An improved tetracycline-inducible expression system for fission yeast.

The ability to manipulate gene expression is valuable for elucidating gene function. In the fission yeast Schizosaccharomyces pombe, the most widely used regulatable expression system is the nmt1 promoter and its two attenuated variants. However, these promoters have limitations, including a long lag, incompatibility with rich media, and unsuitability for non-dividing cells. Here, we present a tetracycline-inducible system free of these shortcomings. Our system features the enotetS promoter, which achieves a similar induced level and a higher induction ratio compared to the nmt1 promoter, without exhibiting a lag. Additionally, our system includes four weakened enotetS variants, offering an expression range similar to the nmt1 series promoters but with more intermediate levels. To enhance usability, each promoter is combined with a Tet-repressor-expressing cassette in an integration plasmid. Importantly, our system can be used in non-dividing cells, enabling the development of a synchronous meiosis induction method with high spore viability. Moreover, our system allows for the shutdown of gene expression and the generation of conditional loss-of-function mutants. This system provides a versatile and powerful tool for manipulating gene expression in fission yeast.

Regulation of cell size and Wee1 kinase by elevated levels of the cell cycle regulatory protein kinase Cdr2.

Many cell cycle regulatory proteins catalyze cell cycle progression in a concentration-dependent manner. In the fission yeast Schizosaccharomyces pombe, the protein kinase Cdr2 promotes mitotic entry by organizing cortical oligomeric nodes that lead to inhibition of Wee1, which itself inhibits the cyclin-dependent kinase Cdk1. cdr2Δ cells lack nodes and divide at increased size due to overactive Wee1, but it has not been known how increased Cdr2 levels might impact Wee1 and cell size. It also has not been clear if and how Cdr2 might regulate Wee1 in the absence of the related kinase Cdr1/Nim1. Using a tetracycline-inducible expression system, we found that a 6× increase in Cdr2 expression caused hyperphosphorylation of Wee1 and reduction in cell size even in the absence of Cdr1/Nim1. This overexpressed Cdr2 formed clusters that sequestered Wee1 adjacent to the nuclear envelope. Cdr2 mutants that disrupt either kinase activity or clustering ability failed to sequester Wee1 and to reduce cell size. We propose that Cdr2 acts as a dosage-dependent regulator of cell size by sequestering its substrate Wee1 in cytoplasmic clusters, away from Cdk1 in the nucleus. This mechanism has implications for other clustered kinases, which may act similarly by sequestering substrates.

Chlamydia suis undergoes interclade recombination promoting Tet-island exchange.

BACKGROUND: The obligate intracellular bacterial family Chlamydiaceae comprises a number of different species that cause disease in various vertebrate hosts including humans. Chlamydia suis, primarily found in the gastrointestinal tract of pigs, is the only species of the Chlamydiaceae family to have naturally gained tetracycline resistance (TetR), through a genomic island (Tet-island), integrated into the middle of chromosomal invasin-like gene inv. Previous studies have hypothesised that the uptake of the Tet-island from a host outside the Chlamydiaceae family was a unique event, followed by spread among C. suis through homologous recombination. In vitro recombination studies have shown that Tet-island exchange between C. suis strains is possible. Our aim in this study was to gain a deeper understanding of the interclade recombination of the Tet-island, among currently circulating C. suis field strains compared to in vitro-generated recombinants, using published whole genome sequences of C. suis field strains (n = 35) and in vitro-generated recombinants (n = 63). RESULTS: We found that the phylogeny of inv better reflected the phylogeny of the Tet-island than that of the whole genome, supporting recombination rather than site-specific insertion as the means of transfer. There were considerable differences between the distribution of recombinations within in vitro-generated strains compared to that within the field strains. These differences are likely because in vitro-generated recombinants were selected for a tetracycline and rifamycin/rifampicin resistant background, leading to the largest peak of recombination across the Tet-island. Finally, we found that interclade recombinations across the Tet-island were more variable in length downstream of the Tet-island than upstream. CONCLUSIONS: Our study supports the hypothesis that the occurrence of TetR strains in both clades of C. suis came about through interclade recombination after a single ancestral horizontal gene transfer event.

Omadacycline pharmacokinetics/pharmacodynamics and efficacy against multidrug-resistant Mycobacterium tuberculosis in the hollow fiber system model.

Seventy-five years ago, first-generation tetracyclines demonstrated limited efficacy in the treatment of tuberculosis but were more toxic than efficacious. We performed a series of pharmacokinetic/pharmacodynamic (PK/PD) experiments with a potentially safer third-generation tetracycline, omadacycline, for the treatment of multidrug-resistant tuberculosis (MDR-TB). Mycobacterium tuberculosis (Mtb) H37Rv and an MDR-TB clinical strain (16D) were used in the minimum inhibitory concentration (MIC) and static concentration-response studies in test tubes, followed by a PK/PD study using the hollow fiber system model of TB (HFS-TB) that examined six human-like omadacycline doses. The inhibitory sigmoid maximal effect (Emax) model and Monte Carlo experiments (MCEs) were used for data analysis and clinical dose-finding, respectively. The omadacycline MIC for both Mtb H37Rv and MDR-TB clinical strain was 16 mg/L but dropped to 4 mg/L with daily drug supplementation to account for omadacycline degradation. The Mycobacteria Growth Indicator Tube MIC was 2 mg/L. In the test tubes, omadacycline killed 4.39 log10 CFU/mL in 7 days. On Day 28 of the HFS-TB study, the Emax was 4.64 log10 CFU/mL, while exposure mediating 50% of Emax (EC50) was an area under the concentration-time curve to MIC (AUC0-24/MIC) ratio of 22.86. This translates to PK/PD optimal exposure or EC80 as AUC0-24/MIC of 26.93. The target attainment probability of the 300-mg daily oral dose was 90% but fell at MIC ≧4 mg/L. Omadacycline demonstrated efficacy and potency against both drug-susceptible and MDR-TB. Further studies are needed to identify the omadacycline effect in combination therapy for the treatment of both drug-susceptible and MDR-TB.

Phenazine-1 carboxylic acid of Pseudomonas aeruginosa induces the expression of Staphylococcus aureus Tet38 MDR efflux pump and mediates resistance to phenazines and antibiotics.

In this study, we showed that phenazine-1 carboxylic acid (PCA) of Pseudomonas aeruginosa induced the expression of Tet38 efflux pump triggering Staphylococcus aureus resistance to tetracycline and phenazines. Exposure of S. aureus RN6390 to supernatants of P. aeruginosa PA14 and its pyocyanin (PYO)-deficient mutants showed that P. aeruginosa non-PYO phenazines could induce the expression of Tet38 efflux pump. Direct exposure of RN6390 to PCA compound at 0.25× MIC led to a five-fold increase in tet38 transcripts. Expression of Tet38 protein was identified through confocal microscopy using RN6390(pRN-tet38p-yfp) that expressed YFP under control of the tet38 promoter by PCA at 0.25× MIC. The MICs of PCA of a Tet38-overexpressor and a Δtet38 mutant showed a three-fold increase and a two-fold decrease, respectively, compared with that of wild-type. Pre-exposure of RN6390 to PCA (0.25× MIC) for 1 hour prior to addition of tetracycline (1× or 10× MIC) improved bacteria viability of 1.5-fold and 2.6-fold, respectively, but addition of NaCl 7% together with tetracycline at 10× MIC reduced the number of viable PCA-exposed RN6390 of a 2.0-log10 CFU/mL. The transcript levels of tetR21, a repressor of tet38, decreased and increased two-fold in the presence of PCA and NaCl, respectively, suggesting that the effects of PCA and NaCl on tet38 production occurred through TetR21 expression. These data suggest that PCA-induced Tet38 protects S. aureus against tetracycline during coinfection with P. aeruginosa; however, induced tet38-mediated S. aureus resistance to tetracycline is reversed by NaCl 7%, a nebulized treatment used to enhance sputum mobilization in CF patients.

Doxycycline for transgene control disrupts gut microbiome diversity without compromising acute neuroinflammatory response.

The tetracycline transactivator (tTA) system provides controllable transgene expression through oral administration of the broad-spectrum antibiotic doxycycline. Antibiotic treatment for transgene control in mouse models of disease might have undesirable systemic effects resulting from changes in the gut microbiome. Here we assessed the impact of doxycycline on gut microbiome diversity in a tTA-controlled model of Alzheimer's disease and then examined neuroimmune effects of these microbiome alterations following acute LPS challenge. We show that doxycycline decreased microbiome diversity in both transgenic and wild-type mice and that these changes persisted long after drug withdrawal. Despite the change in microbiome composition, doxycycline treatment had minimal effect on basal transcriptional signatures of inflammation the brain or on the neuroimmune response to LPS challenge. Our findings suggest that central neuroimmune responses may be less affected by doxycycline at doses needed for transgene control than by antibiotic cocktails at doses used for experimental microbiome disruption.

Bi-Doped and Bi Nanoparticles Loaded CeO2 Derived from Ce-MOF for Photocatalytic Degradation of Formaldehyde Gas and Tetracycline Hydrochloride.

Bi/CeO2 (BC-x) photocatalysts are successfully prepared by solvothermal loading Bi nanoparticles and Bi-doped CeO2 derived by Ce-MOF (Ce-BTC). Formaldehyde gas (HCHO) and tetracycline hydrochloride (HTC) are used to evaluate the photocatalytic activity of the synthesized Bi/CeO2. For BC-1000 photocatalyst, the degradation of HTC by 420 nm < λ < 780 nm light reaches 91.89% for 90 min, and HCHO by 350 nm < λ < 780 nm light reaches 94.66% for 120 min. The photocatalytic cycle experiments prove that BC-1000 has good cyclic stability and repeatability. The results of photoluminescence spectra, fluorescence lifetime, photocurrent response, and electrochemical impedance spectroscopy showed that the SPR (Surface Plasmon Resonance) effect of Bi nanoparticles acted as a bridge and promoted electron transfer and enhanced the response-ability of Bi/CeO2 to visible light. Bi-doping produced more oxygen vacancies to provide adsorption sites for adsorbing oxygen and generated more ·O2 - thus promoting photocatalytic reactions. The mechanism of photocatalytic degradation is analyzed in detail utilizing active free radical capture experiments and electron paramagnetic resonance (EPR) characterization. The experimental results indicate that ·O2 - and h+ active free radicals significantly promote the degradation of pollutants.

Elimination of Trace Tetracycline with Alkyl Modified MIL-101 in Water.

The overuse of antibiotics poses a serious threat to human health and ecosystems. Therefore, the development of high-performance antibiotic removal materials has attracted increasing attention. However, the adsorption and removal of trace amounts of antibiotics in aqueous systems still face significant challenges. Taking tetracycline (TC) as a representative antibiotic and based on its structural characteristics, a series of TC adsorbents are prepared by grafting alkyl groups to the framework of MIL-101(Cr). The adsorptive capacity of the modified materials for tetracycline markedly surpasses that of MIL-101(Cr), with MIL-101-dod achieving the best adsorption performance. MIL-101-dod demonstrated an outstanding ability to adsorb tetracycline at low concentrations, where a 5.0 mg sample of MIL-101-dod can reduce the concentration of a 90 mL 5 ppm tetracycline solution to below 1 ppb, significantly superior to other sorbents. XPS and IR tests indicate that MIL-101-dod has multiple weak interactions with tetracycline molecules, including C─H…O and C─H…π. This work provides theoretical and experimental support for the development of adsorbents for low-concentration antibiotics.

Preparation of Activated Biocarbons from Cones and their Potential Application for Adsorption of Antibiotics (Tetracycline).

The pine cones (PC), spruce cones (SC) and fir cones (FC) were used for biocarbons preparation. Chemical activation with sodium hydroxide was applied to prepare activated biocarbons. All the materials under investigation were characterized by the N2 adsorption, scanning electron microscopy (SEM), elemental analysis (CHNS), infrared spectroscopy (ATR FT-IR), and the Boehm's titration method. Moreover, pHpzc (the point of zero charge) was determined. It was shown that cones are a good, cheap precursor from which biocarbons with a developed porous structure, characterized by good adsorption properties, can be obtained. All the obtained adsorbents are characterized mainly by a microporous structure. Moreover, they contain both acidic and basic surface functional groups (acidic ones prevail over basic ones). The tested activated biocarbons have large specific surface area values ranging from 578 to 1182 m2 g-1. The efficacy of selected materials in the adsorption of an essential contaminant of increasing concern, tetracycline (TC), was investigated. The experimental data were described using the Langmuir and Freundlich adsorption isotherm models. The maximum adsorption capacity of the tested biocarbons ranges from 200 to 392 mg g-1. Thermodynamic studies proved that adsorption is a spontaneous and endothermic process. In summary, economical and environmentally friendly adsorbents were obtained.

Compliance with tetracycline eye ointment during annual mass drug administration for trachoma control in the Amhara region, Ethiopia.

OBJECTIVES: A 6-week course of tetracycline eye ointment is an alternative to single -dose oral azithromycin in annual mass drug administration for trachoma control. Compliance with the recommended tetracycline eye ointment regimen has not been well characterised when administered as part of a trachoma control program. METHODS: A routine mass drug administration for trachoma was carried out in 40 communities in the Amhara region of Ethiopia. Two tubes of tetracycline eye ointment, to be administered twice daily for 6 weeks, was offered to all children under 6 months of age, to pregnant women who declined to take azithromycin, and to all individuals with a macrolide allergy. Seven weeks following the mass drug administration, a treatment compliance survey was performed for all community members documented to have received tetracycline eye ointment during the mass drug administration. RESULTS: Of the 491 individuals documented as having received tetracycline eye ointment from the treatment records, 367 completed the survey, of which 214 recalled being offered tetracycline eye ointment. A total of 105 (49%) respondents reported taking ≥1 daily dose of tetracycline eye ointment on most days of the week for at least the first week. Only 20 (9%) respondents reported taking at least 1 tetracycline eye ointment dose per week for 6 weeks. The most common reasons for low compliance included 'saving it for a future infection' and 'stopped because I (or my child) seemed healthy'. The odds of low compliance were greater for those who reported not having adequate counselling (e.g., odds ratio [OR] 5.3, 95% CI 2.5-28.9 when low compliance was defined as not taking a tetracycline eye ointment dose for most days of at least the first week). CONCLUSIONS: Compliance with tetracycline eye ointment was low when administered by a trachoma program during a routine mass drug administration, especially for those reporting inadequate counselling. Further research with a larger sample size and varied settings is warranted to better understand and improve compliance.

Tetracycline Three Times Daily Versus Four Times Daily in Bismuth-Containing Quadruple Therapy as the First-Line Treatment of Helicobacter pylori Infection: A Multicenter, Noninferiority, Randomized Controlled Trial.

BACKGROUND: Current guidelines recommend bismuth-containing quadruple therapy for patients newly diagnosed with Helicobacter pylori (H. pylori) infection. We aimed to compare the efficacy and safety of tetracycline administered three times daily versus four times daily in bismuth-containing quadruple therapy for first-line treatment of H. pylori infection. METHODS: This multicenter, noninferiority, randomized controlled study, conducted in China, recruited treatment-naïve adults with H. pylori infection, randomized 1:1 into two treatment groups to receive either of the following bismuth-containing quadruple therapies: esomeprazole 20 mg twice-daily; bismuth 220 mg twice-daily; amoxicillin 1000 mg twice-daily; and tetracycline 500 mg three times daily (TET-T) versus 500 mg four times daily (TET-F). At least 6 weeks post-treatment, a 13C-urea breath test was performed to evaluate H. pylori eradication. RESULTS: In total, 406 patients were randomly assigned to the two treatment groups. Intention-to-treat eradication rates were 91.63% (186/203; 95% confidence interval [CI] 87.82%-95.44%) versus 90.15% (183/203; 95% CI 86.05%-94.25%) (p = 0.0005) and per-protocol eradication rates were 95.34% (184/193; 95% CI 92.36%-98.31%) versus 95.72% (179/187; 95% CI 92.82%-98.62%) (p = 0.0002) for the TET-T and TET-F group, respectively. TET-T-treated patients had a lower incidence of adverse effects than TET-F-treated patients (21.61% vs. 31.63%, p = 0.024), with no significant differences in compliance to treatment between the groups. CONCLUSION: As a first-line therapy for H. pylori infection, the eradication rate of the TET-T therapy was noninferior to that of the TET-F therapy while significantly reducing the incidence of adverse reactions. TRIAL REGISTRATION: ClinicalTrials.gov identifier: NCT05431075.

Optimization of Minocycline-Containing Bismuth Quadruple Therapy for Helicobacter pylori Rescue Treatment: A Real-World Evidence Study.

BACKGROUND: The optimal dosage of minocycline remains unclear for Helicobacter pylori (H. pylori) eradication. We aimed to evaluate the efficacy and safety of four different regimens with minocycline and metronidazole compared to classical bismuth quadruple therapy for H. pylori rescue treatment. MATERIALS AND METHODS: From March 2021 to March 2024, refractory H. pylori-infected patients with at least two previous treatment failures who received 14-day therapy with b.i.d. proton pump inhibitor 20 mg and bismuth 220 mg, plus tetracycline 400 mg q.i.d and metronidazole 400 mg q.i.d (BQT), or minocycline 50 mg q.i.d and metronidazole 400 mg q.i.d (PBMn4M4), or minocycline 50 mg t.i.d and metronidazole 400 mg t.i.d (PBMn3M3), or minocycline 50 mg b.i.d and metronidazole 400 mg q.i.d (PBMn2M4), or minocycline 50 mg b.i.d and metronidazole 400 mg t.i.d (PBMn2M3) were included in this retrospective study. H. pylori eradication was assessed by 13C-urea breath test at least 6 weeks after treatment. All adverse effects during treatment were recorded. RESULTS: Totally, 823 patients were enrolled: 251 with BQT, 97 with PBMn4M4, 191 with PBMn3M3, 108 with PBMn2M4, and 176 with PBMn2M3. The eradication rates of BQT, PBMn4M4, PBMn3M3, PBMn2M4, and PBMn2M3 were 89.2%, 87.6%, 91.6%, 88.0%, and 91.5%, respectively, by intention-to-treat analysis; 96.1%, 97.7%, 97.8%, 96.9%, and 97.6%, respectively, by modified intention-to-treat analysis; 97.1%, 97.5%, 97.7%, 96.8%, and 97.6%, respectively, by per-protocol analysis. Metronidazole resistance did not affect the efficacy of all groups. PBMn2M3 group achieved the greatest compliance and the fewest moderate and severe adverse events. CONCLUSIONS: The novel bismuth-containing quadruple therapy with a low dose of minocycline and metronidazole is an alternative to classical bismuth quadruple therapy for H. pylori rescue treatment with superior safety and compliance. TRIAL REGISTRATION: ClinicalTrials.gov identifier: NCT06332599.

Root surface biomodification in periodontal therapy: Biological rationale and clinical applications.

Regenerative periodontal therapy aims to form new cementum, periodontal ligament, and alveolar bone, all sealed by gingival tissue. The root surface acts as the wound margin during this regeneration process. Root surface biomodification (root conditioning/root decontamination), therefore, seems instrumental in promoting surface decontamination and enhancing tissue attachment by removing the smear layer, exposing collagen fibrils, and facilitating blood clot formation and stabilization. This review attempted to provide an all-encompassing, evidence-based assessment of the role of root surface biomodification in regenerative periodontal therapy, particularly in intrabony defects, furcation defects, and root coverage procedures. The reviewed evidence suggested that root conditioning agents, whether used independently or in conjunction with bone graft materials, biological agents, membranes, or connective tissue grafts, do not offer any clinical advantage regarding clinical attachment gain. Thus, integrating chemical methods with the mechanical root instrumentation process does not necessarily contribute to superior clinical outcomes.

Enhanced electrocatalytic degradation of tetracycline by ZIF-67@CNT coupled with a self-standing aligned carbon nanofiber anodic membrane.

Due to the misuse and overuse of the antibiotic tetracycline (TC), as well as its refractory degradability, it has become a stubborn environmental contaminant. In this study, a self-standing polyacrylonitrile-based ZIF-67@CNT/ACF aligned anodic membrane was fabricated by innovatively incorporating ZIF-67@CNT nanoparticles into an aligned carbon nanofiber (ACF) membrane to treat the TC. The flow-through nanoporous construction of the ZIF-67@CNT/ACF membrane reactor can compress the diffusion boundary layer on the electrode surface to enhance mass transfer under microscopic laminar flow, which can further enhance the degradation rate. In addition, the enhanced degradation performance also benefited from the significant electrooxidation capacity of the ZIF-67@CNT/ACF membrane. At the optimal electrocatalytic condition of 3.0 V applied potential and pH 6, the degradation rate reached 81% in 1 h for an initial TC concentration of 10 mg l-1. The refractory and highly toxic TC was electrochemically degraded into small non-toxic molecules. Our results indicate that electrocatalytic TC degradation can be enhanced by ZIF-67@CNT/ACF membrane.

Products from Photolysis Reactions of Tetracycline Mediated by Clay and Humic Substance Induce Contrasting Expressions of Target Resistance Genes.

Phototransformation is a key process affecting the fate of many antibiotics in the environment, but little is known about whether their photoproducts exert selective pressure on bacteria by inducing antibiotic resistance genes (ARGs). Here, we examined the expression of tetracycline resistance gene tet(M) of a fluorescent Escherichia coli whole-cell bioreporter influenced by the phototransformation of tetracycline. The presence of suspended smectite clay (montmorillonite or hectorite, 1.75 g/L) or dissolved humic substance (Pahokee Peat humic acid or Pahokee peat fulvic acid, 10 mg C/L) in aqueous solutions markedly facilitated the transformation of tetracycline (initially at 400 µg/L) with half-life shortened by 1.4-2.6 times. Despite the similar phototransformation ratios (80-90%) of the total loaded tetracycline after 60 min irradiation, the decreased ratios of cell fluorescence intensity (which was proportional to the expression amount of ARG tet(M)) were much higher with the two clays (94 and 93%) than with the two humic substances (44 and 69%) when compared to the respective dark controls. As illustrated by mass spectroscopic and chemical analyses, tetracycline was proposed to be mainly transformed to amide (ineffective in inducing ARGs) with the presence of clays by reaction with self-photosensitized singlet oxygen (1O2), while the humic substances might catalyze the production of another two demethylated and/or deaminated compounds (still effective in inducing ARGs) in addition to the amide compound via reaction with triplet excited state dissolved organic matter (3DOM*). As clay minerals and humic substances are important soil constituents and ubiquitously present in surface environments, the observed clay and humic-dependent photooxidation pathways of tetracycline and the differing selective pressures of the associated products highlight the need for monitoring the transformation compounds of antibiotics and provide critical insight into the development of antibiotic treatment protocols.

45 years of tetracycline post exposure prophylaxis for STIs and the risk of tetracycline resistance: a systematic review and meta-analysis.

There is considerable interest in the use of doxycycline post exposure prophylaxis (PEP) to reduce the incidence of bacterial sexually transmitted infections (STIs). An important concern is that this could select for tetracycline resistance in these STIs and other species. We searched PubMed and Google Scholar, (1948-2023) for randomized controlled trials comparing tetracycline PEP with non-tetracycline controls. The primary outcome was antimicrobial resistance (AMR) to tetracyclines in all bacterial species with available data. Our search yielded 140 studies, of which three met the inclusion criteria. Tetracycline PEP was associated with an increasedprevalence of tetracycline resistance in Neisseria gonorrhoeae, but this effect was not statistically significant (Pooled OR 2.3, 95% CI 0.9-3.4). PEP had a marked effect on the N. gonorrhoeae tetracycline MIC distribution in the one study where this was assessed. Prophylactic efficacy was 100% at low MICs and 0% at high MICs. In the one study where this was assessed, PEP resulted in a significant increase in tetracycline resistance in commensal Neisseria species compared to the control group (OR 2.9, 95% CI 1.5-5.5) but no significant effect on the prevalence of tetracycline resistance in Staphylococcus aureus. The available evidence suggests that PEP with tetracyclines could be associated with selecting tetracycline resistance in N. gonorrhoeae and commensal Neisseria species.

Monitoring antimicrobial resistance in Campylobacter isolates of chickens and turkeys at the slaughter establishment level across the United States, 2013-2021.

Foodborne infections with antimicrobial-resistant Campylobacter spp. remain an important public health concern. Publicly available data collected by the National Antimicrobial Resistance Monitoring System for Enteric Bacteria related to antimicrobial resistance (AMR) in Campylobacter spp. isolated from broiler chickens and turkeys at the slaughterhouse level across the United States between 2013 and 2021 were analysed. A total of 1,899 chicken-origin (1,031 Campylobacter coli (C. coli) and 868 Campylobacter jejuni (C. jejuni)) and 798 turkey-origin (673 C. coli and 123 C. jejuni) isolates were assessed. Chicken isolates exhibited high resistance to tetracycline (43.65%), moderate resistance to ciprofloxacin (19.5%), and low resistance to clindamycin (4.32%) and azithromycin (3.84%). Turkey isolates exhibited very high resistance to tetracycline (69%) and high resistance to ciprofloxacin (39%). The probability of resistance to all tested antimicrobials, except for tetracycline, significantly decreased during the latter part of the study period. Turkey-origin Campylobacter isolates had higher odds of resistance to all antimicrobials than isolates from chickens. Compared to C. jejuni isolates, C. coli isolates had higher odds of resistance to all antimicrobials, except for ciprofloxacin. The study findings emphasize the need for poultry-type-specific strategies to address differences in AMR among Campylobacter isolates.

Aluminium-doped Carbon Dots for the Simultaneous Selective Detection of Five Tetracycline Antibiotics.

In this paper, the aluminium-doped carbon dots (Al-CDs) were developed for simultaneous selective detection of five tetracycline antibiotics (TCs), including minocycline (MC), tetracycline (TC), oxytetracycline (OTC), doxycycline (DOC) and chlortetracycline (CTC). With the bright blue fluorescence, Al-CDs displayed excellent stability and showed no obvious fluorescence intensity changes under different ionic strength, acidic or alkaline environment, continuous ultraviolet light illumination, and even longtime storage at room temperature. As adding different antibiotics, the fluorescence of Al-CDs was strongly quenched by five TCs and showed no distinguished changes with the addition of other kinds of antibiotics. The presence of interferential metal ions, anions and small organic molecules imposed no effect on the simultaneous selective detection of five TCs. A good linear relationship was achieved for five TCs in the range of 0-100 µM, and the limit of detection for MC, TC, OTC, DOC, and CTC were 13.91 (0-100 µM), 15.54 (0-100 µM), 14.26 (0-100 µM), 13.48 (0-100 µM) and 13.88 nM (0-100 µM), respectively. Moreover, Al-CDs was successfully used to the detection of five TCs in real samples with recovery ranging from 92.47% to 122.05%, confirming a bright future for the practical applications in the assays of foods, medicines, and environments.

Development of europium(III) complex functionalized silica nanoprobe for luminescence detection of tetracycline.

Increasing awareness of the health and environment impacts of the antibiotics misuse or overuse, such as tetracycline (TC) in treatment or prevention of infections and diseases, has driven the development of robust methods for their detection in biological, environmental and food systems. In this work, we report the development of a new europium(III) complex functionalized silica nanoprobe (SiNPs-Eu3+) for highly sensitive and selective detection of TC residue in aqueous solution and food samples (milk and meat). The nanoprobe is developed by immobilization of Eu3+ ion onto the surface of silica nanoparticles (SiNPs) as the emitter and TC recognition unit. The ß-diketone configuration of TC can further coordinate with Eu3+ steadily on the surface of nanoprobe, facilitating the absorption of light excitation for Eu3+ emitter activation and luminescence "off-on" response. The dose-dependent luminescence enhancement of SiNPs-Eu3+ nanoprobe exhibits good linearities, allowing the quantitative detection of TC. The SiNPs-Eu3+ nanoprobe shows high sensitivity and selectivity for TC detection in buffer solution. Time resolved luminescence analysis enables the elimination of autofluorescence and light scattering for highly sensitive detection of TC in milk and pork mince with high accuracy and precision. The successful development of SiNPs-Eu3+ nanoprobe is anticipated to provide a rapid, economic, and robust approach for TC detection in real world samples.

A europium (III) functionalized hydrogen-bonded organic framework for sensitively ratiometric fluorescent sensing of tetracycline.

As a kind of antibiotic, tetracycline (TC) might remain in animal blood and milk products during use, which poses a risk to humans after consumption. Therefore, a ratiometric fluorescence probe was proposed for the detection of TC, which was based on an Eu3+ functionalized hydrogen-bonded organic framework (HOF). Since there are a large number of N and O atoms in the skeleton of HOF, more Eu3+ could be loaded onto HOF by forming coordinate bonds, while preserving the fluorescence of luminol monomer in HOF. In the presence of TC, the fluorescence of luminol monomer was attenuated at 425 nm due to inner filter effect (IFE), while TC selectively enhanced the fluorescence peak at 617 nm of Eu3+ under the influence of antenna effect (AE). This highly sensitive probe could detect TC in the range of 0.1-60 µM and had a low limit of detection of 8.51 nM. Besides, the HOF@Eu probe was able to detect TC in actual samples (milk and tap water) with good recoveries (95.09%-111.51%) and precision (R < 4.78%), indicating this probe has great application potential for the detection of TC in food.