Search Results (3,372)

Background/Objectives: Recent investigations point to red foxes (Vulpes vulpes) as a very potent sentinel species for monitoring the dissemination of antimicrobial bacteria in wildlife habitats. Methods: This study investigated antimicrobial resistance in red foxes from 16 hunting grounds (peri-urban and peri-rural) in western Romania, between 2022 and 2024, in order to evaluate the species as “One Health” sentinels at the wildlife–human–animal interface. During this period, 137 bacterial strains previously identified from 216 samples were phenotypically tested using both the Kirby–Bauer disk diffusion method and the Vitek 2 Compact system. Results: Among the Gram-negative isolates, particularly Escherichia coli and Salmonella enterica, notable antimicrobial resistance and multidrug-resistant (MDR) phenotypes were observed, including resistance to third-generation cephalosporins (ceftazidime) and reduced susceptibility to carbapenems. Resistance patterns observed in Proteus spp. largely reflected intrinsic resistance traits. Methicillin-resistant and MDR staphylococci (Staphylococcus aureus, S. pseudintermedius and S. sciuri) were detected in both peri-urban and peri-rural hunting grounds, with higher frequencies observed in peri-rural areas. Although MDR prevalence was slightly higher in peri-urban compared to peri-rural sites, no statistically significant association was identified between area of isolation and antimicrobial resistance or MDR status. Antimicrobial susceptibility results obtained by disk diffusion and the Vitek 2 Compact system showed a high level of concordance for antibiotics tested in common. Conclusions: Overall, these findings support the use of red foxes as effective One Health sentinels for monitoring environmental antimicrobial resistance occurrence across wildlife, domestic animals, and human-impacted habitats. Full article

Objectives: Acute obstructive pyelonephritis (AOP) is a urological emergency that combines bacterial infection with upper urinary tract obstruction. This retrospective study focuses on the microbial etiology and causes of obstruction, clinical manifestations, antibacterial therapy, drainage type, and outcomes in patients diagnosed with AOP at a tertiary urology center between 1 January 2020 and 30 December 2024. Methods: One hundred patients with a mean age of 61.30 years were included in this retrospective study, which examines demographic data, comorbidities, clinical features, pathogens involved, antimicrobial regimens, and hospital outcomes. Results: Urolithiasis was the most frequent cause of obstruction (62%), followed by ureteral stenosis (14%) and tumors (11%). AOPs were mainly produced by Escherichia coli (58%), followed by Klebsiella spp. (21%); 18% of all identified bacteria were ESBL-producing Gram-negative bacilli, and 29% were MDR bacteria. The most used IV antibiotics were fluoroquinolones (52%), followed by cephalosporins (19%) and carbapenems (18%). Carbapenems were administered to all patients with AOP caused by ESBL-producing pathogens and to 62% of those with MDR bacteria. The duration of antibiotic therapy was individualized based on clinical response. Switch to oral administration was made after 4.3 ± 1.5 days, and the antibiotic treatment lasted 10.8 ± 3.2 days. Conclusions: The results of the present study support integrating evidence-based guidelines with regional patterns of bacterial susceptibility to optimize therapeutic approaches and reduce severe outcomes in patients with AOP, most of whom have multiple comorbidities. Full article

Bacillus anthracis displays susceptibility to penicillin despite harboring a β-lactamase gene, a phenotype governed by the anti-sigma factor RsiP. While RsiP represses σ^P-dependent β-lactamase expression, its broader roles in physiology and virulence remain unclear. This study aimed to define the global regulatory functions of RsiP beyond antibiotic resistance. Deletion of rsiP significantly upregulated the nprR gene, which is an important quorum-sensing (QS) system regulator and enhanced protease secretion. The ΔrsiP mutant caused higher mortality in cellular and Galleria mellonella models and triggered elevated inflammatory cytokines (IL-6, IL-1β, TNF-α, MIP-2) in macrophages models. Surprisingly, in DBA/2 mice models, ΔrsiP was attenuated, with increased host survival and reduced bacterial loads. Competitive indices (CI) confirmed fitness defects in mice (spleen CI = 0.39; liver CI = 0.42). These defects were not due to altered oxidative stress tolerance but were attributed to impaired macrophage internalization of ΔrsiP spores, reducing early colonization. Our findings indicate that RsiP not only modulates β-lactam resistance but also influences extracellular protease activity and host adaptation. Full article

Antimicrobial Resistance (AMR) is a critical public health challenge requiring a coordinated One Health approach. Escherichia coli is a key indicator of AMR and fecal contamination, as well as a zoonotic pathogen transmissible from animals to humans, often through contaminated products like meat and eggs. This study assessed the presence of antibiotic-resistant E. coli and associated resistance genes in 248 cloacal/eggshell samples collected from four autochthonous Portuguese laying hen breeds (Preta Lusitânica, Amarela, Branca, and Pedrês Portuguesa) raised under low antibiotic exposure. A total of 81 E. coli isolates were analyzed for phenotypic antibiotic susceptibility (EUCAST/CLSI) and genotypic resistance, using PCR. Resistance to at least one antibiotic was observed in 98.0% of the isolates. Gentamicin resistance was particularly high (97.1% cloacal; 95.7% eggshell isolates), followed by tetracycline (31.0% cloacal; 41.0% eggshell) and ampicillin (14.0% cloacal; 24.0% eggshell). Multidrug resistance (MDR) was observed in 14.3% of cloacal and 17.4% of eggshell isolates. Notably, no resistance was found against critically important antibiotics. The most prevalent resistance genes were sul2 (45.0% cloacal; 48.0% eggshell) and bla_TEM (45.0% cloacal; 36.0% eggshell). Detection of resistant and MDR E. coli in low input systems suggests environmental acquisition, with chickens as reservoirs, highlighting the need for One Health surveillance. Full article

Mycoplasma bovis (M. bovis) is a major pathogen responsible for bovine respiratory disease, mastitis, and arthritis, causing significant economic losses to the cattle industry worldwide. To elucidate the genetic and biological characteristics of M. bovis circulating in Yunnan Province, China, twenty PCR-positive bovine respiratory samples were collected from cattle farms in Kunming; three isolates—M.bo-YNXD-1, A1, and A8—were successfully cultured and identified through colony morphology, biochemical assays, and molecular characterization. Antimicrobial susceptibility testing showed that M.bo-YNXD-1 exhibited multidrug resistance to six antibiotics, including ciprofloxacin and lincomycin, while A1 and A8 were resistant to one or two agents, respectively. Multilocus sequence typing (MLST) analysis revealed that isolates M.bo-YNXD-1 and M.bo-YNXD-A8 belonged to sequence type ST52, whereas isolate M.bo-YNXD-A1 was assigned to ST90, indicating the coexistence of distinct genetic lineages in this region. Virulence gene screening showed that isolate M.bo-YNXD-A8 was positive for VspX and p81, whereas all three isolates were positive for p48 and Vpam. A SYBR Green I-based quantitative PCR (qPCR) assay targeting the oppD/F gene was established, exhibiting high specificity, a detection limit of 10 copies/μL, and intra-/inter-assay variation below 3%. Validation using clinical samples demonstrated superior sensitivity compared with conventional PCR. Taken together, these findings indicate the presence of distinct MLST genotypes and virulence-associated genetic heterogeneity among regional Mycoplasma bovis isolates, and introduce a rapid, sensitive, and reliable qPCR assay for early detection and epidemiological surveillance. This study provides critical insights for rational antimicrobial use and targeted control strategies against M. bovis infections. Full article

The overuse of antibiotics has accelerated the evolution and mutation of drug-resistant bacteria, creating an urgent need for novel antimicrobial drugs and feed additives. Antimicrobial peptides, with their unique membrane-disrupting mechanism that resists the development of resistance, hold promise as antibiotic alternatives. To overcome the limitations of natural antimicrobial peptides—such as poor stability, susceptibility to protease degradation, and short in vivo half-lives—self-assembling peptide technology has emerged. This approach employs non-covalent interactions to orderly assemble monomeric peptides into stable, structured nanomaterials like nanofibers, nanotubes, and hydrogels. This paper outlines the molecular design principles and smart response mechanisms of antimicrobial peptide nanoassemblies, elucidates their core advantages over monomeric peptides, summarizes their application scenarios in anti-infection fields, and discusses limitations and future directions across various domains. It provides insights for future antimicrobial peptide design. Full article

Background/Objetives: The objective of this study was to determine the in vitro susceptibility profiles of clinical Clostridioides difficile isolates to metronidazole (MTZ), vancomycin (VAN), fidaxomicin (FDX), tigecycline (TGC), and eravacycline (ERV) in a multicenter Spanish cohort, and to evaluate their association with clinical factors. Methods: Strains were obtained from prospectively included patients in the ICD-ANCRAID-SEICV cohort (ClinicalTrials.gov ID: NCT04801862) in Andalucía and the Valencian Community between 1 January 2020 and 30 April 2023. Antimicrobial susceptibility testing was performed using E-test for MTZ, VAN, TGC, and ERV, and agar dilution for FDX. Results: The results were interpreted following EUCAST clinical breakpoints and ECOFF criteria. A total of 107 patients were included (median age 70 years; 65.4% women). Nearly half of the cases were community-acquired, 30% nosocomial, and the remainder healthcare-associated. Most infections were non-severe, and 32.7% experienced recurrence. Overall resistance levels were low: VAN and TGC each showed resistance in 2.8% of isolates, followed by MTZ (1.9%). Only one isolate was resistant to FDX (0.9%), and none to ERV. MIC90 values were low for all agents. Some resistant isolates displayed co-resistance and were recovered from patients with prior antibiotic exposure. Among the seven patients carrying resistant strains, most were women, and the cases were predominantly community-acquired. Clinical characteristics, including age, comorbidity, infection origin, and severity, did not differ from those with susceptible isolates. All patients achieved clinical cure without recurrent infection. No association was found between elevated MIC values and recurrence or greater severity. Conclusions: FDX and ERV demonstrated excellent in vitro activity. Resistance to MTZ, VAN, and TGC was uncommon but detectable. Findings highlight the need for continued antimicrobial resistance surveillance and evaluation of its potential clinical impact. Full article

Background/Objectives: Canine otitis externa (OE) is frequently complicated by Pseudomonas aeruginosa (P. aeruginosa) infections, which are often associated with treatment failure due to intrinsic and acquired antimicrobial resistance. This study aimed to assess the prevalence and antimicrobial susceptibility of P. aeruginosa isolates from dogs with OE in Timiș County, Romania, with a focus on aminoglycosides and fluoroquinolones, to provide region-specific, clinically relevant data and address potential public health implications. Methods: Exudate samples were collected from 435 dogs diagnosed with OE across multiple veterinary clinics between 2022 and 2025. P. aeruginosa isolates were identified using standard culture methods, and antimicrobial susceptibility was determined using the VITEK^® 2 Compact system according to CLSI VET01, Fifth Edition (2018) guidelines. Tested antibiotics included amikacin, gentamicin, enrofloxacin, marbofloxacin, and pradofloxacin. Resistance profiles were analyzed at both the individual antibiotic and class levels. Results:P. aeruginosa was isolated in 14.0% (61/435) of dogs. All isolates were susceptible to amikacin and gentamicin, whereas resistance to enrofloxacin and marbofloxacin was 27.9%, and pradofloxacin resistance reached 63.9%. A total of 24.6% of isolates were susceptible to all tested antibiotics. The most frequent multidrug-resistant combination among fluoroquinolones was ENR (R) + MAR (R) + PRA (R), observed in 23.0% of isolates. Conclusions: This study provides recent, region-specific data on P. aeruginosa prevalence and antimicrobial susceptibility in canine OE, offering clinically relevant insights into aminoglycoside and fluoroquinolone resistance. The findings highlight the potential public health significance of resistant P. aeruginosa strains at the human–animal interface and underscore the importance of antimicrobial stewardship in veterinary practice. Full article

The rise in antimicrobial-resistant Neisseria gonorrhoeae (NG) strains poses major challenges to gonorrhea treatment worldwide. Ceftriaxone remains the first-line antibiotic therapy; however, emerging resistance, particularly driven by the mosaic penA 60.001 allele, necessitates vigilant surveillance. This study assesses the antimicrobial susceptibility patterns of NG isolates in the northwestern region of Croatia and evaluates the correlation between phenotypic susceptibility testing for extended-spectrum cephalosporins (ESC) and genotypic detection of the penA 60.001 allele. A total of 39 clinical NG-positive specimens by a multiplex PCR panel for urogenital infections were collected between 1 July 2022, and 30 June 2024. Phenotypic antimicrobial susceptibility testing was performed using the Etest method. Genotypic detection of ceftriaxone resistance determinants was performed using a multiplex nested PCR assay. All NG isolates were susceptible to ceftriaxone and cefixime. High resistance rates were observed for ciprofloxacin (70.6%), tetracycline (44.1%), and azithromycin (20.6%). Mutations in the penA gene associated with decreased susceptibility to ceftriaxone were detected in three samples, although phenotypic resistance was not observed. The high resistance rates to ciprofloxacin, tetracycline, and azithromycin limit their use for empirical therapy in Croatia. While ceftriaxone remains effective, the detection of penA mutations highlights the need for ongoing surveillance. Full article

Riemerella anatipestifer (R. anatipestifer) is a pathogenic bacterium belonging to the genus Riemerella within the family Flavobacteriaceae, which has multidrug resistance (MDR) and can cause high pathogenicity in waterfowl. The aim of this study was to investigate the antimicrobial resistance and genomic characteristics of R. anatipestifer strains isolated from several regions of China from 2023 to 2024. Two strains were selected for challenge tests, and virulence protection tests were conducted on florfenicol-resistant and florfenicol-sensitive strains. A total of 88 strains of R. anatipestifer were collected from the Shandong, Jiangsu, Guangdong, Hebei and Henan regions. The results showed that the 88 strains included serotypes 1, 2, 5, 6, 7 and 10. Serotype 5 was the most prevalent in the Shandong region. All strains were multidrug-resistant, with the hexaresistance accounting for the highest proportion (42.1%). A total of five resistance genes (tet(X), floR, ermF, qnrS, rmtB) and seven virulence genes were found (ompA, camp, AS87_04050, SIP, Fur, TbdR1, luxE). The challenge test showed that the LD₅₀ of RA12 was 2.75 × 10⁷ CFU/mL, and that of RA26 was 2.57 × 10⁷ CFU/mL. Phylogenetic tree analysis revealed that strain RA26 was closely related to strain 20190403E1-1, and strain RA16 was closely related to strain JW1. In addition, serotypes 2 and 7 identified in this study have been undergoing clonal transmission in China. Virulence protection tests indicated that the results of in vitro drug susceptibility tests were consistent with the therapeutic effects after in vivo treatment, and no R. anatipestifer was found in the visceral tissues of surviving ducklings. This study provides a reference for the rational use of antibiotics. Full article

The microevolutionary pathways and molecular mechanisms by which the important pathogen Vibrio parahaemolyticus acquires resistance in the aquatic environment under continuous selective pressure from quinolone antibiotic residues are still unknown. Here, the study successfully simulated the long-term pressure of antibiotic residues in aquaculture by susceptible V. parahaemolyticus (VPD14) which was isolated from seafood, to a 30-day in vitro induction with sublethal concentrations of levofloxacin, which yielded the mutants (VPD14M). A phenotypic analysis revealed that VPD14M exhibited resistance to ampicillin, levofloxacin and ciprofloxacin, compared to VPD14. These changes were accompanied by adaptations, including a decreased growth rate and an enhanced biofilm formation capacity. Whole-Genome Sequencing identified that the acquired resistance was primarily attributable to key point mutations in three Quinolone Resistance-Determining Regions (QRDRs). Specifically, a G → T substitution at nucleotide position 248 in the gyrA gene, leading to a serine-to-isoleucine substitution at the 83rd amino acid position (Ser83Ile) of the DNA gyrase subunit A; a C → T substitution at position 254 in the parC gene, resulting in a serine-to-phenylalanine substitution at position 85 (Ser85Phe) of the topoisomerase IV subunit A; and a C → T substitution at position 2242 in the gyrB gene, causing a proline-to-serine substitution at position 748 (Pro748Ser) of the DNA gyrase subunit B. Collectively, the study demonstrated that sublethal antibiotic levels rapidly drive quinolone resistance in V. parahaemolyticus, and the specific mutations identified offer critical support for resistance monitoring and seafood safety alerts. Full article

Infectious diseases present persistent and complex challenges to global public health, with conventional antibiotic therapies increasingly limited by antimicrobial resistance, microbiota disruption, and adverse effects. There is a critical need to explore complementary strategies that augment host defense mechanisms without exacerbating these limitations. Accumulating evidence underscores the integral role of the gut microbiota—a diverse microbial ecosystem within the gastrointestinal tract—in regulating systemic immunity and pathogen susceptibility. This review synthesizes recent advances from animal models to delineate the multi-faceted mechanisms by which commensal microbes and their metabolites confer protection against enteric and respiratory infections. Key processes include competitive exclusion for nutrients and ecological niches, production of antimicrobial compounds, reinforcement of intestinal barrier integrity, and orchestration of local and systemic immunity via gut–lung axes. We further discuss the potential of microbiota-targeted interventions to enhance treatment efficacy and patient outcomes. By integrating mechanistic insights with translational applications, this review aims to inform the rational design of next-generation anti-infective strategies grounded in microbial ecology and host immunobiology. Full article

Vultures are extraordinarily adapted to feed on carrion, providing them with a constant microbiologically hostile environment. This peculiar ecological position has influenced the evolution of their gut microbiota, potentially conferring its uncommon antimicrobial traits and resistance to stress. In this study, we report on the isolation and comprehensive characterization of a lactic acid bacterium strain, identified as Ligilactobacillus agilis, from vulture feces via 16S rRNA gene sequencing. This strain exhibited potent antagonistic activity against several clinically relevant bacterial pathogens, including Salmonella enterica Typhimurium (25.26 ± 0.26 mm), Escherichia coli (23.5 ± 0.88 mm), Staphylococcus aureus (23.1 ± 1.8 mm), and Listeria monocytogenes (24.88 ± 0.61 mm), as demonstrated by agar well diffusion assays. Remarkably, it also demonstrated considerable resilience in simulated gastrointestinal conditions, with survival rates of 52.5 ± 7.4% in artificial gastric juice and 61.1 ± 3.7% in intestinal fluids. Antimicrobial susceptibility profiling confirmed its sensitivity to a broad range of commonly used antibiotics, including gentamicin, streptomycin, clindamycin, and penicillin. Whole-genome sequencing further revealed a complete repertoire of core genes associated with genetic information processing, robust carbohydrate metabolism, and nutrient assimilation, underscoring its adaptability and probiotic potential. It is important to note that the analysis of the assembled genome against VFDB did not show the presence of any known virulence factor according to the given criteria, which is preliminary evidence of safety-related aspects that are to be followed with the help of guideline-based analyses. Taken together, the unique ecological origin and in vitro inhibitory activity against the tested pathogens, gastrointestinal robustness, genomic features, and safety credentials position this L. agilis strain as a promising probiotic candidate for mitigating enteric infections in animal production systems, warranting further functional validation and in vivo efficacy studies. Full article

Citrus fruits are susceptible to ‘Huanglongbing’, leading to widespread antibiotic use during planting. Additionally, to enhance economic efficiency, plant growth regulators (PGRs) are also applied to citrus fruits. To rapidly screen for antibiotics and plant growth regulators in citrus fruits, a method was developed for the simultaneous detection of exogenous contaminants in mandarin, orange, pomelo, and lemon using QuEChERS combined with liquid chromatography–quadrupole/orbitrap mass spectrometry. By comparing the responses or recoveries of compounds under different conditions, the optimal extraction and purification were determined. The method was used to verify the methodological parameters for four citrus fruits. The results showed that the detection limits for 10 antibiotics and 53 plant growth regulators in the four citrus fruits ranged from 1 to 50 μg/kg, and the limits of quantitation ranged from 1 to 80 μg/kg. And the coefficient of determination (R²) was ≥ 0.99. The recovery of all compounds was between 60% and 120%, and the relative standard deviation (RSD) was less than 20%. The method was applied to the 42 real samples, and a total of nine compounds were detected at concentrations ranging from 0.002 to 0.852 mg/kg. The results demonstrated that the method was simple, sensitive, accurate, and reliable, making it suitable for detecting antibiotics and plant growth regulators in citrus fruits. Full article

Background/Objectives: Multidrug-resistant (MDR) strains of Streptococcus suis are increasingly prevalent and present significant challenges in clinical management. Given that the development of new antibiotics is a resource-intensive process and time-consuming, there is an urgent need for alternative therapeutic strategies to address resistance in the short term. One promising approach is the use of combination therapy, which involves pairing potent antibiotics with agents that may be less effective on their own, to enhance therapeutic efficacy and potentially overcome resistance mechanisms. This study aimed to investigate the in vitro antibacterial activity of combining two classes of antibiotics with distinct mechanisms of action—cell wall synthesis inhibitors and protein synthesis inhibitors—against MDR S. suis strains isolated from diseased pigs. Methods: A total of 36 MDR S. suis strains were tested using a microbroth dilution checkerboard assay to determine the minimum inhibitory concentration (MIC) of four cell wall synthesis inhibitors —amoxicillin/clavulanic acid (AMC), ampicillin (AMP), penicillin G (PEN), and vancomycin (VAN)— in combination with four protein synthesis inhibitors —gentamicin (GEN), neomycin (NEO), tilmicosin (TMS), and tylosin (TYL). Time–kill curve assays were conducted to evaluate the in vitro bactericidal activity of synergistic antibiotic combinations (PEN–GEN and AMP–NEO) against Beta-lactam-resistant and Beta-lactam-susceptible MDR S. suis strains. Results: Checkerboard analysis revealed that penicillin-gentamicin combination exhibited the most effective synergistic activity against the MDR S. suis strains (10/19, 52.6%), with ∑FIC values of 0.25–1.06 and MIC reductions from resistant to susceptible levels. Time-kill assays further confirmed the synergistic bactericidal effect of the combination, demonstrating complete bacterial clearance within 6–9 h, markedly rapid bacterial killing compared to monotherapy. Conclusions: This study demonstrates that antibiotic combinations, particularly Beta-lactams combined with aminoglycosides, show synergistic activity against pig-isolated S. suis MDR strains. The PEN-GEN combination exhibited strong synergistic and bactericidal effects, supporting combination therapy as a potential strategy to address antimicrobial resistance. Further evaluation in diverse strain backgrounds and prudent antibiotic use are essential to confirm efficacy and limit the emergence of antibiotic resistance. Full article