Search Results (1,604)

Background/Objectives: Antimicrobial resistance in food–animal environments threatens sustainable production and public health, yet small farms remain poorly characterized as potential reservoirs of antimicrobial resistant bacteria. To address this, we investigated the prevalence and antimicrobial resistance profiles of Escherichia coli, Klebsiella spp., and Enterococcus spp. from small-scale cattle farms in Tennessee, USA. Methods: Over one year, 153 environmental samples (soil, manure, water) were collected from 17 farms. Target bacteria were isolated and confirmed using selective agar, biochemical tests, and PCR, and tested against 12 antibiotics using the Kirby–Bauer disk diffusion test. Multiple Antibiotic Resistance Index (MARI) and multidrug resistance (MDR) profiles were summarized. A complementary farmer survey of 26 farmers captured veterinary access, antibiotic use, manure handling, record keeping, and awareness of antimicrobial resistance. Results: Prevalence was highest for Enterococcus spp. (41.8%), followed by E. coli (23.5%) and Klebsiella spp. (12.4%). Seasonal variation was significant for E. coli and Enterococcus (p < 0.05). Winter manure yielded highest detection of E. coli (55.6%) and Enterococcus (53.8%), whereas Klebsiella peaked in Fall soil (19.1%). Resistance patterns varied across species, with Enterococcus showing consistent resistance to all three. E. coli frequently resisted erythromycin, ampicillin, and azithromycin; and Klebsiella commonly resisted erythromycin, ampicillin, and cefotaxime, though some of these reflect intrinsic resistance rather than acquired clinical resistance. MARI values were 0.92 in manure and soil, identifying them as high-risk reservoirs. We identified 29 distinct MDR pattern. Bipartite network visualization highlighted “resistance hubs” around erythromycin, ampicillin, and vancomycin, particularly in Enterococcus. In our study, 76.9% of farmers consulted veterinarians before antibiotic use, 57.7% kept written antibiotic records, and 65.4% were aware of AMR as a public health issue. Small-scale cattle farms are potential reservoirs of multidrug resistant commensal bacteria. Conclusions: These findings provide an evidence-based foundation to guide targeted antimicrobial stewardship and promote sustainable management practices in small-scale food animal farms. Full article

The global rise in antimicrobial resistance among the ESKAPE pathogens represents a major challenge to public health. Here, we report the broad-spectrum antibacterial activity of the synthetic antimicrobial and pore-forming peptide C14R against all six ESKAPE species. Using a radial diffusion assay and resazurin-based viability testing, C14R exhibited a potent bactericidal effect with minimum inhibitory concentrations (MICs), defined as the lowest concentration of an antimicrobial agent that completely inhibits visible growth of planktonic microorganisms, ranging from 3.4 µg/mL (Enterococcus faecium, vancomycin-resistant) to 45.2 µg/mL (Klebsiella quasipneumoniae, ESBL). C14R also inhibited biofilm formation by Gram-positive pathogens, with minimum biofilm inhibitory concentrations (MBICs), referring to the minimal concentration required to prevent the development of biofilms, of 15.0 µg/mL (Staphylococcus aureus, MRSA) and 22.0 µg/mL (E. faecium, VRE), whereas Gram-negative biofilms showed higher tolerance. Together, these findings demonstrate that C14R retains high activity against multidrug-resistant ESKAPE strains, highlighting its potential as a lead compound for the development of next-generation antimicrobial drugs to expand the portfolio of available antibiotics and brace health systems against emerging severe infections. Full article

Antimicrobial resistance (AMR) in food-producing animals is a growing One Health concern. However, data on AMR in indicator microorganisms from clinically healthy dairy cattle in Latvia remain limited. This study aimed to characterize the AMR profiles of Escherichia coli and Enterococcus spp. isolated from rectal swabs and bulk-tank milk collected from 18 dairy farms between February and May 2025. Bacterial identification was performed using conventional culturing and MALDI-TOF mass spectrometry, and antimicrobial susceptibility was determined using the disk diffusion (Kirby–Bauer) method, interpreted according to European Committee on Antimicrobial Susceptibility Testing (EUCAST) guidelines. Resistance levels were further quantified using resistance scores (R-scores) and the Multiple Antibiotic Resistance Index (MARI). In total, 582 E. coli and 428 Enterococcus spp. isolates were recovered from rectal swabs, with E. coli showing the highest resistance to ampicillin (12.5%) and amoxicillin–clavulanic acid (6.7%), whereas resistance to tetracycline was rare (0.3%). Enterobacteriaceae from milk exhibited higher resistance to ampicillin (45.8%) and amoxicillin–clavulanic acid (20.8%). Among Enterococcus spp., resistance was highest to an antibiotic not used in dairy cows in Latvia quinupristin–dalfopristin (69.2%), while resistance to vancomycin and linezolid remained low (0.5% each). Milk-derived enterococci showed a comparable pattern, with additional resistance to streptomycin (25%). Overall, resistance levels and multidrug resistance were low. However, the presence of sporadic resistant isolates and elevated MARI values, particularly in large-scale farms and milk-derived bacteria, highlights the importance of continued AMR surveillance and prudent antimicrobial use in the Latvian dairy sector. Full article

Background. The aim of this study is to analyze changing trends in isolated organisms and antibiotic resistance of bacterial keratitis (BK) over 26 years. Methods. A retrospective medical record review included 542 strains isolated from 462 BK patients between 1998 and 2023. We analyzed routinely generated in vitro antibiotic susceptibility testing results recorded in the laboratory information system and did not perform additional susceptibility testing for research purposes. The entire period was divided into two (first half: 1998–2010, 297 isolates from 255 patients; second half: 2011–2023, 245 isolates from 207 patients) and compared. Results. During the entire period, Staphylococcus spp. (32.3%) and Pseudomonas spp. (18.1%) were common isolates, and a significant increase in Acinetobacter spp. (1.3% vs. 10.6%, p < 0.001) was observed. Among Gram-positive bacteria, methicillin resistance rates remained stable between the two periods (52.6% vs. 46.7%, p = 0.525), and an increase in vancomycin-resistant Enterococci (VRE, 0% vs. 26.1%, p = 0.074) was found. Among Gram-negative bacteria (GNB), ciprofloxacin (7.5% vs. 14.4%, p = 0.108) and imipenem (2.9% vs. 6.5%, p = 0.255) resistance increased slightly, resistance to ceftazidime (resistance to ceftazidime (8.3% vs. 8.8%, p > 0.999) was maintained, and resistance to aminoglycosides (17.8% vs. 7.2%, p = 0.010) decreased. Conclusions. Our study suggests that conventional topical fortified antibiotic eye drops (tobramycin, ceftazidime) can still be considered as an empirical treatment option for BK. However, our findings revealed a long-term trend of increasing Acinetobacter spp. and VRE, as well as a slight trend of increasing resistance to ciprofloxacin and imipenem in GNB, which may present future challenges in BK treatment. Full article

Healthcare-associated bacterial conjunctivitis is an underrecognized yet preventable infection in neonatal intensive care units (NICUs). This study aimed to determine the incidence, risk factors, microbiological profile, and treatment approaches of healthcare-associated bacterial conjunctivitis in neonates. This descriptive, cross-sectional study included neonates diagnosed with bacterial conjunctivitis and followed in the NICU between January 2019 and January 2024. Pathogens were identified by MALDI-TOF MS and antimicrobial susceptibility determined using VITEK 2 according to EUCAST breakpoints. During the five-year period, 104 (2.5%) of 4107 neonates admitted to the NICU developed healthcare-associated bacterial conjunctivitis. Of the pathogens isolated in cultures, 70.2% were Gram-positive bacteria, with coagulase-negative staphylococci being the most common (52.9%), followed by Staphylococcus aureus, Klebsiella pneumoniae, and Serratia marcescens. Empirical treatment consisted of 0.3% topical gentamicin eye drops. In resistant cases, fortified vancomycin drops (32.7%), 0.5% moxifloxacin (4.8%), or 0.3% tobramycin (1.9%) eye drops were administered according to antibiogram results. Compared with Gram-positive infections, Gram-negative conjunctivitis was associated with longer durations of intubation, orogastric feeding, and hospitalization. These findings indicate a predominance of Gram-positive pathogens in NICU-acquired neonatal conjunctivitis, while Gram-negative infections confer greater clinical burden. Fortified antibiotic eye drops are an effective treatment option for resistant cases in high-risk newborns. Full article

This study evaluated the viability, microbiological composition, functional traits, and safety of probiotic bacteria isolated from commercial products marketed as containing Limosilactobacillus reuteri. Viable cell counts, biochemical characterization, strain-level identification, functional properties, gastrointestinal tolerance, and safety attributes were assessed. Among the evaluated products, only four presented colony-forming units (CFU) counts consistent with label claims (products E, F, G, and H), while two showed no detectable viable microorganisms (products B and L). All isolates were Gram-positive, catalase-negative, and predominantly rod-shaped. rep-PCR analysis revealed strain homogeneity in most products, whereas others (products A and K) exhibited heterogeneous microbial compositions. Molecular identification based on 16S rRNA sequencing showed a predominance of Lmb. reuteri and Lacticaseibacillus rhamnosus, with some products containing additional species such as Lactiplantibacillus plantarum and Lactobacillus acidophilus. Functional assays demonstrated strain-dependent proteolytic and diacetyl-producing capacities, as well as variable tolerance to simulated gastrointestinal conditions. Most strains preferentially produced L-lactate, although some generated substantial amounts of D-lactate. All isolates were susceptible to antibiotics recommended by EFSA, except for intrinsic vancomycin resistance, and no transferable virulence markers, biogenic amine production, or Salmonella contamination were detected. Furthermore, virulence-related genes such as hdc, tdc, odc, hyl, cylA, and ace were not identified. Overall, the results highlight pronounced discrepancies between label claims and microbiological quality among commercial probiotic products and reinforce the importance of strain-level characterization to ensure safety, functional performance, and regulatory compliance. Full article

Prosthetic-valve endocarditis (PVE) represents one of the most serious forms of infective endocarditis, marked by high mortality and considerable management complexity. The 2023 European Society of Cardiology (ESC) Guidelines emphasise the diagnostic centrality of repeatedly positive blood cultures. Nonetheless, a significant area of uncertainty remains regarding the diagnostic and prognostic value of cultures from explanted prosthetic valves—particularly in centres lacking access to molecular diagnostics. Case Presentation: We report a case of prosthetic-valve endocarditis on a bioprosthesis, in which repeated blood-culture sets yielded Streptococcus acidominimus, whereas culture of the explanted valve revealed Staphylococcus warnerii. The patient received six weeks of intravenous vancomycin, with treatment tailored according to the patient’s clinical and laboratory parameters and in alignment with international endocarditis guidelines, obtaining a clear clinical and laboratory improvement. Discussion: The literature reports that discordance between blood-culture and valve-culture results in infective endocarditis may range from approximately 10% to 29%, attributable to contamination, biofilm formation or polymicrobial infection. In our case, management guided by the microorganism repeatedly isolated from blood cultures proved effective and aligned with the 2023 European Society of Cardiology (ESC) guidelines. The case underlines the importance of a multidisciplinary team and an integrated interpretation of microbiological, clinical and surgical data. Conclusions: Infective endocarditis with discordant isolates presents a complex diagnostic challenge. The etiological diagnosis must rely primarily on the results of blood cultures, whereas valve culture plays a complementary role—useful more for prognostic stratification than for initial diagnostic purposes. A multidisciplinary approach and a critical interpretation of microbiological findings are essential to optimise therapeutic management and improve patient outcomes. Full article

Staphylococcus aureus (MRSA) and vancomycin-resistant enterococci (VRE) are high-burden healthcare-associated pathogens that increase mortality, prolong hospitalisation, and drive substantial healthcare costs worldwide. These infections are associated with high morbidity, increased mortality, prolonged hospital stays, and significant costs, particularly among immunocompromised patients or those with extended hospitalizations. This systematic review was conducted and reported in accordance with PRISMA 2020, aiming to synthesise existing data on the epidemiology, resistance mechanisms, clinical manifestations, and strategies for the diagnosis, treatment, and prevention of MRSA and VRE infections. Data were qualitatively synthesised. A total of 113 records published between 2020 and 2025 met the inclusion criteria and were identified through searches in multiple bibliographic databases and publisher platforms (e.g., PubMed, Scopus, Web of Science). MRSA and VRE are implicated in numerous severe infections, including ventilator-associated pneumonia, catheter-associated urinary tract infections, endocarditis, and bacteraemia. Antimicrobial resistance is driven by the mecA, vanA, and vanB genes, while biofilm formation further complicates therapeutic efforts. Biofilm formation can promote antibiotic tolerance (slower killing without an increase in MIC) and persistence (survival of ‘persister’ cells), distinct from genetic resistance, and may complicate therapy in selected infections. Effective strategies include appropriate anti-MRSA/anti-VRE agents (e.g., ceftaroline for MRSA; linezolid or daptomycin for VRE), active screening, stringent infection prevention and control measures, and antimicrobial stewardship programmes. Implementation is often hindered by institutional barriers, limited resources, and insufficient staff training. A multidisciplinary, evidence-based approach is essential for the effective management of these infections. Reducing this burden requires coordinated implementation of rapid diagnostics, stringent infection prevention and control, and antimicrobial stewardship, supported by sustained institutional and public health investment. Full article

The rapid global spread of antimicrobial resistance (AMR) has significantly reduced the effectiveness of many modern antibiotics, creating an urgent need for alternative therapeutic strategies. One promising approach is the revival and repurposing of older antimicrobial agents whose clinical potential was previously limited by toxicity concerns, pharmacokinetic challenges, or the availability of newer drugs. Recent advances in drug delivery, dosing optimization, and antimicrobial stewardship have renewed interest in these compounds as viable options for the treatment of multidrug-resistant infections. The aim of this review is to provide a comparative, clinically oriented analysis of selected “old” antibiotics, fosfomycin, colistin, streptomycin, and vancomycin, with emphasis on their current therapeutic roles, pharmacokinetic/pharmacodynamic (PK/PD) targets, toxicity mitigation strategies, resistance mechanisms, and evidence supporting combination therapies and alternative routes of administration. This narrative review was conducted using a structured PubMed search and manual reference screening, focusing on clinical, PK/PD, and translational studies relevant to the contemporary use of legacy antibiotics. The review summarises current evidence on the re-emerging clinical applications of these agents, each discussed in the context of historical use, mechanism of action, resistance patterns, and newly identified indications. Attention is given to novel formulations, combination strategies, and alternative routes of administration that enhance efficacy while limiting toxicity, including applications in biofilm-associated infections. Overall, strategic repurposing of older antibiotics represents a valuable complementary approach in the fight against AMR and may extend the therapeutic lifespan of existing agents in an era of limited antibiotic innovation. Full article

Objectives: Clostridioides difficile infection (CDI) remains a major healthcare challenge, particularly in resource-limited settings. Methods: This retrospective, single-center study analyzed CDI epidemiology and treatment outcomes among 528,887 hospitalized patients at the University Hospital in Kraków, Poland, between 2016 and 2022. Results: A total of 2341 CDI cases were confirmed, with an overall incidence of 4.32 per 1000 admissions. The highest rates were observed in geriatric and infectious diseases units. During the COVID-19 pandemic, healthcare-associated CDI cases surged, accounting for up to 89.2% of infections in 2020 with an incidence rate of 3.8 per 1000 admissions, compared with 2.5 per 1000 admissions in 2016. Vancomycin-based therapy was associated with significantly lower mortality (OR 0.73, 95% CI 0.56–0.95) compared to metronidazole, while combination therapy (vancomycin, metronidazole) showed the highest recurrence rate (17%). Fidaxomicin use was minimal (0.4%) due to limited availability. Recurrent CDI occurred in 14.2% of cases, with a relapse-free survival advantage observed in vancomycin-treated patients. The overall in-hospital case fatality rate associated with CDI was 22.5%. Conclusions: Despite stable overall CDI incidence, the study highlights the impact of increased antibiotic consumption during the pandemic on HA-CDI dynamics. The findings underscore the need for improved antimicrobial stewardship, broader access to advanced therapies such as fidaxomicin and bezlotoxumab, and enhanced diagnostic protocols. In settings with restricted therapeutic options, vancomycin remains a valuable treatment, particularly for reducing mortality. Full article

Background: Conservative management of port-related bacteremia often includes locally administered antimicrobials, known as antimicrobial lock therapy (ALT). Current guidelines recommend daily replacement of antimicrobial lock solutions (ALSs). We aimed to evaluate whether ALSs could remain effective with extended dwell times of up to 10 days. Methods: In this randomized clinical trial, patients with noninfected, recently implanted ports were assigned to one of five ALS dwell-time groups, ranging from 1 to 10 days. Each ALS contained heparin plus an antimicrobial at standard intraluminal concentrations: vancomycin 2 mg/mL, teicoplanin 10 mg/mL, linezolid 1.8 mg/mL, daptomycin 5 mg/mL, or tigecycline 4.5 mg/mL. The primary endpoint was the time at which intraluminal drug concentrations decreased below 1 mg/mL (ClinicalTrials.gov NCT01592032). Results: Vancomycin and linezolid concentrations fell significantly below 1 mg/mL after 3 days of dwell time. Daptomycin and tigecycline concentrations decreased significantly after 7 days but remained above 1 mg/mL. Teicoplanin concentrations did not decline significantly after 7 days. Conclusions: Optimal ALS dwell time depends on the antimicrobial agent. Vancomycin and linezolid locks require daily replacement, whereas daptomycin, tigecycline, and teicoplanin locks maintain therapeutic concentrations for up to 7 days. These findings support individualized ALS replacement strategies, potentially reducing the need for daily interventions. 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: 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

Vancomycin-resistant Enterococcus faecium (VREfm) is an emerging pathogen responsible for healthcare-associated infections. For this reason, 44 VREfm isolates collected during 2021–2023 were characterized using phenotypic and genomic approaches. VREfm isolates were identified by MALDI-TOF and antimicrobial susceptibility tests were performed with Vitek 2, Sensititre, or E-test. Sequence type (ST), antibiotic resistance genes, virulence factors and genetic relatedness were determined using Next Generation Sequencing. Forty-three isolates had a VanA phenotype and vanHAX genotype and one had a VanB phenotype and vanHBX genotype. Isolates showed high antibiotic resistance to various antibiotics, but generally remained susceptible to quinupristin/dalfopristin, tigecycline and eravacycline. Two isolates were resistant to linezolid, showing the chromosomal mutation G2576T in domain V of the 23S rRNA gene in one isolate, and the transferable linezolid resistance genes cfr(D) and optrA in the other. Thirty-eight isolates belonged to ST80, one to ST17 (ST80 and ST17 are included in CC17) and one to ST697. Genomic analysis of the ST80 isolates showed that nearly all of them belonged to a single cluster. To prevent further spread of VREfm in the nosocomial environment, in addition to the application of up-to-date infection control strategies and antibiotic stewardship programs, the implementation of genomic surveillance is recommended. Full article

Background: Vancomycin is a critically important antimicrobial in human medicine, and vancomycin-non-susceptible enterococci represent a One Health concern when animal reservoirs contribute to the wider resistance ecology. We aimed to characterize vancomycin non-susceptibility among poultry-derived Enterococcus spp. from Hungary, using a combined phenotypic–genomic approach. Methods: Following a phenotypic pre-screen with antimicrobials authorized for poultry, 218 isolates with elevated minimum inhibitory concentrations (MICs) were selected for extended broth microdilution testing including vancomycin. Vancomycin susceptibility was interpreted using Clinical and Laboratory Standards Institute (CLSI) clinical breakpoints and European Committee on Antimicrobial Susceptibility Testing (EUCAST) epidemiological cut-off values (ECOFFs). Whole-genome sequencing was performed on a targeted multidrug resistant (MDR) subset (n = 42), enriched for elevated or borderline vancomycin MICs and stratified by region and host species (chicken, turkey), and resistance determinants were annotated against the Comprehensive Antibiotic Resistance Database (CARD) using stringent similarity/coverage thresholds. Results: Among the 218 pre-screened isolates (126 from chickens; 92 from turkeys), 196 (89.9%) met MDR criteria. For vancomycin, 15.6% of isolates were resistant and 9.2% intermediate by CLSI, while EUCAST ECOFF classification placed 34.9% in the non-wild-type group. The vancomycin MIC distribution was right shifted, with high-end MICs observed. In the sequenced subset, vancomycin-associated determinants consistent with the vanC pathway (including regulatory and auxiliary components) were detected in five isolates. Beyond vancomycin-related determinants, the WGS subset harbored common resistance genes consistent with the observed multidrug-resistant phenotypes. Conclusions: Vancomycin non-susceptibility was detected among pre-screened poultry-derived Enterococcus isolates in Hungary, and genomic analysis revealed vanC-associated and other peptide antibiotic resistance signatures. These findings support targeted One Health surveillance integrating MIC distributions with genomic resistance determinants in food animal reservoirs. Full article