Antibacterial and Antibiofilm Potency of Menadione Against Multidrug-Resistant S. aureus

Exploring naphthoquinone and anthraquinone derivatives as antibiotic adjuvants against Staphylococcus aureus biofilms: Synergistic effects of menadione

Given the ability of Staphylococcus aureus to form biofilms and produce persister cells, making infections difficult to treat with antibiotics alone, there is a pressing need for an effective antibiotic adjuvant to address this public health threat. In this study, a series of quinone derivatives were evaluated for their antimicrobial and antibiofilm activities against methicillin-susceptible and methicillin-resistant S. aureus reference strains. Following analyses using broth microdilution, growth curve analysis, checkerboard assay, time-kill experiments, and confocal laser scanning microscopy, menadione was identified as a hit compound. Menadione exhibited a notable antibacterial profile (minimum inhibitory concentration, MIC = 4-16 μg/ml; minimum bactericidal concentration, MBC = 256 μg/ml) against planktonic S. aureus and its biofilms (minimum biofilm inhibitory concentration, MBIC50 = 0.0625-0.25 μg/ml). When combined with oxacillin, erythromycin, and vancomycin, menadione exhibited a synergistic or additive effect against planktonic cells and biofilms of two S. aureus reference strains and six clinical isolates, highlighting its potential as a suitable adjuvant for further development against S. aureus biofilm-associated infections.

Impact of eugenol on biofilm development in Shigella flexneri 1457: a plant terpenoid based-approach to inhibit food-borne pathogen

Shigella flexneri is a gram-negative bacterium responsible for shigellosis and bacterial dysentery. Despite using various synthetic antimicrobial agents and antibiotics, their efficacy is limited, prompting concerns over antibiotic resistance and associated health risks. This study investigated eugenol, a polyphenol with inherent antioxidant and antibacterial properties, as a potential alternative treatment. We aimed to evaluate eugenol's antibacterial effects and mechanisms of action against S. flexneri and its impact on biofilm formation. We observed significant growth suppression of S. flexneri with eugenol concentrations of 8-10 mM (98.29%). Quantitative analysis using the Crystal Violet assay demonstrated a marked reduction in biofilm formation at 10 mM (97.01 %). Assessment of Cell Viability and morphology via Fluorescence-Activated Cell Sorting and Scanning Electron Microscopy confirmed these findings. Additionally, qPCR analysis revealed the downregulation of key genes responsible for adhesion (yebL), quorum sensing (rcsC, sdiA), and EPS production (s0482) associated with bacterial growth and biofilm formation. The present study suggests eugenol could offer a promising alternative to conventional antibiotics for treating shigellosis caused by S. flexneri.

Anti-Biofilm Effect of Hybrid Nanocomposite Functionalized with Erythrosine B on Staphylococcus aureus Due to Photodynamic Inactivation

Resistant biofilms formed by Staphylococcus aureus on medical devices pose a constant medical threat. A promising alternative to tackle this problem is photodynamic inactivation (PDI). This study focuses on a polyurethane (PU) material with an antimicrobial surface consisting of a composite based on silicate, polycation, and erythrosine B (EryB). The composite was characterized using X-ray diffraction and spectroscopy methods. Anti-biofilm effectiveness was determined after PDI by calculation of CFU mL-1. The liquid PU precursors penetrated a thin silicate film resulting in effective binding of the PU/silicate composite and the PU bulk phases. The incorporation of EryB into the composite matrix did not significantly alter the spectral properties or photoactivity of the dye. A green LED lamp and laser were used for PDI, while irradiation was performed for different periods. Preliminary experiments with EryB solutions on planktonic cells and biofilms optimized the conditions for PDI on the nanocomposite materials. Significant eradication of S. aureus biofilm on the composite surface was achieved by irradiation with an LED lamp and laser for 1.5 h and 10 min, respectively, resulting in a 10,000-fold reduction in biofilm growth. These results demonstrate potential for the development of antimicrobial polymer surfaces for modification of medical materials and devices.

Beyond the Coagulation Cascade: Vitamin K and Its Multifaceted Impact on Human and Domesticated Animal Health

Vitamin K (VK) is an essential micronutrient impacting many systems in the body. This lipid-soluble vitamin is found in various plant and animal products and is absorbed via the lymphatic system. This biomolecule's importance to human health includes but is not limited to its promotion of brain, cardiovascular, bone, and immune functions. These biological properties are also necessary for maintaining domesticated animal health. The synergistic impact of both VK and vitamin D (VD) maximizes these health benefits, specifically for the circulatory and skeletal systems. This manuscript reviews VK's properties, molecular structures, nutrikinetics, mechanisms of action, daily requirements, safety in supplemental form, biomarkers used for its detection, and impacts on various organs. The purpose of synthesizing this information is to evaluate the potential uses of VK for the treatment or prevention of diseases.

Quercetin disrupts biofilm formation and attenuates virulence of Aeromonas hydrophila

Aeromonas hydrophila poses significant health and economic challenges in aquaculture owing to its pathogenicity and prevalence. Overuse of antibiotics has led to multidrug resistance and environmental pollution, necessitating alternative strategies. This study investigated the antibacterial and antibiofilm potentials of quercetin against A. hydrophila. Efficacy was assessed using various assays, including antibacterial activity, biofilm inhibition, specific growth time, hemolysis inhibition, autoaggregation, and microscopic evaluation. Additionally, docking analysis was performed to explore potential interactions between quercetin and virulence proteins of A. hydrophila, including proaerolysin, chaperone needle-subunit complex of the type III secretion system, and alpha-pore forming toxin (PDB ID: 1PRE, 2Q1K, 6GRK). Quercetin exhibited potent antibacterial activity with 21.1 ± 1.1 mm zone of inhibition at 1.5 mg mL-1. It also demonstrated significant antibiofilm activity, reducing biofilm formation by 46.3 ± 1.3% at the MIC and attenuating autoaggregation by 55.9 ± 1.5%. Hemolysis was inhibited by 41 ± 1.8%. Microscopic analysis revealed the disintegration of the A. hydrophila biofilm matrix. Docking studies indicated active hydrogen bond interactions between quercetin and the targeted virulence proteins with the binding energy -3.2, -5.6, and -5.1 kcal mol⁻1, respectively. These results suggest that quercetin is an excellent alternative to antibiotics for combating A. hydrophila infection in aquaculture. The multifaceted efficacy of quercetin in inhibiting bacterial growth, biofilm formation, virulence factors, and autoaggregation highlights the potential for aquaculture health and sustainability. Future research should delve into the precise mechanisms of action and explore synergistic combinations with other compounds for enhanced efficacy and targeted interventions.

Staphylococcus aureus biofilm: Formulation, regulatory, and emerging natural products-derived therapeutics

Staphylococcus aureus can readily form biofilm which enhances the drug-resistance, resulting in life-threatening infections involving different organs. Biofilm formation occurs due to a series of developmental events including bacterial adhesion, aggregation, biofilm maturation, and dispersion, which are controlled by multiple regulatory systems. Rapidly increasing research and development outcomes on natural products targeting S. aureus biofilm formation and/or regulation led to an emergent application of active phytochemicals and combinations. This review aimed at providing an in-depth understanding of biofilm formation and regulation mechanisms for S. aureus, outlining the most important antibiofilm strategies and potential targets of natural products, and summarizing the latest progress in combating S. aureus biofilm with plant-derived natural products. These findings provided further evidence for novel antibiofilm drugs research and clinical therapies.

Vitamin D and vitamin K1 as novel inhibitors of biofilm in Gram-negative bacteria

BACKGROUND

The persistent surge in antimicrobial resistance represents a global disaster. The initial attachment and maturation of microbial biofilms are intimately related to antimicrobial resistance, which in turn exacerbates the challenge of eradicating bacterial infections. Consequently, there is a pressing need for novel therapies to be employed either independently or as adjuvants to diminish bacterial virulence and pathogenicity. In this context, we propose a novel approach focusing on vitamin D and vitamin K1 as potential antibiofilm agents that target Gram-negative bacteria which are hazardous to human health.

RESULTS

Out of 130 Gram-negative bacterial isolates, 117 were confirmed to be A. baumannii (21 isolates, 17.9%), K. pneumoniae (40 isolates, 34.2%) and P. aeruginosa (56 isolates, 47.9%). The majority of the isolates were obtained from blood and wound specimens (27.4% each). Most of the isolates exhibited high resistance rates to β-lactams (60.7-100%), ciprofloxacin (62.5-100%), amikacin (53.6-76.2%) and gentamicin (65-71.4%). Approximately 93.2% of the isolates were biofilm producers, with 6.8% categorized as weak, 42.7% as moderate, and 50.4% as strong biofilm producers. The minimum inhibitory concentrations (MICs) of vitamin D and vitamin K1 were 625-1250 µg mL-1 and 2500-5000 µg mL-1, respectively, against A. baumannii (A5, A20 and A21), K. pneumoniae (K25, K27 and K28), and P. aeruginosa (P8, P16, P24 and P27) clinical isolates and standard strains A. baumannii (ATCC 19606 and ATCC 17978), K. pneumoniae (ATCC 51503) and P. aeruginosa PAO1 and PAO14. Both vitamins significantly decreased bacterial attachment and significantly eradicated mature biofilms developed by the selected standard and clinical Gram-negative isolates. The anti-biofilm effects of both supplements were confirmed by a notable decrease in the relative expression of the biofilm-encoding genes cusD, bssS and pelA in A. baumannii A5, K. pneumoniae K28 and P. aeruginosa P16, respectively.

CONCLUSION

This study highlights the anti-biofilm activity of vitamins D and K1 against the tested Gram-negative strains, which emphasizes the potential of these vitamins for use as adjuvant therapies to increase the efficacy of treatment for infections caused by multidrug-resistant (MDR) strains and biofilm-forming phenotypes. However, further validation through in vivo studies is needed to confirm these promising results.

"Antibacterial effect and possible mechanism of action of 1,3,4-oxadiazole in Staphylococcus aureus"

Staphylococcus aureus is one of the main etiological agents causing foodborne diseases, and the development of new antibacterial agents is urgent. This study evaluated the antibacterial activity and the possible mechanism of action of the 1,3,4-oxadiazole LMM6 against S. aureus. The minimum inhibitory concentration (MIC) of LMM6 ranged from 1.95 to 7.81 µg ml-1. The time-kill assay showed that 48-h treatment at 1× to 8× MIC reduced S. aureus by 4 log colony forming unit (CFU), indicating a bacteriostatic effect. Regarding the possible mechanism of action of LMM6, there was accumulation of reactive oxygen species (ROS) and an increase in the absorption of crystal violet (∼50%) by the cells treated with LMM6 at 1× and 2× MIC for 6-12 h. In addition, there was increased propidium iodide uptake (∼84%) after exposure to LMM6 for 12 h at 2× MIC. After 48 h of treatment, 100% of bacteria had been injured. Scanning electron microscopy observations demonstrated that LMM6-treated cells were smaller compared with the untreated group. LMM6 exhibited bacteriostatic activity and its mechanism of action involves increase of intracellular ROS and disturbance of the cell membrane, which can be considered a key target for controlling the growth of S. aureus.

Synergistic and Additive Effects of Menadione in Combination with Antibiotics on Multidrug-Resistant Staphylococcus aureus: Insights from Structure-Function Analysis of Naphthoquinones

Antimicrobial resistance (AMR) interferes with the effective treatment of infections and increases the risk of microbial spread and infection-related illness and death. The synergistic activities of combinations of antimicrobial compounds offer satisfactory approaches to some extent. Structurally diverse naphthoquinones (NQs) including menadione (-CH3 group at C2) exhibit substantial antimicrobial activities against multidrug-resistant (MDR) pathogens. We explored the combinations of menadione with antibiotic ciprofloxacin or ampicillin against Staphylococcus aureus and its biofilms. We found an additive (0.590 %) were also observed. However, preformed biofilms were not affected. Dent formation was also evident in S. aureus treated with the test compounds. The structure-function relationship (SFR) of NQs was used to determine and predict their activity pattern against pathogens. Analysis of 10 structurally distinct NQs revealed that the compounds with -Cl, -Br, -CH3 , or -OH groups displayed the lowest MICs (32-256 μg/mL). Furthermore, 1,4-NQs possessing a halogen or -CH3 moiety showed elevated ROS activity, whereas molecules with an -OH group affected cell integrity. Improved activity of antimicrobial combinations and SFR approaches are significant in antimicrobial therapies.

Antimicrobial Peptide MPX with Broad-Spectrum Bactericidal Activity Promotes Proper Abscess Formation and Relieves Skin Inflammation

Bacteria have developed antibiotic resistance during the large-scale use of antibiotics, and multidrug-resistant strains are common. The development of new antibiotics or antibiotic substitutes has become an important challenge for humankind. MPX is a 14 amino acid peptide belonging to the MP antimicrobial peptide family. In this study, the antibacterial spectrum of the antimicrobial peptide MPX was first tested. The antimicrobial peptide MPX was tested for antimicrobial activity against the gram-positive bacterium S. aureus ATCC 25923, the gram-negative bacteria E. coli ATCC 25922 and Salmonella enterica serovar Typhimurium CVCC541, and the fungus Candida albicans ATCC 90029. The results showed that MPX had good antibacterial activity against the above four strains, especially against E. coli, for which the MIC was as low as 15.625 μg/mL. The study on the bactericidal mechanism of the antimicrobial peptide revealed that MPX can destroy the integrity of the cell membrane, increase membrane permeability, and change the electromotive force of the membrane, thereby allowing the contents to leak out and mediating bacterial death. A mouse acute infection model was used to evaluate the therapeutic effect of MPX after acute infection of subcutaneous tissue by S. aureus. The study showed that MPX could promote tissue repair in S. aureus infection and alleviate lung damage caused by S. aureus. In addition, skin H&E staining showed that MPX treatment facilitated the formation of appropriate abscesses at the subcutaneous infection site and facilitated the clearance of bacteria by the skin immune system. The above results show that MPX has good antibacterial activity and broad-spectrum antibacterial potential and can effectively prevent the invasion of subcutaneous tissue by S. aureus, providing new ideas and directions for the immunotherapy of bacterial infections.

Antibacterial activity of menadione alone and in combination with oxacillin against methicillin-resistant Staphylococcus aureus and its impact on biofilms

Introduction. Antibiotic resistance is a major threat to public health, particularly with methicillin-resistant Staphylococcus aureus (MRSA) being a leading cause of antimicrobial resistance. To combat this problem, drug repurposing offers a promising solution for the discovery of new antibacterial agents.Hypothesis. Menadione exhibits antibacterial activity against methicillin-sensitive and methicillin-resistant S. aureus strains, both alone and in combination with oxacillin. Its primary mechanism of action involves inducing oxidative stress.Methodology. Sensitivity assays were performed using broth microdilution. The interaction between menadione, oxacillin, and antioxidants was assessed using checkerboard technique. Mechanism of action was evaluated using flow cytometry, fluorescence microscopy, and in silico analysis.Aim. The aim of this study was to evaluate the in vitro antibacterial potential of menadione against planktonic and biofilm forms of methicillin-sensitive and resistant S. aureus strains. It also examined its role as a modulator of oxacillin activity and investigated the mechanism of action involved in its activity.Results. Menadione showed antibacterial activity against planktonic cells at concentrations ranging from 2 to 32 µg ml-1, with bacteriostatic action. When combined with oxacillin, it exhibited an additive and synergistic effect against the tested strains. Menadione also demonstrated antibiofilm activity at subinhibitory concentrations and effectively combated biofilms with reduced sensitivity to oxacillin alone. Its mechanism of action involves the production of reactive oxygen species (ROS) and DNA damage. It also showed interactions with important targets, such as DNA gyrase and dehydroesqualene synthase. The presence of ascorbic acid reversed its effects.Conclusion. Menadione exhibited antibacterial and antibiofilm activity against MRSA strains, suggesting its potential as an adjunct in the treatment of S. aureus infections. The main mechanism of action involves the production of ROS, which subsequently leads to DNA damage. Additionally, the activity of menadione can be complemented by its interaction with important virulence targets.

How Structure-Function Relationships of 1,4-Naphthoquinones Combat Antimicrobial Resistance in Multidrug-Resistant (MDR) Pathogens

Antimicrobial resistance (AMR) is one of the top ten health-related threats worldwide. Among several antimicrobial agents, naphthoquinones (NQs) of plant/chemical origin possess enormous structural and functional diversity and are effective against multidrug-resistant (MDR) pathogens. 1,4-NQs possess alkyl, hydroxyl, halide, and metal groups as side chains on their double-ring structure, predominantly at the C-2, C-3, C-5, and C-8 positions. Among 1,4-NQs, hydroxyl groups at either C-2 or C-5 exhibit significant antibacterial activity against Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, Enterobacter spp. (ESKAPE) and MDR categories. 1,4-NQs exhibit antibacterial activities like plasmids curing, reactive oxygen species generation, efflux pumps inhibition, anti-DNA gyrase activity, membrane permeabilization, and biofilm inhibition. This review emphasizes the structure-function relationships of 1,4-NQs against ESKAPE and MDR pathogens based on a literature review of studies published in the last 15 years. Overall, 1,4-NQs have great potential for counteracting the antimicrobial resistance of MDR pathogens.

Characterization of Novel Klebsiella Phage PG14 and Its Antibiofilm Efficacy

The increasing frequency of infections caused by multidrug-resistant Klebsiella pneumoniae demands the development of unconventional therapies. Here, we isolated, characterized, and sequenced a Klebsiella phage PG14 that infects and lyses carbapenem-resistant K. pneumoniae G14. Phage PG14 showed morphology similar to the phages belonging to the family Siphoviridae. The adsorption curve of phage PG14 showed more than 90% adsorption of phages on a host within 12 min. A latent period of 20 min and a burst size of 47 was observed in the one step growth curve. Phage PG14 is stable at a temperature below 30°C and in the pH range of 6 to 8. The PG14 genome showed no putative genes associated with virulence and antibiotic resistance. Additionally, it has shown lysis against 6 out of 13 isolates tested, suggesting the suitability of this phage for therapeutic applications. Phage PG14 showed more than a 7-log cycle reduction in K. pneumoniae planktonic cells after 24 h of treatment at a multiplicity of infection (MOI) of 10. The phage PG14 showed a significant inhibition and disruption of biofilm produced by K. pneumoniae G14. The promising results of this study nominate phage PG14 as a potential candidate for phage therapy. IMPORTANCE Klebsiella pneumoniae is one of the members of the ESKAPE (Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, and Enterobacter species) group of pathogens and is responsible for nosocomial infections. The global increase of carbapenem-resistant K. pneumoniae has developed a substantial clinical threat because of the dearth of therapeutic choices available. K. pneumoniae is one of the commonly found bacteria responsible for biofilm-related infections. Due to the inherent tolerance of biofilms to antibiotics, there is a growing need to develop alternative strategies to control biofilm-associated infections. This study characterized a novel bacteriophage PG14, which can inhibit and disrupt the K. pneumoniae biofilm. The genome of phage PG14 does not show any putative genes related to antimicrobial resistance or virulence, making it a potential candidate for phage therapy. This study displays the possibility of treating infections caused by multidrug-resistant (MDR) isolates of K. pneumoniae using phage PG14 alone or combined with other therapeutic agents.