Search Results (517)

Implant-associated infections are often caused by biofilm-forming pathogens such as Staphylococcus (S.) aureus. While local antibiotic delivery systems aim to prevent adhesion and biofilm establishment, declining drug concentrations may result in sub-inhibitory exposure, which can modulate bacterial adaptation linked to antibiotic resistance, biofilm formation, and regulatory responses. We investigated the effects of sub-inhibitory antibiotic exposure on biofilm formation in S. aureus SA113 and associated transcriptional responses. The biofilm-producing strain S. aureus SA113 was exposed to sub-inhibitory concentrations of rifampicin, minocycline, and dalbavancin during early biofilm formation. Phenotypic effects were assessed by crystal violet staining, enumeration of colony-forming units, and scanning electron microscopy, while transcriptional responses were analyzed by qPCR. Despite stable counts of culturable adherent bacteria, sub-inhibitory antibiotic exposure differentially altered biofilm formation and transcriptional responses. Rifampicin was associated with increased biomass at higher sub-inhibitory concentrations and increased early expression of icaA, icaD (+4.2 log₂) and fnbA (+2.7 log₂) at 1/2× MIC. Minocycline reduced biomass at lower concentrations with partial recovery toward control levels at 1/2× MIC, while transcriptional analysis at 1/4× MIC after 6 h showed increased expression of icaA, icaD (+2.1 log₂) and fnbA (+4.3 log₂). Dalbavancin induced a distinct transcriptional response characterized by increased expression of vraS (+1.1 log₂) and lrgA (+1.8 log₂), without induction of matrix-associated genes, while adherent biofilm biomass was reduced to 42.9% at 1/2× MIC. Morphologically, this was associated with compact aggregates rather than diffuse biofilm structures. Sub-inhibitory antibiotic exposure differentially modulated early biofilm formation in SA113 in a drug-specific manner. Overall, the distinct dalbavancin-associated response may be relevant for the development of preventive local drug-delivery systems. Full article

Background: Dental caries is a biofilm-associated disease in which Streptococcus mutans plays a central role. This study evaluated HT-2-1-3, a Vespidae venom-derived antimicrobial peptide, as a potential topical anti-caries lead. Methods: Candidate peptides were synthesized by Fmoc solid-phase peptide synthesis and characterized by RP-HPLC and ESI-MS. Antibacterial activity against S. mutans UA159 was assessed using MIC, MBC, growth-curve, and time-kill assays. Membrane damage, antibiofilm activity, cytocompatibility, hemolysis, and preliminary oral safety in mice were further evaluated. Results: HT-2-1-3 showed the strongest activity among the tested peptides, with MIC and MBC values of 2 µg/mL. It inhibited bacterial growth in a concentration-dependent manner and achieved complete killing at 4×MIC (8 µg/mL) within 2 h. Mechanistic assays showed rapid membrane depolarization, increased PI uptake, and concentration-dependent release of extracellular DNA and proteins. MD simulations further indicated that HT-2-1-3 entered the model S. mutans UA159 membrane at 1857 ns, supporting membrane permeabilization as a central component of its bactericidal activity. Scanning electron microscopy revealed dose-dependent membrane disruption, cell collapse, and rupture. HT-2-1-3 inhibited biofilm formation by approximately 58–63% and eradicated up to 89.0% of mature biofilms. Hemolysis remained below 4% at concentrations up to 64×MIC (128 µg/mL), and mammalian-cell viability exceeded 95% at concentrations up to 16×MIC (32 µg/mL). Repeated oral administration caused no obvious gingival irritation in mice. Conclusions: HT-2-1-3 showed strong bactericidal and antibiofilm activity against S. mutans UA159 and favorable preliminary biocompatibility. Its mode of action may involve membrane disruption, and it showed favorable preliminary biosafety. These findings support further optimization of HT-2-1-3 as a topical antimicrobial candidate for caries prevention and control. Full article

Background: Enterococcus species have emerged as significant multidrug-resistant nosocomial pathogens. Linezolid remains a vital last-resort therapeutic option for the management of severe infections caused by vancomycin-resistant Enterococci. However, resistance to linezolid occurs through several mechanisms, including the presence of the cfr, cfr(D), and optrA genes, as well as mutations in domain V region of the 23S ribosomal RNA gene. This study aimed to detect and characterize linezolid resistance in clinical Enterococcus species. Methodology: A total of 266 clinical isolates belonging to the Enterococcus species were analyzed in this study. Antimicrobial susceptibility testing was performed using the disc diffusion method. The Minimum Inhibitory Concentration (MIC) of linezolid was determined by the agar dilution technique. PCR was performed to detect the presence of cfr, cfr(D), and optrA genes, along with mutations in domain V of the 23S rRNA gene. Results: Among the 266 isolates analyzed, 25 (9.4%) were found to be resistant to linezolid, with MIC values ≥ 8 µg/mL. Of these resistant isolates, the cfr gene was detected in one isolate, cfr(D) in sixteen isolates, and optrA in nine isolates. Notably, four isolates carried mutations in the domain V region of the 23S rRNA gene, including a novel C2626T mutation (in India) along with the previously reported G2592T mutation. Conclusions: This study reports the detection of cfr- and cfr(D)-mediated linezolid resistance among Enterococcus species in India. Furthermore, the presence of optrA and a novel C2626T mutation, alongside the G2592T mutation, was identified among resistant isolates. These findings underscore the urgent need for molecular surveillance to prevent further dissemination of these multidrug-resistant pathogens. Full article

Background/Objectives: Colibacillosis, caused by enteropathogenic strains of Escherichia coli (EPEC), is one of the most common infectious diseases in rabbit farms. In the past, antimicrobials were widely used to control colibacillosis, but their use in prevention is currently prohibited. Therefore, the adoption of new prevention strategies as alternatives to the use of antibiotics is very important. The aim of this study was to evaluate the antimicrobial efficacy of cinnamon essential oil (Cinnamomum zeylanicum) against EPEC strains responsible for colibacillosis in rabbits. Methods: For the experiment, 124 strains of E. coli isolated from rabbits that had died of colibacillosis in 10 industrial farms were used. Suspensions of each strain prepared according to CLSI standards with a bacterial density of 1 × 10⁸ CFU/mL were tested using 100% pure commercial cinnamon essential oil (CEO) at concentrations ranging from 0.2 to 0.8 μL/mL. Minimum inhibitory concentrations MIC₅₀ and MIC₉₀ were determined according to a protocol described previously. Results: MIC₅₀ and MIC₉₀ were 0.5 μL/mL and 0.6 μL/mL, inhibiting 64.5% and 94.3% of strains, respectively. Furthermore, strains exposed to 0.4 μL/mL were 12.9 times more likely to be inhibited than those exposed to 0.3 μL/mL (p = 0.0001). Conclusions: CEO was found to be effective against E. coli strains tested at high bacterial densities that can usually be found per gram of faeces in rabbits affected by colibacillosis. Consequently, cinnamon should be useful in preventing colibacillosis by limiting the replication of E. coli, as it is usually found in lower densities in the intestines of healthy rabbits, preventing the onset of colibacillosis and reducing the use of antibiotics in rabbit farms. Full article

Background: This study evaluated the antibacterial, antibiofilm, and biofilm eradication activities of biogenically synthesized silver nanoparticles (AgNPs-L, AgNPs-R) mediated by extracts of Lavandula angustifolia and Salvia rosmarinus, individually and in combination with their respective essential oils (EOs) and ampicillin (AMP), against a multidrug-resistant biofilm-forming Staphylococcus equorum strain. Physicochemical characterization confirmed the successful biosynthesis of spherical AgNPs-L (10–25 nm) and AgNPs-R (5–15 nm). Individual treatments exhibited distinct antibacterial activity, with MIC values of 25 µg/mL for AgNPs-L, 12.5 µg/mL for AgNPs-R, and 0.1% (v/v) for both EOs; however, they showed no ability to eradicate preformed biofilms. Dual AgNPs/EO combinations at subinhibitory concentrations demonstrated borderline additive effects (FICI = 0.501) and significantly potentiated antibacterial and antibiofilm activity compared with individual treatments. Triple AgNPs/EO/AMP combinations exhibited the most pronounced biological effects, with predominantly additive interactions depending on AMP concentration. Lavender-based triple combinations achieved up to 63.9% inhibition of planktonic growth, 78.1% prevention of biofilm formation, and 37.3% eradication of mature biofilms, whereas rosemary-based combinations resulted in 57.1%, 69.4%, and 42.7% inhibition, respectively. These findings highlight the potential of multi-component systems integrating biogenic nanomaterials, phytochemicals, and conventional antibiotics as a promising strategy to enhance antimicrobial efficacy against persistent biofilm-forming non-aureus staphylococci. Full article

Chitosan, a chitin-derived biopolymer, is widely used in agriculture and food preservation. Fungal-derived chitosan offers a sustainable alternative to crustacean sources, and Ganoderma lucidum represents a promising source of this functional material. This study characterized fungal chitosan (F.Cs) extracted from G. lucidum cell-wall chitin by FT-IR, molecular weight, viscosity, and degree of deacetylation. Its antimicrobial activity was evaluated in vitro, and its preservative and disease control efficacy against Monilinia fructicola on postharvest apples was compared to commercial chitosan (C.Cs). DNA/protein leakage of the studied FGs and C.Cs were investigated to reveal the antimicrobial mechanisms. In particular, F.Cs exhibited promising in vitro antimicrobial activity, with MIC/MFC values of 0.75/0.75 mg/mL against M. fructicola and 0.75/1.5 mg/mL against Botrytis cinerea, compared to C.Cs. In addition, F.Cs induced greater membrane damage in M. fructicola than C.Cs, as evidenced by higher DNA leakage (24% vs. 13%) and more pronounced protein leakage (102% vs. 98%). In vivo assay demonstrated that F.Cs formed an effective protective coating layer, reducing fruit moisture loss, preserving firmness s, and significantly limiting M. fructicola-induced decay compared to C.Cs. Particularly, F.Cs (1.5%) were most effective, reducing disease incidence to 12.5% (preventive) and 20.8% (curative), with decay rates of 18 and 31%, respectively. C.Cs (1.5%) provided moderate protection, with disease incidences of 37.5 and 43.7% in preventive and curative treatments, respectively. These results demonstrate the superior efficacy of F.Cs over C.Cs in preserving apple quality and enhancing resistance to M. fructicola, highlighting the potential of G. lucidum-derived chitosan as a sustainable, multifunctional biopolymer for postharvest disease control and fruit quality preservation. Full article

Streptococcus mutans is the primary etiological agent of dental caries due to its ability to form acidogenic biofilms on tooth surfaces. Natural monoterpenes have attracted considerable interest as potential antibiofilm agents for oral healthcare. The present study investigated the antibiofilm activity and possible mechanism of action of (+)-endo-borneol isolated from the essential oil of Achillea millefolium against S. mutans. The chemical composition of the essential oil was characterized by gas chromatography–mass spectrometry (GC–MS), and (+)-endo-borneol was isolated by chromatographic separation. Antibiofilm activity was evaluated using the crystal violet biofilm assay, while antimicrobial activity was determined by minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) assays. The influence of subinhibitory concentrations of (+)-endo-borneol on the expression of the biofilm-associated genes gtfB and yycF was assessed by quantitative real-time PCR. Molecular docking was performed to investigate ligand–protein interactions, using a ligand geometry pre-optimized by density functional theory (DFT, B3LYP/6-31G**). The essential oil inhibited S. mutans biofilm formation by up to 98%, whereas isolated (+)-endo-borneol reduced biofilm biomass by 97–98% at concentrations of 2–10 mg/mL. The MIC and MBC values of (+)-endo-borneol were 2.5 and 5.0 mg/mL, respectively. Gene expression analysis demonstrated that subinhibitory concentrations of (+)-endo-borneol modulated the transcription of gtfB and yycF, indicating activation of bacterial regulatory responses. Molecular docking revealed favorable binding of (+)-endo-borneol to biofilm-related protein targets. These findings demonstrate that (+)-endo-borneol is a promising natural antibiofilm compound with potential application in the development of novel preventive and therapeutic oral healthcare products targeting S. mutans biofilms. Full article

Multidrug-resistant hypervirulent Klebsiella pneumoniae caused by the improper use of antibiotics has become a major threat to the dairy industry and public health, posing a major challenge to the treatment of bovine mastitis. The resurgence of phage (and its lysozyme therapy) provides a novel strategy to combat such infections. In this study, bovine Klebsiella pneumoniae phage vB_Kpn_B01 nucleic acid was used as a template to successfully achieve the prokaryotic expression of its endolysin. The results of protein gene annotation and prediction showed that Lysin K had the function of lyase, and was designated Lysin K. After optimizing the production conditions, Lysin K could be produced in a soluble form after induction with 0.25 mmol/L IPTG at 37 °C for 16 h, and the concentration was 100 μg/mL after purification. The stability test confirmed that Lysin K can maintain stable antibacterial activity over a wide temperature and pH range. The minimum inhibitory concentration (MIC) of Lysin K was 0.01 μg/mL and remained stable in milk. The Lysin K showed strong lysis activity in vitro and could effectively lyse three types of multidrug-resistant hypervirulent Klebsiella pneumoniae. In the mouse mastitis model induced by Klebsiella pneumoniae KP18 (10⁸ CFU/mL), the intervention of Lysin K can significantly reduce the bacterial load, alleviate the inflammatory response, and restore the normal functional structure of the target mammary gland. In summary, Lysin K has valuable application prospect in the prevention and treatment of bovine mastitis caused by drug-resistant Klebsiella pneumoniae and the development of phage lysin preparations. Full article

Industrial effluents containing toxic dyes, pathogenic microorganisms, and other hazardous contaminants pose a serious threat to environmental and public health, creating an urgent need for multifunctional materials capable of addressing both environmental pollution and microbial contamination. Silver nanoparticles (AgNPs) have attracted considerable attention because of their broad-spectrum antimicrobial and photocatalytic properties. In this study, AgNPs were biosynthesized for the first time using Lotus sanguineus, an endemic plant rich in bioactive phytochemicals, through an environmentally friendly green synthesis approach. To comprehensively evaluate their multifunctional performance, the photocatalytic, antimicrobial, and antibiofilm activities of the biosynthesized AgNPs were investigated, while molecular docking analysis was performed to elucidate their interactions with quorum-sensing-related proteins. AgNPs were characterized using UV–Vis spectroscopy, FTIR, XRD, DLS, and SEM. Under sunlight, AgNPs showed degradation efficiencies of 60.6% for methylene blue and 29.5% for eriochrome black T, indicating higher photocatalytic activity toward the cationic dye. Antimicrobial evaluation demonstrated notable antimicrobial activities against Escherichia coli, Bacillus cereus, Pseudomonas aeruginosa, and Staphylococcus aureus, with minimum inhibitory concentration (MIC) values ranging from 31.25 to 62.5 μg/mL and minimum bactericidal concentration (MBC) values between 125 and 250 μg/mL. Additionally, AgNPs exhibited a maximum inhibition of 94.5% at 62.5 μg/mL against Pseudomonas aeruginosa. Furthermore, molecular docking results revealed favorable binding affinities between the ligand and quorum-sensing transcriptional activator (LasR), N-terminal domain of anthranilate-CoA ligase (PqsA), P. aeruginosa aminopeptidase (PaAP), and peptidoglycan N-acetylglucosamine deacetylase (Pgd) proteins. Overall, the results highlighted the potential of AgNPs for pharmaceutical applications, prevention of bacterial surface colonization, and environmental remediation. Full article

Methicillin-resistant Staphylococcus aureus (MRSA) poses a serious threat to public health and can form biofilms to enhance its drug resistance. Caffeic acid phenethyl ester (CAPE), which is primarily extracted from propolis, possesses diverse biological activities. However, its effect on anti-MRSA biofilms and the relevant mechanisms have not been fully clarified. Therefore, this study explored the ability of CAPE to combat MRSA biofilms. The results showed that CAPE has significant antibiofilm activities against MRSA. The minimum inhibitory concentration (MIC) values of CAPE were 256 µg/mL for the MRSA strains ATCC 33591, CI2, and CI3. Crystal violet (CV) assay and XTT assays demonstrated that CAPE could inhibit the formation and consolidation of MRSA CI2 biofilms. Experiments on scanning electron microscopy (SEM), bacterial adhesion assays, and the levels of extracellular polysaccharides confirmed that CAPE can inhibit bacterial adhesion, as well as the synthesis of extracellular polysaccharides in MRSA CI2. Real-time quantitative PCR (RT-qPCR) experiments confirmed that CAPE can affect the expression of MRSA icaADBC, sarA, fnbAB, and clfAB genes. Therefore, the proposed antibiofilm mechanism of CAPE involves the downregulation of aforementioned genes, leading to reduced production of extracellular polysaccharides and adhesion-related proteins, thereby weakening MRSA adhesion and ultimately exerting an antibiofilm effect. In conclusion, these findings suggest CAPE is a promising candidate drug as an antimicrobial agent for managing and preventing biofilm-associated infections caused by MRSA. Full article

Background/Objectives: Persistent infections are characterized by recurrent treatment failure and relapse despite apparent antibiotic susceptibility by standard testing, a clinical reality not fully explained by conventional resistance paradigms. Bacterial persister cells, genetically susceptible but phenotypically tolerant subpopulations, survive otherwise lethal antibiotic exposure through reversible physiological adaptations. This review proposes a pharmacological framework linking antimicrobial exposure, bacterial tolerance, persistence, relapse, and the emergence of antimicrobial resistance (AMR). Methods: A structured narrative review was conducted using PubMed/MEDLINE, ClinicalTrials.gov, Centers for Disease Control and Prevention (CDC), and World Health Organization/Global Antimicrobial Resistance and Use Surveillance System (WHO/GLASS) sources (inception to 19 June 2026, priority 2010–2026), following Scale for the Assessment of Narrative Review Articles (SANRA) framework principles. Results: Resistance, tolerance, and persistence are pharmacologically distinct phenotypes. Persistence occurs without minimum inhibitory concentration (MIC) elevation and is shaped by antimicrobial exposure, target-site penetration, biofilm barriers, intracellular localization, and host stress. The review operationalizes persistence prevention exposure (PPE) in relation to minimum duration for killing 99%/99.99% of cells (MDK₉₉/MDK_99.99), persister fraction, minimum biofilm eradication concentration (MBEC), and biphasic time-kill modeling. Conclusions: Antimicrobial therapy should evolve from a model centered solely on MIC suppression and killing of actively growing bacteria toward one that also includes the prevention and eradication of persister reservoirs. Persistence prevention may reduce relapse, repeated antibiotic exposure, and the evolutionary path toward stable AMR. Full article

During the SARS-CoV-2 pandemic, healthcare systems faced an increased burden of secondary infections, including those caused by Candida auris, an emerging multidrug-resistant pathogen associated with hospital outbreaks worldwide. We aimed to describe the clinical and microbiological characteristics of a hospital outbreak of Candida auris fungemia in patients with COVID-19 in a tertiary care center. This retrospective observational study included 14 patients diagnosed between November 2020 and April 2021. Infection was initially identified using VITEK2^® and confirmed using MALDI-TOF MS, with antifungal susceptibility determined using broth microdilution. All patients developed fungemia, were mechanically ventilated, and had central venous access and prolonged hospital stays; 64.2% had comorbidities. Resistance frequencies based on CDC tentative MIC thresholds were observed for fluconazole (64.2%) and amphotericin B (71.4%). In-hospital mortality was 50%; exploratory analyses of factors associated with mortality should be interpreted cautiously given the small sample size. These findings highlight the significant clinical impact of Candida auris in critically ill COVID-19 patients, particularly in the context of invasive care and antimicrobial resistance. The outbreak underscores the importance of early identification, appropriate antifungal therapy, and strict infection prevention and control measures. Further studies are needed to better define risk factors and optimize management strategies in similar settings. Full article

Background: Toxoplasmosis is a prevalent zoonotic disease worldwide, affecting approximately one-third of the global human population. Primary infection with Toxoplasma gondii during pregnancy can induce miscarriage or congenital infection, leading to irreversible damage to the foetus. Moreover, reactivation of T. gondii infection in immunosuppressed individuals can result in fatal outcomes. No vaccine exists to prevent human disease caused by this parasite. Thus, a vaccine that could induce complete and lasting protection against human toxoplasmosis is an unmet need. Method: In this work, BALB/cByJ mice were intranasally immunised with a subunit vaccine consisting of T. gondii membrane proteins (TGMP) from the T. gondii Me49 strain plus CpG-oligodeoxynucleotide adjuvant (CpG). Antibody responses were analysed by ELISA, while T-cell responses were evaluated by flow cytometry. The immunogenic proteins present in TGMP were identified by mass spectrometry, and parasite burden was quantified by qPCR. Result: The results showed raised TGMP-specific serum IgG and intestinal IgA antibody levels, and parasite-specific IFN-γ-producing CD4⁺ and CD8⁺ memory T cells. Dense granule proteins (GRA) 2 and 7, surface antigen (SAG)-related sequences 25, 29B, and 34A, microneme protein (MIC) 10, toxofilin, nascent polypeptide-associated complex (NAC) domain-containing protein, and NAC subunit beta were identified as immunogenic proteins. Mice immunised with TGMP+CpG were challenged with T. gondii tachyzoites and showed a significant reduction in the parasitic burden in the peritoneal exudate, spleen, and lungs, compared to mice sham-immunised with CpG alone. Conclusions: Altogether, these results indicate that mucosal immunisation with TGMP plus CpG adjuvant is worth exploring as a vaccination approach to prevent toxoplasmosis. Full article

This case study investigates the rapid through-wall perforation of newly installed hot-dip galvanized (HDG) fire sprinkler pipes in a coastal Mediterranean environment. Failure occurred along the internal waterline of horizontal sections within a short service period. Forensic analysis—comprising metallography, SEM, and EDS—identified a synergistic atmospheric–aqueous corrosion mechanism. Marine aerosol exposure during pre-service storage led to significant chloride enrichment and localized depletion of the 40–50 μm zinc coating, initiating early-stage pitting. Upon commissioning, stagnant water established oxygen concentration gradients and differential-aeration cells, driving localized anodic dissolution. Additionally, sulfate-reducing bacteria (SRB) contributed to accelerated degradation through microbiologically influenced corrosion (MIC), as suggested by sulfur-bearing tubercles. The findings demonstrate that standard galvanizing thickness alone does not ensure longevity in high-salinity environments if atmospheric “preconditioning” occurs. These results underscore the necessity of shielding internal pipe surfaces during storage and construction to prevent premature failure. This case study informs predictive maintenance and material selection for stagnant-water systems in coastal regions. Full article

This study evaluates the antifungal activity of Lippia gracilis Schauer essential oil traditionally used in northeastern Brazil for the treatment of skin disorders. The essential oil isolated from fresh leaves collected in Ceará, Brazil, was chemically characterized by GC–MS, showing a thymol-dominant profile (37.52%), accompanied by p-cymene (12.13%), γ-terpinene (9.29%), and gurjunene (10.95%). Antifungal assays revealed significant activity against several dermatophyte species with MIC and MFC values ranging from 50 to 100 μg/mL. Biofilm assays against Epidermophyton floccosum demonstrated strong inhibitory effects by disrupting biofilm formation, altering fungal morphology, and promoting in vitro skin cells migration, while also showing effective preventive effects in an ex vitro nail infection model. These findings support the potential of L. gracilis essential oil as a multifunctional natural antifungal agent for the management of refractory dermatophytosis and onychomycosis, and provide scientific validation for its traditional use in skin infection treatment. Full article