Search Results (338)

Objective: The emergence and spread of multi-drug-resistant (MDR) bacteria pose a growing threat in veterinary medicine, particularly in equine hospitals. This study investigated the colonization and infection dynamics of horses undergoing emergency laparotomy with two distinct antibiotic protocols (single-shot versus 5-day protocol) during hospitalization. Methods: Nasal swabs and fecal samples were collected from 67 horses undergoing emergency laparotomy at clinic admission as well as on postoperative days 3 and 10. These were screened for multi-drug-resistant indicator pathogens. As multi-drug-resistant indicator pathogens, methicillin-resistant Staphylococcus aureus (MRSA), extended-spectrum β-lactamase (ESBL)-producing Enterobacterales (ESBL-E), and bacteria belonging to the Acinetobacter baumannii complex were defined. Results: Preoperatively, 6.2% of horses tested positive for MRSA and 13% for ESBL-E. An increase in colonization was observed on day 3 postoperatively, with 62.1% of nasal swabs and 86.4% of fecal samples testing positive for MDR organisms. On day 10, 53.4% of nasal swabs and 62.5% of fecal samples tested positive for indicator pathogens. Surgical site infection developed in five horses, two of which tested positive for MRSA in both nasal and wound samples during hospitalization, supporting the potential role of nasal carriage as a source of infection. Furthermore, all horses tested positive for ESBL-E during at least one time-point during hospitalization, and Enterobacterales (MDR in two surgical site infections (SSI)) were involved in all surgical site infections. No significant differences were observed between the two antibiotic treatment groups regarding colonization rates with indicator pathogens during hospitalization. However, the results indicate that hospitalization itself contributes to increased colonization with resistant bacteria. A clear limitation of the study is the restricted number of sampled horses and the lack of environmental contamination data. Non-sampled hospitalized horses with and without antibiotic treatment may have acted as reservoirs for MDR bacteria. Conclusion: The findings emphasize the need for routine environmental monitoring and strict adherence to hygiene protocols in equine clinics to reduce the risk of nosocomial transmission. Ongoing surveillance and infection control strategies are essential to mitigate the spread of MDR pathogens in veterinary settings. Full article

Pseudomonas aeruginosa is an opportunistic pathogen commonly associated with nosocomial infections and environmental dissemination. Among its high-risk clones, ST244 is notable for its global distribution and distinctive genomic traits. This study reports whole-genome sequencing of ten ST244 isolates from hospitalized patients and wastewater in a healthcare complex in Southeastern Brazil. Genomic comparisons revealed a highly conserved clonal group, with nine isolates forming a tight monophyletic cluster based on rMLST, SNP phylogeny, and average nucleotide identity (>99.5%). One isolate showed close phylogenetic proximity to strains from Asia and North America, suggesting international dissemination. Serotype analysis revealed both O5 and O12 variants, indicating intra-lineage antigenic diversity. Resistance profiling identified multidrug-resistant phenotypes carrying carbapenemase genes (bla_OXA-494, bla_OXA-396) and diverse insertion sequences (ISPa1, ISPa6, ISPa22, ISPa32, and ISPa37), facilitating horizontal gene transfer. Virulence gene analysis showed conserved elements related to adhesion, iron uptake, secretion systems, and quorum sensing, while the cytotoxin gene exoU was absent. These results highlight clonal persistence, possible intra-hospital transmission, and links to globally circulating ST244 sublineages. Our findings underscore the importance of genomic surveillance to track high-risk P. aeruginosa clones at the clinical–environmental interface. Full article

Salmonella is a major foodborne pathogen, and its increasing antimicrobial resistance poses a significant public health challenge. In this study, we conducted a comprehensive genomic epidemiological investigation of Salmonella isolates recovered from meat products across multiple provinces in China. A total of 141 isolates were collected and subjected to antimicrobial susceptibility testing and whole-genome sequencing. Core genome MLST and hierarchical clustering (HierCC) were performed using EnteroBase, while SNP phylogeny and phylodynamic analyses were conducted to characterize the evolutionary dynamics of Salmonella populations. The predominant serovars were Enteritidis and Infantis, with a high proportion of multidrug-resistant isolates. Potentially transferable plasmids carrying ARGs, such as bla_CTX-M, qnrS1, sul2, and mcr-1.1, were frequently detected, indicating a risk of horizontal transfer during transmission. Genomic epidemiological investigation of our sequenced strains and their associated cgMLST HierCC clusters revealed both persistent Salmonella lineages, such as Enteritidis HC50-87 and Agona HC20-419, and emerging China-specific lineages, including Enteritidis HC20-10145 and Typhimurium HC50-2304. The estimated divergence times of these lineages mostly dated to the late mid-20th century, coinciding with the intensification of poultry farming in China. These findings highlight the power of genomic epidemiology in uncovering antimicrobial resistance patterns and transmission dynamics, underscoring the need for strengthened Salmonella surveillance. Full article

Background and Objectives: Healthcare-associated infections (HAIs) significantly increase morbidity and mortality in critically ill patients, and their burden became more pronounced during the COVID-19 pandemic. However, data describing the temporal evolution of HAIs, pathogen distribution, and associated risk factors across consecutive pandemic waves remain limited. This study aimed to characterize the epidemiology, microbiology, and outcomes of HAIs in COVID-19 intensive care units (ICU) patients and to identify clinical and laboratory predictors of mortality. Materials and Methods: This retrospective observational study included adult patients with RT-PCR–confirmed COVID-19 who developed at least one HAI ≥ 48 h after ICU admission between March 2020 and December 2020, encompassing the first three pandemic waves in Türkiye, in a tertiary-care ICU. Demographic, clinical, laboratory, and microbiological data were collected. Inflammatory markers and severity scores (SAPS-II, MCCI, and NLR) were analyzed. Receiver operating characteristic (ROC) curve analysis was used to determine optimal cut-off values for mortality prediction. Results: Among the 1656 ICU admissions, 145 patients (8.7%) developed HAIs; after exclusions, 136 patients were included in the final analysis. Bloodstream infections were the most frequent HAI (57%), followed by urinary tract infections (31%), ventilator-associated pneumonia (9%), and surgical site infections (1%). Klebsiella pneumoniae was the predominant pathogen, followed by Candida albicans and Acinetobacter baumannii. Multidrug-resistant organisms, including MRSA and VRE, showed variable distribution across pandemic periods. Overall in-hospital mortality was 74.3%. Non-survivors had significantly higher SAPS-II, MCCI, and NLR values. ROC analysis identified NLR > 38.8 and SAPS-II > 35.5 as mortality-predictive thresholds. Dynamic inflammatory marker patterns correlated with infection timing, and early peaks of CRP, WBC, and IL-6 were associated with worse outcomes. Conclusions: HAIs imposed a substantial clinical burden on critically ill COVID-19 patients, with high mortality driven predominantly by multidrug-resistant bloodstream infections. Severity indices and inflammation-based biomarkers demonstrated strong prognostic value. Temporal shifts in pathogen ecology across pandemic waves underscore the need for adaptive infection-prevention strategies, continuous microbiological surveillance, and strengthened antimicrobial stewardship in critical care settings. Full article

The antimicrobial resistance crisis necessitates novel therapeutics. Selenium nanoparticles (SeNPs) offer promise, but their precise bactericidal mechanism remains poorly defined. This study aimed to define the antibacterial action of SeNPs synthesized via a green method with ascorbic acid and sodium citrate. The resulting SeNPs were monodisperse (17.8 ± 0.66 nm), crystalline, and highly stable (zeta potential: −69.9 ± 4.3 mV), exhibiting potent bactericidal activity against multidrug-resistant E. coli. To generate a mechanistic hypothesis, we integrated phenotypic analyses with a preliminary, single-replicate proteomic profiling. Recognizing this as an exploratory step, we focused our analysis on proteins with the most substantial changes. This revealed a coherent pattern of a targeted dual assault on core cellular processes. The data indicate that SeNPs simultaneously induce oxidative stress while severely depleting key components of the primary antioxidant glutathione system; key detoxification enzymes—glutathione S-transferase and glutaredoxin 2—were depleted 18- to 19-fold, while the stress protein HchA was reduced by over 63-fold. Concurrently, the patterns point toward a crippling of central energy metabolism; iron–sulfur enzymes in the TCA cycle, including aconitate hydratase (8.1-fold decrease) and succinate dehydrogenase (13.9-fold decrease), were severely suppressed, and oxidative phosphorylation was impaired (e.g., 4.7-fold decrease in NADH dehydrogenase subunit B). We propose that this coordinated disruption creates a lethal feedback loop leading to metabolic paralysis. Consequently, this work provides a detailed and testable mechanistic hypothesis for SeNPs action, positioning them as a candidate for a potent, multi-targeted antimicrobial strategy against drug-resistant pathogens. Full article

The emergence and spread of mobile colistin resistance (mcr) genes pose a significant challenge in controlling multidrug-resistant Gram-negative pathogens. Understanding the epidemiology of mcr-carrying plasmids is essential for mitigating their dissemination across humans, animals, and the environment. To characterize their spatiotemporal dynamics on a global scale, we analyzed an extensive collection of 5,549 mcr-carrying plasmids spanning 1995 to the present. We found that cross-genera transmission patterns of mcr-carrying plasmids varied across four distinct periods. Initially, IncHI2/HI2A plasmids provided a survival advantage across genera and regions, followed by IncI2, and ultimately by IncX4. Moreover, the three plasmid lineages (i.e., IncX4, IncI2, and IncHI2/HI2A) have reached a stable distribution across diverse bacterial hosts and geographic regions through horizontal gene transfer and clonal expansion. By integrating sequence similarity clustering of plasmids and mcr-related genetic environments, we identified 79 cross-genus, 43 intra-E. coli, and 10 intra-S. enterica transmission units. Molecular dating analysis traced the origin of IncX4 plasmids to 1990 in animal hosts, with phylogenetic evidence indicating potential cross-host, -genus, and -region exchange. Notably, IncP1 plasmids emerged as important vectors of mcr-1 and mcr-3 spread, particularly in Southeast Asia, warranting enhanced surveillance. These findings provide critical insights into the global transmission networks of plasmid-mediated mcr genes and underscore the urgent need for coordinated interventions. Full article

A new iodine–dextrin–lithium complex (IDLC) was synthesized and structurally characterized as a hybrid supramolecular system combining antiseptic, stabilizing, and biocompatible components. The compound integrates iodine as the primary antimicrobial agent, lithium as a coordination and stabilization element, and dextrin as a biodegradable polysaccharide matrix enabling sustained release. Physicochemical analyses confirmed the formation of a uniform, thermally stable complex. Biological evaluation revealed strong bactericidal activity, with minimum bactericidal concentrations (MBCs) ranging from 1.95 to 15.63 µg mL⁻¹ against both Gram-positive and Gram-negative pathogens, including multidrug-resistant Staphylococcus aureus and Acinetobacter baumannii. Cytotoxicity studies revealed moderate, concentration-dependent effects on human peripheral blood mononuclear cells (CC₅₀ = 0.23–0.48 mg/mL; 11.7–24.4 μg I/mL) and low toxicity toward MDCK cells (CC₅₀ = 10–20 mg/mL; 507–1014 μg I/mL), confirming a favorable safety profile. IDLC exhibited cytotoxic effects on tumor cell lines (HepG2, HeLa, AGS, K562, and H9) as well as on the normal MeT-5A cell line; however, the CC₅₀ values are similar, and selectivity indices are close to 1, indicating no selective cytotoxicity toward tumor cells. Thus, IDLC demonstrates non-specific cytotoxicity at high concentrations, consistent with its iodine content. The research confirms that iodine can be effectively stabilized within a dextrin-lithium framework to yield a biologically active, thermally resistant complex, suitable for pharmaceutical use. Full article

Avian pathogenic Escherichia coli (APEC) infections cause substantial economic losses in the poultry industry, primarily due to high mortality rates, reduced productivity, and increased treatment costs. With the emergence of antibiotic-resistant APEC strains, including multidrug-resistant (MDR) variants, alternative therapeutic strategies have gained increasing attention. This study reports the isolation and characterization of an Escherichia phage, vB_EcoG_APECPW12 (phage vAPECPW12), which specifically targets MDR APEC. Both antibacterial and antibiofilm activities of the phage were evaluated. Phage vAPECPW12 produced small plaques with halos and exhibited strong lytic activity against MDR APEC. Whole-genome sequencing revealed a genome size of 77,812 base pairs with 123 open reading frames. No tRNA, antibiotic-resistant, or lysogenic genes were identified. Phylogenetic analysis and genome comparison suggest that phage vAPECPW12 is a novel member of the genus Kuravirus within the Gordonclarkvirinae family. It also demonstrated good stability across a range of temperatures and pH levels and remained viable after exposure to UV radiation. Phage vAPECPW12 showed a high adsorption rate, a short latent period of 10 min, and a burst size of 258 plaque-forming units per cell. A depolymerase domain was identified in the genome, prompting investigation of its antibiofilm efficacy. Results showed that vAPECPW12 significantly inhibited biofilm formation and removed preformed biofilms, indicating its potential as an alternative antimicrobial agent for controlling MDR APEC and their biofilms in poultry farming. Full article

Glyoxal (GO) and methylglyoxal (MGO) are highly toxic metabolic byproducts that induce carbonyl stress in bacteria and eukaryotes. Their accumulation in cells is linked to non-enzymatic glycosylation (glycation) of proteins, nucleic acids, and lipids, leading to the formation of advanced glycation end products (AGEs). In humans, AGEs are associated with several health problems, such as diabetes, Alzheimer’s disease, cancer, and aging. Recent studies indicate that, despite their short lifespan, bacteria are also affected by AGEs formation. In this review, we summarize the pathways and mechanisms that help bacteria cope with GO, MGO, and AGEs. We also discuss the impact of dietary AGEs on gut microbiota and the antibacterial activity of host-derived GO/MGO. Recent studies highlight three main areas for future research: the role of AGEs in dysbiosis, the regulation of protein activities by MGO/GO-dependent modifications, and the potential use of glyoxalase pathway inhibitors to combat pathogens. This last point is especially important due to the rising prevalence of multidrug-resistant strains and the failure of antibiotic therapies. Full article

Milk is an important agricultural product and is consumed worldwide. However, the dairy sector faces a significant challenge due to bovine mastitis, a common disease that has a substantial impact on the dairy industry. In more severe cases, it leads to the culling of chronically infected cows. Mastitis poses a risk due to the frequent use of antibiotics in treatment, which contributes to the spread of bacteria with antimicrobial resistance. The present study aimed to evaluate the antimicrobial and antibiofilm potential of a pyroligneous extract of Eucalyptus urograndis (clone I144) against multidrug-resistant Staphylococcus aureus, the causative agent of mastitis. Sensitivity profiles to various conventional antibiotics were assessed, including the minimum inhibitory concentration (MIC), the minimum bactericidal concentration (MBC), and biofilm inhibition, in ten Staphylococcus aureus strains using the crystal violet method. The results showed that the multidrug-resistant strains were sensitive to the pyroligneous extract of Eucalyptus urograndis (clone I144) at a concentration of 12.5% and exhibited antibiofilm activity starting at a concentration of 3.13%. In conclusion, our findings show that the pyroligneous extract of Eucalyptus urograndis (clone I144), at 12.5%, inhibited different multidrug-resistant S. aureus and MRSA strains isolated from bovine mastitis. These results indicate that the extract represents an effective preventive strategy against mastitis-causing pathogens that are difficult to treat, making it a promising alternative to reduce the dependence on synthetic antibiotics. In vivo studies are needed to confirm these findings and provide a basis for evidence-based clinical guidelines. Full article

Objectives: Pseudomonas aeruginosa is an opportunistic pathogen of high clinical relevance due to its ability to form biofilms, its inherent virulence regulated by quorum-sensing systems, and its multidrug resistance. In the present study, we evaluated the inhibitory potential of nine extracts from Inula species (chloroform and methanolic fractions, including a sesquiterpene lactone-enriched fraction) against biofilm formation and virulence-associated traits of P. aeruginosa PAO1 and three multidrug-resistant clinical isolates, as well as their cytotoxicity, biocompatibility, and ability to affect cytokine and nitric oxide production in infected skin explants. Methods: The following methods were applied: fractionation and extraction of plant extracts; cytotoxicity assessment on HFF cells; crystal violet assay for determining antibiofilm activity; fluorescence microscopy for evaluating biofilm viability; electron microscopy for assessing the 3D structure of biofilms and morphological alterations; inhibition assays of pyocyanin pigment, protease activity, bacterial motility, interleukin-17, and nitric oxide production; histological analysis of mouse skin explants. Results: Quantitative analyses of antibiofilm activity revealed that five of the tested extracts inhibited biofilm formation by more than 50%. Structural and functional analyses using confocal laser scanning microscopy and scanning electron microscopy demonstrated a substantial reduction in biofilm thickness, exfoliation of biofilm biomass, the presence of isolated bacterial clusters, metabolically inactive cell populations, and morphological abnormalities associated with cell elongation, invaginations, and polar deformations as a consequence of treatment. In addition, the plant extracts strongly affected virulence factors regulated by quorum sensing. The methanolic fractions from I. britannica and I. bifrons significantly suppressed pyocyanin synthesis. In contrast, the chloroform fractions from I. helenium and I. spiraeifolia produced the largest inhibition zones in assays for extracellular protease activity. Furthermore, all chloroform extracts suppressed bacterial motility, with the lowest swarming diameter observed for the chloroform and lactone-enriched fractions from I. britannica. The chloroform extracts of I. helenium and I. bifrons, methanolic extracts of I. britannica, and chloroform and methanolic extracts of I. spiraeifolia showed relatively low toxicity to normal diploid human fibroblasts. Methanolic and chloroform fractions from I. britannica disrupted biofilm integrity and reduced IL-17A and nitric oxide production in infected skin explants. Conclusions: All these findings indicate a possible synergistic action of the chemical constituents within the fractions on quorum-sensing regulation, biofilm formation, cellular viability, and modulation of host inflammatory responses. Full article

The use of clinically important antibiotics in U.S. poultry production has decreased drastically over the past decade. They can only be used to treat diseases under the supervision of a veterinarian. Reducing antibiotic use, even for disease treatment, can improve the long-term sustainability of the industry. In the current study, we examined the effect of supplementation of a low dose of trans-cinnamaldehyde (TC; 0.03%), a GRAS-status plant-derived compound, with or without oxytetracycline (OTC; 16 μg/mL), an anti-30S ribosomal subunit targeting antibiotic, on the multidrug-resistant (MDR) S. Heidelberg (SH) in turkey poults. Two independent experiments were conducted (N = 96). In each experiment, 48, straight-run, day-old, commercial Hybrid Converter turkey poults were randomly assigned to 6 treatments of 8 birds each: Negative Control [NC; −SH, −TC, −OTC, −0.06% Miglyol (MIG, emulsifier for TC in water)], Positive Control (PC; +SH, −TC, −OTC, −MIG), MIG Control (MIG; +SH, −TC, −OTC, +MIG), TC Group (TC; +SH, +TC, −OTC, +MIG), OTC group (OTC; +SH, −TC, +OTC, −MIG), and TC+OTC group (TC+OTC; +SH, +TC, +OTC, +MIG). OTC was supplemented from day 1 through drinking water throughout the experiment. The birds in the TC and TC+OTC groups were supplemented with TC in their drinking water for 7 days post-challenge. All birds were challenged on day 7 with 6 log₁₀ CFU of SH/bird via crop gavage. On day 14, all birds were euthanized to collect the cecum, liver, and spleen for pathogen recovery. TC at 0.03% emulsified in MIG was highly effective in reducing MDR SH colonization in turkey poults (p < 0.05) compared to the SH control (>4.5 log₁₀ CFU/g reduction) on day 14. The OTC group reduced the pathogen load by 2.5 log₁₀ CFU/g by day 14. TC enhanced the effect of OTC, reducing pathogen load by ~3.9 log₁₀ CFU/g compared to the SH control after 7 days. TC significantly reduced SH invasion into the liver and spleen compared with the SH control on day 14. The results of the study indicate that TC at 0.03% can augment OTC at 16 μg/mL for the treatment of MDR SH infection in poults and could be an industry-sustainable strategy. Full article

As viromics advances, the diversity and ecological significance of RNA viruses in global ecosystems are gaining growing recognition. Nevertheless, studies on RNA viruses in wildlife, especially non-model avian species, are still relatively scarce. This study employed viral metagenomics to systematically characterize the gut RNA viromes of three widely distributed corvid species on the Qinghai–Tibet Plateau: the Red-billed chough (Pyrrhocorax pyrrhocorax), Daurian jackdaw (Coloeus dauuricus), and Rook (Corvus frugilegus). These three corvid species are closely associated with human-inhabited areas on the Qinghai–Tibet Plateau and display distinctive scavenging behaviors that may lower their exposure to environmental pathogens while concurrently elevating their risk of viral infection, rendering them key targets for viral surveillance and research into zoonotic disease transmission. The analysis annotated viral communities into 4 phyla and 8 classes, with Pisuviricota and Kitrinoviricota emerging as the predominant phyla in all samples. Alpha diversity analysis indicated no significant differences among groups, while beta diversity showed significant compositional differences. KEGG annotation revealed that enriched functional pathways were mainly concentrated in “Global and overview maps”, “Drug resistance: antimicrobial”, and “Biosynthesis of other secondary metabolites”. Furthermore, 4 antibiotic resistance genes and 13 putative virulence factor genes were identified. Phylogenetic analysis further indicated that several identified viruses have the potential for cross-species transmission, underscoring the pivotal role of wild birds in viral ecosystems and disease spread. This study uncovered multi-faceted features of the gut RNA viromes in the three crow species, spanning structural, functional, and evolutionary dimensions. These results offer novel perspectives on the viromes of wild corvids and their potential contributions to viral emergence and dissemination in the Qinghai–Tibet Plateau ecosystem. Full article

Polymyxin antibiotics are often the last line of defense against multidrug-resistant Gram-negative pathogens. A key resistance mechanism involves the addition of 4-amino-4-deoxy-L-arabinose (L-Ara4N) to lipid A, mediated by the bifunctional enzyme ArnA. However, the evolutionary rationale and structural basis for ArnA’s domain fusion, hexameric assembly, and catalytic coordination remain mechanistically unresolved. Here, we integrate evolutionary genomics, high-resolution cryo-electron microscopy (cryo-EM), and computational protein design to provide a comprehensive mechanistic analysis of ArnA. Our evolutionary analysis reveals that the dehydrogenase (DH) and formyltransferase (TF) domains evolved independently and were selectively fused in Gammaproteobacteria, suggesting an adaptive advantage. A 2.89 Å cryo-EM structure of apo-ArnA resolves the flexible interdomain linker and reveals a DH-driven hexameric architecture essential for enzymatic activity. 3D variability analysis captures intrinsic conformational dynamics, indicating a molecular switch that may coordinate sequential catalysis and substrate channeling. Structure-based peptide inhibitors targeting the hexamerization and predicted ArnA–ArnB interaction interfaces were computationally designed, offering a novel strategy for disrupting L-Ara4N biosynthesis. These findings illuminate a previously uncharacterized structural mechanism of antimicrobial resistance and lay the groundwork for therapeutic intervention. Full article

Enterococcus faecalis (E. faecalis) is a significant zoonotic pathogen, primarily causing opportunistic infections in humans while often existing as a commensal in animal reservoirs, facilitating its dissemination. Current understanding of the resistance profiles, virulence mechanisms, and host–pathogen interactions of E. faecalis from ruminants, particularly unique species such as the plateau yak, remains limited. This knowledge gap hinders the accurate assessment of their transmission risk and the development of effective control strategies. This study presents a comprehensive analysis of a multidrug-resistant E. faecalis isolate from yak feces, integrating whole-genome sequencing (WGS), an animal challenge model, and transcriptomic profiling. Antimicrobial susceptibility testing revealed resistance to β-lactams, aminoglycosides, glycopeptides, tetracyclines, and fluoroquinolones. WGS identified numerous resistance genes (e.g., parC, gyrA, rpoB) and virulence-associated genes (e.g., prgB/asc10, cpsA/uppS). Phylogenetic analysis indicated a close relationship with a human urinary tract isolate (ASM3679337v1). Mouse challenge experiments demonstrated that this strain induced significant intestinal histopathological damage. A subsequent transcriptomic analysis of infected tissues identified the differential activation of key signaling pathways, including NF-κB and MAPK. Our findings provide crucial insights into the resistance and pathogenic mechanisms of ruminant-derived E. faecalis and establish an experimental foundation for optimizing clinical antimicrobial therapy against such strains. Full article