Search Results (126)

Background/Objectives: The rise in methicillin-resistant Staphylococcus aureus (MRSA) demands new therapeutic strategies. In this study, a series of 2-(amino)quinazolin-4(3H)-one derivatives were synthesized and evaluated for antistaphylococcal activity. Methods/Results: Through screening against S. aureus ATCC25923 and USA300 JE2, several submicromolar inhibitors were identified. Among them, compound 6l, which contains a 7-chloro substituent on the key parental scaffold, exhibited strong overall antibacterial activity (MIC₅₀: 1.0 µM, ATCC25923; 0.6 µM, JE2) and served as a lead for further structural optimization. Structure–activity relationship analysis showed that substitution at the 2-position was critical, with its optimized analog 6y (3,4-difluorobenzylamine) exhibiting the highest potency (MIC₅₀: 0.36 µM, ATCC25923; 0.02 µM, JE2). Cytotoxicity assays in HepG2 cells revealed six compounds with IC₅₀ values above 20 µM, yielding efficacy windows greater than 10. Compound 6y exhibited an exceptional index (~885). Consistently, in an H460 lung epithelial infection model mimicking MRSA pneumonia, 6y significantly reduced intracellular bacterial loads with minimal host cell damage, outperforming comparator compounds. Conclusions: These findings highlight 2-(amino)quinazolin-4(3H)-one derivatives, particularly 6y, as promising leads for the development of new antistaphylococcal agents. Full article

The resistance of Staphylococcus aureus to conventional pharmacological treatments has gradually increased. Thus, new therapeutic strategies are needed. Three tricyclic antidepressants (TCAs), amitriptyline (AMT), nortriptyline (NOR), and clomipramine (CLO), stand out with potential in this regard. Thus, the objective of this study was to evaluate the antibacterial activity of TCAs against S. aureus. The methodology used broth microdilution, checkerboard, flow cytometry, fluorescence microscopy, and scanning electron microscopy (SEM) techniques. The results showed that the minimum inhibitory concentration (MIC) of AMT was 256 µg/mL, while the MIC of NOR was 128 µg/mL, and the MIC of CLO was between 64 and 128 µg/mL. The TCAs exhibited bactericidal activity. In the analysis of the association with oxacillin (OXA), AMT exhibited 75% synergism, while NOR and CLO obtained 62.5%. In combination with vancomycin (VAN), AMT and NOR presented 100% additive interactions, while CLO exhibited 62.5% indifferent interactions. The mechanism of TCAs, isolated and combined with OXA, was associated with a reduction in cell viability, resulting from their action on the bacterial genetic material and generation of oxidative stress. Furthermore, the action of the drugs produced intense morphological changes in the bacterial cells. In conclusion, TCAs are a potential alternative for antistaphylococcal therapy. Full article

Background: The opportunistic pathogen Staphylococcus aureus causes skin and soft tissue infections that are associated with biofilm formation, and in immunocompromised patients can progress to surgical site infections, pneumonia, bacteremia, sepsis, and even death. Most antibiotics actively damage living, dividing cells on the surface of the biofilm, where there is a high concentration of nutrients and oxygen, while in the depths, where these factors are scarce, slowly growing cells remain. Objectives: The aim of our study was to evaluate the antibiofilm potential of ethyl acetate roots (EtOAcR) and aerial parts (EtOAcAP) extracts from the perennial Bulgarian plant Geum urbanum L. against methicillin-resistant S. aureus (MRSA) NBIMCC 8327. Methods: The effects of both extracts on the expression of biofilm-related genes, icaA and icaD, were investigated. The cytotoxicity of EtOAcR and EtOAcAP on A-375 (human melanoma), A-431 (epidermoid skin cancer) and HaCaT (normal keratinocytes) cell lines, and the induction of apoptosis were determined. Finally, the in vivo skin irritation potential of the most active extract was studied. Results: Both tested extracts inhibited biofilm formation at concentrations that did not affect bacterial growth. Interestingly, the expression of icaA and icaD was upregulated, although the biofilm development was inhibited 72.4–90.5% by EtOAcAP and 18.9–20.4% by EtOAcR at sub-MICs. EtOAcAP extract showed a more favorable cytotoxic profile on non-tumorigenic cells and stronger antineoplastic activity (IC₅₀ = 6.7–14.68 µg/mL) as compared to EtOAcR extract (IC₅₀ = 8.73–23.67 µg/mL). Therefore, a skin irritation test was performed with the EtOAcAP extract at ten-times higher concentrations than the minimum inhibitory one, and, resultantly, the primary irritation index was equal to zero (no skin irritation observed). Conclusions: The EtOAcAP extract was proven to be an effective antistaphylococcal agent with favorable skin tolerance. The extract showed strong antineoplastic activity and antibiofilm effect at sub-MICs, which outlines new prospects for its development as a natural product for specific skin applications in medical practice. Full article

Raw goat milk-derived Lactococcus lactis MK1/3 (CCM 9209) was studied to show its potential for use in the dairy industry. Finding an innovative strain indicates having a new safe, original additive for functional food. The strain has been shown to be safe using a model experiment with Balb/c mice, when no mortality was noted. Its counts were increased continually during 120 days, with the highest value on day 90 (4.38 ± 1.24 colony-forming unit per gram (CFU/g, log 10). In vivo (in the experimental mice), anti-staphylococcal effect was noted with difference 1.82 log cycles. The safety of the strain MK1/3 has been also indicated by the fact that it did not produce damaging enzymes, it has been susceptible to antibiotics, and it has shown low-grade biofilm-forming ability (0.126 ± 0.35). This strain has tolerated bile, and low pH sufficiently. It produced a postbiotic active substance with inhibitory activity against cheese and milk contaminants (Enterococci), reaching antimicrobial activity up to 3200 AU/mL. The count of the strain MK1/3 was higher in yogurts from ewe goat milk (4.66 ± 0.30 CFU/g, log 10), in comparison with its count in yogurts from ewe milk (4.10 ± 0.10 CFU/g, log 10), with no influencing yogurt pH. Its use in 100% starter culture to process fresh cheese based on goat milk was revealed in the standard cheese quality with sufficient amount of lactic acid microbiota. To support the benefit of the strain MK1/3, additional human trials have been reinforced. Full article

Background/Objectives: The optimal therapy for polymicrobial wound infections is poorly defined. We sought to characterize the ability of linezolid to combat mixed cultures of Staphylococcus aureus and Pseudomonas aeruginosa. Methods: The antistaphylococcal activity of linezolid was assessed in 24-h time-killing experiments that used S. aureus and P. aeruginosa isolated from polymicrobial wound infections. Clindamycin was also evaluated as a comparator. A Hill-type mathematical model was used to assess the maximum killing of S. aureus (E_max). The ability of linezolid to potentiate the activity of host defense peptides against P. aeruginosa was evaluated using LL-37. Results: In the presence of P. aeruginosa, the E_max of linezolid decreased in 5/9 co-culture experiments and increased in 4/9 co-culture experiments in comparison to linezolid against S. aureus alone. The potency of linezolid was not significantly impacted by the presence of P. aeruginosa. In comparison, the maximal S. aureus killing achieved by clindamycin decreased in eight out of nine experiments, and somewhat paradoxically, the potency increased in nine out of nine experiments. In the host defense peptide assay, the supratherapeutic linezolid concentration of 64 mg/L did not significantly enhance the killing of the LL-37 peptides (p ≥ 0.121), but the concentration of linezolid was significantly associated with the killing of one of three P. aeruginosa isolates (p = 0.005). Conclusions: P. aeruginosa had a minimal impact on the antistaphylococcal activity of linezolid in comparison to clindamycin. Linezolid did not exert a consistent ability to enhance the antipseudomonal activity of host defense peptides. These data may help inform antimicrobial selection during polymicrobial wound infections. Full article

Acne vulgaris is one of the most common dermatological diseases and has a complex etiology. Despite the wide range of available therapeutic options, modern and effective solutions are still being sought, particularly in the area of topical therapy. The aim of this study was to develop hydrogel formulations that provide stability for the antibiotics they contain—tetracycline or chlortetracycline enriched with azeloglycine—the latter an ingredient supporting acne-prone skin care. The physicochemical parameters, stability, and antimicrobial activity of the obtained formulations were analyzed. HPLC analysis showed that tetracycline exhibited greater stability than chlortetracycline, especially in mildly acidic and neutral environments. The addition of azeloglycine improved the rheological properties of the hydrogels, reduced tetracycline degradation under alkaline conditions, and enhanced the penetration of active ingredients into the model sebum. All tested formulations demonstrated antimicrobial activity against Staphylococcus aureus. In the artificial sebum biofilm model, hydrogels containing azeloglycine more effectively reduced staphylococcal biofilm mass. No formulations showed toxicity towards Galleria mellonella larvae. The results indicate the potential usefulness of the developed hydrogels as modern multifunctional formulations for topical acne treatment. Hydrogel formulations containing tetracycline and azeloglycine may represent a promising future anti-acne preparation exhibiting synergistic antibacterial, anti-inflammatory, and sebum-cleansing effects. Full article

In this study, a global response analysis was performed to explore the mechanism of action of Usnic acid and its synergy with Norfloxacin, a well-known quinolone antibiotic to which MRSA clinical isolates showed resistance (MIC, 500 µg/mL). A microdilution assay, a growth kinetics analysis, a microscopic analysis, and cell-based assays consistently showed that Usnic acid possesses strong anti-staphylococcal activity (MIC, 7.8 µg/mL), causes cell leakage, modulates efflux pump activity, and synergizes with Norfloxacin against the multi-drug-resistant clinical isolate MRSA 2071. Whole-cell proteome profiling using gel-free proteomics-based nano-LC-ESI-QTOF-MS/MS revealed several proteins whose expression was significantly modulated by Usnic acid and Norfloxacin alone or in combination. Usnic acid downregulated the abundance of RNA polymerase subunits (RpoB and RpoC), carbamoyl phosphate synthase large subunit (PyrAB), chaperone (GroEL), and adenylosuccinate synthetase (PurA). Interestingly, proteins found to be upregulated in the presence of Usnic acid and Norfloxacin included oxidative-stress-related proteins such as peroxidase (Tpx), alkyl hydroperoxide reductase (AphC), and general stress protein (UspA). This study clearly shows that Usnic acid affects numerous cellular targets and can potentiate the action of Norfloxacin. Furthermore, an in vivo study showed that UA at low concentrations prevents body weight gain, but changes in other tested toxicological parameters were found to be within normal limits. Thus, UA at low doses appears to be a promising candidate for repurposing old antibiotics through combination therapy against MRSA infections. Full article

Staphylococcus aureus and Pseudomonas aeruginosa are classified as ESKAPE pathogens that present a significant challenge to treatment due to their increased resistance to a considerable number of antimicrobial agents. Background/Objective: Biofilms exacerbate treatment challenges by providing enhanced antimicrobial and environmental protection. Mixed-species biofilms further complicate treatment options through numerous complex interspecies interactions, leading to potentially severe adverse clinical outcomes. Methods: This study assessed the interaction between clinical S. aureus and P. aeruginosa isolates during biofilm formation using microplate biofilm formation assays, scanning electron microscopy, and confocal microscopy. Results: We identified a competitive relationship between P. aeruginosa and S. aureus, where both pathogens exhibited a reduction in biofilm formation during mixed-species biofilms compared with monocultures, although P. aeruginosa outcompeted S. aureus. Furthermore, we found that the cell-free conditioned media (CFCM) of P. aeruginosa significantly reduced the S. aureus biofilms. Using fractioned CFCM, we identified that the anti-staphylococcal activity of the >10 kDa fraction was almost identical to the non-fractioned CFCM. Our confocal microscopy results suggest that P. aeruginosa CFCM depolarize S. aureus membranes and reduces the biofilm burden. Conclusions: These findings contribute to our understanding of the mechanisms underlying the interactions between these pathogens, suggesting that there is an antagonistic relationship between S. aureus and P. aeruginosa in a biofilm setting. Full article

Background/Objectives: Staphylococcus aureus is a leading cause of bacteraemia in Danish hospitals. Approximately 70% of clinical S. aureus isolates are penicillin-resistant, which is predominantly due to blaZ-mediated β-lactamase production. Methods: A collection of 489 S. aureus strains derived from bacteraemia were cultured and their genomes sequenced. Results: From this collection, 71% of isolates were methicillin-susceptible S. aureus (MSSA) harbouring blaZ. While most isolates contained the blaZ gene belonging to the well-characterised A, B, C and D variants, three strains (1%) produced a BlaZ protein characterised by having threonine residues on both positions 128 and 216 and, therefore, belonged to neither of the established blaZ variants. We named this variant, variant F. We report that clinical isolates expressing blaZ variant F were resistant to oxacillin. The β-lactamase production phenotype in isolates carrying either of the A, B, C or D variants was only weakly discernible on MIC gradient strip and disk diffusion tests. When the β-lactamases were expressed either from a T7 promoter or from their endogenous promoters in Escherichia coli, variant F was significantly better at degrading ampicillin than variant A. We also showed that variant F conferred oxacillin resistance when expressed in an isogenic S. aureus strain, while variant A did not. Finally, we demonstrated that the F variant threonine 216 played a role in the enzyme’s superior activity. Conclusions: Our findings demonstrate that the new F variant of BlaZ is sufficient to render S. aureus a BORSA strain, which is superior in the degradation of common anti-staphylococcal β-lactam antibiotics, such as benzylpenicillin, cloxacillin, and oxacillin. It is sensitive to β-lactamase inhibitors and rapidly degrades nitrocefin. We provide a genetic explanation for the borderline oxacillin-resistant S. aureus (BORSA) phenotype. Full article

Coagulase-negative bacteria of the Staphylococcus genus are currently frequent food contaminants. The increase in antibiotic resistance means that these microorganisms are becoming the cause of many serious infections and toxications. Their resistance to routinely used chemical compounds has led to the search for alternative methods to combat food-borne pathogens. For this purpose, plant extracts rich in phenolic compounds are increasingly used. The aim of this study was to assess the effect of extracts obtained from the pseudo-fruits and flesh of Rosa canina, Rosa rugosa and Rosa pomifera ‘Karpatia’ on the growth dynamics of bacterial strains of the Staphylococcus genus (72-h co-culture; plate inoculation method). The conducted studies allowed us to conclude that extracts from Rosa spp. show high antistaphylococcal activity. However, it is not proportional to the dose used. Rosa spp. extracts already at concentrations of ¼ MIC limit the growth of the biomass of bacteria of the Staphylococcus genus. The above-described dependencies are very individual—strain-specific, not species-specific. However, based on SEM analysis, it can be observed that the antistaphylococcal mechanism of action of Rosa spp. extracts is associated with the coating of cell walls by the extracts and the disintegration of cell membranes, as a result of which the cells are destroyed. Full article

Introduction/Objectives: Nosocomial infections caused by S. aureus and S. epidermidis resistant strains are an important cause of morbidity and mortality worldwide. Due to the increasing rate of resistance to conventional antibiotics, the discovery of new antibiotic drugs is crucial to keep pace with the evolution of these pathogenic bacterial species. Methods: The 3-nitro-2H-chromene moiety is present in several compounds with potent antibacterial activity; based on these previous studies, we report herein the synthesis of 20 new 2-aryl-3-nitro-2H-chromene derivatives and the evaluation of their antibacterial potential in vitro. Results: Mono-halogenated nitrochromenes showed moderate anti-staphylococcal activity with MIC values of 8–32 μg/mL, whereas tri-halogenated 3-nitro-2H-chromenes displayed potent anti-staphylococcal activities with MIC values of 1–8 μg/mL. Notably, 2-(4-bromophenyl)-6-bromo-8-chloro-3-nitro-2H-chromene 5s was the best antibacterial agent in the series against multidrug-resistant strains of S. aureus and S. epidermidis with MIC values of 4 μg/mL and 1–4 μg/mL, respectively. Conclusions: nitrochromene 5s shows a good safety profile, so it can be considered as a lead for further development. Full article

Background: In the era of resistance, the design and search for new “small” molecules with a narrow spectrum of activity that target a protein or enzyme specific to a certain bacterium with high selectivity and minimal side effects remains an urgent problem of medicinal chemistry. In this regard, we developed and successfully implemented a strategy for the search for new hybrid molecules, namely, the not broadly known [2-(3-R-1H-[1,2,4]-triazol-5-yl)phenyl]amines. They can act as “building blocks” and allow for the introduction of certain structural motifs into the desired final products in order to enhance the antistaphylococcal effect. Methods: The “one-pot” synthesis of the latter is based on the conversion of substituted 4-hydrazinoquinazolines or substituted 2-aminobenzonitriles and carboxylic acid derivatives to the target products. The possible molecular mechanism of the synthesized compounds (DNA gyrase inhibitors) was investigated and discussed using molecular docking, and their further study for antistaphylococcal activity was substantiated. Results: A significant part of the obtained compounds showed high antibacterial activity against Staphylococcus aureus (MIC: 10.1–62.4 µM) and 5-bromo-2-(3-(furan-3-yl)-1H-1,2,4-triazol-5-yl)aniline and 5-fluoro-2-(3-(thiophen-3-yl)-1H-1,2,4-triazol-5-yl)aniline, with MICs of 5.2 and 6.1 µM, respectively, approaching the strength of the effect of the reference drug, “Ciprofloxacin” (MIC: 4.7 µM). The conducted SAR and ADME analyses confirm the prospects of the further structural modification of these compounds. The obtained [2-(3-R-1H-[1,2,4]-triazol-5-yl)phenyl]amines reveal significant antimicrobial activity and deserve further structural modification and detailed study as effective antistaphylococcal agents. The SAR analysis revealed that the presence of a cycloalkyl or electron-rich heterocyclic fragment in the third position of the triazole ring was essential for the antibacterial activity of the obtained compounds. At the same time, the introduction of a methyl group into the aniline moiety led to an enhancement of activity. The introduction of halogen into the aniline fragment has an ambiguous effect on the level of antistaphylococcal activity and depends on the nature of the substituent in the third position. Conclusions: Obtained [2-(3-R-1H-[1,2,4]-triazol-5-yl)phenyl]amines reveal significant antistaphylococcal activity and deserve for further detailed study as effective antibacterial agents. Full article

Many indigenous plants of the Philippines, including essential oil-bearing species, remain phytochemically and pharmacologically unexplored. In this study, the chemical composition of leaf essential oils (EOs) hydrodistilled from Litsea leytensis (Lauraceae) and Piper philippinum (Piperaceae) was determined using dual-column (HP-5MS/DB-WAX)/dual-detector gas chromatography and mass spectrometry analysis. Caryophyllene oxide (15.751/16.018%) was identified as the main compound in L. leytensis EO, followed by β-caryophyllene (11.130/11.430%) and α-copaene (9.039/9.221%). Ishwarane (25.937/25.280%), nerolidol (9.372/10.519%) and 3-ishwarone (6.916/2.588%) were the most abundant constituents of P. philippinum EO. Additionally, the in vitro growth-inhibitory activity of the EOs in the liquid and vapour phases against Staphylococcus aureus was evaluated using the broth microdilution volatilisation assay. Although the results showed no anti-staphylococcal effect, the presence of various bioactive compounds in both EOs suggests their potential future use in industrial applications. Full article

Introduction: This study explores the bioactive properties of extracts obtained from Robin’s pincushion (Diplolepis rosae) collected in Sokobanja, Serbia. Results: Comprehensive in vitro assessments reveal high concentrations of total phenolics (186.37 mg GAE/g), along with significant levels of carotenoids (44.10 μg β-car/g). Robin’s pincushion exhibited superior antioxidant capacities across DPPH, ABTS, and reducing power assays, significantly outperforming comparable extracts from rosehip (Rosa canina) and black rosehip (Rosa spinosissima) in these activities. Additionally, high inhibitory effects were observed in antimicrobial assays, with the extract demonstrating minimal inhibitory concentrations (MIC) as low as 1.56 mg/mL against the Staphylococcus species. Notably, the extract achieved full bactericidal effect within 24 h in time-kill kinetic studies which additionally highlight its potent antistaphylococcal potential. Materials and methods: Analyzing their phytochemical profiles and evaluating their potential as antioxidant, anti-inflammatory, antihyperglycemic, and antimicrobial agents, wide-ranging evaluation of bioactivity of Robin’s pincushion was conducted. Conclusions: These findings highlight Robin’s pincushion as a promising natural source of bioactive compounds with potential applications in traditional and modern medicine for managing oxidative stress, inflammation, hyperglycemia, and microbial infections. Full article

Staphylococcus aureus is a leading cause of bloodstream infection (SAB), with up to 30% mortality. Despite treatment with standard antibiotics, one in three patients develops a persistent infection, which portends a five-fold increase in the risk of death. Persistent SAB has been attributed in part to the inability of antistaphylococcal antibiotics to eradicate intracellular S. aureus surviving inside macrophages. (-)- Epigallocatechin gallate (EGCG) is a catechin found in green tea that has been widely studied for its broad biological activities, ranging from anticancer to antibacterial activity. However, EGCG is greatly limited by its poor drug-like properties in terms of stability, membrane permeability, and bioavailability. In this study, we established through a series of in vitro experiments that structural modifications of EGCG enhanced drug-like properties while maintaining or improving its antistaphylococcal activity. Our lead EGCG analogs (MCC-1 and MCC-2) showed improved biochemical properties along with increased potency against extracellular S. aureus and restored susceptibility of β-lactam agents to methicillin-resistant S. aureus (MRSA). Importantly, the lead analogs but not EGCG potentiated macrophage- and antibiotic-mediated clearance of intracellular bacteria. Overall, EGCG analogs showed promise for further development as adjunctive therapy candidates for the treatment of SAB. Full article