Search Results (1,440)

Background/Objectives: Methicillin-resistant Staphylococcus aureus (MRSA) colonization in geriatric long-term care facilities (LTCFs) is a global concern. However, the transmission dynamics of MRSA among LTCF residents in Japan remain largely unknown. Methods: Whole-genome sequencing was conducted on 85 MRSA isolates obtained from 76 residents across 4 geriatric LTCFs in Japan. Single-nucleotide polymorphism (SNP) analysis was performed to identify the transmission dynamics, with a threshold of ≤15 pairwise core-genome SNP distances defining recent transmission clusters (genomic clusters). Antimicrobial susceptibility testing and investigation of antimicrobial resistance genes were also performed. Results: Among the 76 MRSA-carrying residents, 34 (44.7%) belonged to 14 genomic clusters, including strains from clinical specimens of 7 individuals. Three individuals acquired MRSA strains within the LTCFs, which were part of genomic clusters. Conversely, 14 residents who underwent testing immediately after admission carried MRSA strains within genomic clusters, suggesting transmission prior to their LTCF admission. MRSA isolates that were prevalent among LTCF residents were generally susceptible to trimethoprim–sulfamethoxazole but resistant to levofloxacin and clindamycin. Conclusions: Acquisition of MRSA genomic cluster strains among LTCF residents can occur both during and before admission to the facility. These findings underscore the need for measures that mitigate MRSA transmission inside and outside LTCFs. Full article

Background/Objectives: Ceftaroline (CPT) is a broad-spectrum, fifth-generation cephalosporin with in vitro activity against methicillin-resistant Staphylococcus aureus (MRSA) and drug-resistant Streptococcus pneumoniae. Real-world data on its use in pediatric patients remain limited. This study aimed to the describe clinical characteristics and outcomes associated with CPT use in pediatric patients at a pediatric academic medical center. Methods: This retrospective case series evaluated patients under 18 years of age who received CPT between November 2016 and August 2023. The primary outcome was clinical success, defined as a composite of 30-day survival, absence of microbiological recurrence within 30 days, and/or resolution of acute infection signs and symptoms without therapy modification due to clinical failure. The secondary outcomes included adverse effects potentially attributable to CPT and the clinical rationale guiding its use. Results: Among 25 patients, most were male (68%) with a median (IQR) age of 3.4 (1.4–14.3) years. The indications for use commonly included respiratory infections (48%), bacteremia (16%), and/or skin and soft tissue (12%) infections. The frequently used dosing regimens included 12 mg/kg (36%) and 8 mg/kg (28%) q8hr, with a median (IQR) duration of therapy of 4.6 (1.7–10.0) days. Clinical success was achieved in 96% of patients. No adverse effects attributable to CPT were observed and CPT was commonly used for escalation (40%) and/or issues with alternative therapies (36%). Conclusions: CPT use was associated with high clinical success rates and no observed adverse effects in this pediatric report. These findings support its use as a therapeutic option when the alternatives are limited. Larger multicenter studies are needed to further evaluate the clinical outcomes and safety of CPT use in pediatric patients. Full article

Persistent bacteria (PB) are a subpopulation of dormant cells that tolerate high antibiotic concentrations and cause chronic, hard-to-treat infections, posing a serious global health threat. In this study, the antibacterial efficacy of six cationic polymers, poly(hexamethylene guanidine) (PHMG), polyethyleneimines of different molecular weights, α-polylysine, ε-polylysine, and polyacrylamide, against persistent bacteria was systematically evaluated. The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of these cationic polymers against susceptible and persistent methicillin-susceptible Staphylococcus aureus (MSSA), methicillin-resistant S. aureus (MRSA), and Escherichia coli (E. coli) were determined using a microbroth dilution method, while cytotoxicity to mouse fibroblast (L929) cells was assessed via MTT assay. PHMG demonstrated superior antibacterial activity, with MBC values as low as 2 μg/mL against persistent MSSA, markedly outperforming the other polymers tested. The key novelties of this work are (i) the first establishment of a cationic polymer library with diverse structural parameters for persistent bacteria clearance, offering a potential strategy for treating recalcitrant infections; and (ii) the elucidation of quantitative correlations between polymer charge density and hydrophobic chain segments with antimicrobial efficacy through structure–activity relationship analysis, providing a theoretical basis for the rational design of anti-persistent materials. Full article

Objective: This study aims to evaluate free vancomycin concentrations in tissues of septic patients that received empirical doses. Methods: A PBPK model was built in PK-Sim to simulate vancomycin concentrations in healthy volunteers and septic patients. Literature data were used to validate the model. A strain of MRSA (methicillin-resistant Staphylococcus aureus) was evaluated through time-kill curves. Based on the information obtained from the time-kill study, a PD model, including adaptive resistance, was developed using NONMEM. The PBPK and PD models were combined to evaluate the vancomycin effect in plasma and tissues against MRSA. Results: A PBPK model was successfully built for both healthy volunteers and septic patients. The tissue concentrations were found to be significantly lower than plasma concentrations. The studied strain of MRSA was found to have an MIC of 2 µg/mL, and the PD model described the EC50 as 1.05 µg/mL. The PBPK and PD models were successfully combined, and septic patients infected with MRSA strains with MIC of 2 µg/mL had effective treatment response. However, septic patients infected with MRSA strains with MICs of 4 µg/mL and 8 µg/mL did not have adequate response to vancomycin treatment. Conclusions: In septic patients, response was limited against resistant MRSA strains. These findings should be considered hypothesis-generating and interpreted with caution, underscoring the need for individualized approaches and rigorous monitoring. Full article

Micro-organisms are abundant in nature and can also be found in hospital settings, causing high rates of infections. This study aimed to identify bacteria isolated from a veterinary hospital, as well as to perform antimicrobial susceptibility testing using the disk diffusion method (Kirby–Bauer), biofilm production tests using 96-well polystyrene microtiter plates and crystal violet dye, and genetic analysis of the ica operon of Staphylococcus isolates. Three collections were made from eleven surfaces and objects in the hospital’s non-critical areas (general areas) and critical areas (surgical center), totaling thirty-three samples. A total of 66 different bacterial isolates were obtained, with 77% (51/66) Gram-positive and 23% (29/66) Gram-negative. Resistance profiles were found for multidrug-resistance (MDR), methicillin-resistant Staphylococcus aureus (MRSA), methicillin-resistant Staphylococcus epidermidis (MRSE), and other unidentified species of methicillin-resistant coagulase-negative (MRCNS) and extended-spectrum beta-lactamase (ESBL), as well as biofilm production rates of 57% (38/66) of the isolates. Analysis of the operon genes for Staphylococcus sp. showed divergence in some samples when compared to the phenotypic test performed. In summary, there is a high presence of micro-organisms with resistance and virulence factors spread throughout the various areas of the veterinary hospital. Full article

Combating antibiotic resistance is critically significant for global public health. The development of new antibacterial nanomaterial is a promising way to do this. In this study, a bottom-up approach was employed to fabricate antibacterial carbon dots (ACDs). During the synthesis, quaternary ammonium function groups with long alkyl chains were successfully grafted on ACDs’ surfaces. The obtained ACDs exhibited potent inhibitory against methicillin-resistant Staphylococcus aureus (MRSA) bacteria with minimum inhibitory concentrations of 2.5 µg/mL. Crucially, 2.5 µg/mL of ACDs could inhibit the growth of MRSA for as long as 72 h, which highlighted their long-term activity. Mechanistic investigations revealed that ACDs exerted bactericidal effects for MRSA bacteria primarily through disrupting the cell wall/membrane, destroying cell membrane potential, inducing the generation of excessive ROS, and triggering the leakage of nucleic acids and intracellular components. In sum, this work provided a kind of ACD with high efficiency and long-term antibacterial activity, offering promising potential for combating drug-resistant bacterial infections. Full article

Hydrogel materials have become an efficient, bioactive, and multifunctional alternative with great potential for biomedical applications. In this work, photoactive films were successfully designed for optical processing, and their photoactivity was tested in photodynamic therapy (PDT), such as antimicrobial patches. The stimulus-response hydrogel films are made of a hydrophilic polymer based on vinyl monomers, specifically 2-hydroxyethyl methacrylate (HEMA) and acrylamide (AAm), in a 1:1 molar ratio, along with the photochromic agent, 3,3-dimethylindolin-6′-nitrobenzoespiropirano (BSP), and a crosslinking agent, N,N’-methylenebisacrylamide (MBA). These hydrogel films were successfully created using the photoinitiator 2-hydroxy-4′-(2-hydroxyethoxy)-2-methylpropiophenone (IRGACURE 2959), MBA, and BSP in different concentrations (0.1, 0.3, and 0.5 mol%), which were later tested in photodynamic therapy (PDT) with the photosensitizer Ru(bpy)₂²⁺ against Staphylococcus aureus. The results showed that, while free Ru(bpy)₂²⁺ needed concentrations of 4–8 µg/mL to eliminate methicillin-sensitive (MSSA) strains, only partial inactivation was achieved for methicillin-resistant (MRSA) strains. The addition of the hydrogel films with BSP improved their effectiveness, lowering the minimum inhibitory concentration (MIC) to 2 µg/mL to fully inactivate MSSA and MRSA strains. These findings demonstrate that the combined use of hydrogel films containing BSP and Ru(bpy)₂²⁺ within a hydrogel matrix not only boosts antimicrobial activity but also highlights the potential of these photoactive films as innovative photosensitive antimicrobial coatings. This synergistic effect of BSP and Ru(bpy)₂²⁺ indicates that these materials are promising candidates for next-generation antimicrobial coatings and creative photosensitive materials. Full article

Methicillin-resistant Staphylococcus aureus (MRSA), characterized by high-level β-lactam resistance and increasing multi-drug resistance, poses a severe and growing global threat to human health and public safety. This review examines MRSA’s complex resistance mechanisms, including mecA/mecC-mediated expression of low-affinity PBP2a, regulatory roles of auxiliary genes like fem and vanA, enzymatic inactivation by β-lactamases and modifying enzymes, efflux pump activity, and biofilm formation. We also systematically review novel therapeutic strategies, such as combination therapies, phage-derived biofilm disruptors, membrane-targeting silver nanoparticles, cell-penetrating antimicrobial peptides, colonization-competitive probiotics, and antibiotic-synergizing phytochemicals. These advances provide critical insights for developing effective countermeasures against MRSA, while highlighting the urgent need for global collaboration, antibiotic stewardship, and innovative drug development to combat antimicrobial resistance. Full article

Methicillin-resistant Staphylococcus aureus (MRSA) and carbapenem-resistant Acinetobacter (CRA) cause significant mortality and morbidity among the elderly population. We conducted a territory-wide point prevalence survey in Hong Kong to estimate the prevalence of MRSA and resistant Acinetobacter among residents of residential care homes of the elderly (RCHEs). A total of 26 RCHEs with 1529 residents were recruited, including 20 private homes and 6 non-private homes. The size of the homes ranged from 13 to 135 residents, with a median of 57 residents. Overall, the prevalence rates of MRSA, CRA, and multidrug-resistant Acinetobacter were 33.9% (95% CI: 31.5–36.3%), 8.1% (95% CI: 6.8–9.6%), and 0.8% (95% CI: 0.4–1.4%), respectively. Private homes had a greater prevalence of MDROs than non-private homes did, whereas RCHEs in the Hong Kong region had a greater prevalence of most resistant organisms, followed by those in the Kowloon region and then those in the New Territories. We detected a high prevalence of MRSA during the COVID-19 pandemic, with additional information on CRA that was not previously known. Continuous surveillance and stringent infection control measures are needed to combat these resistant pathogens among this vulnerable population. Full article

Introduction: Staphylococcus aureus is a high-priority foodborne pathogen contributing to several food poisoning outbreaks. Methicillin- and vancomycin-resistant S. aureus (MRSA and VRSA), pose significant public health concerns due to their potential for serious illness, antibiotic resistance, and transmission within both healthcare and community settings. These bacteria can cause numerous infections, ranging from skin and soft tissue infections to life-threatening conditions like bloodstream infections, pneumonia, and endocarditis. Although several publications are concerned with Staphylococcus aureus contamination in ready-to-eat (RTE) food products, little published data is available about its prevalence in pizza, which is widely distributed and consumed worldwide. Methods: The current study is intended to determine the prevalence, virulence genes, and antimicrobial resistance profiles of S. aureus in three hundred ready-to-eat pizza samples (100 each of meat, chicken, and canned tuna pizzas) collected from different restaurants in Mansoura City, Egypt. The typical colonies on Baird–Parker selective agar supplemented with egg yolk tellurite emulsion were counted and further confirmed based on Gram staining, coagulase testing, catalase testing, carbohydrate fermentation, and thermostable nuclease production. The genomic DNA of the confirmed coagulase-positive isolates was prepared and subjected to PCR analyses for detecting the nuc gene, mecA (methicillin resistance gene), and vancomycin resistance gene (vanA), as well as six selected S. aureus virulence genes: sea, seb, sec, sed, hla, and tsst. The antimicrobial resistance profile of the S. aureus isolates was determined against 16 antimicrobial agents belonging to six classes using the agar disc diffusion method according to the Clinical and Laboratory Standards Institute guidelines (CLSI), except for oxacillin and vancomycin, which were assessed using the MIC test. Results: The results revealed that 56% (56/100), 56% (56/100), and 40% (40/100) of chicken, meat, and canned tuna pizzas were positive for S. aureus, with an overall prevalence of 50.7% (152/300). All 560 isolates (100%) were verified as S. aureus based on molecular confirmation of the nuc gene. Interestingly, 48.6% (272/560) and 8.6% (48/560) of the isolates tested were identified as methicillin- and vancomycin-resistant S. aureus (MRSA and VRSA) through detection of mecA and vanA genes, respectively. Among the S. aureus isolates tested, the hla gene was detected in 87.1% (488/560), while the enterotoxin genes sea, seb, sec, and sed were identified in 50% (280/560), 78.6% (440/560), 9.8% (55/560), and 24.5% (137/560) of isolates, respectively. All recovered isolates (n = 560) were classified as multidrug-resistant and were resistant to penicillin, oxacillin, and ampicillin. Moreover, 77% (431/560), 24% (134/560), 8% (45/560), and 8.6% (48/560) of isolates were resistant to cefotaxime, ciprofloxacin, azithromycin, and vancomycin, respectively. Conclusions: The current study emphasizes that ready-to-eat pizza is highly contaminated with multidrug-resistant S. aureus, highlighting the urgent need for rationalizing antibiotic use in both veterinary and human medicine to prevent the transmission of resistant bacteria through the food chain. Additionally, strict adherence to good hygienic practices throughout all stages of the food chain is essential to minimize overall contamination and enhance food safety. Full article

Chronic wounds pose a great challenge due to their slow healing and susceptibility to infections, hence the need for innovative alternatives to conventional antibiotics, as increasing bacterial resistance limits the efficacy of current treatments. This paper addresses the development of novel electrospun membranes based on polyvinyl alcohol (PVA) and sodium alginate, incorporating therapeutic ZnO and bioglass (54SiO₂:40CaO:6P₂O₅) nanoparticles. While nanocomposites presented smaller fiber diameters than pure polymers, ternary nanocomposites displayed higher values, e.g., in porous areas, values were in the ca. 80–240 nm range and 0.06–0.60 μm², respectively. The Young’s modulus of the PVA/SA membrane, initially 15.9 ± 2.0 MPa, decreased by 65% with 10 wt.% ZnO NPs, whereas 10 wt.% BG NPs increased it by 100%. The membranes demonstrated efficacy against Gram-positive bacteria, including methicillin-resistant Staphylococcus aureus (MRSA) isolated from a human wound secretion, as well as two ATCC strains: Staphylococcus aureus and Staphylococcus epidermidis. A cell viability assay conducted with HaCaT cells demonstrated nearly complete survival following 72 h of membrane exposure. Their combined Gram-positive antibacterial activity and cytocompatibility support their potential application as biofunctional dressings for the management of chronic and hospital-acquired topical infections, while also contributing to the global effort to combat antibiotic resistance. Full article

Background/Objectives: Methicillin-resistant Staphylococcus aureus (MRSA) infections remain a significant challenge in healthcare. Conventional and molecular techniques used for MRSA identification are either time-consuming or costly. Alternatively, Matrix-Assisted Laser Desorption/Ionization Time-Of-Flight Mass Spectrometry (MALDI-TOF MS) offers a rapid method for microbial identification and has the potential to detect biomarkers that distinguish methicillin resistance in S. aureus isolates. The aim of this study was to identify methicillin-resistant discriminative biomarkers for S. aureus obtained using MALDI-TOF MS. Methods: A systematic review was conducted by searching databases such as PubMed and Web of Science for studies that focused on MRSA detection with biomarkers by MALDI-TOF MS, including all relevant studies published up to July 2024. The review protocol was registered in PROSPERO registry. Results: A total of 15 studies were selected for analysis. Data were extracted on study location, sample size, MALDI-TOF MS analyzer, sample preparation, methicillin resistance and sensitivity biomarkers, and the use of Artificial Intelligence (AI) models. Notably, PSM-mec and delta toxin were frequently reported as informative biomarkers, detectable at 2414 ± 2 Da and 3006 ± 2 Da, respectively. Additionally, eight studies used AI models to identify specific biomarkers differentiating methicillin-resistant and methicillin-sensitive strains, based on differences in peak intensities or the exclusive presence of certain peaks. Moreover, two studies employed detection of MRSA in low concentrations from biological samples and others employed an optimized matrix solution for improved analysis. Conclusions: Overall, MALDI-TOF MS is not only a powerful tool for the identification of bacterial isolates but also shows strong potential for rapid, cost-effective detection of methicillin resistance in S. aureus through biomarker analysis. Given that it is already implemented in several clinical laboratories, this approach could be adopted without significant additional cost. Full article

Background/Objectives: Methicillin-resistant Staphylococcus aureus (MRSA) remains a critical public health concern due to its multidrug resistance and capacity to form persistent infections, particularly in the context of implanted medical devices. Alternative therapeutic strategies that target bacterial virulence instead of viability are increasingly explored. This study aimed to evaluate the antimicrobial and antivirulence activity of an extract derived from Lacticaseibacillus rhamnosus CRL 2244 against two MRSA strains—USA300 and M86—and to elucidate its effects on bacterial physiology and gene expression under host-mimicking conditions. Methods: Antimicrobial activity was assessed using agar diffusion, MIC, and time-kill assays. Scanning electron microscopy of cells exposed to the extract confirmed decreased cellular density and morphological changes. Phenotypic assays evaluated biofilm formation, staphyloxanthin production, and adhesion to fibronectin. RT-qPCR analyzed transcriptional responses. Viability was assessed in the presence of human serum and type I collagen. Results: The CRL 2244 extract demonstrated bactericidal activity with up to 6-log₁₀ CFU/mL reduction at 1× MIC. In USA300, the extract reduced the expression of hla, lukAB, fnbA, and icaA, correlating with decreased staphyloxanthin levels. In M86, a significant reduction in biofilm formation and repression of lukAB, nucA, and fnbA were observed. Adhesion to fibronectin was impaired in both strains. The extract showed no cytotoxicity in human serum but reduced viability in collagen-enriched conditions. Conclusions: The Lcb. rhamnosus CRL 2244 extract modulates MRSA virulence in a strain-specific manner, targeting key regulatory and structural genes without inducing cytotoxic effects. Full article

Bovine mastitis, particularly that caused by Staphylococcus aureus, presents a major challenge to dairy production worldwide due to its economic impact, animal welfare concerns, and zoonotic potential. This narrative review synthesizes current literature on the epidemiology, pathogenesis, resistance patterns, and control strategies related to S. aureus-associated mastitis in dairy cattle. It highlights the pathogen’s virulence mechanisms, such as biofilm formation, immune evasion, and toxin production, that facilitate persistent infections. The review compiles global prevalence data, revealing significant geographic variation and disparities between clinical and subclinical cases. Antimicrobial resistance, especially the emergence of methicillin-resistant S. aureus (MRSA), is extensively examined alongside resistance gene profiles. Diagnostic approaches, including culture, PCR, MALDI-TOF MS, and AI-based systems, are evaluated for their sensitivity and field applicability. Additionally, the review addresses public health implications, zoonotic risks, and One Health perspectives, culminating in an exploration of prevention strategies, including improved hygiene, vaccination, dry cow therapy, and AI-driven herd management. The findings emphasize the urgent need for integrated surveillance, precision diagnostics, and targeted interventions to mitigate the burden of S. aureus mastitis. Full article

Combining antibiotics with propolis is an effective method to combat bacterial drug resistance. Nanoparticles are of interest in the antimicrobial field because of their higher drug stability, solubility, penetration power, and treatment efficacy. In this study, propolis nanoparticles (PNPs) were synthesized, and their antibacterial and anti-biofilm activities against methicillin-resistant Staphylococcus aureus (MRSA) in combination with ampicillin sodium (AS) were analyzed. The PNPs had an average particle diameter of 118.0 nm, a polydispersity index of 0.129, and a zeta potential of −28.2 mV. The fractional inhibitory concentration indices of PNPs and AS against tested MRSA strains highlighted this synergy, ranging between 0.375 and 0.5. Crystal violet staining showed that combined PNPs and AS significantly inhibited biofilm formation and reduced existing biofilm biomass. We then discovered that PNPs inhibited bacterial adhesion, extracellular polysaccharide synthesis, and mecR1, mecA, blaZ, and icaADBC gene expression. These results indicated that PNPs exerted a synergistic antibacterial effect with AS by inhibiting mecR1, mecA, and blaZ gene expressions to reduce the drug resistance of MRSA. Meanwhile, PNPs weakened bacterial adhesion and aggregation by suppressing icaADBC gene expression, allowing antibiotics to penetrate the biofilm, and exhibiting significant synergistic anti-biofilm activity. In summary, PNPs are promising candidates for combating MRSA-related diseases. Full article