Search Results (4,830)

Moraxella osloensis is an infrequently reported component of the human skin microbiota, but it has recently been recognized as a potential source of intraoperative contamination. Its pathogenic role remains poorly defined, particularly in shoulder arthroplasty. This study describes the recovery and characterization of M. osloensis from intraoperative periprosthetic tissue samples collected immediately after reverse total shoulder arthroplasty in five patients. All isolates exhibited low colony counts (10–50 CFU/mL), were uniformly susceptible to the antimicrobial agents tested, and did not produce β-lactamases. Biofilm formation—an important virulence determinant in periprosthetic joint infections—was detected in two of the five isolates. Clinically, no patient developed postoperative infection within 12 months, and only one experienced a transient superficial wound-healing delay, which resolved with a short administration of oral antibiotics. These findings indicate that M. osloensis may be present in the operative field despite stringent skin preparation and aseptic protocols, likely reflecting endogenous colonization rather than environmental contamination. Although its clinical impact appears limited in this context, the bacteria’s biofilm-forming potential and underrecognized presence in the operating room underscore the importance of continued surveillance and careful interpretation when isolated from surgical specimens. Full article

This work involved the laboratory modeling of biogenic and biogenically mediated corrosion of AISI 304 stainless steel under geochemical conditions representative of the geological disposal of radioactive waste at the Yeniseisky site (Russia). Experiments with a single glucose stimulation of a microbial community sampled from a depth of 450 m established that the initial dominance of organotrophic microflora (primarily genera such as Xanthobacterium, Novosphingobium, Hydrogenophaga, and Pseudomonas) during the first stage (up to 30 days) led to the formation of a microbial biofilm. This biofilm resulted in uniform surface corrosion at a rate of up to 16 µm/year, which is more than 30 times higher than the corrosion rate in the abiotic control. This acceleration is attributed to the accumulation of microbial metabolites, including acetate, ethanol, formate, succinate, n-butyrate, and lactate. The subsequent development of chemotrophic iron- and sulfur-cycling microflora (dominated by genera such as Sideroxydans, Pseudomonas, Geobacter, Desulfuromonas, Desulfovibrio, and Desulfomicrobium) during the second stage of microbial succession (days 60–120) led to the formation of a pit density 10 times greater than that in the abiotic control. It is important to note that the maximum corrosion rates and pit densities were observed upon the addition of a mixture of glucose and sulfate. An assessment of the role of various microbial metabolites and medium components using the potentiodynamic method demonstrated that the combined presence of hydrocarbonate, sulfide, and microbial metabolites in the solution caused a more than fivefold increase in the corrosion current. Thus, the results demonstrate the complex nature of corrosion processes under conditions modeling the geological disposal of radioactive waste, where biological and abiotic factors interact, creating a synergistic effect that significantly enhances corrosion. Full article

N-tetradecanoyl-L-homoserine lactone (C₁₄-HSL) is a long-chain signaling molecule belonging to acyl-homoserine lactones (AHLs), which is widely present in the quorum sensing (QS) system of Gram-negative bacteria. In this study, the effects of C₁₄-HSL on chalcopyrite bioleaching mediated by Acidithiobacillus ferrooxidans (A. ferrooxidans) were investigated. After cultivating A. ferrooxidans with different energy substrates and exploring the potential mechanisms of signal molecule production, chalcopyrite was selected as the energy substrate for further study. Molecular docking analysis revealed that the high binding affinity between AHL and the receptor protein AfeR in A. ferrooxidans was beneficial for the activation of transcription by the AfeR-AHL complex, promoting their biological impact. The variations in the physicochemical parameters of pH, redox potential, and copper ions revealed that after adding C₁₄-HSL, the leaching rate of chalcopyrite increased (1.15 times during the initial 12 days). Further analysis of the mechanism of extracellular polymers formation indicated that the presence of C₁₄-HSL could promote the formation of biofilms and the adhesion of bacteria, facilitating mineral leaching rate of A. ferrooxidans. This research provides a theoretical basis for regulating the biological leaching process of chalcopyrite and metal recovery using signaling molecules, which could also be used to control environmental damage caused by acid mine/rock drainage. Full article

Background: Gram-positive bacteria, once considered incapable of producing extracellular vesicles (EVs) due to their thick peptidoglycan layer, are now known to secrete EVs that transport virulence factors and modulate host immunity. These EVs contribute to bacterial pathogenicity by facilitating biofilm formation, immune evasion, and inflammation. Granulicatella adiacens, an oral commensal associated with infective endocarditis, represents a clinically relevant model to study EV-mediated virulence. Objectives: This study’s aim was to investigate whether the proteomic composition and immunomodulatory activity of G. adiacens EVs differ between biofilm and planktonic lifestyles, thereby contributing to distinct pathogenic behaviours. Methods: EVs isolated from G. adiacens CCUG 27809 cultures were characterized using nano LC-ESI-MS/MS, followed by comprehensive bioinformatic and cytokine assays. Results: Quantitative proteomic profiling identified 1017 proteins, revealing distinct signatures between biofilm- and planktonic-derived EVs. Principal component analysis showed clear segregation between the two states, with biofilm EVs enriched in proteins linked to stress adaptation, adhesion, and structural integrity, while planktonic EVs exhibited growth- and metabolism-related proteins. A total of 114 virulence-associated proteins were identified, including several novel candidates. Functionally, EVs from both conditions significantly induced pro-inflammatory cytokines IL-8 and IL-1β in a dose-dependent manner (p < 0.05), whereas IL-17 remained unchanged. Conclusions: G. adiacens EVs exhibit lifestyle-dependent proteomic and immunomodulatory differences, underscoring their role in host–pathogen interactions and endocardial infection. These findings provide a foundation for future mechanistic and in vivo studies exploring EV-mediated virulence and potential therapeutic modulation. Full article

Mycobacterium tuberculosis, the causative agent of tuberculosis, utilizes biofilm formation as a key mechanism to withstand host-derived stresses. To identify novel factors involved in this process, we performed a CRISPRi screen in the model organism Mycobacterium smegmatis. This screen identified trypsin HtrA as a critical factor for growth and biofilm formation. Deletion of htrA led to a profound upregulation of the cell wall amidase Ami3. We demonstrated that Ami3 is a crucial negative regulator of biofilm formation, as overexpression of ami3 recapitulated the biofilm and growth defects of the ΔhtrA strain. Furthermore, we found that the essential role of periplasmic protease HtrA for normal growth could be suppressed by novel mutations in pmt, a gene encoding a phosphomyoinositol mannosyltransferase, at residues F53 and N55, distinct from the previously reported D68 site. Our findings establish a novel regulatory pathway in which HtrA modulates mycobacterial biofilm formation by controlling the levels of Ami3 and reveal new genetic interactions within this network. Full article

Chronic, non-healing wounds represent a major global health challenge, often aggravated by microbial dysbiosis and impaired host responses. Wound healing progresses through four overlapping phases—hemostasis, inflammation, proliferation, and remodeling—yet recent findings reveal that the skin microbiota actively participates in each step through immune, metabolic, and signaling mechanisms. Beneficial microorganisms such as Staphylococcus epidermidis and Lactobacillus plantarum promote tissue repair by inducing antimicrobial peptides and modulating cytokine production, whereas opportunistic pathogens (Staphylococcus aureus, Pseudomonas aeruginosa, Enterococcus faecalis) delay closure via biofilm formation and proteolytic activity. This review integrates current molecular insights and bibliometric trends to highlight advances and remaining challenges in understanding the wound–microbiome axis. A deeper grasp of these interactions can inform next-generation, microbiome-targeted therapies for chronic wounds. Full article

Biofilm-forming pathogens are a major cause of persistent infections, showing limited response to antibiotic treatment. The search for alternative strategies has therefore driven extensive research into the antimicrobial potential of beneficial microorganisms. In the present study, the antibacterial and antibiofilm activity of the commercial probiotic strain Lacticaseibacillus casei ATCC 393 (Lc393) was examined against clinical isolates of Staphylococcus aureus, Salmonella enterica subsp. enterica serovar Enteritidis and Escherichia coli. Lc393 reduced pathogen viability and attachment to the colon adenocarcinoma cell line HT-29, with maximal effects recorded against S. aureus. Confocal microscopy visualization of the lactobacilli-pathogens-host interface revealed that Lc393 binds loosely to both host cells and pathogens. The Lc393 cell-free culture supernatant (CFCS) significantly reduced planktonic growth, biofilm mass, and viability of cells in biofilm (>2 logCFU reduction, p < 0.05) and downregulated genes involved in the early stages of biofilm formation in S. aureus (i.e., icaA, fnbpA, eno). In silico analysis of the Lc393 genome identified two bacteriocin clusters, along with genes related to ethanol and organic acid production. Based on in silico predictions and a bacteriocin zymogram, the strain cannot produce functional antimicrobial peptides. Untargeted metabolomics based on UPLC/MS further revealed the presence of putative antimicrobial metabolites. Collectively, our findings highlight the antimicrobial potential of Lc. casei ATCC 393 and support its further investigation for combating clinically relevant human pathogens. Full article

Background: Enteropathogenic Escherichia coli (EPEC) disrupts intestinal barrier integrity by adhering to epithelial cells, leading to diarrhea, impaired nutrient absorption, oxidative stress, and intestinal inflammation in young animals. This study aimed to isolate and characterize a neutral exopolysaccharide (EPS-T1) from Enterococcus faecium HDRsEf1, evaluate its functional activities in vitro, and assess its protective effects against EPEC-induced enteritis in vivo. Results: EPS-T1, with a molecular weight of 81.21 ± 1.28 kDa, was mainly composed of glucose, galactose, rhamnose, and mannose, and exhibited a porous, sheet structure with relatively high thermal stability. In vitro, EPS-T1 (200 μg/mL) significantly inhibited EPEC growth and biofilm formation, reduced bacterial adhesion to intestinal epithelial cells, and exhibited broad-spectrum free radical scavenging activity. In vivo, EPS-T1 treatment alleviated EPEC-induced weight loss and intestinal tissue damage, reduced the intestinal EPEC load, downregulated pro-inflammatory cytokines (TNF-α, IL-1β, and IL-6), upregulated the anti-inflammatory cytokine IL-10, and improved serum antioxidant indices (T-AOC, SOD, and GSH-PX) while decreasing MDA levels. Conclusions: These results demonstrate that EPS-T1 derived from Enterococcus effectively mitigates EPEC-induced intestinal inflammation and oxidative stress, highlighting its potential as an immunobiotic functional candidate. Full article

This study aimed to evaluate the antibacterial activity of Cistus salviifolius L. and Helichrysum stoechas (L.) DC extracts against S. aureus, including methicillin-resistant S. aureus (MRSA) strains. To this end, assays were conducted to assess killing kinetics, antibiotic combination effects, modulatory effects on ethidium bromide, inhibition of quorum sensing, and biofilm formation. H. stoechas extract demonstrated the strongest activity, with MIC values ranging from 7.8 to 62.5 µg/mL. When combined with antibiotics such as ampicillin, ciprofloxacin, or vancomycin, the extracts of C. salviifolius and H. stoechas predominantly exhibited synergistic (FICI value ≤ 0.5) or additive effects (0.5 < FICI ≤ 1), with some combinations resensitizing resistant strains. The aerial parts of C. salviifolius displayed modulatory effects on ethidium bromide MIC, reducing the concentration from 32 to 8 µg/mL, suggesting efflux pump inhibitory activity. In addition, this extract displayed slight quorum-sensing inhibition at a concentration of 125 µg/mL. Moreover, C. salviifolius and H. stoechas extracts inhibit the formation of biofilm by S. aureus strains, even at subinhibitory concentrations (0.5× and 0.25× MIC). The presence of compounds such as myricetin 3 O-galactoside, catechin derivatives, gallic acid, kaempferol, and chlorogenic acid in the extracts may contribute to their anti-Staphylococcus activity. These results demonstrated the dual antimicrobial and antivirulence potential of C. salviifolius and H. stoechas extracts, highlighting their promise as therapeutic agents or adjuvants against S. aureus. These extracts can be promising candidates for further studies on the development of novel strategies targeting multiple pathogenic pathways. Full article

Continuous use of clear aligners modifies the oral environment and may favor bacterial colonization. Integration of topical fluoride-based agents could strengthen enamel and reduce biofilm formation. This study evaluated the effects of a galenic fluoride-mint spray (225–250 ppm fluoride and 1–2% peppermint essential oil) on salivary fluoride concentration and bacterial biofilm during orthodontic treatment. Ten patients using 3D-printed nighttime aligners were enrolled. Saliva samples were analyzed with an ion-selective electrode (ISE) at baseline, immediately after inserting the sprayed aligners and after 15, 30, 45 min post application. Biofilm morphology was qualitatively assessed by scanning electron microscope (SEM) in three aligners: unused, worn 14 nights without spray, worn 14 nights with spray. Salivary fluoride increased from 0.7–0.8 mg/L at baseline to 5.96 mg/L when the spray was applied on a new aligner and 8.42 mg/L on a used aligner, then progressively decreased, returning close to baseline at 45 min with the new aligner and remaining higher with the used aligner. SEM images showed mature and heterogeneous biofilm on used aligners without the spray, while aligners with nightly spray application exhibited qualitatively reduced and less organized surface deposits. The fluoride- and mint-based spray rapidly increases salivary fluoride and reduces biofilm formation on nighttime clear aligners, improving preventive oral health during orthodontic treatment. Full article

The increasing prevalence of antibiotic resistance necessitates the development of novel antimicrobial agents and therapeutic strategies. This study reports the extracellular biosynthesis of silver selenide nanoparticles (Ag₂Se NPs) using Meyerozyma guilliermondii PG-1 and evaluates their antimicrobial and antibiofilm efficacy, both alone and in combination with gentamicin. The NPs were thoroughly characterized, confirming their nanoscale size, crystallinity, and biomolecule-mediated stability. Ag₂Se NPs exhibited broad-spectrum antibacterial activity against Gram-positive (Staphylococcus aureus) and Gram-negative (Pseudomonas aeruginosa, Escherichia coli) pathogens and showed strong synergy with gentamicin, particularly against P. aeruginosa and E. coli, as demonstrated through checkerboard and time–kill assays. The NPs also significantly inhibited biofilm formation and disrupted pre-formed biofilms. Mechanistic studies revealed that the antibacterial effects involved membrane disruption, ATP leakage, and elevated oxidative stress, while gene expression analysis in S. aureus indicated triggered stress responses related to biofilm formation. These findings suggest that biosynthesized Ag₂Se NPs represent a promising synergistic agent for enhancing antibiotic efficacy and combating biofilm-related infections. Full article

The global spread of tigecycline resistance conferred by tet(X3) poses a serious threat to clinical treatment of multidrug-resistant (MDR) Acinetobacter infections. Despite tet(X3) being detected in diverse Acinetobacter species, its transposition mechanism and fitness in these pathogens remain poorly characterized. Here, we reported the first plasmid-borne ISAba52-mediated transposable element harboring tet(X3) in Acinetobacter amyesii YH16040. Conjugation experiments demonstrated the transferability of tet(X3) into the chromosome of Acinetobacter baylyi ADP1 at an efficiency of (7.1 ± 2.5) × 10⁻⁸. High-throughput sequencing revealed six tandem copies of ISAba52-flanked tet(X3), floR, and sul2 forming a 231.6 Kb complex transposon in the obtained transconjugant A. baylyi YH16040C. Phenotypic assays showed that YH16040C exhibited elevated resistance to tigecycline, chlortetracycline, florfenicol, and trimethoprim-sulfamethoxazole by 64- to 256-fold. Notably, YH16040C exhibited a growth advantage, reduced competition ability, and non-significant difference in biofilm formation compared to ADP1 in antibiotic-free backgrounds. Under moderate antibiotic treatment of tigecycline, chlortetracycline, florfenicol, and trimethoprim-sulfamethoxazole, the competition ability of YH16040C against ADP1 was significantly higher than that without antibiotics. All of these highlight the importance of ISAba52-mediated transposition in disseminating tet(X3) between Acinetobacter species and elucidate the fitness changes employed by MDR strains under antibiotic selection pressures. Our study advocates the urgent need for surveillance of ISAba52-associated resistance elements in human, animal, and environmental settings. Full article