Tetracycline Research Articles

Enhanced Visible-Light-Assisted Photocatalytic Removal of Tetracycline Using Co/La@g-C3N4 Ternary Nanocomposite and Underlying Reaction Mechanisms

Graphitic carbon nitride (g-C3N4) is a promising material for photocatalytic applications. However, it suffers from poor visible-light absorption and a high recombination rate of photogenerated electron–hole pairs. Here, Co/La@g-C3N4 with enhanced photocatalytic activity was prepared by co-doping Co and La into g-C3N4 via a facile one-pot synthesis. Co/La@g-C3N4 displayed better performance, achieving 94% tetracycline (TC) removal within 40 min, as compared with g-C3N4 (BCN, 65%). It also demonstrated promising performance in degrading other pollutants, which was ~2–4-fold greater relative to BCN. The improved photocatalytic activity of Co/La@g-C3N4 was associated with improved photogenerated charge separation, reduced charge transfer resistance, a built-in electric field arising from the p-n-p heterojunction, and the synergistic effect of ternary components for the separation and transfer of the photogenerated charge carriers. Superoxide radicals are suggested to be the most notable reactive species responsible for the photocatalytic reaction. Environmental factors, including the pollutant concentration, catalyst dosage, solution pH, inorganic salts, water matrices, and mixture with dyes, were considered in the photocatalytic reactions. Co/La@g-C3N4 showed good reusability for five cycles of the photocatalytic degradation of TC. The facile one-pot co-doping of Co and La in g-C3N4 formed a p-n-p heterojunction with boosted photocatalytic activity for the highly efficient removal of TC from various water matrices.

Oxygen Vacancy Engineering and Constructing Built-In Electric Field in Fe-g-C3N4/Bi2MoO6 Z-Scheme Heterojunction for Boosting Photo-Fenton Catalytic Degradation Performance of Tetracycline.

A novel Fe-g-C3N4/Bi2MoO6 (FCNB) Z-scheme heterojunction enriched with oxygen vacancy is constructed and employed for the photo-Fenton degradation of tetracycline (TC). The 2% FCNB demonstrates prominent catalytic performance and mineralization efficiency for TC wastewater, showing activity of 8.20 times greater than that of pure photocatalytic technology. Density-functional theory (DFT) calculations and degradation experiments confirm that the formation of Fe-N4 sites induces spin-polarization in the material, and the difference in Fermi energy levels results in the formation of built-in electric field at the contact interface, which facilitates the continuous generation and migration of photogenerated carriers to address the issue of insufficient cycling power of Fe (III)/Fe (II).The reactive radicals persistently target the extremely reactive sites anticipated by the Fukui function, causing the mineralization of TC molecules into "non-toxic" compounds through processes of hydroxylation, demethylation, and deamidation. This work holds significant importance in the domain of eliminating organic pollutants from water.

Photocatalysis Inhibits the Emergence of Multidrug-Resistant Bacteria in an Antibiotic-Resistant Bacterial Community in Aquatic Environments.

Bacterial antibiotic resistance has recently attracted increasing amounts of attention. Here, an artificially antibiotic-resistant bacterial community (ARBC) combined with five different constructed antibiotic-resistant bacteria (ARB) with single antibiotic resistance, namely, kanamycin (KAN), tetracycline (TET), cefotaxime (CTX), polymyxin B (PB), or gentamicin (GEM), was studied for the stress response to photocatalysis. With photocatalytic inactivation, the transfer and diffusion of antibiotic resistance genes (ARGs) in the ARBC decreased, and fewer multidrug-resistant bacteria (MDRB) emerged in aquatic environments. After several days of photocatalytic inactivation or Luria broth cultivation, >90% ARB were transformed to antibiotic-susceptible bacteria by discarding ARGs. Bacteria with double antibiotic resistance were the dominant species (99%) of residual ARB. The changes in ARG abundance varied, decreasing for the GEM and TET resistance genes and increasing for the KAN resistance genes. The change in the antibiotic resistance level was consistent with the change in ARG abundance. Correspondingly, point mutations occurred for the KAN, CTX and PB resistance genes after photocatalytic inactivation, which might be the reason why these genes persisted longer in the studied ARBC. In summary, photocatalytic inactivation could reduce the abundance of some ARGs and inhibit the emergence of MDRB as well as block ARG transfer in the bacterial community in aquatic environments. This work highlights the advantages of long-term photocatalytic inactivation for controlling antibiotic resistance and facilitates a better understanding of bacterial communities in real aquatic environments.

Aging of microplastics and its photo-catalytic degradation of coexisting tetracycline

Photodegradation processes play a crucial role in the transforming of antibiotics in aqueous environments, while photochemical aging influences the properties of microplastics (MPs). In this study, the efficacy of ultraviolet (UV) irradiation in eliminating tetracycline (TC) was examined. Especially, TC degradation was mediated by polyethylene microplastics (PE-MPs) was subjected to aging through UV exposure and a combination of UV and thermal-activated persulfate treatments. The effects of MPs concentration, salinity, and pH on TC degradation were investigated. The characteristics of aging PE-MPs and the corresponding active free radicals were analyzed to understand the mechanism of TC degradation. The results showed that the existence of PE-MPs significantly influenced TC degradation under photosensitized conditions. However, as the concentration of PE-MPs increased, the degradation rate initially increased and subsequently declined. TC degradation increased from approximately 35 % to 85 % when pH increased from 3 to 11 mediated by aged PE-MPs. Moreover, the TC degradation ability increased with increasing salinity, and a higher aging degree facilitated the photodegradation of TC, achieving a removal rate of 62 %. At the same time, free radical quenching confirmed that the singlet oxygen (1O2), hydroxyl radical (OH), and superoxide radical (O2·−) produced all involved in the photolysis process of TC mediated by PE-MPs, especially 1O2. The analysis of the degradation products of TC and prediction of its toxicity revealed that the ecological risk associated with the degradation solution diminished compared with that of the TC mother solution.

Paper-Based Fluorescent Sensor for Rapid Multi-Channel Detection of Tetracycline Based on Graphene Quantum Dots Coated with Molecularly Imprinted Polymer.

In this paper, we developed a paper-based fluorescent sensor using functional composite materials composed of graphene quantum dots (GQDs) coated with molecularly imprinted polymers (MIPs) for the selective detection of tetracycline (TC) in water. GQDs, as eco-friendly fluorophores, were chemically grafted onto the surface of paper fibers. MIPs, serving as the recognition element, were then wrapped around the GQDs via precipitation polymerization using 3-aminopropyltriethoxysilane (APTES) as the functional monomer. Optimal parameters such as quantum dot concentration, grafting time, and elution time were examined to assess the sensor's detection performance. The results revealed that the sensor exhibited a linear response to TC concentrations in the range of 1 to 40 µmol/L, with a limit of detection (LOD) of 0.87 µmol/L. When applied to spiked detection in actual water samples, recoveries ranged from 103.3% to 109.4%. Overall, this paper-based fluorescent sensor (MIPs@GQDs@PAD) shows great potential for portable, multi-channel, and rapid detection of TC in water samples in the future.

Rational design of Boerhavia diffusa derived CoFe2O4-Carbon dots@Boehmite platform for photocatalysis and ultra trace monitoring of hazardous pesticide and UO22+ ions

In view of exploiting natural resources for designing of effectual materials in favor of detection and obliteration of water pollutants, a fluorescent nanomaterial (CDBHCF) based on biomass derived carbon dots (CDs) was constructed. The CDs and cobalt ferrite (CF) particles were anchored on boehmite (BH) which served as a support material for CDs. The CDBHCF nanocomposite was prepared via facile hydrothermal treatment for selective recognition of Methyl parathion (MP) pesticide and uranyl ions (UO22+). The corresponding structural, morphological and opto-electronic properties of the nanomaterials have been investigated by different physicochemical techniques. The fluorescent CDBHCF probe was employed to detect extremely low concentration of MP and UO22+ with detection limit of 22.4 nM and 4.4 nM, respectively. Ultimately, the proposed sensing platform was validated through real sample analysis. Besides, CDBHCF nanocomposite was utilized for photocatalytic abolition of Tetracycline (TC) in water samples. Initially, the impact of various operational parameters on the degradation efficiency, including catalyst dosage and initial pH were thoroughly examined. Under optimized conditions, the fabricated CDBHCF nanocomposite demonstrated excellent results for photocatalytic degradation of TC (92 % degradation in 120 min) under visible light illumination. Thus, the proposed strategy delivered an innovative insight for dual purpose of CDBHCF nanocomposite: as a fluorescent probe for real time monitoring and as a photocatalyst for removal of pollutants via simple photocatalytic degradation.

CuO-Fe3C-C modified PVDF membrane for catalysis and antifouling

Modification of membranes is an effective method for degrading organic pollutants and alleviating membrane fouling. In this study, CuO-Fe3C-C catalyst was prepared by high-temperature pyrolysis. The membrane modified by CuO- Fe3C-C was prepared by vacuum filtration. The bacteriostatic rate of the modified membrane can reach to 96.8 %. Compared to the pristine membrane, the pure water flux of the modified membrane increased from 223.43 L m−2h−1 bar−1 to 422.27 L m−2h−1 bar−1, the flux recovery ratio (FRR) of modified membranes increased from 39.7 % to 79.25 %. Removal rate of TC (Tetracycline) by modified membrane activated PMS can reach to 90.75 %. After 5 cycles, the degradation efficiency of modified membranes was still 83.77 %, which was only 6.39 % lower than that of the first cycle. Free radical quenching experiments and ESR tests explored the possible catalysis and antifouling mechanisms of the modified membrane system, the results showed main active species were SO4−•, OH•, O2−• and 1O2. This study prepared membranes with excellent antifouling properties, providing a theoretical reference for alleviating membrane fouling in membrane-based water treatment.

Unlocking solar energy's potential: Dual photocatalytic activities of g-C3N4/Sb2S3 for hydrogen evolution and tetracycline degradation in sunlight

This study focuses on developing a g-C3N4/Sb2S3 heterojunction photocatalyst with different g-C3N4 to Sb2S3 weight ratios (1:1, 1:3, and 3:1) for degrading tetracycline (TC) pollutants. The 1:3 ratio (13 GS) exhibited optimal photocatalytic performance, achieving 99% TC degradation under sunlight within 120 min, compared to 78.4% under visible light and 38% under UV light. The 13 GS catalyst demonstrated strong reusability, maintaining 80% degradation efficiency after six cycles. Scavenger experiments identified hydroxyl radicals as crucial for TC degradation, with DMSO reducing activity by 30%. The photocatalyst also showed high hydrogen production with an apparent quantum efficiency (AQE) of 19.8% under standard conditions, and improved AQE in acidic (23%) and basic (22.7%) conditions, and with CH3OH (23.2%). This g-C3N4/Sb2S3 heterojunction offers a promising solution for degrading toxic contaminants and has the potential for solar-powered applications.

Constructing an S-scheme MnFe2O4/ZnIn2S4 heterojunction with photothermal effect to achieve efficient degradation of tetracycline and 2,4,6-trinitrotoluene

In this work, the S-scheme MnFe2O4/ZnIn2S4 (MFO/ZIS) heterostructure was prepared by hydrothermal method, which can degrade tetracycline (TC) and 2,4,6-trinitrotoluene (TNT) efficiently. Under simulated sunlight irradiation, 88.9 % of TC can be degraded within 75 minutes, and 82.7 % of TNT can be degraded within 120 minutes. The photocurrent response of 3 %MFO/ZIS (0.45 µA cm-2) surpassed that of ZIS (0.15 µA cm−2) and MFO (0.08 µA cm−2). This is mainly due to the synergistic effect of the S-scheme electron transport pathway and the photothermal effect in MFO/ZIS, which improves its utilization rate of photogenerated electrons. After being used four times, 3 %MFO/ZIS can still degrade 80.2 % of TC, showing excellent stability. In addition, the TC degradation process was analyzed and the low toxicity of TC after degradation was confirmed by LC-MS, ECOSAR and experiments of cultivating mung bean sprouts, demonstrating the potential application value of MFO/ZIS heterojunction in the wastewater treatment field.

A stable 2D Cd (II) coordination polymer based on mixed ligands as a fluorescence sensor for detection of tetracycline antibiotic in milk and honey

An innovative two-dimensional Cd (II) coordination polymer, namely, [Cd(L)(dibp)] (CP 1) (dibp= 4,4′-di(1H-imidazol-1-yl)-1,1′-biphenyl; H2L= 5-(1-oxoisoindolin-2-yl)isophthalic acid), have been successfully synthesized under solvothermal condition and characterized by X-ray single crystal diffraction, PXRD, IR, TGA, elemental analysis and solid-state fluorescence analysis. Single-crystal X-ray structural analysis suggests that CP 1 crystallizes in monoclinic system with a space group of P21/c and displays a 2D layer based on centrosymmetric binuclear [Cd2(CO2)4N4] units. Sensing experiments have shown that CP 1, as an emerging fluorescent sensor, can selectively, sensitively and quickly detect Tetracycline antibiotic (TC) with fantastic reusability and low detection limit (LOD = 0.092 μM). At the same time, the fluorescence quenching mechanism of CP 1 may be the FRET and PET. Excitingly, CP 1 as a novel fluorescent sensor can detect TC in milk and honey with recovery rates of 96.8–101.2 % and 97.2–100.8 %, respectively.

Organically coordinated Cu(II) activated peroxymonosulfate for enhanced degradation of emerging contaminants

Copper ion Cu(II) is generally considered ineffective in activating peroxymonosulfate (PMS). However, our study demonstrates that organically coordinated Cu(II), namely, org-Cu(II) with contaminants such as amoxicillin (AMO), ofloxacin (OFX), sulfadiazine (SDZ), and tetracycline (TET) can efficiently activate PMS under neutral conditions, leading to faster degradation of these emerging contaminants. In contrast, organic contaminants that do not coordinate with Cu(II) do not facilitate PMS activation. Unlike traditional PMS-induced advanced oxidation processes (AOPs), our study identifies trivalent Cu(III) as the primary oxidant intermediate, with monovalent Cu(I) serving as its precursor. In addition, basic conditions was found to be beneficial for the degradation of target pollutants in org-Cu(II)/PMS systems. Moreover, this promotion effect extends to realistic wastewater, suggesting promising application prospects. The potential mechanism of the rate-limiting reduction step from Cu(II) to Cu(I) was further investigated. The interaction strength between the lowest unoccupied molecular orbital (LUMO) of the copper complex formed with organic compounds and the highest occupied molecular orbital (HOMO) of PMS influences the energy of the bonding orbitals. Coordination with organic ligands alters the LUMO of Cu(II), facilitating electron transfer from the HOMO of PMS to copper. This process activates PMS, ultimately leading to the production of Cu(I) and Cu(III). These findings deepen our understanding of PMS-induced AOPs for degrading emerging contaminants and underscore the importance of further research into PMS activation by Org-Cu(II).

Fabrication of dual-functional smart materials: 2D-WO3/rGO nanocomposite for electrochemical detection and photocatalytic degradation of tetracycline

The extensive utilization of the antibacterial agent tetracycline (TC) in pharmaceuticals and livestock farming has sparked considerable health apprehensions for the welfare of both animals and humans. The presence of TC drug residues in soil, rivers, lakes, and groundwater further exacerbates these concerns. To address these issues, we synthesized WO3/rGO nanocomposites using a simple hydrothermal method and explored their bifunctional catalyst properties for the first time. These nanocomposites were investigated for their potential applications in electrochemical sensing and photocatalytic degradation of TC drug. The electrocatalytic oxidation of TC drug using the WO3/rGO/Glassy Carbon Electrode (GCE) nanocomposites demonstrated good sensitivity, low detection limit, low quantification limit and wide linear range of 1.708 µA µM−1 cm−2, 202 nM, 0.202 µM and 0.1–400 µM, respectively. Moreover, we assessed the WO3/rGO/GCE nanocomposites effectiveness in detecting TC drug in real samples, including milk, lake water, fish, and tap water, and found the recovery results to be satisfactory. Additionally, the nanocomposites displayed noteworthy photocatalytic activity in degrading the TC drug. The as-prepared WO3/rGO nanocomposites exhibited an impressive degradation efficiency of 87.5 % over 120 minutes under UV–visible light irradiation. Radical trapping tests confirmed that the *OH- radicals played a significant role in the degradation process. Our study highlights the outstanding electrochemical and photocatalytic properties of WO3/rGO nanocomposites, positioning them as highly promising materials for future biomedical and environmental applications.

Formulating InVO4/α-Fe2O3 Heterojunction Composites for Photocatalytic Tetracycline Hydrochloride Degradation.

This study reports the synthesis of InVO4/α-Fe2O3 heterojunction photocatalysts with different stoichiometric ratios via a two-step hydrothermal synthesis reaction. The prepared photocatalysts were characterized by XRD, SEM, TEM, XPS, and other methods. The prepared composites exhibited good photocatalysis of tetracycline hydrochloride. Among the InVO4/α-Fe2O3 heterojunction photocatalysts with different ratios, the InVO4/0.25α-Fe2O3 photocatalyst showed the highest degradation rate for 20 mg L-1 tetracycline hydrochloride. After three photocatalytic runs, it still exhibited excellent stability and reusability. Meanwhile, this study also found that superoxide radical anion (-O2-), electron (e-), hydroxyl radical (·OH), and photogenerated hole (h+) are the basic active substances in the photocatalytic process.

Self-Assembled Nanostructure of Ionic Sn(IV)porphyrin Complex Based on Multivalent Interactions for Photocatalytic Degradation of Water Contaminants.

[Sn(H2PO4)2(TPyHP)](H2PO4)4∙6H2O (2), an ionic tin porphyrin complex, was synthesized from the reaction of [Sn(OH)2TPyP] (1) with a dilute aqueous solution of a polyprotic acid (H3PO4). Complex 2 was fully characterized using various spectroscopic methods, such as X-ray single-crystal crystallography, 1H NMR spectroscopy, elemental analysis, FTIR spectroscopy, UV-vis spectroscopy, emission spectroscopy, EIS mass spectrometry, PXRD, and TGA analysis. The crystal structure of 2 reveals that the intermolecular hydrogen bonds between the peripheral pyridinium groups and the axially coordinated dihydrogen phosphate ligands are the main driving force for the supramolecular assembly. Simultaneously, the overall association of these chains in 2 leads to an open framework with porous channels. The photocatalytic degradation efficiency of methyl orange dye and tetracycline antibiotic by 2 was 83% within 75 min (rate constant = 0.023 min-1) and 75% within 60 min (rate constant = 0.018 min-1), respectively. The self-assembly of 2 resulted in a nanostructure with a huge surface area, elevated thermodynamic stability, interesting surface morphology, and excellent catalytic photodegradation performance for water pollutants, making these porphyrin-based photocatalytic systems promising for wastewater treatment.

Effective sonophotocatalytic degradation of tetracycline in water: Optimization, kinetic modeling, and degradation pathways

Hybrid advanced oxidation processes (AOPs) are gaining interest in degradation of variety of recalcitrant compounds for water and wastewater treatment, due to possible synergistic effects. The present study systematically evaluated the degradation of tetracycline (TC) with a sonophotocatalytic process combining acoustic cavitation (sonocavitation) and photocatalysis based on N-doped TiO2 catalyst. The TC degradation rate constant was 2.4 × 10−2 min−1, i.e., much higher than individual sonocatalytic (0.5 × 10−2 min−1) and photocatalysis (0.6 × 10−2 min−1) processes at the optimized conditions. The synergy index was 2.14, which reveals a significant improvement in the process performance. Maximum TC degradations of 55.5 ± 1.8 % for photocatalysis, 66.4 ± 1.8 % for sonocatalysis, and 79.5 ± 0.3 % for sonophotocatalysis were observed for 10 mg L−1 initial TC concentration after 90 min of treatment. The photocatalytic experiments were extended further to 210 min to achieve a maximum degradation of 78.9 ± 0.2 % at the optimized condition. Scavenging experiments confirmed that hydroxyl radicals (•OH), electron holes (h+), and superoxide radical anions (O2−•) played a significant role in the degradation of TC. Further, the degradation intermediates for each process were identified and degradation pathways were proposed. Empirical kinetic models based on operational parameters were also developed and validated.

Heterogeneous Photocatalytic Degradation of Selected Pharmaceuticals and Personal Care Products (PPCPs) Using Tungsten Doped TiO2: Effect of the Tungsten Precursors and Solvents.

Pharmaceuticals and personal care products (PPCPs) which include antibiotics such as tetracycline (TC) and ciprofloxacin (CIP), etc., have attracted increasing attention worldwide due to their potential threat to the aquatic environment and human health. In this work, a facile sol-gel method was developed to prepare tungsten-doped TiO2 with tunable W5+/W6+ ratio for the removal of PPCPs. The influence of solvents in the synthesis of the three different tungsten precursors doped TiO2 is also taken into account. WCl6, ammonium metatungstate (AMT), and Na2WO4●2H2O not only acted as the tungsten precursors but also controlled the tungsten ratio. The photocatalyst prepared by WCl6 as the tungsten precursor and ethanol as the solvent showed the highest photodegradation performance for ciprofloxacin (CIP) and tetracycline (TC), and the photodegradation performance for tetracycline (TC) was 2.3, 2.8, and 7.8 times that of AMT, Na2WO4●2H2O as the tungsten precursors and pristine TiO2, respectively. These results were attributed to the influence of the tungsten precursors and solvents on the W5+/W6+ ratio, sample crystallinity and surface properties. This study provides an effective method for the design of tungsten-doped TiO2 with tunable W5+/W6+ ratio, which has a profound impact on future studies in the field of photocatalytic degradation of PPCPs using an environmentally friendly approach.

Hyper-Cross-Linked Polyindole for Selective Adsorption and Resource Utilization of Organic Pollutants in Water.

Efficient treatment and utilization of organic pollutants in water are difficult for environmental remediation. A new hyper-cross-linked polymer (PIn-HCP) with high specific surface area was constructed via polyindole (PIn) as building blocks. Rich pore structures and abundant adsorption sites in PIn-HCP were obtained by hyper-cross-linking. The specific surface area of PIn-HCP was enhanced from 14.85 to 431.89 m2/g. The adsorption capacities of PIn-HCP-2 for methylene blue (MB), methyl orange (MO), rhodamine B (RhB), and tetracycline hydrochloride (TH) are 902.0, 275.2, 16.0, and 0.0 mg/g, respectively. PIn-HCP also realized selective adsorption of MB, which can better separate MB/RhB and MB/TH. MB is adsorbed onto PIn-HCP via a synergistic mechanism including π-π stacking, electrostatic interaction, cation-π interaction, hydrogen bonding interaction, and ion exchange. The huge conjugated structure of PIn promotes PIn-HCP to selectively adsorb MB. In addition, PIn-HCP also retains the electrochemical properties of PIn. MB can improve the specific capacitance of PIn-HCP up to five times, and it has potential as a supercapacitor electrode. PIn-HCP offers a promising and practical solution for the efficient treatment and utilization of organic pollutants in water.

Exploring Bismuth Oxide Supported Kaolinite for Photocatalytic Application

Bismuth oxide (Bi2O3) and Bi2O3–supported Kaolin were synthesized using household microwave–assisted methods (350 W, 5 min), with catalyst characteristics analyzed. XRD patterns confirmed the monoclinic structure of Bi2O3. Incorporating 20%w/w Kaolin increased the specific surface area of Bi2O3 from 6.2879 to 16.1345 m2/g, observed in FESEM images showing a hierarchical flower-like morphology resembling French fries alongside Kaolin plates. XRF analysis identified elements in Kaolin contributing to self–doping in band structure of Bi2O3, reducing its band gap and PL intensity. Kaolin/Bi2O3 composites demonstrated enhanced photocatalytic degradation of tetracycline (TC) under visible light, attributed to Bi2O3-generated radicals and increased surface area. The composite photocatalyst can be recycled up to three times. This research not only enhances the photocatalytic activity of Bi2O3 but also increases the value of a local waste material, Kaolin clay. Such enhancements could potentially extend to other metal oxides and abundant waste materials within the country.

Self-supporting CoFe2O4 nanoparticles on 2D g-C3N4/2D loofah activated carbon mediated peroxymonosulfate activation for tetracycline degradation

For antibiotic contaminants, biomass have been regarded as one of the most resource of functional carbonaceous materials due to its biocompatibility, biodegradability, and good adsorption/degradation performance. Herein, a self-supporting CoFe2O4 nanoparticles on 2D g-C3N4/2D loofah activated carbon (CoFe2O4/g-C3N4/BC) is successfully synthesized by simple hydrothermal method using loofah as carbon source and melamine as nitrogen source. The obtained CoFe2O4/g-C3N4/BC materials have a stable hierarchical sandwich structure with macroporous and mesoporous and a large surface area (189.52 m2/g), which can be used as an adsorbent/catalyst for the adsorption/degradation of organic pollutants. With these beneficial properties, the CoFe2O4/g-C3N4/BC material mediated peroxymonosulfate activation exhibits superior catalytic activity in the degradation of organic pollutants under ambient conditions. A model pollutant tetracycline (TC) can be rapidly degraded by 94.97 % within 25 min. The degradation efficiency was sustained at 88.21 % even after five operational cycles, with the cobalt metal leaching rate consistently below 50 μg/L. The inhibition experiment indicates that the main active species in the CoFe2O4/g-C3N4/BC + PMS system are SO4•−, HO• and 1O2, and the degradation of TC is achieved by the synergistic effect of free radical and non-radical pathways. This study provides a new perspective on the treatment of antibiotic wastewater via the sulfate radicals based-advanced oxidation processes (SR-AOPs).

Emergence of plasmid-borne tet(X4) resistance gene in clinical isolate of eravacycline- and omadacycline-resistant Klebsiella pneumoniae ST485.

Omadacycline and eravacycline are gradually being used as new tetracycline antibiotics for the clinical treatment of Gram-negative pathogens. Affected by various tetracycline-inactivating enzymes, there have been reports of resistance to eravacycline and omadacycline in recent years. We isolated a strain carrying the mobile tigecycline resistance gene tet(X4) from the feces of a patient in Zhejiang Province, China. The strain belongs to the rare ST485 sequence type. The isolate was identified as Klebsiella pneumoniae by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS). The MICs of antimicrobial agents were determined using either the agar dilution method or the micro broth dilution method. The result showed that the isolate was resistant to eravacycline (MIC = 32 mg/L), omadacycline (MIC > 64 mg/L), and tigecycline (MIC > 32 mg/L). Whole-genome sequencing revealed that the tet(X4) resistance gene is located on the IncFII(pCRY) conjugative plasmid. tet(X4) is flanked by ISVsa3, and we hypothesize that this association contributes to the spread of the resistance gene. Plasmids were analyzed by S1-nuclease pulsed-field gel electrophoresis (S1-PFGE), Southern blotting, and electrotransformation experiment. We successfully transferred the plasmid carrying tet(X4) to the recipient bacteria by electrotransformation experiment. Compared with the DH-5α, the MICs of the transformant L3995-DH5α were increased by eight-fold for eravacycline and two-fold higher for omadacycline. Overall, the emergence of plasmid-borne tet(X4) resistance gene in a clinical isolate of K. pneumoniae ST485 underscores the essential requirement for the ongoing monitoring of tet(X4) to prevent and control its further dissemination in China.IMPORTANCEThere are still limited reports on Klebsiella pneumoniae strains harboring tetracycline-resistant genes in China, and K. pneumoniae L3995hy adds a new example to those positive for the tet(X4) gene. Importantly, our study raises concerns that plasmid-mediated resistance to omadacycline and eravacycline may spread further to a variety of ecological and clinical pathogens, limiting the choice of medication for extensively drug-resistant bacterial infections. Therefore, it is important to continue to monitor the prevalence and spread of tet(X4) and other tetracyclines resistance genes in K. pneumoniae and diverse bacterial populations.