Freundlich isotherm model. Pseudo-second-order kinetic model was the best model for describing the adsorption reactions. [ABSTRACT FROM AUTHOR]

In recent years, carbon dots (CDs) have attracted widespread attention for their unique structure and excellent optical properties. In this study, orange‐red emission CDs were prepared using the one‐pot solvothermal carbonization method in ethanol medium. The fluorescence of the CDs was enhanced significantly in the presence of chlortetracycline (CTC), which was accompanied by the blue shift of emission wavelength in ethanol medium, and the enhancement of fluorescence intensity was proportional to CTC concentration in the range of 1.00×10−8 to 5.00×10−6 mol/L with the detection limit of 3.30 nmol/L. As revealed by the mechanism study, the enhanced fluorescence of the CDs by CTC was attributed to the aggregation‐induced emission (AIE). Besides, the AIE effect on the mixture of CDs and CTC was down‐regulated significantly in the presence of water, while the down‐regulated fluorescence intensity was proportional to water concentration in the range between 2.21×10−4 and 1.35×10−3 mol/L with the detection limit of 3.29×10−5 mol/L. Based on the above‐mentioned fact, a simple method for dual response to CTC and trace water was developed, and it exhibited excellent sensitivity and selectivity. [ABSTRACT FROM AUTHOR]

Background: Chlortetracycline (CTC) is one of the commercially important tetracyclines (TCs) family product and is mainly produced by Streptomyces. CTC is still in a great demand due to its broad-spectrum activity against pathogens. Engineering transcriptional control allows the cell to allocate its valuable resources towards protein production and provides an important method for the build-up of desired metabolites. Despite extensive efforts concerning transcriptional regulation for increasing the productivities of TCs, the regulatory mechanisms of the CTC biosynthesis remain poorly understood. Results: In this study, the possible regulatory function of CtcS, a potential member of MarR (multiple antibiotic resistance regulator) family of transcriptional regulators in S. aureofaciens F3, was demonstrated. Knockdown of ctcS altered the transcription of several biosynthesis-related genes and reduced the production of tetracycline (TC) and CTC, without obvious effect on morphological differentiation and cell growth. Especially, CtcS directly repressed the transcription of the adjacent divergent gene ctcR (which encodes a putative TC resistance efflux protein). A CtcS-binding site was identified within the promoter region of ctcR by DNase I footprinting and an inverted repeat (5′-CTTGTC-3′) composed of two 6-nt half sites in the protected region was found. Moreover, both CTC and TC could attenuate the binding activity of CtcS with target DNA. Conclusion: ctcS regulated the production of TC and CTC in S. aureofaciens F3 and the overexpression of it could be used as a simple approach for the construction of engineering strain with higher productivity. Meanwhile, CtcS was characterized as a TC- and CTC-responsive MarR family regulator. This study provides a previously unrecognized function of CtcS and will benefit the research on the regulatory machinery of the MarR family regulators. [ABSTRACT FROM AUTHOR]

The kinetics of the dissipation of chlortetracycline in the aquatic environment was studied over a period of 90 days using microcosm experiments and distilled water controls. The distilled water control experiments, carried out under dark conditions as well as exposed to natural sunlight, exhibited biphasic linear rates of dissipation. The microcosm experiments exhibited triphasic linear rates of degradation both in the water phase (2.7 × 10−2, 7 × 10−3, 1.3 × 10−3 μg g−1 day–1) and the sediment phase (3.4 × 10−2, 6 × 10−3, 1 × 10−3 μg g−1 day–1). The initial slow rate of dissipation in the dark control (3 × 10−3 μg g−1 day–1) was attributed to a combination of evaporation and hydrolysis, whereas the subsequent fast rate (1.8 × 10−3 μg g−1 day–1) was attributed to a combination of evaporation, hydrolysis, and microbial degradation. For the sunlight‐exposed control, the initial slow rate of dissipation (1.5 × 10−3 μg g−1 day–1) was attributed to a combination of evaporation, hydrolysis, and photolysis, whereas the subsequent fast rate was attributed to a combination of evaporation, hydrolysis, photolysis, and microbial degradation (5.1 × 10−3 μg g−1 day–1). The initial fast rate of dissipation in the water phase of the microcosm experiment is attributed to a combination of evaporation, hydrolysis, photolysis, and microbial degradation, whereas all subsequent slow rates in the water phase and all rates of degradation in the sediment phase are attributed to microbial degradation of the colloidal and sediment particle adsorbed antibiotic. A multiphase zero‐order kinetic model is presented that takes into account (a) dissipation of the antibiotic via evaporation, hydrolysis, photolysis, microbial degradation, and adsorption by colloidal and sediment particles and (b) the dependence of the dissipation rate on the concentration of the antibiotic, type and count of microorganisms, and type and concentration of colloidal particles and sediment particle adsorption sites within a given aquatic environment. [ABSTRACT FROM AUTHOR]

High-yielding industrial Streptomyces producer is usually obtained by multiple rounds of random mutagenesis and screening. These strains have great potential to be developed as the versatile chassis for the discovery and titer improvement of desired heterologous products. Here, the industrial strain Streptomyces rimosus 461, which is a high producer of oxytetracycline, has been engineered as a robust host for heterologous expression of chlortetracycline (CTC) biosynthetic gene cluster. First, the industrial chassis strain SR0 was constructed by deleting the whole oxytetracycline gene cluster of S. rimosus 461. Then, the biosynthetic gene cluster ctc of Streptomyces aureofaciens ATCC 10762 was integrated into the chromosome of SR0. With an additional constitutively expressed cluster-situated activator gene ctcB, the CTC titer of the engineering strain SRC1 immediately reached 1.51 g/L in shaking flask. Then, the CTC titers were upgraded to 2.15 and 3.27 g/L, respectively, in the engineering strains SRC2 and SRC3 with the enhanced ctcB expression. Further, two cluster-situated resistance genes were co-overexpressed with ctcB. The resultant strain produced CTC up to 3.80 g/L in shaking flask fermentation, which represents 38 times increase in comparison with that of the original producer. Overall, SR0 presented in this study have great potential to be used for heterologous production of tetracyclines and other type II polyketides. [ABSTRACT FROM AUTHOR]

The changes of enzyme activities, microbial community structure and function, and the diversity and resistance level of antibiotic-resistant bacteria (ARB) were studied in soil during ten repeated treatments with chlortetracycline (CTC) and/or ciprofloxacin (CIP) together with organic manure (OM) under laboratory conditions. The activities of neutral phosphatase (NPA) and catalase (CAT) displayed the suppression-recovery-stimulation trend in the OM&CTC treatment but the stimulation trend in the OM&CTC&CIP treatment. The NPA was stimulated but the CAT was little affected in the OM&CIP treatment. Soil microbial functional diversity displayed the suppression-recovery-stimulation trend in the OM&CTC and OM&CTC&CIP treatments and the stimulation-suppression trend in the OM&CIP treatment with the treatment frequency. Metagenomic analysis showed that the relative abundances of Actinobacteria and Firmicutes in the antibiotic treatment significantly increased by 0.5–235.6%, but that of Proteobacteria decreased by 0.2–27.3% compared to the control with the treatment frequency. Furthermore, the relative abundances of dominant bacterial genera including Streptomyces , Actinomadura , Mycobacterium , and Streptococcus in the antibiotic treatment significantly increased by 1.1–10433.3% compared to the control. Meanwhile, repeated antibiotic treatments induced a significant increase in the diversity and resistance level of ARB isolates, especially in the OM&CTC treatment. It is concluded that repeated treatments with CTC and/or CIP can alter enzyme activities, microbial community structure and function, and increase the diversity and resistance level of ARB isolates. Image 1 • The suppression-recovery-stimulation trend in the NPA and CAT was found in the OM&CTC treatment. • The stimulation trend in the NPA was found in the OM&CIP and OM&CTC&CIP treatments. • The suppression-recovery trend in soil microbial functional diversity was found in the antibiotic treatments. • Repeated antibiotic treatments altered the soil microbial community structure. • Repeated antibiotic treatments significantly increased the diversity and resistance level of ARB isolates. [ABSTRACT FROM AUTHOR]