Search Results (3,788)

Katak, a traditional Bulgarian fermented dairy product distinguished by its unique sensory characteristics and extended shelf life, represents a valuable source of autochthonous microorganisms whose functional and genomic properties remain insufficiently explored. In the present study, strain L3, isolated from katak, was comprehensively characterized by a polyphasic approach integrating classical microbiological methods, molecular identification, and whole-genome sequencing. Functional assessment revealed a broad spectrum of antimicrobial activity against pathogenic bacteria and food-associated fungi, accompanied by pronounced radical-scavenging and antioxidant capacities. The strain also exhibited high transit tolerance in simulated gut passage and a favorable antibiotic susceptibility profile, indicating its potential as a probiotic candidate. Whole-genome sequencing confirmed the taxonomic affiliation of the isolate as Lactiplantibacillus plantarum and enabled the identification of genetic determinants associated with stress response, environmental adaptation, oxidative stress protection, biofilm formation, and antimicrobial activity. The genomic analysis complemented the in vitro findings by identifying genetic determinants consistent with the observed phenotypic traits, supporting the genetic potential of strain L3 for probiotic-associated functions. The integration of phenotypic and genomic evidence allowed a comprehensive evaluation of L. plantarum L3 and demonstrated that its probiotic-related properties are underpinned by a diverse repertoire of functional genes. These findings identify L3 as a promising candidate for further biotechnological/probiotic assessment. Full article

Bacillus megaterium isolated from coffee fermentation demonstrated potential probiotic properties against Bacillus cereus ATCC 11778, Escherichia coli ATCC 8739, and Salmonella enterica subsp. enterica serovar Typhimurium ATCC 13311 through the production of active compounds, including δ-valerolactam and ε-caprolactam. This is the first report on its potential utility in producing active compounds, forming protective biofilms, or blocking cell adhesion and aggregation of foodborne pathogenic bacteria on material mimicking the intestinal mucosa. The quorum-sensing signal molecule N-butanoyl-L-homoserine lactone, an auto-inducer for biofilm formation, was detected in the crude culture supernatant, supporting its capability for biofilm formation. Characterization assays showed B. megaterium to tolerate up to 6% bile salt and to survive at pH 1.5. In addition, it demonstrated negative hemolytic activity and sensitivity to antibiotics at the level. It also produced various bioactive compounds that function with therapeutic properties. Therefore, B. megaterium has potential to be used as a human and animal probiotic in the future. Full article

Bovine mastitis, caused by both contagious and environmental pathogens, represents a major infectious disease burden in the global dairy industry. Antibiotics remain the primary treatment option, but their effectiveness is limited by the blood–milk barrier, drug residues, and the growing threat of multidrug-resistant bacteria. Among the various alternatives, phage therapy has drawn particular attention due to its specificity, ability to disrupt biofilms, low impact on commensal flora, and self-replication at infection sites. In this review, we summarize recent advances in the isolation of lytic phages targeting major mastitis-causing pathogens, their bactericidal mechanisms, and their performance in vitro and in vivo. We also discuss key obstacles to clinical translation including formulation stability, narrow host range, and safety concerns. Moreover, the potential strategies to overcome these issues are explored. This review provides a useful reference for research on phage therapy against bovine mastitis. Full article

Background: Bacterial biofilms play a key role in causing periprosthetic joint infection (PJI). Current PJI management strategies commonly combine systemic antibiotic therapy with localized delivery such as antibiotic-loaded cement or beads to achieve effective tissue penetration and high antimicrobial concentrations at the implant site. We hypothesized that antibiotic-loaded calcium sulfate beads would effectively eradicate early Staphylococcus aureus biofilms but exhibit reduced efficacy against mature biofilms formed in synovial fluid (SF). This study evaluated the efficacy of vancomycin combined with gentamicin (V+G) or tobramycin (V+T) against GFP-expressing S. aureus biofilms grown in the presence of SF. Methods: Biofilms were established on clinically relevant orthopedic implant materials such as titanium (Ti), stainless steel (316L), and polyethylene (PE). Early (1-day) and mature (3-day) biofilms were treated with calcium sulfate beads loaded with V+G or V+T. Antimicrobial efficacy was quantified by colony-forming unit (CFU) enumeration. Minimum inhibitory concentration (MIC) testing was performed on surviving populations to assess potential development of antibiotic resistance. Results: Both antibiotic combinations resulted in no detectable viable bacteria in the 1-day biofilm across all tested materials following treatment, demonstrating strong reduction in early biofilm burden below the detection limit. Treatment of mature biofilms resulted in a 4–5 log reduction. MIC analysis of representative bacteria surviving post-treatment indicated no substantial increase in resistance. Conclusions: These findings show that while locally delivered antibiotic combinations eliminate early biofilms, mature biofilms demonstrate significant tolerance. MIC analysis showed little or no change in vancomycin, gentamicin, and tobramycin susceptibility after treatment, indicating no evident increase in planktonic antibiotic resistance among the surviving isolates. Together, these results highlight the importance of early intervention and the need for strategies that disrupt biofilm structure or improve antibiotic penetration to enhance PJI treatment outcomes. Full article

Background: Dental caries is a highly prevalent, biofilm-mediated disease characterized by microbial dysbiosis, excessive acid production, and progressive enamel demineralization. Although traditionally managed through restorative treatment, increasing attention has shifted toward preventive strategies focused on modulation of the oral microbiota and maintenance of ecological balance within the oral cavity. Methods: This narrative review summarizes current evidence regarding the ecological and mechanistic basis of dental caries and microbiota-centered prevention strategies. Literature published between January 2000 and March 2026 was retrieved from PubMed/MEDLINE, Scopus, Web of Science, and Google Scholar using keywords related to dental caries, oral microbiota, cariogenic bacteria, biofilms, probiotics, prebiotics, salivary diagnostics, metabolomics, quorum sensing, and artificial intelligence. Results: Current evidence demonstrates that dental caries is driven by ecological shifts favoring acidogenic and aciduric microorganisms within cariogenic biofilms. Emerging preventive approaches include dietary modification, oral hygiene optimization, probiotics, prebiotics, synbiotics, and functional dietary agents aimed at restoring microbial homeostasis and inhibiting cariogenic biofilm maturation. In addition, advances in salivary microbiome profiling, metabolomics, artificial intelligence-assisted predictive modeling, and smart responsive materials have shown promising potential for improving early diagnosis, risk assessment, and personalized prevention strategies. Conclusions: Microbiota-based approaches represent a promising paradigm shift in dental caries prevention by emphasizing ecological modulation rather than pathogen eradication alone. Continued interdisciplinary research integrating microbial ecology, diagnostics, biomaterials, and digital technologies may facilitate the development of personalized and preventive oral healthcare strategies. Full article

Bacterial extracellular vesicles (BEVs) are nano-sized lipid bilayer particles secreted by bacteria, capable of carrying various proteins, lipids, nucleic acids, and pathogen-associated molecular patterns (PAMPs). The biosynthetic pathway of BEVs determines their load components, physicochemical properties, and different biological activities. Increasing evidence indicates that BEVs play an important role in mediating host immune responses and the dynamic regulation of bacterial biofilms. Additionally, BEVs may serve as a molecular bridge between the two. BEVs derived from pathogens can trigger pro-inflammatory cascades, assist bacteria in immune evasion, and further accelerate the maturation of biofilms, forming a vicious cycle of persistent infection and inflammatory damage. In contrast, BEVs derived from probiotics can maintain host immune homeostasis and exert direct anti-biofilm and synergistic antibacterial effects, thereby breaking the pathological cycle. However, significant methodological research bottlenecks have greatly hindered the comparability and clinical translation of BEVs research. This article systematically summarizes the classification of BEVs and their biosynthetic mechanisms, compares the differential effects of BEVs from pathogenic bacteria and probiotic bacteria on immunity, clarifies the dual regulatory role of BEVs throughout the life cycle of biofilms, and highlights the bridging function of BEVs in the immune–biofilm interaction. Additionally, this article also discusses the current development of BEVs in clinical translation applications, such as vaccine development, antibiotic delivery, and mucosal inflammation intervention, and outlines the key industrial and clinical challenges faced in the future development of BEVs-based therapeutic approaches. Full article

The increased occurrence of tetracycline resistance (conferred by the tet(X3)/tet(X4) resistance genes) poses a major challenge to the clinical treatment of infections using tetracyclines, including tigecycline, which is the “last-resort” therapeutic agent. Thus, there is an urgent need to develop inhibitors targeting Tet(X3)/Tet(X4) to address the crisis of tetracycline resistance. This study revealed that quercetin is an inhibitor of Tet(X3)/Tet(X4), which, when combined with different tetracyclines, can exert synergistic growth-inhibitory effects against Tet(X3)/Tet(X4)-positive bacteria (fractional inhibitory concentration < 0.5). Quercetin + tigecycline significantly decreased the biofilm-forming ability of bacteria. Mechanistic investigations revealed that quercetin inhibits the catalytic activity of Tet(X4) against tetracycline antibiotics by binding to the catalytic active site. In the Galleria mellonella larval infection model of Tet(X4)-positive E. coli J53p47EC or Tet(X4)-negative E. coli J53, tigecycline + quercetin enhanced the survival rate, decreased melanization, and suppressed bacterial load. Thus, the findings of this study will enable the development of novel Tet(X3)/Tet(X4)-targeted therapeutic strategies for clinical infections caused by drug-resistant Enterobacteriaceae and Acinetobacter baumannii, especially Tet(X3)/Tet(X4)-positive pathogens. Full article

Bacteria in the human intestinal tract express more than 46 million genes, suggesting that interbacterial communication and communication with human cells are well-controlled and synchronized. Many papers have been published on quorum sensing (QS) and other forms of bacterial communication, e.g., nanotubes, nanovibrations, and electromagnetism. Autoinducers (AIs) such as AI-1 N-acyl homoserine lactones (AHLs), AI-2 boron-containing furanosyl borate diesters, AI-3 pyrazinone derivatives, a combination of AI-3/Epi (epinephrine)/NE (norepinephrine), auto-inducer peptides (AIPs), and SdiA (suppressor of division inhibition), along with their receptors, have been well-studied. However, little is known about the roles of quantum mechanics, quantum tunneling, and quantum entanglement in bacterial communication. Most proposals are hypothetical and remain conceptual frameworks supported by indirect evidence rather than validated experiments. The wave-like behavior of ions (quantum tunneling) may facilitate crossing potential energy barriers, such as cell membranes, in concert with protein channels. If this is indeed the case, ions in a quantum-tunneling state would, hypothetically, be able to pass through any part of the cell membrane and cell wall. This would, in theory, enhance biochemical reactions, interbacterial communication, and interactions with human cells. The long-range signaling ability of quanta could allow bacterial cells to maintain contact over long distances, modify their metabolic activities, and activate DNA repair systems. The wave-like behavior of subatomic particles and molecules may cause nanovibrations and generate electromagnetic fields. We argue that electrical signals generated within a biofilm by quanta may attract distant cells and enable cross-species communication. We propose a hypothetical “two-pillar” bacterial communication system, i.e., QS and quantum mechanics/tunneling/entanglement (QMTE), and discuss the advantages of combining both. Full article

Background: Prosthetic joint infection (PJI) following total shoulder arthroplasty (TSA) is a rare but clinically relevant complication, largely attributable to the distinctive shoulder skin microbiome, predominantly composed of Cutibacterium acnes and coagulase-negative staphylococci (CoNS), which are considered low-virulence pathogens. Standard skin disinfection protocols do not completely prevent bacterial infiltration into the surgical field; therefore, the World Health Organization (WHO) recommends the use of intraoperative irrigation to reduce the risk of shoulder PJIs. Recently, the use of povidone–iodine (PVI) irrigation has been shown to significantly reduce both bacterial load and diversity after TSA; however, its activity against C. acnes remains suboptimal. Therefore, the aim of this study was to evaluate improved in vitro disinfection protocols by combining PVI and hydrogen peroxide for use as intraoperative irrigation in shoulder arthroplasty, which is characterized by a distinctive microbiome. Methods: In vitro broth dilution assays and time-kill experiments were performed to test PVI and H₂O₂, alone or in combination, against CoNS, Staphylococcus aureus, and Escherichia coli as representative aerobic bacteria, and against C. acnes as an anaerobic pathogen. Results: The results revealed that, when used alone, PVI exerted a more pronounced bactericidal effect against staphylococci, whereas H₂O₂ was more effective against C. acnes, even at a high bacterial inoculum, although at cytotoxic concentrations, particularly for PVI. Notably, when the disinfectants were used in combination, bacterial killing was achieved against all the tested pathogens, starting from short exposure times, mainly 3 min, and at low concentrations. Moreover, the antiseptics significantly reduced mature biofilm, although complete eradication was not achieved. Conclusions: A targeted irrigation protocol to prevent shoulder PJI can be achieved by combining PVI and H₂O₂ at non-toxic concentrations and for short exposure times that do not interfere with operating room costs or increase the risk of infection. Full article

Background/Objectives: Bacteria of the genus Klebsiella are opportunistic pathogens frequently responsible for severe urinary tract infections (UTIs). Biofilm formation is a critical virulence factor that facilitates bacterial persistence and promotes the dissemination of antimicrobial resistance. This study aimed to characterize the biofilm-forming capacity and the prevalence of the fimH adhesin gene among clinical Klebsiella isolates in Gabon, and to evaluate their association with resistance to third-generation cephalosporins and aminoglycosides. Methods: A total of 114 urinary isolates, including Klebsiella pneumoniae (n = 96), Klebsiella oxytoca (n = 7), and Klebsiella aerogenes (n = 11), were analyzed. Biofilm formation was assessed using the crystal violet staining method and quantified by spectrophotometry. The fimH gene was detected using conventional PCR. Susceptibility to cefotaxime, ceftazidime, gentamicin, and amikacin was determined using an automated system. Results: The study revealed that 81.58% of the clinical Klebsiella isolates were biofilm producers. Quantitative analysis showed a predominance of weak (43.86%) and moderate (26.32%) producers, while only 5.26% were categorized as strong producers. The fimH gene was detected in 95.61% of the isolates, reaching 100% prevalence in Klebsiella pneumoniae. Interestingly, non-biofilm-producing Klebsiella spp. isolates exhibited the highest resistance rates to 3GC (67.90% for both cefotaxime and ceftazidime), suggesting that resistance to this class may be independent of biofilm-forming capacity in this cohort. Conversely, the highest resistance rates to aminoglycosides were observed among strong biofilm producers, reaching 60% for gentamicin and 40% for amikacin. Conclusions: Uropathogenic Klebsiella spp. in Gabon exhibit a high capacity for biofilm formation, with resistance patterns appearing to be antibiotic-class dependent. These findings suggest that considering biofilm phenotypes could be relevant for microbiological surveillance to improve the understanding of UTI resistance dynamics. Full article

Product Shezi (PS) is a polyherbal African traditional medicine (ATM) formulated from six known South African medicinal plants and is used for treating cutaneous wounds. However, its ethnopharmacological properties have not been scientifically validated. This study aimed to evaluate the antioxidant, anti-inflammatory, and antimicrobial activities of PS in vitro. Aqueous and methanolic extracts were prepared and qualitatively screened for phytochemical constituents. Cytotoxicity in fibroblasts and macrophages was assessed using an ATP-based viability assay. Antioxidant activity was evaluated using the 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging and a hydrogen peroxide (H₂O₂)-induced oxidative stress model. Anti-inflammatory effects in lipopolysaccharide (LPS)-stimulated macrophages were measured using the Griess reagent system, a human prostaglandin E₂ (PGE₂) ELISA, and a bovine serum albumin (BSA) anti-denaturation assay. Antimicrobial activity was assessed by twofold serial broth microdilution, agar well diffusion, and a crystal violet biofilm assay. Phytochemical screening confirmed the presence of saponins, alkaloids, tannins, glycosides, terpenoids, flavonoids, and steroids. PS exhibited IC₁₀ values of 3 and 10 μg/mL in fibroblasts and macrophages, respectively. PS (1–5 μg/mL) showed 70% DPPH scavenging potential and potent H₂O₂ cytoprotection (p < 0.001). Nitric oxide inhibition was non-significant (p > 0.05) whilst PGE₂ decreased significantly (p < 0.05) compared to LPS-stimulated cells. BSA denaturation was inhibited in a dose-dependent manner (p < 0.05). Staphylococcus aureus and S. epidermidis were the only microorganisms susceptible to PS (MIC 650–5000 μg/mL) with low SI (SI ≈ 0.05–0.06), while others were resistant. PS showed no antibiofilm activity (crystal-violet assay). Overall, PS demonstrated antioxidant and anti-inflammatory activities and selective antibacterial effects against planktonic bacteria in vitro. However, further optimization of extraction methods, detailed mechanistic studies, and in vivo investigations are warranted to substantiate therapeutic relevance. Full article

Background/Objectives: Pericoronitis is a polymicrobial, biofilm-associated odontogenic infection; however, selected facultative Gram-positive bacteria may contribute to oral infectious persistence. This study compared the residual antibacterial activity of chlorhexidine (CHX), low-level laser therapy (LLLT), injectable platelet-rich fibrin (i-PRF), and amoxicillin-loaded i-PRF against selected oral and odontogenic bacterial strains. Methods: Standardized planktonic suspensions of Streptococcus mutans ATCC 25175, Staphylococcus aureus ATCC 25923, and Enterococcus faecalis ATCC 29212 were prepared at 0.5 McFarland turbidity. Five conditions were evaluated: 0.2% CHX, i-PRF, amoxicillin-loaded i-PRF, 976 nm diode LLLT, and 0.9% sodium chloride as the negative control. Twelve independent tubes were used for each treatment and species, yielding 180 experimental units. After a residual 24-h exposure/incubation period, samples were serially diluted, plated on 5% sheep blood agar, and quantified as CFU/mL. Data were analyzed using non-parametric tests. Results: Significant treatment-dependent differences were observed for all species (p < 0.001). CHX showed the most consistent antibacterial activity, with median residual counts of 550 CFU/mL for S. mutans, 1 CFU/mL for S. aureus, and 5.5 CFU/mL for E. faecalis. i-PRF alone was comparable to the negative control. Amoxicillin-loaded i-PRF markedly reduced S. aureus counts, whereas S. mutans and E. faecalis remained at high residual levels. LLLT showed partial, variable inhibition mainly against S. aureus. Conclusions: CHX demonstrated the most consistent antibacterial effect in this planktonic residual 24-h in vitro model. i-PRF alone showed no measurable antibacterial activity, while amoxicillin-loaded i-PRF and LLLT exhibited limited, species-dependent effects. Full article

Staphylococcus aureus (S. aureus), a leading cause of nosocomial infections, contributes significantly to increased morbidity and mortality, especially when it forms biofilms on medical devices. This pathogen, specifically methicillin-resistant S. aureus (MRSA), remains a challenge to treat due to its ability to form biofilms and rapidly develop resistance against antibiotics. Biofilm formation allows bacteria to adhere to biotic and abiotic surfaces, creating a protective matrix that shields them from immune responses and antibiotic therapies. The widespread prevalence of multidrug-resistant S. aureus biofilms poses a significant therapeutic challenge in clinical settings. Several novel therapeutic strategies have been developed to combat S. aureus biofilm-associated infections. Accumulating evidence suggests that natural plants and their derivatives possess antimicrobial and chemo preventive properties that can disrupt established biofilms. Several plant-derived compounds with anti-biofilm activities have been reported to target the regulatory proteins involved in the Agr quorum sensing (Agr-QS) system, underscoring their potential as therapeutic candidates for the prevention and treatment of biofilm-associated infections. However, despite these encouraging findings, clinical validation of these plant-based agents is essential to ensure their efficacy, safety, and optimal application in treating S. aureus biofilm infections. The continued exploration of natural biofilm inhibitors anticipates the urgent need for new treatments to combat biofilm-associated infections and multidrug-resistant pathogens like MRSA. This review provides a detailed overview of preventive and therapeutic interventions to eradicate biofilm-forming S. aureus infections. Full article

Gram-negative bacteria pose a significant threat to global health due to their high prevalence, multidrug resistance, and association with various infections. Zinc, an essential trace element, plays a dual role in host–microbe interactions, being crucial for both host immune function and bacterial metabolism. Maintaining optimal zinc homeostasis is essential for effective host defense and microbial survival. We comprehensively examine the multifaceted roles of zinc in host–microbe interactions, particularly focusing on its implications for the pathogenicity of Gram-negative bacteria and host immunity. As part of nutritional immunity, hosts have evolved zinc-mediated antimicrobial strategies that manipulate metal availability at the host–pathogen interface, including zinc limitation that restricts bacterial access to this essential nutrient and zinc intoxication that exposes invading bacteria to cytotoxic zinc concentrations. In Gram-negative bacteria, zinc homeostasis, maintained through zinc transporters and efflux systems, critically governs bacterial virulence, biofilm formation, and survival under host-imposed nutritional immunity. By integrating current advances, this review highlights zinc homeostasis as a central determinant of host–pathogen interactions and a promising target for combating multidrug-resistant Gram-negative infections. Understanding these complex zinc-mediated mechanisms provides new perspectives for developing metal-targeted therapeutic strategies. Full article

The emergence of multidrug-resistant (MDR) bacteria, particularly methicillin-resistant Staphylococcus aureus (MRSA), represents a major global health challenge by limiting the current therapeutic options. In this context, antimicrobial peptides (AMPs) have been widely studied for their potent antimicrobial properties. In this study, we evaluated the anti-MRSA effect of a novel AMP, LyeTx I mnΔKL, derived from a toxin of Lycosa erythrognatha. Its activity was evaluated in vitro by minimal inhibitory and bactericidal concentrations (MIC and MBC), antibiofilm effect, membrane interaction, cytotoxicity, synergistic interaction with vancomycin, and in vivo in an MRSA murine wound/abscess infection model. LyeTx I mnΔKL showed enhanced antimicrobial activity against clinical MRSA isolates compared to its prototype (LyeTx I mnΔK), with MIC₅₀ and MBC₅₀ of 2 and 8 µM and 16 and 32 µM, respectively. Furthermore, LyeTx I mnΔKL exhibited a rapid bactericidal effect and a pronounced ability to inhibit biofilm formation and disrupt mature biofilms. LyeTx I mnΔKL interacts with bacterial membranes, adopts an α-helical structure, and induces membrane disruption and leakage of intracellular material. In vivo, topical treatment with LyeTx I mnΔKL reduced MRSA burden compared with LyeTx I mnΔK and untreated controls (log₁₀ CFU/g of wound of 2.4, 4.4, and 6.5 for LyeTx I mnΔKL, LyeTx I mnΔK, and the saline group, respectively). However, increased cytotoxicity remains a significant limitation. Overall, LyeTx I mnΔKL is a promising anti-MRSA candidate for topical use with potent antibiofilm and in vivo activity. Full article