Tetracycline antibiotics: mode of action, applications, molecular biology, and epidemiology of bacterial resistance

Facile synthesis of silicon nanoparticles chelated lanthanide(III)-based electrospun nanofiber membranes for rapid on-site visual detection of tetracycline

Tetracycline (TC) is a broad-spectrum antibiotic, and its residues in the environment and food are harmful to human health. Therefore, it is essential to rapidly, sensitively, and conveniently detect TC. In this work, we developed a portable silicon nanoparticles chelated Europium(III)-based polyacrylonitrile (Eu-SiNPs/PAN) nanofiber membrane for rapid, sensitive, and convenient detection of TC. The Eu-SiNPs were synthesized with a facile one-pot method. The Eu-SiNPs/PAN nanofiber membrane was fabricated by electrospinning, combining Eu-SiNPs and PAN with three-dimensional porous membrane structures and UV resistance. Both the Eu-SiNPs and the Eu-SiNPs/PAN nanofiber membranes have good selectivity and anti-interference ability towards TC. The combined merits of rapid response, long storage life, easy portability, and naked-eye recognition of TC make the Eu-SiNPs/PAN nanofiber membrane a promising material for convenient TC detection applications. The practicability of these nanofiber membranes was further verified by detecting TC in real samples, such as lake water, drinking water and honey, and achieved quantitative detection.

A novel coumarin-incorporated lanthanide coordination nanoprobe for ratiometric sensing of tetracycline

Tetracycline (Tc), a broad-spectrum antibiotic for treating bacterial infections, poses significant risks to human health and the environment. This study presents a novel lanthanide coordination probe, AMP/Eu/CMP, for the ratiometric detection of Tc. The pyridine-appended coumarin derivative, CMP, acting as a stable internal reference, combines with AMP and Eu3+ to form the robust ratiometric probe AMP/Eu/CMP. Upon binding to Tc, Eu3+ fluorescence (emission at 616 nm) is sensitized while CMP fluorescence (emission at 505 nm) remains unchanged, resulting in a clear fluorescence shift from blue-green to red, enabling effective ratiometric detection of Tc. By integrating a smartphone color recognition app, rapid and visual detection of tetracycline concentrations is achieved. Additionally, paper-based test strips were developed for on-site Tc detection, exhibiting a linear response across a wide concentration range, making this method suitable for applications in food safety, pharmaceutical analysis, and environmental monitoring. The use of a fluorescent molecule with unique photophysical properties as an internal reference enables the construction of a high-performance, ratiometric lanthanide coordination polymer probe that is rapid, simple, and cost-effective, providing valuable insights for the development of future fluorescence sensors.

Antagonistic effects of polystyrene microplastics and tetracycline on Chlorella pyrenoidosa as revealed by infrared spectroscopy coupled with multivariate analysis

Microplastics and antibiotics are typical emerging contaminants in the environment, posing considerable risks to the ecosystem and human health. Previous studies have reported synergistic or antagonistic effects in the presence of both microplastics and antibiotics, destructing cell membrane, inhibiting photosynthetic capability, and inducing antioxidant enzyme activity. However, there is still lack of comprehensive understanding of the mechanisms. This study applied infrared biospectroscopy and multivariate analysis to explore the physiological and biochemical toxicity of polystyrene microplastics and tetracycline co-exposure on Chlorella pyrenoidosa. Either tetracycline or polystyrene microplastics alone posed toxicities on C. pyrenoidosa, mainly due to changes in photosynthetic content, cell membrane permeability, MDA content and antioxidant enzyme activity. Co-exposure of tetracycline and polystyrene microplastics exhibited an antagonistic effect. Infrared spectroscopy coupled with multivariate analysis isolated the discriminating biomarkers representing different toxicity mechanisms, successfully explaining the mechanism of antagonism as reducing ROS production, regulating antioxidant enzyme activity, stabilizing cell membrane, and interfering with signaling and protein synthesis. A random forest model was developed and satisfactorily recognized the toxicity of individual toxins (accuracy of 98.75 %, sensitivity of 99.22 % and specificity of 99.65 %). It also rapidly apportioned toxicity origin and evidenced that tetracycline contributed to the majority of binary toxicities. This study provided scientific guidance and a theoretical basis for assessing and apportioning the binary toxicities of emerging contaminants.

Assessment of seasonal variations in antibiotic resistance genes and microbial communities in sewage treatment plants for public health monitoring

The spread of antimicrobial resistance (AMR) around the globe, especially in the urban cities with high population, is a major concern. Therefore, the current study aims at identifying antibiotic resistant bacteria, microbial community compositions and the quantification of antimicrobial resistant genes from six sewage treatment plants (STPs) across Pune city in Maharashtra, India. A total of 106 isolates obtained were tested against six antibiotics in which the highest resistance was observed against trimethoprim (24.53 %). The qPCR assays of seven antibiotic resistance genes revealed abundance of blaimp-1 and mecA genes in the summer and monsoon seasons followed by blaNDM-1 gene in the summer and winter seasons. The alpha diversity indices depicted highest microbial diversity of inlet samples during winter, followed by inlet samples during the summer and monsoon seasons. Comparative analysis revealed Bifidobacterium (51 %), Pseudomonas (28.7 %) and Zoogloea (17.6 %) as the most abundant genera in the inlet samples during the summer, monsoon and winter seasons respectively while Acinetobacter (31 %) and Flavobacterium (23 % in winter and 18.2 % in summer) dominated the outlet samples. The co-network analysis revealed positive and negative interactions in the winter and monsoon but only positive interactions in the summer season. Venn diagrams showed higher abundance of ASVs in the outlet samples than the inlet. The top genera correlated exactly opposite with the pH compared to BOD and COD. PICRUSt2-based functional prediction revealed a higher abundance of methicillin resistance, β-lactamase resistance and multidrug resistance genes in inlet samples while chloramphenicol resistance was found higher in outlet samples. Further, we observed that potential pathogens causing infectious disease such as pertussis, shigellosis and tuberculosis were present in all three seasons.

Nanomaterial-modified electrochemical aptasensors for tetracycline detection: a review

Excessive residues of tetracyclines in the livestock, food products and environment can lead to their accumulation in the human body through the food chain, unavoidably posing a threat to the human health. Therefore, it is essential to establish detection methods with high specificity, stability, and sensitivity. Among the numerous detecting techniques, electrochemical sensors with aptamers working as biorecognition elements have been increasingly applied to monitor tetracyclines. Notably, the synergy of a wide range of nanomaterials with aptamer-based sensors has improved the charge transfer efficiency and signal sensitivity. In this review, the advantages of aptamer-based recognition methods are discussed, and the measuring processes of electrochemical detection are introduced. Then, advances in electrochemical aptasensors used for detecting tetracyclines are summarized with an emphasis on the role of nanomaterials, such as carbon-based nanomaterials and gold-based nanomaterials, functioning as -transducing media and electrically conductive polymers. Finally, the current challenges and emerging trends in this field are also discussed, shedding light on the prospects for developing new aptasensors for tetracycline detection.

Synthesis of terbium-labelled tetracycline-loaded calcium phosphate nanoparticle and its mode of action on multi-drug-resistant pathogenic bacteria Escherichia coli and Salmonella kentucky

This study dealt with synthesis of a luminescent nano-form of tetracycline, characterization of its important physico-chemical properties, and molecular mechanism of its antibacterial action on tetracycline-resistant bacterial species. Nanonization was done by entrapping tetracycline (Tet) molecules within calcium phosphate nanoparticles (CPNPs) and doping them with fluorescent terbium (Tb) ions. To characterize the particles, techniques like AFM, SEM, TEM, DLS, absorption-fluorescence-FTIR spectrometry and dialysis were used and to investigate their antibacterial potency and mechanism of action, techniques of agar plating, Ni2+-NTA chromatography, absorption-fluorescence-CD spectroscopy, gel electrophoresis and NS-TEM were used. Tet-Tb-CPNPs, prepared as colloidal suspension, were highly mono-dispersed, moderately stable, spherical in shape, ∼30 nm in size and ∼220 kDa in MW; entrapment efficiency of tetracycline within the nanocomposite particles was about 55 % and its release from them was sustained, bringing out above 95 % of entrapped tetracycline over seven days. The bactericidal concentration of Tet-Tb-CPNP on diarrhoea-causing MDR (including tetracycline) bacteria E. coli and S. kentucky was about 40-45 μg/mL. Binding of Tet-Tb-CPNPs with bacterial ribosome resulted in disruption and degradation of ribosomal proteins and RNAs; such ribosomal degradation was the root cause of its antibacterial action. Moreover, the nanonized tetracycline had no significant toxicity on human neuroblastoma SH-SY5Y cells at its antibacterial dose. Therefore, further pharmacological and clinical investigations are utmost important before commercializing Tet-Tb-CPNP as a potential nano-antibiotic.

Electrochemical detection of tetracycline using Cu-MOF functionalised screen-printed electrodes

This study offers a novel approach to fabricating an electrochemical sensor based on a screen-printed electrode (SPE) modified with a monometallic copper metal-organic framework (Cu-MOF) for detecting tetracycline. Despite tetracycline is an antibiotic used extensively in both human and animal healthcare, overuse of the drug has polluted the environment and caused antibiotic resistance. To protect the public's health and stop the development of resistant bacterial strains, it is essential to detect tetracycline in the supply of food and water. Furthermore, Cu-MOF was synthesized by a solvothermal technique utilizing terephthalic acid as the building block. Several characterization examinations verified the synthesis of the MOF. Because of the metal synergism between Cu ions, the monometallic Cu-MOF showed strong tetracycline adsorption and electrocatalytic capabilities. For the tetracycline electro-determination, it was therefore used as the electrode material. Differential Pulse Voltammetry was employed in the electroanalysis, with a linearity range of 0.0001-100 µmol L-1 and a detection limit as low as 1.007 µmol L-1. The sensor was successfully applied to real-sample matrices, including tap water and RO water, demonstrating good recovery values ranging from 97.05 to 105.71%; the suggested sensor showed good recovery of the antibiotic that had been spiked.

A bacterial regulatory uORF senses multiple classes of ribosome-targeting antibiotics

Expression of many bacterial genes is regulated by cis- and trans-acting elements in their 5' upstream regions (URs). Cis-acting regulatory elements in URs include upstream ORFs (uORFs), short ORFs that sense translation stress that manifests as ribosomes stalling at specific codons within the uORF. Here, we show that the transcript encoding the Escherichia coli TopAI-YjhQ toxin-antitoxin system is regulated by a uORF that we name 'toiL'. We propose that in the absence of translation stress, a secondary structure in the UR represses translation of the topAI transcript by occluding the ribosome-binding site. Translation repression of topAI leads to premature Rho-dependent transcription termination within the topAI ORF. At least five different classes of ribosome-targeting antibiotics relieve repression of topAI. Our data suggest that these antibiotics function by stalling ribosomes at different positions within toiL, thereby altering the RNA secondary structure around the topAI ribosome-binding site. Thus, toiL is a multipurpose uORF that can respond to a wide variety of translation stresses.

Synergy of Tetracyclines and Potassium Azeloyl Diglycinate (Azeloglycine) in Hydrogels: Evaluation of Stability, Antimicrobial Activity, and Physicochemical Properties

Acne vulgaris is one of the most common dermatological diseases and has a complex etiology. Despite the wide range of available therapeutic options, modern and effective solutions are still being sought, particularly in the area of topical therapy. The aim of this study was to develop hydrogel formulations that provide stability for the antibiotics they contain-tetracycline or chlortetracycline enriched with azeloglycine-the latter an ingredient supporting acne-prone skin care. The physicochemical parameters, stability, and antimicrobial activity of the obtained formulations were analyzed. HPLC analysis showed that tetracycline exhibited greater stability than chlortetracycline, especially in mildly acidic and neutral environments. The addition of azeloglycine improved the rheological properties of the hydrogels, reduced tetracycline degradation under alkaline conditions, and enhanced the penetration of active ingredients into the model sebum. All tested formulations demonstrated antimicrobial activity against Staphylococcus aureus. In the artificial sebum biofilm model, hydrogels containing azeloglycine more effectively reduced staphylococcal biofilm mass. No formulations showed toxicity towards Galleria mellonella larvae. The results indicate the potential usefulness of the developed hydrogels as modern multifunctional formulations for topical acne treatment. Hydrogel formulations containing tetracycline and azeloglycine may represent a promising future anti-acne preparation exhibiting synergistic antibacterial, anti-inflammatory, and sebum-cleansing effects.

Targeting TetR-family transcription regulators for combating tetracycline resistance in resilient Acinetobacter baumannii: in silico identification of potent inhibitors

Acinetobacter baumannii stands out as a potent pathogenic microbe responsible for healthcare-associated infections characterized by elevated morbidity and mortality. This bacterium has acquired a range of mechanisms for resisting antibiotics, resulting in the emergence of strains that can withstand antibiotics from multiple classes. Effectively addressing this urgent concern requires finding ways to overcome these resistance mechanisms. In this context, our study focuses on TetR Transcriptional Factor Regulators (TetR-FTRs). It coordinates functions of tetracycline efflux pump proteins (TetA and TetR) and exert influence over metabolic pathways, quorum sensing, and biofilm formation. The primary objective is to identify potent inhibitors targeting TetR-FTRs through scaffold-based shape screening across thirteen distinct databases. A wide array of in silico techniques was employed, including molecular docking, molecular dynamics simulations, Swiss Similarity search, Virtual Screening, MM/GBSA analysis, ADMET assessment, PAINS assay, SIFT analysis, and MM/PBSA calculations. The initial Swiss similarity search yielded 2178 compounds for subsequent virtual screening, with the application of PAINS analysis rigorously pruning the list, eliminating 14 false positive hits. Further refinement through SIFT approach discriminated closely related interacting compounds into three distinct clusters - ChemBridge5963254, BDH33906706, and ZINC000013607604, which fulfilled all SIFT criteria. Comparative evaluation against reference compounds revealed favorable glide scores, lower binding free energies, and interactions with crucial active site residue Hsd128-Mg2+. Molecular dynamics simulations consistently exhibited stable binding for these clusters in contrast to reference compounds. Our analysis underscores three specific compounds, namely ChemBridge5963254, BDH33906706, and ZINC000013607604, as promising candidates for addressing tetracycline resistance and combating A. baumannii infections.

Genotypic characterization of extended-spectrum beta-lactamase-producing E. coli from dogs in northern Germany

Antimicrobial resistance (AMR) is a growing concern in veterinary and public health, with extended-spectrum beta-lactamase (ESBL)-producing Escherichia coli playing a significant role. This study examined 1,000 healthy and sick dogs from a veterinary clinic in northern Germany and identified 85 ESBL-producing E. coli. Whole-genome sequencing of these isolates revealed seven phylogroups. A (38.8%) and B1 (32.9%) were the most common. Multilocus sequence typing identified 42 sequence types (STs), with the globally occurring lineages ST744 and ST10 being predominant. Single nucleotide polymorphism analysis showed the clonal circulation of ST744 among dogs in shared environments, such as households or breeders, whereas ST10 isolates displayed greater genetic diversity. ST131, a pathogenic international high-risk clonal lineage often associated with humans, was assigned to one isolate. Virulence-associated genes (VAGs) were abundant across the isolates, with siderophore systems, biofilm formation, and adherence traits being prominent. All isolates carried enterobactin genes with additional siderophore systems, such as yersiniabactin and aerobactin, present in 36 isolates. The highest number of VAGs (25) was observed in isolates belonging to the pathogenic lineages ST648 and ST405. Sixty-nine percent of the isolates were multidrug-resistant, carrying resistance genes for three or more antibiotic classes, with beta-lactam, aminoglycoside, and tetracycline resistance being the most frequent. This study highlights globally occurring E. coli lineages in companion animals and the role of close contact environments in their dissemination. Although dog-to-human transmission was not investigated in this study, these findings support the need for a One Health approach to address AMR, emphasizing the interconnected health of humans, animals, and the environment.IMPORTANCEThis study demonstrated the presence of globally significant Escherichia coli lineages in dogs and highlighted the impact of close-contact environments, such as households and breeders, on their spread. Many of the isolates exhibited genetic multidrug resistance and virulence features, posing challenges for effective treatment and control. These findings emphasize the interconnected nature of human, animal, and environmental health, underlining the need for a One Health approach to address antimicrobial resistance.

Reaction time oriented a two-step DRST with three heterometallic UOFs: Rapid and selective detection of antibiotics and pesticides in food samples by using a smartphone-integrated fluorescent probe

Three heterometallic uranyl organic frameworks (UOFs): [Zn(5,5'-dmbpy)3]2[(UO2)4O2(npa)4] (1), [Zn(5,5'-dmbpy)2(H2O)2]2[(UO2)2(npa)4]·2H2O (2) and [Zn(UO2)(5,5'-dmbpy)(npa)2(H2O)]·H2O (3) (H2npa = 3-nitrophthalic acid, 5,5'-dmbpy = 5,5'-dimethyl-2,2'-bipyridine) were synthesized with varying reaction times under solvothermal conditions. It is worthing noting that a two-step dissolution and recrystallization structural transformation (DRST) process was observed. The DRST process was investigated and the transformation pathway was deduced. Notably, compound 3 exhibits a fluorescence quenching with tetracycline antibiotics (TCs) and metronidazole (MMT), and a fluorescence enhancement with the tebuconazole (TEB). The detection mechanisms for different substances were detailed discussion through multiple analyses. Furthermore, a smartphone-assisted detection platform was developed for the visual and quantitative detection TCs, MMT and TEB in selected food samples. On-site detection of these samples achieved high recoveries and low relative standard deviations. This innovative detection platform introduced a rapid, cost-effective, portable and user-friendly method for detecting antibiotics and pesticides in food samples.

Genomics Revealed Novel Chromosomal Integration of Antimicrobial Resistance Cluster tet(B), sul2, blaTEM-1B, aph(3″)-Ib, and aph(6)-Id in Salmonella Typhimurium

Antimicrobial-resistant Salmonella has posed a huge threat to food safety and public health, and tetracycline is the commonly used antibiotic for treating salmonellosis. In this study, eight Salmonella Typhimurium isolates from diarrhea patients (n = 7) and clam (n = 1) exhibited high-level tetracycline resistance (minimum inhibitory concentration = 128 μg/mL), and these isolates were further resistant to ampicillin and sulfonamides, formatting the R-type ASuT (ampicillin, sulfonamides, and tetracycline). Then, these eight isolates were sequenced using PacBio platform, revealing the presence of tetracycline resistance gene tet(B), along with sulfonamide-resistance gene sul2, extended-spectrum-β-lactamase gene blaTEM-1B, and aminoglycoside resistance genes aph(3″)-Ib and aph(6)-Id on the chromosome, which was associated with R-type ASuT. Four types (A, B1, B2, and C) of genetic arrangement for chromosomally encoding tet(B) were found, inserted into fljBA operon. Type C (fljBA operon-tet(B)-sul2-blaTEM-1B-aph(3″)-Ib-aph(6)-Id-merACDEPTR) was the most common type and was accompanied by various insertion sequences (ISs) (IS26, IS1, and ISVsa5) and recombinases. Pairwise sequence alignment showed that type C arrangement likely resulted from stepwise acquisitions and rearrangements facilitated by the actions of ISs, followed by integration into the chromosome by prophages. Phylogenomic analysis showed that all eight Salmonella Typhimurium isolates from China in this study, along with a human-borne Salmonella Typhimurium isolate (DA34821) from Germany and a foodborne Salmonella Typhimurium isolate (CFSA629) from China, clustered into a single clade, sharing ≤67 SNPs, which suggested that clone spread occurred. These findings underline the emergence of R-type ASuT in Salmonella Typhimurium, which is attributed to the presence of an antimicrobial resistance gene cluster (tet(B), sul2, blaTEM-1B, aph(3″)-Ib, and aph(6)-Id) encoded on the chromosome.

Complete degradation of polycyclic antibiotic methacycline by a micro/nanostructured biogenic Mn oxide composite from engineered Mn(II)-oxidizing Pseudomonas sp. MB04B

The misuse and improper disposal of methacycline (MTC), a widely used broad-spectrum antibiotic in human clinical settings and livestock production, poses significant threats to both human health and the ecological environment. In this study, a wild-type Mn(II)-oxidizing Pseudomonas strain MB04B was modified through multiple gene deletions, leading to a maximum 35% increase in Mn oxide deposit amount (MnODA) in the engineered strain MB04R-14, and accelerated formation of biogenic Mn oxide (BMO) aggregates, which exhibited the capability to degrade and detoxify MTC completely. After constructing a mini-Tn5 transposon insertion mutant library and screening for MnODA-increased mutants, a total of 10 target genes located in the corresponding mutant loci were identified using the high-efficiency thermal asymmetric interlaced PCR (hiTAIL-PCR) method. These genes were systematically knocked out singly or in multiple combinations, and the highest MnODA-promoted mutant (MB04R-14) was obtained, in which seven genes were knocked out. Following the characterization of the BMO aggregate complex formed in MB04R-14 as a micro-/nanostructured ramsdellite (MnO2) composite through means of several analysis methods, the complex was assessed for MTC degradation under laboratory trials. Complete MTC degradation was revealed after 24 h of treatment with the BMO complex, and the metal ions Mg2+, Cu2+, Ni2+, and Co2+ significantly inhibited MTC degradation efficiency. Liquid chromatography-mass spectrometry identified three intermediates in the degradation pathway, and a possible degradation-metabolic pathway of MTC by the BMO complex was proposed. Finally, the residual antibiotic activity, continuous degradation cycle performance, and treatment of MTC-containing hospital wastewater were evaluated.

IMPORTANCE

Due to the common usage and recalcitrance to degradation, methacycline is often found in various surface water and wastewater as a persistent antibiotic toxicant, posing significant risks to the environment and public health. By engineering a Pseudomonas strain, we developed a dynamic oxidative composite comprising engineered Pseudomonas cells and biogenic Mn oxides. This system not only enhances oxidative capacities but also accelerates the formation of biogenic Mn oxides, leading to the complete degradation of methacycline. The findings highlight the potential of engineered Pseudomonas strain as a sustainable solution for mitigating antibiotic pollution, thereby contributing to cleaner water resources and protecting ecosystems.

Randomized multicenter trial comparing minocycline and ornidazole with classical quadruple therapy in Helicobacter pylori treatment

This study evaluated the efficacy, safety, and cost of minocycline, ornidazole, esomeprazole, and bismuth (MOEB) therapy versus classical therapy (amoxicillin, clarithromycin, esomeprazole, and bismuth potassium citrate, ACEB) for Helicobacter pylori eradication. In a randomized trial of 390 patients, MOEB demonstrated superior eradication rates (93.2% per-protocol, 78.5% intention-to-treat) compared to ACEB (82.5% per-protocol, 72.8% intention-to-treat). Adverse events were significantly lower with MOEB (19.3% vs. 33.8%, p = 0.0019). MOEB was also more cost-effective, with a direct cost of 675.7 CNY versus 970.1 CNY for ACEB, yielding an incremental cost-effectiveness ratio of -27.5 CNY per eradication rate. MOEB is a safe, effective, and cost-efficient first-line regimen for H. pylori eradication.

Antimicrobial resistance in Campylobacter spp. focussing on C. jejuni and C. coli - A narrative review

OBJECTIVES

Campylobacter species represent one of the leading causes of human foodborne infections, including gastroenteritis and bloody diarrhoea. Overuse of antibiotics in veterinary, agriculture, and humans has led to an increase in multidrug antimicrobial resistance (AMR). Fluoroquinolones and macrolides resistant Campylobacters are WHO and CDC priority pathogens, with fluoroquinolone resistance doubling in the past 20 years, complicating treatment.

METHODS

Published studies relating to AMR and associated molecular mechanisms in both Campylobacter jejuni (C. jejuni) and C. coli from animals, humans and environment (1981-2024), were retrieved from PubMed and Google Scholar using relevant keywords. In addition, genomic analyses of publicly available C. jejuni and C. coli genomes along with multilocus sequence typing results from the PubMLST database were used to analyse these AMR determinants and their phylogenomic relationships. Review articles were excluded from the analyses.

RESULTS

A total of 429 research papers were reviewed to get insights into multidrug resistance in C. jejuni and C. coli. Fluroquinolone resistance has been predominantly associated with international travel. The gyrA subunits were associated with ecological niches and overall, it is suggestive that C. coli might be the donor. A positive synergism was observed between cmeA gene expression and quinolone resistance. Additionally, the results speculated the possibility of horizontal gene transfers in chromosomal resistance clusters between C. coli and C. jejuni.

CONCLUSIONS

This review indicated significant concern of multidrug resistance in C. jejuni and C. coli. This requires continent-wide surveillance and research for standard practices to achieve effective antimicrobial stewardship.

Mineral-Based Advanced Oxidation Processes for Enhancing the Removal of Antibiotic Resistance Genes from Domestic Wastewater

Wastewater treatment plants (WWTPs) release antibiotic-resistant bacteria (ARB) and antibiotic-resistant genes (ARGs) into the environment. Advanced oxidation processes (AOPs) can remove ARB and ARGs, but they often require impractically high chemical or energy use. Here, we explore a low-energy AOP that uses Fe-bearing clay mineral (NAu-1) either combined with H2O2 (H2O2/NAu-1) or as prereduced structural Fe (rNAu-1) to degrade selected ARGs (i.e., tetM, tetQ, and bla OXA-10), int1 (a mobile genetic element), and the 16S rRNA gene in postsecondary WWTP effluents. Addition of H2O2/NAu-1 significantly increased tetM and int1 removals relative to UV irradiation and H2O2/UV (p ≤ 0.02). Removals increased with greater H2O2 doses and contact times, reaching maximum values of 1.2 and 2.3 log units at H2O2 doses of 0.26 and 10 mM and contact times of 4 and 8 h, respectively. Bacterial regrowth after 24 h of contact was probably due to H2O2 depletion. However, the addition of rNAu-1 achieved the highest removals, up to 2.9 log units after 0.5 h, and suppressed bacterial regrowth over 24 h. Similar removals were observed with rNAu-1 under oxic and anoxic conditions. Results show that mineral-based AOPs offer the potential for elevated ARG removal and lower chemical and energy demands in tertiary wastewater treatment.

Pharmacokinetics of Antibiotics in Crocodiles: A Review

This review aims to provide an overview of the pharmacokinetics of antibiotics in crocodilian species, focusing on species-specific variations in drug absorption, distribution, metabolism, and elimination (ADME), as well as the influence of environmental factors. A review of the available literature across crocodilian species reveals notable pharmacokinetic variability. Environmental influences, such as temperature and metabolic rate, are shown to impact these pharmacokinetic parameters significantly. Despite the frequent use of antibiotics in clinical and conservation settings, the lack of standardized dosing regimens presents risks of under- or over-dosing. This variability is compounded by limited research on species-specific drug metabolism and elimination processes. The review highlights the need for further pharmacokinetic studies to develop evidence-based dosing protocols, optimize therapeutic outcomes, and address concerns related to antimicrobial resistance. Future research should focus on filling the gaps in PK data to refine dosing strategies and ensure both efficacy and safety in crocodilian species.

Biological activity of secondary metabolites of actinomycetes and their potential sources as antineoplastic drugs: a review

Actinomycetes are an important group of Gram-positive bacteria, renowned for their ability to produce a wide array of structurally diverse and biologically active secondary metabolites. These secondary metabolites have significant applications in fields such as antimicrobial and antifungal treatments and show tremendous potential in cancer research. To comprehensively review the antitumor potential of actinomycetes-derived secondary metabolites, we conducted a systematic literature search across PubMed, Web of Science, and Scopus databases, covering the period from January 2019 to January 2024. The search used keywords including "actinomycetes," "secondary metabolites," "antitumor," "cancer therapy," "bioactivity," and "clinical application." A total of 95 relevant articles were identified through database searches. After applying inclusion and exclusion criteria, 87 articles were deemed eligible and fully reviewed in this article. These studies highlighted diverse structural classes of actinomycetes-derived antitumor compounds, including polyketides, non-ribosomal peptides, alkaloids, and terpenoids. Many of these metabolites exhibit potent anticancer properties through mechanisms such as inducing apoptosis, inhibiting proliferation, disrupting tumor microenvironment, and targeting key oncogenic signaling pathways. This review underscores the crucial role of actinomycetes secondary metabolites as an invaluable resource for antitumor drug discovery, offering new scientific insights into natural product-based cancer therapies, expanding the molecular toolbox for clinical oncology, and ultimately contributing to public health by advancing effective and innovative treatment options for cancer patients.

Binding assays enable discovery of Tet(X) inhibitors that combat tetracycline destructase resistance

The Tet(X) flavin-dependent monooxygenases enable tetracycline antibiotic resistance by catalysing inactivating hydroxylation, so preventing inhibition of bacterial ribosomes. Tet(X) resistance is growing rapidly, threatening the efficacy of important last-resort tetracyclines such as tigecycline. Tet(X) inhibitors have potential to protect tetracyclines in combination therapies, but their discovery has been hampered by lack of high-throughput assays. We report the development of an efficient fluorescence polarisation Tet(X) binding assay employing a tetramethylrhodamine-glycyl-minocycline conjugate that enables inhibitor discovery. The assay was applied to tetracycline substrates and reported inhibitors, providing insight into their binding modes. Screening of a bioactive molecule library identified novel Tet(X) inhibitors, including psychoactive phenothiazine derivatives and the 5-HT4 agonist tegaserod, the activities of which were validated by turnover assays. Crystallographic studies of Tet(X4)-inhibitor complexes reveal two new inhibitor binding modes, importantly providing evidence for active site binding of Tet(X) inhibitors that do not share structural similarity with tetracycline substrates. In some cases, potentiation of tigecycline activity was observed in bacteria expressing Tet(X4). The combined results provide non-tetracycline scaffolds for development of potent Tet(X) inhibitors and highlight the need to evaluate the impact of non-antibiotics on antimicrobial resistance.

The Y58D mutation in rpsJ gene is correlated with tigecycline and eravacycline combined resistance in ST80 vancomycin-resistant Enterococcus faecium isolates

OBJECTIVES

To describe the phenotypic and genetic features of vancomycin-resistant Enterococci (VRE) isolates exhibiting resistance to tetracycline (TET), tigecycline (TGC), and eravacycline (ERV).

METHODS

Between December 2023 and September 2024, 32 VRE were collected from clinical samples at the Policlinico Foggia, Italy. Bacterial identification was carried out by matrix-assisted laser desorption ionization-time of flight mass spectrometry analysis. Antimicrobial susceptibility testing for vancomycin, TET, TGC, and ERV was performed by the reference broth microdilution method. Whole-genome sequencing was carried out to explore the content of tetracycline resistance determinants, and the phylogenetic relationship between isolates (in silico multilocus sequence typing [MLST] and single-nucleotide polymorphisms [SNPs] analysis).

RESULTS

Among the studied isolates, 30 and 2 were vancomycin-resistant Enterococcus faecium (VREfm) and vancomycin-resistant Enterococcus faecalis (VREfs), respectively. Overall, eight isolates (six VREfm and two VREfs) were resistant to TET (8/32, 25%), with four (all VREfm) being resistant to TGC and ERV (4/32, 12.5%), also. The two TET-resistant VREfs strains belonged to sequence type (ST)6 and carried the tet(M) gene only. All the TET-resistant VREfm were ST80 and carried the tet(L) and tet(M) genes. Among these, the four TGC-resistant and ERV-resistant strains showed an uncommon Y58D substitution in the ribosomal S10 protein (rpsJ gene). SNPs analysis revealed that Y58D-carrying strains formed a separate cluster, within ST80 VREfm.

CONCLUSIONS

In this study, we correlated the presence of the Y58D mutation in the rpsJ gene with resistance to TGC and ERV in a cluster of VREfm ST80 clinical strains. The Y58D mutation was invariably found in co-presence with the tet(L) and tet(M) genes.

Potential of lavender essential oil to inhibit tetracycline resistance and modulate gut microbiota in black soldier fly larvae

The misuse of tetracycline in livestock farming leads to environmental residues that promote the proliferation of antibiotic resistance genes (ARGs), particularly tetracycline resistance (tet) genes. Black soldier fly (BSF) larvae, used for organic waste bioconversion, may carry tetracycline residues in their guts, raising concerns about ARG spread. To address this issue, plant-derived additives such as lavender essential oil (LEO) have been explored as alternative antibiotics. This study investigated the effects of LEO on tet gene suppression and gut microbiota modulation in BSF larvae. Results showed that oxytetracycline treatment increased tet gene relative abundance threefold compared to the control, reaching 1.13 ± 0.29 and enriched pathogens Klebsiella oxytoca and Enterobacter hormaechei. Conversely, LEO treatment (100 mg/kg) reduced tet gene abundance by 46.67 %, from 0.15 ± 0.02 to 0.08 ± 0.02, and enhanced beneficial microorganisms like Leuconostoc pseudomesenteroides. Furthermore, LEO reduced tet gene relative abundance in oxytetracycline-treated larvae from 1.13 ± 0.29 to 0.49 ± 0.19 and 0.70 ± 0.11 in separate treatments. LEO modified fungal composition and nutrient pathways. Network analysis revealed that LEO promoted a more integrated and modular gut microbiota, enhancing functional specialization and resilience. These findings suggest LEO can mitigate ARGs in BSF larvae, offering a sustainable approach for antibiotic resistance management in organic waste recycling and livestock farming.

Population pharmacokinetic model of oral minocycline in critically ill adult patients with ventilator-associated pneumonia

OBJECTIVES

Multidrug-resistant Acinetobacter baumannii (MDR-A. baumannii) has become an emerging pathogen, causing ventilator-associated pneumonia (VAP), with limited treatment options available. MIN has re-emerged as a potential treatment option for MDR pathogens. However, evidence regarding MIN pharmacokinetic properties in critically ill patients is scarce and primarily limited to IV administration. To address the knowledge gap in regions where IV MIN is unavailable, a prospective, open-label study was conducted to describe the pharmacokinetic properties of orally administered MIN.

METHODS

The study included 24 critically ill patients with MDR-A. baumannii VAP. A population PK (popPK) model was developed and the PTA for different MICs was assessed by Monte Carlo simulations. A one-compartment model with first-order absorption and linear elimination best described the data.

RESULTS

The values of the estimated population parameters were found equal to 183.3 L, 6.55 L/h and 1.66 h⁻¹, for the apparent volume of distribution (V/F), the apparent clearance (CL/F) and the absorption rate constant (ka), respectively (F representing oral bioavailability). PTA analysis showed that for a daily dose of 400 mg, adequate exposure [free AUC/MIC (fAUC/MIC > 25)] was achieved only for MICs ≤ 0.25 mg/L, while for the ratio of fAUC/MIC = 13.75, high PTA values are calculated up to MIC = 0.5 mg/L.

CONCLUSIONS

This study provides a popPK model for oral MIN in critically ill adults. The developed popPK model contributes to a better understanding of MIN's PK and can inform dosing strategies and future studies on MIN use in critical care settings.

Tracing antibiotics in sewers: Concentrations, measurement techniques, and mathematical approaches

Antibiotic contamination in sewer networks has significant environmental and health concerns worldwide, primarily due to its role in promoting bacterial resistance. In this literature review, antibiotic concentrations reported in urban sewers and hospital effluents, techniques for antimicrobial compound detection and quantification, and current modeling strategies are analyzed and discussed based on 91 papers published between 2014 and 2024. One-hundred and nine antibiotic compounds were reported across 80 studies, with sulfonamides, fluoroquinolones, and macrolides being the most frequently detected classes, while amphenicols and aminocyclitols were the least monitored. Advanced analytical techniques such as liquid chromatography and mass spectrometry are the most common approaches used for antibiotic quantification. Modeling efforts remain limited, with kinetic models, Risk Quotient (RQ) assessments, and Wastewater-Based Epidemiology (WBE) representing the main approaches identified. This review compiles 992 reports into a comprehensive dataset intended to support future research, especially for global monitoring, the development of predictive models, and the formulation of regulatory frameworks for managing antibiotic pollution in sewer systems.

Tetrapyrrole organics-modified cerium nanozyme with enhanced oxidase-like activity for integration of detection and degradation of antibiotic

The massive accumulation of antibiotics accelerates the emergence of antibiotic resistance causing inevitable risks to human and ecosystem. To realize the integration of detection and degradation of antibiotics, it is urgent for exploring novel nanozyme materials with the excellent catalytic activity. Integrating nanozyme with tetrapyrrole-based organics is an effective strategy to enhance the catalytic activity. Herein, a series of tetrapyrrole organics with different energy levels are severally modified on cerium oxysulfate clusters (Ce-clusters) surface to fabricate nanozyme. The mechanism of nanozyme with enhanced catalytic activity was importantly explored by the energy band matching principle. At present, there are no studies that systematically research the enhancement mechanism of tetrapyrrole-based organics with different energy levels on the catalytic activity of nanozyme. Especially, Ce-clusters modified with meso-tetra (4-carboxyphenyl) porphyrin (TCPP) has the best energy band matching, resulting in the highest catalytic activity. Remarkably, the resultant nanozyme exhibits rapid and sensitive colorimetric response to tetracycline within the range of 0-0.3 mg mL-1, and the limit of detection was determined to 0.027 mg mL-1. It also possesses favorable degradation performance to tetracycline under natural light with pH adaptability, strong inorganic ions and organic matter interference tolerance, high reusability, and strong stability. Its degradation efficiency is up to 97.6 % in 60 min, much higher than other types degradation strategies. This study provides a useful principle for designing highly activity nanozyme and a powerful tool to simultaneous detection and degradation of antibiotic, holding great promise for practical application.

A competitive aptamer binding-based CRISPR-cas biosensor for sensitive detection of tetracycline residues in biological samples

Tetracycline (TC) is widely used in veterinary medicine and animal feed; however, TC residues in food pose a risk to human health. Thus, the sensitive and selective detection of TC is needed to ensure food safety. Herein, we developed a CRISPR-Cas12a biosensor with competitive aptamer binding to detect TC residues. The aptasensor, formed by hybridizing activator DNA with TC-specific aptamers on streptavidin-modified magnetic beads, releases activator DNA in a TC concentration-dependent manner. This activated the Cas12a-crRNA complex, which cleaved single-strand DNA reporters to generate a detectable fluorescence signal. The TC signal was amplified through a two-step incubation reaction, with a detection limit as low as 9.45 × 10-5 μg L-1. The assay showed high selectivity and good recovery rates in various biological samples (e.g., honey, milk, fish), demonstrating the applicability of the biosensors in pollutant detection.

T cell toxicity induced by tigecycline binding to the mitochondrial ribosome

Tetracyclines are essential bacterial protein synthesis inhibitors under continual development to combat antibiotic resistance yet suffer from unwanted side effects. Mitoribosomes - responsible for generating oxidative phosphorylation (OXPHOS) subunits - share structural similarities with bacterial machinery and may suffer from cross-reactivity. Since lymphocytes rely upon OXPHOS upregulation to establish immunity, we set out to assess the impact of ribosome-targeting antibiotics on human T cells. We find tigecycline, a third-generation tetracycline, to be the most cytotoxic compound tested. In vitro, 5-10 μM tigecycline inhibits mitochondrial but not cytosolic translation, mitochondrial complex I, III and IV expression, and curtails the activation and expansion of unique T cell subsets. By cryo-EM, we find tigecycline to occupy three sites on T cell mitoribosomes. In addition to the conserved A-site found in bacteria, tigecycline also attaches to the peptidyl transferase center of the large subunit. Furthermore, a third, distinct binding site on the large subunit, aligns with helices analogous to those in bacteria, albeit lacking methylation in humans. The data provide a mechanism to explain part of the anti-inflammatory effects of these drugs and inform antibiotic design.

Interaction of Selected Anthracycline and Tetracycline Chemotherapeutics with Poly(I:C) Molecules

Despite the natural ability of the immune system to recognize cancer and, in some patients, even to eliminate it, cancer cells have acquired numerous evading mechanisms. With the increasing knowledge and focus shifting from targeting rapidly proliferating cells with chemotherapy to modulating the immune system, there have been recent efforts to integrate (e.g., simultaneously or sequentially) various therapeutic approaches. Combining the oncolytic activity of some chemotherapeutics with immunostimulatory molecules, so-called chemoimmunotherapy, is an attractive strategy. An example of such an immunostimulatory molecule is polyinosinic:polycytidylic acid [Poly(I:C)], a synthetic analogue of double-stranded RNA characterized by rapid nuclease degradation hampering its biological activity. This study investigated the possible interactions of tetracycline and anthracycline chemotherapeutics with different commercial Poly(I:C) molecules and protection against nuclease degradation. Fluorescence spectroscopy and circular dichroism revealed an interaction of all of the selected chemotherapeutics with Poly(I:C)s and the ability of doxycycline and minocycline to prolong the resistance to RNase cleavage, respectively. The partial protection was observed in vitro as well.

Antimicrobial Resistance in Diverse Ecological Niches-One Health Perspective and Food Safety

Antimicrobial resistance (AMR) is a multi-sectoral, systemic, and global issue worldwide. Antimicrobial use (AMU) is a key factor in the selection of resistant bacteria within different ecological niches, from agriculture to food-producing animals to humans. There is a question regarding the extent to which the use of antibiotics in livestock production and the primary food production sector influences the selection and transmission of resistant bacteria and/or resistant genes throughout the food chain and thus contributes to the complexity in the development of AMR in humans. Although the trends in the prevalence of foodborne pathogens have changed over time, the burden of ecological niches with resistance genes, primarily in commensal microorganisms, is of concern. The implementation of the harmonized surveillance of AMU and AMR would provide comprehensive insights into the actual status of resistance and further interventions leading to its reduction. Tracking AMR in different ecological niches by applying advanced genome-based techniques and developing shared AMR data repositories would strengthen the One Health concept.

Cultural incorporation of the Kirby-Bauer method in introductory microbiology lab

With rising antibiotic resistance, researchers are exploring sourced pharmaceuticals from local plant materials. One avenue is medicinal plants used in Indigenous communities. California State University, Channel Islands (CSUCI), is built on unceded Chumash land, affording collaboration with local Chumash communities to steward the land's natural and cultural ancestry. Utilizing plant extracts derived from California plant species, we developed an exercise incorporating the local cultural heritage and Kirby-Bauer disk diffusion assay (KB assay). In this exercise, students discuss impacting antibiotic resistance and the role of holistic discovery in creating new pharmaceuticals, examining cultural and familial teachings as a source of scientific/academic inquiry. Students then perform KB assays using plant extracts alongside antibiotics, interpret zones of inhibition for each disk, and compare them to susceptibility cutoffs provided by their lab manual and Clinical and Laboratory Standards Institute (CLSI). While most plant extracts proved ineffective against bacterial strains, students engaged in a novel method for a standardized microbiology technique. Using plants accessed from local environments expands the exercise to various regions, utilizing local flora or ingredients in their classrooms.

Single-cell analysis of antimicrobial compound-induced cell death of bacterial cells

Due to the stochasticity of metabolic reactions and cell cycles of bacterial cells, it is necessary to examine the antibacterial activities of antimicrobial compounds (AMCs) such as antibiotics and antimicrobial peptides (AMPs) at the single-cell level. Here, we review recent studies of the bactericidal activities of AMCs at the single-cell level. First, we discuss recent investigations of the interaction of various AMPs with single bacterial cells, as monitored in real time using optical microscopy. This strategy provides information on AMP-induced membrane damage in single cells [e.g. the onset time of damage to the cell membrane (CM) and outer membrane of single cells]. The rate of AMP-induced CM damage is estimated as the fraction of cells with CM damage [Pdamage (t)] at a specific interaction time t. Second, we discuss the use of single-cell analysis of the bactericidal activity of AMCs. The fraction of dead cells after the exposure to AMCs for time t is determined as the fraction of the microcolonies containing only one cell [Psingle (t)]. For some AMPs, the Pdamage (t) and Psingle (t) values are similar, indicating that AMP-induced CM damage is the direct cause of cell death. Third, we discuss single-cell analysis of the processes and mechanisms of antibiotic-induced cell death. For example, fluoroquinolones and aminoglycosides are observed to induce cytoplasmic condensation and cell lysis, leading to cell death. Based on these studies, we provide our perspective on future investigations using single-cell analysis to assess the processes and the mechanisms of the bactericidal activities of AMCs.

Comprehensive Genomic Analysis of Klebsiella pneumoniae and Its Temperate N-15-like Phage: From Isolation to Functional Annotation

Antibiotic resistance to Klebsiella pneumoniae poses a major public health threat, particularly in intensive care unit (ICU) settings. The emergence of extensively drug-resistant (XDR) strains complicates treatment options, requiring a deeper understanding of their genetic makeup and potential therapeutic targets. This research delineated an extensively drug-resistant (XDR) Klebsiella pneumoniae strain obtained from an ICU patient and telomeric temperate phage derived from hospital effluent. The bacteria showed strong resistance to multiple antibiotics, including penicillin (≥16 μg/mL), ceftriaxone (≥32 μg/mL), and meropenem (≥8 μg/mL), which was caused by SHV-11 beta-lactamase, NDM-1 carbapenemase, and porin mutations (OmpK37, MdtQ). The strain was categorized as K46 and O2a types and carried virulence genes involved in iron acquisition, adhesion, and immune evasion, as well as plasmids (IncHI1B_1_pNDM-MAR, IncFIB) and eleven prophage regions, reflecting its genetic adaptability and resistance dissemination. The 172,025 bp linear genome and 46.3% GC content of the N-15-like phage showed strong genomic similarities to phages of the Sugarlandvirus genus, especially those that infect K. pneumoniae. There were structural proteins (11.8%), DNA replication and repair enzymes (9.3%), and a toxin-antitoxin system (0.4%) encoded by the phage genome. A protelomerase and ParA/B partitioning proteins indicate that the phage is replicating and maintaining itself in a manner similar to the N15 phage, which is renowned for maintaining a linear plasmid prophage throughout lysogeny. Understanding the dynamics of antibiotic resistance and pathogen development requires knowledge of phages like this one, which are known for their temperate nature and their function in altering bacterial virulence and resistance profiles. The regulatory and structural proteins of the phage also provide a model for research into the biology of temperate phages and their effects on microbial communities. The importance of temperate phages in bacterial genomes and their function in the larger framework of microbial ecology and evolution is emphasized in this research.

"Cofactors" for Natural Products

Cofactors are non-protein entities necessary for proteins to operate. They provide "functional groups" beyond those of the 20 canonical amino acids and enable proteins to carry out more diverse functions. Such a viewpoint is rarely mentioned, if at all, when it comes to natural products and is the theme of this Concept. Even though the mechanisms of action (MOA) of only a few natural products are known to require cofactors, we believe that cofactor mediated MOA in natural products are far more prevalent than what we currently know. Bleomycin is a case in point. It binds iron cation to form a pseudoenzyme that generates reactive oxygen species. As another example, calcium cations induce laspartomycin to "fold" into the active conformation. Iron and calcium are bona fide cofactors for bleomycin and laspartomycin, respectively, as these natural products do not display their characteristic anticancer and antibacterial activities without Fe(II) and Ca(II). These types of cofactor mediated MOA in natural products were discovered mostly serendipitously, and being conscious of such a possibility is the first step toward identifying more novel chemistry that nature performs.

Impact of Tetracycline Stress on Water Quality and Rhizosphere Microbial Communities of Eichhornia crassipes: Implications for Bioremediation

To examine the impact of antibiotic contamination on water quality and rhizospheric microbial communities, a simulated cultivation experiment was employed to investigate the potential impacts of tetracycline (Tet) stress on water quality and microbial community composition in the rhizosphere of Eichhornia crassipes (E. crassipes), with a focus on its implications for bioremediation strategies. The results showed a significant disruption in microbial diversity and community structure in the rhizosphere at varying accumulated Tet concentrations (0, 2, 5, and 10 mg·L-1). The microbial communities displayed resilience and functional stability from the low (2 mg·L-1) to moderate (5 mg·L-1) accumulated Tet concentrations; while significant root decay and a marked decline in microbial diversity were observed at the high (10 mg·L-1) accumulated Tet concentration. Some bacterial taxa, including Rhizobiaceae (0.34%), Comamonadaceae (0.37%), and Chitinophagaceae (0.38%), exhibited notable enrichment under Tet stress, underscoring their functional roles in nitrogen cycling, organic matter decomposition, and antibiotic degradation. Physicochemical changes in the rhizosphere, such as shifts in low-molecular-weight organic acids (LMWOAs), nutrient cycling, and total organic carbon (TOC), revealed Tet-induced metabolic adaptations and environmental alterations. Correlation analysis between environmental factors and dominant operational taxonomic units (OTUs) highlighted the putative intricate interplay between microbial activity and Tet stress. These findings underscore the dual impact of Tet as both a stressor and a selective agent, favoring antibiotic-resistant taxa while suppressing sensitive groups. This study provides foundational insights into the ecological and functional dynamics of microbial communities under antibiotic contamination conditions and highlights the potential of rhizospheric microbial communities in the rhizosphere for bioremediation in Tet-polluted ecosystems.

Global trends in antimicrobial resistance of Enterococcus faecium: a systematic review and meta-analysis of clinical isolates

Background

Multidrug-resistant bacteria are associated with a high number of deaths and pose a significant global concern. In recent decades, among these resistant bacteria, Enterococcus faecium, a hospital-acquired pathogen, has attracted more attention.

Objective

The present study aims to document the current state of resistance in E. faecium globally by considering several variables, including geographical locations, temporal trends, and sources of infection.

Methods

We searched studies in PubMed, Scopus, and Web of Science (30 November 2022). All statistical analyses were carried out using the statistical package R.

Results

Our meta-analysis of antibiotic resistance across various clinical isolates revealed substantial heterogeneity and variability. The average resistance proportions ranged from 2% for linezolid to 62.8% for erythromycin, with significant differences observed across different time periods, countries, and World Health Organization regional offices.

Conclusion

Our findings confirm the high antibacterial activity of linezolid against E. faecium isolates. Additionally, our investigation reveals a gradual increase and a concerning upward trend in resistance rates for nearly all agents in recent years. However, the significant reduction in resistance rates for certain antibiotics suggests that these drugs could potentially regain their effectiveness in the future.

Recent in vitro advances in the ocular antimicrobial agents against Acanthamoeba

This review examines the advancements in antimicrobial drug discovery with in vitro assays for Acanthamoeba, highlighting the efficacy of current topical antimicrobial agents. In recent decades, the treatment and diagnosis of Acanthamoeba keratitis (AK) have presented clinical challenges. Clinicians often rely on clinical judgment, risk factors, and patient travel history to guide initial treatment decisions. The clinical presentation of AK frequently coincides with bacterial and fungal keratitis, leading to delays in diagnostic confirmation. This review compiles a list of commonly used antimicrobial agents that may be useful in controlling and preventing Acanthamoeba and other microbial infections during the diagnostic waiting period. Due to their unique life cycle, consisting of both trophozoite and cyst stages, amoebae exhibit resistance to various clinical drugs. Current research efforts are focused on identifying alternative and effective treatment options. Despite the ongoing characterization of various cytocidal agents from natural and synthetic sources, chlorhexidine gluconate (CHG) and polyhexamethylene biguanide (PHMB) have emerged as the most effective therapies for AK. Drawing from previous studies, we catalog several commonly used antimicrobial agents that may enhance the efficacy of PHMB and CHG while also preventing other microbial infections. These alternative agents present promising options for treating AK cases. This review evaluates progress in anti-amoebic drug discovery, focusing on antibiotics and cataloging their activity at different stages of Acanthamoeba.

Minocycline and Omadacycline Resistance Among Carbapenem-Resistant Gram-Negative Bacteria: Antimicrobial Susceptibility Testing and Molecular Characterization

Increasing prevalence of multidrug-resistant infections has rendered the healthcare systems ineffective in managing infectious diseases. Drugs of "last resort" like carbapenems and polymyxins are becoming less effective in the management of antibiotic-resistant Gram-negative bacterial infections, leaving the clinicians with limited choices. Evaluation of the efficacy of other available broad-spectrum antibiotics (belonging to a different class) is warranted as a treatment alternative. The current study was undertaken to evaluate the in vitro antibacterial activity of minocycline and a new drug, omadacycline among carbapenem-resistant Gram-negative bacteria (GNB), isolated from clinical samples (pus and sputum) and to genotypically analyze them. A prospective cross-sectional study was conducted in a 3,200-bedded tertiary care medical center, located in Lucknow in the northern part of India. All the clinical isolates recovered from pus and sputum samples of patients admitted in intensive care units were processed according to the standard protocols. Identification and antibiotic susceptibility testing were performed, and carbapenem-resistant Gram-negative bacteria (CRGNB) showing resistance to minocycline were included in the study. Molecular screening of β-lactamase and tetracycline resistance genes was done by the conventional polymerase chain reaction method. Minimum inhibitory concentration analysis was performed using the broth microdilution technique. Among 700 CRGNB, 15.29% (n = 107/700) were minocycline resistant by disk diffusion method. Genetic analysis demonstrated the presence of tetracycline-resistant genes in about one-third isolates, among which the tet(B) gene was present in 41.12% (n = 44/107). Upon broth microdilution analysis, the overall minimum inhibitory concentration for minocycline was raised, wherein 4.76% (n = 5/107) of our clinical Gram-negative isolates were inhibited at ≤8 mg/L and 15.23% (n = 28/107) were inhibited at ≤16 mg/L. Omadacycline was able to inhibit 13.08% (n = 14/107) of the minocycline-resistant isolates at ≤4 mg/L (susceptible breakpoint for Enterobacterales). Based on the cut-off value proposed, 15.09% (n = 16/107) isolates resistant to minocycline were inhibited by omadacycline. High prevalence of multidrug-resistant bugs entails judicious use of minocycline and omadacycline. The presence of tet genes coexisting with blaNDM and blaOXA in our bacterial isolates shows that the resistance pattern in Gram-negative bacilli is regularly evolving, and a fully functional surveillance program across the health care system is needed to prevent the emergence and spread of antimicrobial resistance.

Stability of Oxytetracycline in Different Types of Solutions and Stored at Different Temperatures

Administration of drugs, especially antibiotics, via intravenous injections with different types of solutions is a common and widely applied treatment method in human and veterinary medicine. One of these antibiotics is oxytetracycline, which is a tetracycline. The aim of this article is to study the effect of temperature (5 °C, 40 °C) and light on the stability of oxytetracycline injections after dissolving different types of reconstitution solutions (sodium chloride 0.9%, dextrose 5%, sodium chloride 0.9% with dextrose 5%, Ringer). After 24 h, the concentration of the oxytetracycline was determined by the HPLC method. The results showed a decrease in the concentration of oxytetracycline due to the effect of high temperature (40 °C) and light in all solutions. On the other hand, the decrease in the concentration of oxytetracycline was less than on low temperature (5 °C) and light protection. The effect of the solution reconstitution solution was also evaluated where the stability of oxytetracycline was best in dextrose 5% solution, followed by sodium chloride 0.9%, Ringer's solution, and mixed (dextrose with sodium chloride 0.9%). This paper recommends reconstituting oxytetracycline with 5% dextrose and storage under refrigeration away from light to maintain a better stability of oxytetracycline.

Does the land-use impact the risk of inducing antibiotic tolerance by heavy metal pollution?

The rise of antibiotic-resistant soil microbial communities is a critical global issue. Evidence suggests that heavy metals can select or co-select for tolerance to metals and antibiotics in soil bacteria, but it is unclear if this tolerance varies with land use. We tested the potential of bacterial communities to develop resistance to copper (Cu) or tetracycline (Tet) after amending soils from pristine forests, contaminated forests, and agricultural lands with 3000 mg kg-1 Cu and 6000 mg kg-1 tetracycline, separately. Results showed that bacterial communities of unamended contaminated forest soils had the highest initial tolerance to Cu, while unamended agricultural soils exhibited the highest initial tolerance to tetracycline. The inducibility of bacterial resistance to antibiotics after Cu amendment varied by land use. In pristine forests, Cu amendment significantly increased microbial tetracycline resistance, as indicated by bacterial community tolerance, likely due to higher biodiversity. In contaminated forests, Cu amendment did not induce tetracycline-resistance, as indicated by unchanged bacterial community tolerance, possibly because of existing metal pollution and compromised bacterial communities by metal pollution. In agricultural soils, microbial tetracycline resistance as indicated by bacterial community tolerance developed slowly, becoming evident only after 42 days. These findings reveal significant differences in environmental risks related to soil metal pollution across different land uses, highlighting the need for systematic studies on the mechanisms of bacterial resistance to antibiotics in metal-contaminated soils due to their human health implications.

Synthesis and antibacterial study of anhydrotetracycline derivatives

A novel and new type of tetracycline with a different mechanism of action was necessary, due to the drug resistance of existing tetracyclines. This study outlines the synthesis and antibacterial evaluation of anhydro-tetracycline derivatives, which are unconventional tetracyclines with unique mechanisms of action. These derivatives include C4-NH2, C4-OH, and C9-substituted variations, and our synthetic approach focuses on semi-synthesis using natural tetracyclines as the starting precursors. Several derivatives of C4-NH2, C4-OH, and C9-substituted compounds have demonstrated effective antibiotic activity against both Gram-positive and Gram-negative bacteria.

Unraveling tetracycline and its degradation product: Induction mechanisms of antibiotic resistance in Escherichia coli

In aquatic environments, antibiotics degrade into byproducts, potentially enhancing bacterial resistance. However, the specific mechanisms by which these byproducts induce bacterial resistance remain elusive. This study conducted experimental evolution experiments to explore how E. coli adapts to tetracycline (TC) and its primary degradation products-anhydrotetracycline (ATC), epitetracycline (ETC), and 4-epianhydrotetracycline (EATC)-through evolution experiments. Prolonged exposure to TC and its byproducts significantly increased frequency of resistant mutants in E. coli ATCC25922, with a maximum 106-fold increase. Resistant mutants exhibited markedly elevated minimum inhibitory concentrations (MICs) for TC, ampicillin (AMP), and ciprofloxacin (CIP), indicating multidrug resistance. Transcriptomic analysis showed that the antibiotic resistance phenotype could be related to enhanced target protection, metabolic adaptations, and reduced membrane permeability. The induction pathways between TC and its byproducts were distinct. Specifically, TC20d (where TC20d represents the mutants collected after 20 days of continuous exposure to TC) was associated with more alterations in ribosome-associated genes, which was correlated with an enhanced defensive response as shown by the data. Moreover, variations in energy metabolism gene expression suggest a robust metabolic defense in ATC20d and ETC20d. When TC and its byproducts-ATC, ETC, and EATC-act together, they induce antibiotic resistant mutants at rates of 29.8 %, 18.9 %, 18.3 %, and 31.9 %, respectively. This study provides a descriptive overview of the possible adaptive mechanisms and pathways that may be involved in antibiotic resistance due to environmental exposure.

Sub-inhibitory concentrations of tigecycline could attenuate the virulence of Staphylococcus aureus by inhibiting the product of α-toxin

Staphylococcus aureus (S. aureus) infection is a serious threat to global health. This study aimed to investigate the anti-virulence efficacy of tigecycline against S. aureus. We used highly virulent S. aureus strains SA75 and JP30 to evaluate the effect of tigecycline on virulence, both of them isolated from the clinic. The MIC value of tigecycline against SA75 was 0.125 µg/mL, and that against JP30 was 0.25 µg/mL. Tigecycline did not affect the growth ability of bacteria at 0.015 µg/mL. Thus, subsequent discussions will focus on the effect of antibiotics at the latter subinhibitory concentrations that did not affect growth. First, the sub-MICs of tigecycline not only enhanced the sensitivity of S. aureus to oxidants and human whole blood but also weakened the hemolytic activity and cell adhesion level of S. aureus. Second, it undermined the survival of S. aureus in RAW264.7 and attenuated the macrophage inflammatory response induced by S. aureus. On the contrary, tigecycline decreased the hemolytic activity, as well as the skin abscess formation and bacterial burden in mice. Most importantly, it significantly decreased the expression of hla, hlgB, hlgC, spa, sbi, saeR, sak, tst, and coa genes by RT-qPCR and the protein expression of α-toxin. Altogether, the sub-MICs of tigecycline might be a promising agent to attenuate the virulence of S. aureus and its host immune response by inhibiting the SaeRS two-component system and the product of α-toxin.IMPORTANCEIn this study, the sub-MICs of tigecycline decreased the resistance of S. aureus to oxidants and human whole blood. Moreover, tigecycline weakened the cell adhesion level of S. aureus and skin abscess formation in mice by reducing bacterial burden. Remarkably, tigecycline decreased the hemolytic activity and significantly downregulated the expression of various virulence genes and α-toxin. This research highlighted that the sub-MICs of tigecycline might be a promising agent to attenuate the virulence of S. aureus by inhibiting the product of α-toxin.

C10-Benzoate Esters of Anhydrotetracycline Inhibit Tetracycline Destructases and Recover Tetracycline Antibacterial Activity

Tetracyclines (TCs) are an important class of antibiotics threatened by enzymatic inactivation. These tetracycline-inactivating enzymes, also known as tetracycline destructases (TDases), are a subfamily of class A flavin monooxygenases (FMOs) that catalyze hydroxyl group transfer and oxygen insertion (Baeyer-Villiger type) reactions on TC substrate scaffolds. Semisynthetic modification of TCs (e.g., tigecycline, omadacycline, eravacycline, and sarecycline) has proven effective in evading certain resistance mechanisms, such as ribosomal protection and efflux, but does not protect against TDase-mediated resistance. Here, we report the design, synthesis, and evaluation of a new series of 22 semisynthetic TDase inhibitors that explore D-ring substitution of anhydrotetracycline (aTC) including 14 C10-benzoate ester and eight C9-benzamides. Overall, the C10-benzoate esters displayed enhanced bioactivity and water solubility compared to the corresponding C9-benzamides featuring the same heterocyclic aryl side chains. The C10-benzoate ester derivatives of aTC were prepared in a high-yield one-step synthesis without the need for protecting groups. The C10-esters are water-soluble, stable toward hydrolysis, and display dose-dependent rescue of tetracycline antibiotic activity in E. coli expressing two types of tetracycline destructases, represented by TetX7 (Type 1) and Tet50 (Type 2). The best inhibitors recovered tetracycline antibiotic activity at concentrations as low as 2 μM, producing synergistic scores <0.5 in the fractional inhibitory concentration index (FICI) against TDase-expressing strains of E. coli and clinical P. aeruginosa. The C10-benzoate ester derivatives of aTC reported here are promising new leads for the development of tetracycline drug combination therapies to overcome TDase-mediated antibiotic resistance.

Recent advances in the synthesis and application of graphene aerogel and silica aerogel for environment and energy storage: A review

Aerogel materials have gained considerable attention in recent years due to their promising applications in environmental and energy storage fields, owing to their exceptional properties, including high porosity, ultra-low thermal conductivity, low density, and high specific surface area. This review begins by examining novel synthesis techniques, including sol-gel processing, chemical crosslinking, and templating, that enhance both the microstructural and functional properties of aerogels. Next, we explore the applications of graphene and silica aerogels in environmental and energy conservation technologies. Graphene aerogels, in particular, demonstrate significant potential in water purification by effectively removing antibiotics, offering a new approach to water treatment. The combination of silica aerogels with phase change materials, along with their use in supercapacitors, demonstrates their potential for energy conservation. Additionally, we discuss the synergistic effects of silica and graphene aerogels, which further broaden their applications. Finally, the paper concludes by summarizing the potential of graphene and silica aerogels as functional materials for environmental applications and outlining the challenges and future directions for their development and industrial use.

Rapid diagnosis and precision treatment of Helicobacter pylori infection in clinical settings

Helicobacter pylori is a gram-negative bacterium that colonizes the stomach of approximately half of the worldwide population, with higher prevalence in densely populated areas like Asia, the Caribbean, Latin America, and Africa. H. pylori infections range from asymptomatic cases to potentially fatal diseases, including peptic ulcers, chronic gastritis, and stomach adenocarcinoma. The management of these conditions has become more difficult due to the rising prevalence of drug-resistant H. pylori infections, which ultimately lead to gastric cancer and mucosa-associated lymphoid tissue (MALT) lymphoma. In 1994, the International Agency for Research on Cancer (IARC) categorized H. pylori as a Group I carcinogen, contributing to approximately 780,000 cancer cases annually. Antibiotic resistance against drugs used to treat H. pylori infections ranges between 15% and 50% worldwide, with Asian countries having exceptionally high rates. This review systematically examines the impacts of H. pylori infection, the increasing prevalence of antibiotic resistance, and the urgent need for accurate diagnosis and precision treatment. The present status of precision treatment strategies and prospective approaches for eradicating infections caused by antibiotic-resistant H. pylori will also be evaluated.

The Efficacy of Orange Terpene and Bacillus mycoides Strain BM103 on the Control of Periwinkle Leaf Yellowing Phytoplasma

Phytoplasmas are obligate phytopathogenic bacteria belonging to the class Mollicutes. The pathogens, transmitted by insect vectors, are associated with hundreds of plant diseases worldwide. Because of the regulations banning the use of antibiotics and the limited efficacy of traditional disease management manners, an eco-friendly alternative is needed. Given that terpene and probiotics have antibiotic activity and the ability to induce systemic resistance, in this study, the effectiveness of orange terpene and a Bacillus mycoides strain, BM103, was evaluated in periwinkle plants infected with periwinkle leaf yellowing (PLY) phytoplasma derived from a shoot-tip tissue culture system. Weekly drenching of 1,000 ppm diluted orange terpene emulsion or preactivated strain BM103 liquid culture dilution exhibited the ability to inhibit PLY phytoplasma accumulation. The expression of the genes associated with plant defense response and flower development was upregulated after treatment. Moreover, pretreatment of orange terpene or strain BM103 delayed PLY infection via cleft-grafting inoculation. Although orange terpene did not suppress the symptoms, strain BM103 did result in a milder symptom expression that might partially attribute to its plant growth-promoting characteristics. Additionally, the preactivation of strain BM103 may contribute to its efficacy. Taken together, this research indicates that orange terpene and B. mycoides BM103, with the ability to rapidly induce plant defense responses, could potentially be developed into biologic control materials as preventive agents or biofertilizers.

Navigating through chemometrics: Unveiling antibiotic-food interactions for improved pediatric formulations ahead

BACKGROUND

Given the challenges of pediatric antibacterial therapy, it is crucial to formulate antibiotics with a lower potential for interaction with dietary interventions and tailor them for optimal administration in children. Chemometric methods allow us to analyze multiple interrelated variables simultaneously and uncover correlations.

AIM

We applied a chemometric approach to examine how food, beverages, antacids, and mineral supplements affect antibiotic bioavailability in adults and children, aiming to explore relationships between antibiotic structure, physicochemical properties, and post-meal changes in pharmacokinetic (PK) parameters.

METHODS

We selected 95 antibacterial drugs for analysis, including beta-lactams (32), quinolones (25), macrolides (13), tetracyclines (16), and others (9). The input dataset comprised information from published clinical trials, chemical records, and calculations. We constructed hierarchical partial least squares (PLS) models with changes in PK parameters (ΔAUC, ΔCmax, ΔTmax, and Δ t ½) as response parameters and nine groups of molecular descriptors (M1-M9) as predictor parameters. We performed analyses separately in children and adults for different dietary interventions.

RESULTS

In the final 10 PLS models, significant components explained 61-90% and 10.3-54.4% of the variance in the predictor and response parameter sets, respectively. We obtained 59 significant positive and negative correlations between antibiotic structure or physicochemical properties (molecular descriptors) and action in the human body in the presence of food, antacids, or mineral supplements (changes in PK parameters), of which 41 concern pediatric patients.

CONCLUSIONS

Chemometric methods can be helpful and valuable in investigating the interactions between antibiotics and dietary interventions. Using chemometrics may pave the way for formulating antibiotics for children with a lower potential to interact with food.

Chitosan-based dental barrier membrane for periodontal guided tissue regeneration and guided bone regeneration: A review

Guided tissue regeneration (GTR) and guided bone regeneration (GBR) are two common dental regenerative procedures used to repair periodontal defects caused by periodontitis. In both procedures, a barrier membrane is placed at the interface between the soft tissue and the periodontal defect, serving to impede the infiltration of soft tissue while creating a secluded space for periodontal regeneration. Recently, barrier membranes based on chitosan (CS) have emerged as a promising avenue for these applications. However, despite numerous studies on the development of CS-based membranes, comprehensive review articles specifically addressing their progress in GTR/GBR applications remain scarce. Herein, we review recent research and advancements in the use of CS-based membranes for periodontal GTR and GBR. The review begins by highlighting the advantageous properties of CS that make it a suitable biomaterial for GTR/GBR applications. Next, the development of composite CS-based membranes, reinforced with various compositions like bioactive fillers and therapeutic agents, is discussed in detail based on recent literature, with a focus on their enhanced efficacy in promoting periodontal regeneration. Finally, the review explores the emergence of functionally graded CS-based membranes, emphasizing their potential to address specific challenges encountered in GTR/GBR procedures.

Polypharmacological strategies for infectious bacteria

Polypharmacological approaches have significant potential for the treatment of various complex diseases, including infectious bacteria-related diseases. Actually, multitargeting agents can achieve better therapeutic effects and overcome the drawbacks of monotherapy. Although multidrug multitarget strategies have demonstrated the ability to inactivate infectious bacteria, several challenges have been pointed out. In this way, multitarget direct ligands approaches appear to be a rational and sustainable strategy to combat antibiotic resistance. By combining different pharmacophores, antibiotic hybrids stand out as a promising application in the field of bacterial infections. These new chemical entities can achieve synergistic interactions that allow to extend the spectrum of action and target multiple pathways. In addition, antibiotic hybrids can reduce the likelihood of resistance development and provide improved chemical stability. It is worth highlighting that despite the efforts of the scientific community to discover new solutions for the most complex diseases, there is a significant lack of studies on biofilm-associated infections. This review describes the different polypharmacological approaches that can be used to treat bacterial infections with a particular focus, whenever possible, on those promoted by biofilms. By exploring these innovative approaches, we aim to inspire further research and progress in the search for effective treatments for infectious bacteria-related diseases, including biofilm-related ones. SIGNIFICANCE STATEMENT: The importance of the proposed topic lies in the escalating challenge of antibiotic resistance, particularly in the context of infectious bacteria-related infections. Polypharmacological approaches, such as antibiotic hybrids, represent innovative strategies to combat bacterial infections. By targeting multiple signaling pathways, these approaches not only enhance therapeutic effect but also reduce the development of resistance while improving the drug's chemical stability. Despite the urgent need to combat bacterial infectious diseases, there is a notable research gap, in particular in biofilm-related ones. This review highlights the critical importance of exploring polypharmacological approaches with the aim of motivating further research and advances in effective treatments for infectious bacteria, including biofilm related infections.

Acquired Bacterial Resistance to Antibiotics and Resistance Genes: From Past to Future

The discovery, commercialization, and regular administration of antimicrobial agents have revolutionized the therapeutic paradigm, making it possible to treat previously untreatable and fatal infections. However, the excessive use of antibiotics has led to develop resistance soon after their use in clinical practice, to the point of becoming a global emergency. The mechanisms of bacterial resistance to antibiotics are manifold, including mechanisms of destruction or inactivation, target site modification, or active efflux, and represent the main examples of evolutionary adaptation for the survival of bacterial species. The acquirement of new resistance mechanisms is a consequence of the great genetic plasticity of bacteria, which triggers specific responses that result in mutational adaptation, acquisition of genetic material, or alteration of gene expression, virtually producing resistance to all currently available antibiotics. Understanding resistance processes is critical to the development of new antimicrobial agents to counteract drug-resistant microorganisms. In this review, both the mechanisms of action of antibiotic resistance (AMR) and the antibiotic resistance genes (ARGs) mainly found in clinical and environmental bacteria will be reviewed. Furthermore, the evolutionary background of multidrug-resistant bacteria will be examined, and some promising elements to control or reduce the emergence and spread of AMR will be proposed.