Search Results (548)

Antimicrobial resistance and the formation of biofilms in Gram-positive pathogens such as Streptococcus pneumoniae and Staphylococcus aureus are making the treatment of infections increasingly difficult. This study systematically evaluates the effect of gliotoxin (GT), an antimicrobial metabolite produced by Aspergillus fumigatus, on bacterial growth and biofilm formation, as well as its activity in combination with antibiotics. Three strains of S. pneumoniae and two strains of S. aureus (one methicillin-susceptible and one methicillin-resistant) were analysed. Planktonic growth was examined, and biofilm prevention assays were conducted by assessing biomass via crystal violet staining and viable cell counts. In addition, the combined effect of GT with cefotaxime and vancomycin was evaluated. GT inhibited planktonic growth and significantly reduced the biomass and viability of biofilms in a concentration-dependent manner. Moreover, its combination with conventional antibiotics (cefotaxime or vancomycin) showed strong synergy, drastically decreasing bacterial survival. These findings highlight the potent antibacterial and anti-biofilm activity of GT and its ability to enhance antibiotic efficacy, providing insight into fungal–bacterial interactions and suggesting potential therapeutic applications. Full article

Background/Objectives: Methicillin-resistant Staphylococcus aureus (MRSA) is a major therapeutic challenge due to its extensive antibiotic resistance. This study examined how bacteriophage exposure affects the genome, proteome and antibiotic susceptibility of a clinical MRSA isolate. Methods: The MRSA isolate was exposed to the PYOFAG bacteriophage cocktail, and small colony variants (SCVs) of the surviving bacteria were compared with the untreated parental strain by phenotypic testing, whole-genome sequencing, comparative proteomics, and transmission electron microscopy. Results: Phage exposure induced marked remodeling in MRSA, including altered growth, colony morphology, and increased susceptibility to various antibiotics, especially β-lactams and aminoglycosides. Genomic analysis identified multiple mutations and the loss of two genomic regions, including changes in tarS, a gene linked to wall teichoic acid glycosylation, phage adsorption, and β-lactam resistance. Proteomic analysis revealed broad changes in metabolic, stress-response, and cell-envelope-associated pathways. Transmission electron microscopy showed a significant reduction in cell wall thickness after phage treatment. Conclusions: Bacteriophage exposure drives phenotypic and molecular adaptation in MRSA and may create evolutionary trade-offs that weaken resistance mechanisms. These findings support the potential of bacteriophages as both direct antibacterial agents and modulators of antibiotic susceptibility. Full article

Background/Objectives: In methicillin-susceptible Staphylococcus aureus (MSSA) bacteremia, randomized evidence indicates comparable efficacy of cefazolin and antistaphylococcal penicillins with less nephrotoxicity; whether this extends to bone and joint infection (BJI) is unknown. We compared both agents in MSSA BJI. Methods: We retrospectively analyzed all adults at a single center with culture-confirmed, monomicrobial MSSA BJI treated with inpatient intravenous cefazolin or flucloxacillin monotherapy (January 2022–January 2025)—a selected population excluding rifampicin-based combination therapy, outpatient parenteral therapy, polymicrobial infection, and concurrent bacteremia/endocarditis. Endpoints, a priori exploratory, comprised effectiveness (mortality; clinical success) and renal safety (peri-treatment acute kidney injury [AKI]); the AKI comparison was additionally adjusted for confounders. Results: Among 110 patients (64 cefazolin, 46 flucloxacillin), baseline characteristics were comparable except for more frequent nephrotoxic co-medication with cefazolin (56.2% vs. 26.1%; p = 0.002). No statistically significant differences in effectiveness were detected: 30-day clinical success was 89.1% versus 80.4% (ARD 8.6 percentage points, 95% CI −4.7 to +23.3) and one-year clinical success 79.7% versus 65.2% (ARD 14.5, 95% CI −2.2 to +31.0); these imprecise estimates are compatible with effects ranging from no difference to a clinically relevant benefit of cefazolin. Peri-treatment AKI occurred in 19.0% versus 30.4% (ARD 11.4, 95% CI −4.7 to +27.7; adjusted odds ratio 2.27, 95% CI 0.87–5.91); the difference was confined to stage 1. Conclusions: In this selected inpatient monotherapy cohort, cefazolin was associated with numerically fewer AKI events, without statistically significant differences in any comparison. These exploratory findings support cefazolin as a rational targeted option for MSSA BJI, pending prospective confirmation. Full article

Background: Community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) infections are increasingly reported among gay, bisexual, and other men who have sex with men (GBMSM) engaging in chemsex, yet data remain limited. This ambispective cohort study conducted at Hospital Clínic of Barcelona (2018–2024) aimed to characterize CA-MRSA infections among GBMSM living with HIV. Methods: Epidemiological, behavioral, and clinical data were collected from medical records and standardized questionnaires. MRSA isolates from clinically indicated samples were identified by mass spectrometry and underwent antimicrobial susceptibility testing. Results: Among 446 participants, 62 (14%) were diagnosed with CA-MRSA, accounting for 109 infection episodes over a median follow-up of 3.21 years (IQR 1.39–5.05). All episodes involved skin and soft-tissue infections; 17% required hospitalization, 35% surgery, and 51% received non-active empirical antibiotics. Recurrent infections occurred in 32% of participants, and detectable HIV viral load was present in 28% of episodes. High levels of polydrug use were reported. Resistance to clindamycin (33%), cotrimoxazole (23%), and mupirocin (96%) was observed. Decolonization was attempted in 65% of participants. Conclusions: CA-MRSA infections were frequent, with substantial recurrence and antimicrobial resistance. These findings highlight challenges for infection control and antimicrobial stewardship and support further evaluation of preventive and decolonization strategies in this population. Full article

Staphylococcus aureus is one of the leading causes of both community- and healthcare-associated infections. Nasal colonization constitutes the primary reservoir for subsequent infection and transmission, while methicillin-resistant Staphylococcus aureus (MRSA) remains a major public health concern because of its resistance to multiple antimicrobial agents. However, data regarding community nasal colonization in rural Portuguese populations remain scarce. The BI-STAPH Project was established to address this knowledge gap through systematic surveillance of rural communities in inland Portugal. To estimate the prevalence of presumptive nasal colonization by Staphylococcus aureus and MRSA among adults living in the municipality of Fundão, Portugal, and to explore potential associations between colonization and demographic, behavioural, occupational, and environmental characteristics. A prospective community-based cross-sectional study was conducted as the second phase of the BI-STAPH Project. A total of 200 adults were recruited from different parishes of the municipality of Fundão. Bilateral nasal swabs were collected and processed using standardized microbiological methods for the presumptive identification of S. aureus. Presumptive MRSA isolates were investigated using a PBP2′ latex agglutination assay. Sociodemographic and exposure-related information was obtained through structured questionnaires. Associations between presumptive colonization and participant characteristics were evaluated using Pearson’s chi-square or Fisher’s exact tests, as appropriate. Presumptive S. aureus nasal colonization was identified in 56 of 200 participants, corresponding to a prevalence of 28.0% (95% CI: 21.8–34.2%). No presumptive MRSA-positive isolates were identified, corresponding to an observed prevalence of 0% (95% CI: 0.0–1.8%). Colonization prevalence was 29.5% among females and 26.8% among males, and ranged from 25.8% to 31.1% across age groups; neither sex nor age was significantly associated with colonization. Participants reporting daily animal contact had a colonization prevalence of 32.3%, compared with 20.5% among those without animal contact, but this difference was not statistically significant (p = 0.075). Overall, no statistically significant associations were identified between presumptive S. aureus colonization and the demographic, behavioural, occupational, or environmental variables evaluated. Presumptive S. aureus nasal colonization was common among adults living in the rural municipality of Fundão, Portugal, whereas no presumptive MRSA-positive isolates were identified in this study population. No statistically significant associations were observed between colonization and the characteristics evaluated. These findings expand the epidemiological evidence generated by the BI-STAPH Project and support continued community-based surveillance of S. aureus in rural Portugal. Future multicentre studies incorporating molecular confirmation, antimicrobial susceptibility testing, and larger populations will be important to better characterize circulating strains and transmission patterns within a One Health framework. Full article

Staphylococcus aureus is a major contagious pathogen causing bovine mastitis, with persistence and antimicrobial resistance posing ongoing challenges in dairy herds. From July 2022 to July 2023, 942 mastitis milk samples (267 clinical, 675 subclinical) from 10 farms in northwestern China yielded 98 S. aureus isolates (10.4%), which were characterized by whole-genome sequencing, antimicrobial susceptibility testing, biofilm assays, and virulence profiling. Ten sequence types, seven clonal complexes, and 16 spa types were identified, dominated by ST1 (42.9%) and ST97 (24.5%). ST1 was mainly associated with subclinical mastitis, whereas ST97 was enriched in clinical cases; a novel ST9955 (13.3%) was exclusively detected in subclinical isolates. No methicillin-resistant S. aureus was detected. Resistance was most frequently observed to penicillin (42.9%), erythromycin (28.6%), clindamycin (22.4%), and tetracycline (10.2%), with higher rates in clinical isolates. 65.3% of isolates exhibited strong biofilm-forming ability, which was significantly more frequent in subclinical cases (70.3% vs. 55.9%, p < 0.05). Virulence genes showed conserved adhesion/biofilm determinants but lineage-dependent distribution of immune evasion and toxin genes, with stable co-occurrence among capsule, biofilm, T7SS, iron acquisition, and immune evasion loci. Overall, the population was diverse but strongly lineage-structured, dominated by a few successful clones, highlighting the value of lineage-resolved surveillance for understanding and controlling bovine mastitis. Full article

Antarctic marine-derived fungi represent an underexplored reservoir of bioactive secondary metabolites shaped by extreme environmental pressures. In this study, nine fungal isolates obtained from Antarctic macroalgae, lichens, sponge tissue, and sediments were evaluated for their antimicrobial, anticancer, antibiofilm, and metabolomic profiles. Untargeted LC–MS/MS molecular networking (GNPS) revealed a chemically rich metabolome, dominated by alkaloids, followed by polyketides, meroterpenoids, and diketopiperazines, with Penicillium crustosum (A15A) emerging as a major biosynthetic contributor. The annotation of structurally diverse metabolites, including roquefortines, viridicatin derivatives, andrastins, and multiple diketopiperazines, highlights the metabolic plasticity of Antarctic fungi. Anticancer evaluation indicated cytotoxicity, with Aspergillus awamori (A30), Alternaria malorum (A36), and Cladosporium malorum (A38) displaying activity toward HCT 116 colorectal cancer cells at IC₅₀ ≥ 30 µg/mL. Extracts were screened against methicillin-resistant Staphylococcus aureus (MRSA, COL), methicillin-susceptible S. aureus (MSSA, NCTC8325 4), and Escherichia coli K12, revealing low to no activity against these pathogens. Six of the nine isolates exhibited strong antibiofilm activity without inhibiting planktonic bacterial growth, indicating selective biofilm inhibition against MSSA and meeting the criteria for clinical developmental “hits”. Biofilm inhibition ranged from 81.10% to 98.50%, with A15A showing the highest activity (98.50% at 250 µg/mL), followed by A36 (91.16% at 31.35 µg/mL). Botrytis sp. (A22A), P. chrysogenum (A7), Ulocladium microsporum (A24B), and A30 also demonstrated strong antibiofilm activity (81.10–85.89%). To our knowledge, this is the first report describing antibiofilm activity of Antarctic fungal extracts. Full article

Background/Objectives: Staphylococcus argenteus is a recently recognized member of the Staphylococcus aureus complex that is almost identical to S. aureus phenotypically and by 16S rRNA gene sequences. Although genomic analyses demonstrate that S. argenteus is phylogenetically distinct from S. aureus, the two species exhibit more than 90% nucleotide identity and routine identification methods—including routine biochemical assays and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS)—cannot reliably distinguish between the two. We develop and validate a MALDI-TOF MS-based model for accurate identification of S. argenteus. Methods: A multiplex PCR assay targeting crtM and NRPS genes served as the reference standard. MALDI-TOF MS spectra from 25 S. argenteus and 25 methicillin-susceptible S. aureus (MSSA) isolates were analyzed using ClinProTools to identify characteristic peaks and develop the identification model. The model was validated using 40 S. argenteus and 80 MSSA isolates, then applied to 130 randomly selected clinical isolates. Results: Five characteristic peaks—m/z values 5005, 5285, 5323, 6440, and 6526—were identified. Isolates exhibiting at least 4 of these 5 peaks were classified as S. argenteus; those exhibiting fewer than 4 were classified as S. aureus. The model achieved 100% specificity and 100% sensitivity in both the development and validation phases. In the clinical application phase, the model correctly classified all isolates, whereas conventional MALDI-TOF MS yielded several misidentifications. Conclusions: The identification model, and the simple peak-based rule it is based on, can accurately distinguish S. argenteus from MSSA, offering a practical diagnostic tool for clinical microbiology laboratories. Full article

Raw-milk and raw dairy products remain a high-sensitivity One Health interface because they bypass a major microbial control step and may carry viable foodborne pathogens, bacteria exhibiting antimicrobial resistance (AMR), and AMR genes from dairy animals, farm environments, milking equipment, handlers, storage systems, and informal or direct-sale chains. This narrative review synthesizes verified scientific evidence on raw milk as a potential vehicle pathway for resistant foodborne pathogens, clinically relevant opportunistic bacteria, indicator organisms, and AMR determinants, and evaluates AMR-related emerging public health risks through a One Health perspective. The review integrates evidence from outbreak investigations, raw milk and raw dairy surveillance, culture-based antimicrobial susceptibility testing, polymerase chain reaction (PCR), whole-genome sequencing (WGS), metagenomics, metaproteomics, risk assessment, and the consumer-risk literature. The synthesis shows that raw-milk-associated AMR evidence should be interpreted by inference level rather than by a single organism or global prevalence estimate. Public health concern becomes stronger when detection or occurrence is supported by viable recovery, plausible consumer exposure, transmission linkage, infection or colonization evidence, source-attribution data, or quantified burden estimates. Evidence is strongest for exposure pathways involving Campylobacter, extended-spectrum beta-lactamase (ESBL)-producing Enterobacterales, methicillin-resistant Staphylococcus aureus (MRSA), Salmonella, Listeria, Enterococcus, Yersinia, and raw-milk resistomes, although causal strength differs across organism groups and study designs. The review distinguishes detection or occurrence, viable recovery, potential exposure, transmission, infection or colonization, source attribution, and attributable AMR burden. One Health control requires mastitis prevention, prudent antimicrobial use, milking hygiene, environmental monitoring, pasteurization or equivalent exposure barriers, WGS-supported outbreak investigation, integrated surveillance, and targeted risk communication. Full article

Background: Preoperative screening for methicillin-resistant Staphylococcus aureus (MRSA) and methicillin-susceptible S. aureus (MSSA) is intended to identify patients at increased risk of surgical site infection and guide decolonization and perioperative antimicrobial prophylaxis. However, many molecular assays reduce this decision to a binary positive/negative result, potentially obscuring clinically important distinctions in organism identity, methicillin resistance attribution, and mupirocin resistance risk. Methods: This structured narrative review organized direct perioperative evidence and indirect mechanistic, implementation, and economic evidence around one question: how MRSA/MSSA screening can move from organism detection to actionable molecular triage. Results: Useful preoperative reporting depends on assigning resistance markers to the correct organism. The proposed multi-target NAAT framework organizes concordant and discordant molecular patterns into provisional reportable categories, including MSSA, MRSA, methicillin-resistant non-aureus Staphylococcus/CoNS, mixed populations, SCCmec dropout patterns, mupirocin resistance marker states, and invalid or indeterminate results. No externally validated composite score, universal molecular cutoff, or prospectively validated target-to-action decision rule currently links all of these categories to specific perioperative actions. Conclusions: Preoperative MRSA/MSSA screening may benefit from moving beyond binary reporting, but the framework presented here is a development-stage rule set rather than a validated clinical decision instrument. Assay-specific analytical thresholds, locked target combination rules, and prospective clinical and implementation validation are required before the framework can be used to assign patients reproducibly to management pathways. Until such validation is completed, the proposed categories should be interpreted as a testable reporting and validation architecture rather than as universal prophylaxis or decolonization instructions. Full article

Background/Objectives: Diabetic foot infections (DFI) drive most non-traumatic lower-limb amputations, and empirical regimens must track local microbiology, which is itself evolving under broad-spectrum antibiotic pressure. Methods: We retrospectively analysed all consecutive bacterial cultures from clinically infected diabetic foot lesions at a single Polish outpatient centre over 2021–2025. Isolates were identified by MALDI-TOF mass spectrometry and susceptibility was interpreted under contemporaneous EUCAST breakpoints (v12.0–v15.0). Results: A total of 274 cultures yielded 443 isolates (polymicrobial index 1.62). Staphylococcus aureus remained the most common pathogen but fell from 55.0% to 38.9% of cultures, while Enterobacterales rose from 36.1% to 47.7% of all isolates. Proteus mirabilis and Streptococcus agalactiae emerged as major contributors, and Enterobacter hormaechei showed an apparent increase (the apparent rise in E. hormaechei reflects, at least in part, improved species-level identification rather than a true increase in incidence). Methicillin-resistant S. aureus was first documented in 2025 (6/38; 15.8%). P. mirabilis showed deteriorating activity against trimethoprim–sulfamethoxazole and ciprofloxacin, the first meropenem-resistant isolate appeared in 2025, and two carbapenem-non-susceptible Enterobacterales were also detected (2/18 carbapenem-tested isolates in 2025; 11%). Conclusions: The DFI profile has shifted from an S. aureus-dominated Gram-positive ecology toward a polymicrobial, increasingly Gram-negative one, with the first documentation of MRSA (on reintroduction of routine oxacillin testing) and of carbapenem-non-susceptible Enterobacterales. Empirical policy for moderate-to-severe DFI should reliably cover Enterobacterales and methicillin-resistant Gram-positives while preserving carbapenems and glycopeptides through active stewardship. Full article

Joint aspiration remains the gold standard and an urgent step in the diagnosis of paediatric septic arthritis (SA). Unlike in acute haematogenous osteomyelitis, it has both diagnostic and therapeutic value. No previous review has specifically addressed when bacteriological sampling is essential and when it may reasonably be omitted. The bacteriological profile in children is highly age-dependent: Kingella kingae predominates before 4 years of age, whereas Staphylococcus aureus—including Panton–Valentine leukocidin (PVL)-producing and methicillin-resistant (MRSA) strains—predominates thereafter. We critically review the evidence through nine clinical questions and propose a conceptual risk-stratified framework in which the sampling approach is tailored to age and clinical context. In children younger than 4 years with a positive oropharyngeal K. kingae PCR and a mild clinical presentation—defined as CRP < 20 mg/L, absence of fever, and preserved weight-bearing—non-invasive confirmation may be sufficient. This proposal is explicitly hypothesis-generating: it is derived from observational data, it has not been validated prospectively, and it is not endorsed by current PIDS/IDSA or ESPID guidance. A positive oropharyngeal PCR alone is never sufficient, given the 10–12% asymptomatic carriage rate and the limited reliability of the Kocher–Caird criteria in this age group; the decision requires a cluster of concordant findings together with mandatory clinical and laboratory reassessment at 48–72 h and a low threshold for escalation to arthrocentesis. In children older than 4 years, arthrocentesis under general anaesthesia remains the standard approach, with pathogen identification and antimicrobial susceptibility testing as the primary microbiological determinants of therapy and toxin profiling as an adjunctive investigation in selected cases. Full article

Staphylococcus aureus causes infections ranging from skin and soft tissue infections to life-threatening systemic disease. The convergence of virulence determinants with antimicrobial resistance, particularly in methicillin-resistant S. aureus (MRSA), complicates management. In the United Arab Emirates (UAE), S. aureus is a major contributor to community- and hospital-acquired infections, and regional surveillance from the Gulf Cooperation Council has documented a shift toward community-associated MRSA lineages. Despite this clinical burden, granular molecular epidemiological data from the UAE remain scarce. Fifty consecutive S. aureus clinical isolates were obtained from Thumbay Laboratories, Ajman, UAE (October 2022–August 2023). Identification and antimicrobial susceptibility testing against 23 agents were performed on the MicroScan WalkAway system. Five virulence genes, namely mecA, Panton-Valentine leukocidin (PVL; lukF-S), exfoliative toxins A (eta) and B (etb), and toxic shock syndrome toxin (tst), were detected by conventional PCR. PVL was the most prevalent virulence gene (48%, 24/50), detected exclusively in pus isolates. mecA carriage, confirming MRSA, was identified in 44% (22/50), with PVL–mecA co-occurrence in 22% (11/50). eta was present in 6% (3/50), and etb and tst each in 2% (1/50). Resistance was highest for ampicillin and penicillin (86% each), while full susceptibility (100%) was retained for vancomycin, linezolid, daptomycin, teicoplanin, rifampin, Synercid, and trimethoprim. mecA carriage was significantly associated with resistance to amoxicillin, clavulanate, ampicillin, imipenem, penicillin, oxacillin, azithromycin, erythromycin, and ciprofloxacin (p < 0.05). This study provides the first integrated molecular characterization of key S. aureus virulence determinants, along with a comprehensive antimicrobial susceptibility profile in the UAE. The high PVL prevalence and substantial MRSA burden highlight the need for structured regional surveillance and antimicrobial stewardship, while retained susceptibility to last-resort agents offer actionable guidance for empirical therapy. Full article

Background/Objectives: This study aimed to evaluate and compare the clinical characteristics and outcomes of patients with methicillin-susceptible Staphylococcus aureus (MSSA) and streptococcal native joint septic arthritis (NJSA). Methods: This retrospective multicenter study included adult patients with NJSA from three tertiary care hospitals between 2004 and 2023. Patients were categorized into three groups based on bacterial virulence and differences among streptococcal species: MSSA, non-viridans streptococci, and viridans streptococci. Results: A total of 213 NJSA cases were identified, comprising 164 MSSA, 35 non-viridans streptococcal, and 14 viridans streptococcal cases. Non-viridans streptococcal NJSA exhibited significantly more acute clinical features associated with systemic inflammation, including frequent fever, leukocytosis, thrombocytopenia, elevated C-reactive protein levels, higher total bilirubin levels, and acute kidney injury, compared to MSSA and viridans streptococcal NJSA. The clinical presentations were similar between the MSSA and viridans streptococcal groups. The non-viridans streptococcal group showed a higher incidence of concomitant bacteremia, but a lower proportion of positive joint culture results. Treatment approaches were consistent across the groups, except for a shorter duration of antibiotic therapy in the viridans group. Treatment failure rates were comparable: 9.8% for MSSA, 14.3% for non-viridans streptococci, and 21.4% for viridans streptococci. Conclusions: This study highlights the heterogeneous nature of streptococcal NJSA, with non-viridans streptococci presenting more aggressive clinical manifestations despite similar treatment responses across groups. These findings challenge conventional views on streptococci as a less virulent pathogen than MSSA and emphasize the need for diagnostic and management strategies tailored to the unique pathogenic traits of these bacteria. Full article

Background: Fish and seafood products may act as vehicles for the dissemination of antimicrobial-resistant bacteria through the food chain. Particular concern is associated with methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin-resistant enterococci (VRE). This study evaluated the occurrence of S. aureus, Enterococcus spp., and presumptive MRSA and VRE in retail fish and seafood products using culture-based screening methods. Methods: A total of 99 fish and seafood samples purchased from retail outlets in northern Poland were analyzed using selective microbiological culture methods. Presumptive MRSA and VRE were screened on chromogenic selective media. Differences between product categories were assessed using non-parametric statistical tests and chi-square analysis. Results: S. aureus was detected in 80.8% of samples, with significantly higher contamination levels in seafood than in fish (p = 0.002). Presumptive MRSA isolates were detected in 27.3% of samples. Enterococcus spp. were found in 49.5% of samples, with significantly higher prevalence and counts in unpackaged products (p < 0.05). Presumptive VRE isolates occurred in 17.2% of samples, while simultaneous occurrence of presumptive MRSA and VRE was observed in 9.1% of samples. Conclusions: Retail fish and seafood products may constitute a reservoir of presumptive antimicrobial-resistant bacteria. The higher contamination of unpackaged products highlights the importance of hygienic handling practices. Molecular confirmation and antimicrobial susceptibility testing are needed to further assess the public health significance of these microorganisms. Full article