Search Results (16)

Multidrug-resistant (MDR) pathogens and biofilm-associated infections represent a major global health concern, particularly in the context of medical devices such as catheters, tubing, and blood sampling devices. Biofilms, responsible for up to 85% of human infections, confer a high level of microbial resistance and compromise device performance and patient safety. In this study, the antibiofilm potential of Syzygium aromaticum (clove) essential oil was investigated through an in vitro assay. GC–MS analysis revealed eugenol (72.77%) as the predominant compound, accompanied by β-caryophyllene (14.72%) and carvacrol (2.09%). The essential oil exhibited notable antimicrobial activity, producing inhibition zones of 30.5 ± 4.5 mm against Staphylococcus aureus, 24.5 ± 0.5 mm against Micrococcus luteus, 16.0 ± 2.0 mm against Escherichia coli, 13.0 ± 1.0 mm against Pseudomonas aeruginosa, 23.5 ± 1.5 mm against Candida albicans, and 24.0 ± 2.0 mm against C. glabrata. A marked reduction in biofilm biomass observed on polyvinyl chloride (PVC) surfaces. The application of clove essential oil as a coating for PVC-based medical devices remains a future possibility that requires formulation and in vivo testing. This strategy is proposed as potentially eco-safe, although environmental toxicity and biocompatibility have not yet been evaluated. It could contribute to the prevention of biofilm formation in arterial sampling systems and other healthcare-related materials, thereby enhancing device safety and longevity. Full article

Bacteriocins from lactic acid bacteria have attracted considerable attention as natural alternatives to conventional antimicrobial agents. Weissellicin LM85, a bacteriocin purified from Weissella confusa LM85, has been less extensively studied in terms of its mechanism of action and potential applications. In this study, purified weissellicin LM85 exhibited potent inhibitory effects against Gram-positive bacteria, with minimum inhibitory and bactericidal concentrations determined against Micrococcus luteus MTCC106. Time-kill assays and fluorescence staining indicated a concentration-dependent reduction in cell viability, accompanied by membrane disruption. Further analyses revealed potassium ion efflux, dissipation of membrane potential (Δψ) and pH gradient (ΔpH), genomic DNA fragmentation, and pronounced morphological alterations in target cells. These findings are strongly suggestive of membrane-targeted bactericidal activity, likely involving pore-forming effects. In addition, weissellicin LM85 inhibited both growth and biofilm formation of Salmonella enterica subsp. enterica serovar Typhimurium ATCC13311 and Staphylococcus aureus subsp. aureus ATCC25923. Mechanistic analyses revealed the disruption of cell membrane integrity, leakage of potassium ions, cytoplasmic contents, and non-specific DNA degradation, indicating a multifaceted antibacterial mode of action. These findings highlight weissellicin LM85 as a promising natural antimicrobial with potential applications in food preservation and the control of foodborne pathogens and biofilm-associated infections. Further studies on cytotoxicity and in vivo efficacy are required to advance its practical application. Full article

This study investigated the essential oils (EOs) from leaf, bark, and fruit of Mespilodaphne cymbarum (Kunth) Trofimov (Lauraceae), focusing on their chemical composition and antimicrobial and antibiofilm activities. EOs were extracted from plants collected in the Amazon during dry and flood seasons and analyzed by gas chromatography–mass spectrometry. Although chemical differences were evident among plant organs and chemotypes, the influence of seasonality was not pronounced. Fruit EO was dominated by α- and β-santalene and limonene. Bark EO was rich in phenylpropanoids, including methyl eugenol, myristicin, and elemicin. Leaf EO showed the greatest metabolic diversity, with chemotype-specific variations. Leaf and bark EOs demonstrated superior antibacterial and antibiofilm activities compared to fruit EO, especially against Gram-positive bacteria such as Staphylococcus epidermidis, Staphylococcus aureus, and Micrococcus luteus. Chemotype-1 leaf and bark EOs inhibited S. epidermidis biofilm formation, while chemotype-2 reduced bacterial growth. The leaf EOs from both chemotypes reduced bacterial growth against S. aureus, and bark EO decreased biofilm formation. All leaf and bark EOs showed antibiofilm activity against M. luteus. These findings highlight the potential of M. cymbarum EOs as natural sources of bioactive compounds and emphasize the importance of chemotype and plant organ selection for optimized applications. Full article

Arthrospira platensis (spirulina) is a cyanobacterium containing various phytochemical compounds associated with various antioxidant, antimicrobial, antiviral, anticancer, anti-inflammatory, and immune-promoting properties. The efficacy of ethanolic and methanolic crude extracts of A. platensis regarding antibacterial, antioxidant, and anticancer effects was determined in this study. The ethanolic extract showed the highest antioxidant activity by 8.96 ± 0.84 mg gallic acid equivalent per gram of extract (mg GAE/g extract), 53.03 ± 4.21 mg trolox equivalent antioxidant capacity per gram of extract (mg TEAC/g extract), and 48.06 ± 0.78 mg TEAC/g extract as determined by DPPH, ABTS, FRAP assays, respectively. Moreover, the ethanolic extract showed the highest total phenolic and flavonoid compound contents by 38.79 ± 1.61 mg GAE/g extract and 27.50 ± 0.53 mg of quercetin equivalent per gram of extract (mg QE/g extract). Gallic acid and quercetin in the extracts were also determined by HPLC. The antibacterial activity was evaluated by agar well diffusion and broth dilution methods on skin pathogenic bacteria, including Staphylococcus aureus, Staphylococcus epidermidis, methicillin-resistant S. aureus (MRSA), Micrococcus luteus, Pseudomonas aeruginosa, and Cutibacterium acnes. The inhibition zone of A. platensis extracts ranges from 9.67 ± 0.58 to 12.50 ± 0.50 mm. In addition, MIC and MBC values ranged from 31.25 to 125 mg/mL. The inhibition of biofilm formation and biofilm eradication by A. platensis ethanolic extract was 87.18% and 99.77%, as determined by the crystal violet staining assay. Furthermore, the anticancer activity of A. platensis on A375 human melanoma cells was examined. The ethanolic and methanolic extracts induced DNA apoptosis through both intrinsic and extrinsic pathways by upregulating the expression of caspase-3, caspase-8, and caspase-9. These findings suggested that A. platensis demonstrated promising antioxidant, antibacterial, and anticancer activities, emphasizing its potential as a natural therapeutic agent for the management of pathological conditions. Full article

In the current study, extensive Orbitrap mass spectrometry analysis was conducted for skin strain Micrococcus luteus C01 planktonic cultures and biofilms after 24 h and 72 h of incubation either in the presence of epinephrine or without any implementations. The investigation revealed the complex and conditionally extensive effect of epinephrine at concentrations closer to normal blood plasma concentrations on both planktonic cultures and biofilms of skin strain M. luteus C01. The concentrations of hundreds of proteins changed during the shift from planktonic growth mode to biofilm and hundreds of proteins were downregulated or upregulated in the presence of epinephrine. Ribosomal, TCA, and cell division proteins appear to be the most altered in their amounts in the presence of the hormone. Potentially, the regulatory mechanism of this process is connected with c-di-GMP and histidine kinases, which were affected by epinephrine in different samples. The phenomenon of epinephrine-based biofilm regulation in M. luteus C01 has wide implications for microbial endocrinology and other research areas. Full article

Synthetic peptides, including tetraspanin CD9 peptides, are increasingly coming into focus as new treatment strategies against various organisms, including bacteria, that cause underarm odour. The use of deodorants and antiperspirants is associated with side effects. Therefore, it is critical to find an alternative therapeutic approach to combat underarm odour. The aim of this study is to investigate the antibacterial effect of tetraspanin CD9 peptides against the skin microbiota that cause malodour in the underarms. The antimicrobial activity of CD9 peptides against Micrococcus luteus (M. luteus), Bacillus subtilis (B. subtilis), Staphylococcus epidermidis (S. epidermidis), and Corynebacterium xerosis (C. xerosis) was investigated by the disc diffusion method. Minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) were determined by broth microdilution assays using CD9 peptide concentrations ranging from 1 mg/mL to 0.0078 mg/mL. In addition, the anti-biofilm activity of the CD9 peptides was determined. The CD9 peptides showed different antibacterial activity with an inhibition zone of 7.67, 9.67, 7.00, and 6.00 mm for S. epidermidis, M. luteus, C. xerosis, and B. subtilis, respectively. All bacteria had the same MBC value of 1 mg/mL. A high MIC of CD9 peptides was observed for S. epidermidis and M. luteus at 0.5 mg/mL. The MIC values of B. subtilis and C. xerosis were 0.125 mg/mL and 0.25 mg/mL, respectively. CD9 peptides significantly inhibited biofilm development of S. epidermidis, B. subtilis, and C. xerosis isolates. The CD9 tetraspanin peptide has excellent antibacterial activity against bacteria that cause underarm odour. Therefore, the CD9 tetraspanin peptide is a promising alternative to deodorants and antiperspirants to combat commensal bacteria of the skin that cause underarm odour. Full article

Biofilms are microbial communities of cells embedded in extracellular matrix, and they are regarded as a major form of the natural and laboratory occurrence of bacteria. Cutaneous microbiota is represented by prokaryotic and eukaryotic organisms, which form biofilms in the different niches including the skin surface, glands, and hair follicles. Despite of a large number of in vitro studies dedicated to the biofilms of cutaneous bacteria, the methods used usually do not closely take into account the specific surroundings of certain skin parts. In this study, we introduce a new simple method of biofilm cultivation on the solid keratine/agarose pellets embedded in polyacrylamide gel. In such a model system, we tried to minimize the amount of liquid phase, which makes a model close to a human comedo, and provide a prominent biofilm formation of selected cutaneous bacteria. Full article

Bacillus licheniformis is used in a broad spectrum of areas, including some probiotic preparations for human and veterinary health. Moreover, B. licheniformis strains are known producers of various bioactive substances with antimicrobial and antibiofilm effects. In searching for new potentially beneficial bacteria for oral health, the inhibitory effect of B. licheniformis strains isolated from canine dental biofilm against pathogenic oral bacteria was evaluated. The antimicrobial effect of neutralized cell-free supernatants (nCFS) was assessed in vitro on polystyrene microtiter plates. Furthermore, molecular and morphological analyses were executed to evaluate the production of bioactive substances. To determine the nature of antimicrobial substance present in nCFS of B. licheniformis A-1-5B-AP, nCFS was exposed to the activity of various enzymes. The nCFS of B. licheniformis A-1-5B-AP significantly (p < 0.0001) reduced the growth of Porphyromonas gulae 3/H, Prevotella intermedia 1/P and Streptococcus mutans ATCC 35668. On the other hand, B. licheniformis A-2-11B-AP only significantly (p < 0.0001) inhibited the growth of P. intermedia 1/P and S. mutans ATCC 35668. However, enzyme-treated nCFS of B. licheniformis A-1-5B-AP did not lose its antimicrobial effect and significantly (p < 0.0001) inhibited the growth of Micrococcus luteus DSM 1790. Further studies are needed for the identification of antimicrobial substances. Full article

The impact of steroid hormones, and particularly estradiol, on human microbiota could be recognized as a substantial part of human-microbiota interactions. However, an area that remains poorly investigated is that of the skin and vaginal microbial communities and biofilms, which contain non-pathogenic bacteria of phyla Firmicutes and Actinobacteria, especially probiotic bacteria of the genus Lactobacillus and the widespread, safe skin genus, Micrococcus. Experiments with Lactobacillus paracasei AK508 and Micrococcus luteus C01 biofilms on PTFE cubes showed dose-dependent effects of estradiol at concentrations of 0.22 nM and 22 nM. The hormone mostly inhibits L. paracasei growth and stimulates M. luteus. The presented studies of colony-forming unit (CFU) amountsand cell aggregation in biofilms on glass fiber filters showed the same general tendencies. Estradiol generally increased the aggregation of cells in monospecies communities and potentially changed the synthesis of antibacterial metabolites in L. paracasei. The balance between two bacteria in mixed-species biofilms depended on the initial adhesion stage, and when this stage was reduced, micrococci were more resistant to the antagonistic action of L. paracasei. Moreover, in mixed-species biofilms, the effect of estradiol on lactobacilli altered from inhibition to stimulation, potentially due to the presence of M. luteus. At the same time, ethanol as a solvent for estradiol at the concentration 0.6% acted mostly as an antagonist of the hormone and had an opposite effect on bacteria; nevertheless, the overlapping of ethanol and estradiol effects was shown to be minimal. The data obtained prove the complexity of microbial interactions and the regulatory effect of estradiol on commensal bacteria biofilms. Full article

Lactic acid bacteria (LAB) produce antimicrobial substances that could potentially inhibit the growth of pathogenic and food spoilage microorganisms. Lacticaseibacillus rhamnosus XN2, isolated from yak yoghurt, demonstrated antibacterial activity against Bacillus subtilis, B. cereus, Micrococcus luteus, Brochothrix thermosphacta, Clostridium butyricum, S. aureus, Listeria innocua CICC 10416, L. monocytogenes, and Escherichia coli. The antibacterial activity was estimated to be 3200 AU/mL after 30 h cultivation. Time-kill kinetics curve showed that the semi-purified cell-free supernatants (CFS) of strain XN2 possessed bactericidal activity. Flow cytometry analysis indicated disruption of the sensitive bacteria membrane by semi-purified CFS, which ultimately caused cell death. Interestingly, sub-lethal concentrations of semi-purified CFS were observed to reduce the production of α-haemolysin and biofilm formation. We further investigated the changes in the transcriptional level of luxS gene, which encodes signal molecule synthase (Al-2) induced by semi-purified CFS from strain XN2. In conclusion, L. rhamnosus XN2 and its bacteriocin showed antagonistic activity at both cellular and quorum sensing (QS) levels. Finally, bacteriocin was further purified by reversed-phase high-performance liquid chromatography (RP-HPLC), named bacteriocin XN2. The amino acid sequence was Met-Lue-Lys-Lys-Phe-Ser-Thr-Ala-Tyr-Val. Full article

The present study was designed to evaluate commercial cedar essential oil (CEO), obtained by hydrodistillation from cedar wood, in relationship to its chemical composition and antioxidant, in vitro and in situ antimicrobial, antibiofilm, and anti-insect activity. For these purposes, gas chromatography–mass spectrometry, DPPH radical-scavenging assay, agar and disc diffusion, and vapor phase methods were used. The results from the volatile profile determination showed that δ-cadinene (36.3%), (Z)-β-farnesene (13.8%), viridiflorol (7.3%), and himachala-2,4-diene (5.4%) were the major components of the EO chemical constitution. Based on the obtained results, a strong antioxidant effect (81.1%) of the CEO was found. CEO is characterized by diversified antimicrobial activity, and the zones of inhibition ranged from 7.33 to 21.36 mm in gram-positive and gram-negative bacteria, and from 5.44 to 13.67 mm in yeasts and fungi. The lowest values of minimal inhibition concentration (MIC) were noted against gram-positive Micrococcus luteus (7.46 µL/mL) and against yeast Candida krusei (9.46 µL/mL). It seems that the vapor phase of CEO can inhibit the growth of the microscopic filamentous fungi of the genus Penicillium according to in situ antifungal analysis on bread, carrots, and celery. This finding confirms the impact of CEO on the change in the protein structure of older biofilms of Pseudomonas fluorescens and Salmonella enterica subsp. enterica. Insecticidal activity of a vapor phase has also been demonstrated against Pyrrhocoris apterus. CEO showed various advantages on antimicrobial activity, and it is an ideal substitute for food safety. Full article

Antimicrobial in vitro and in situ efficacies of Cymbopogon citratus essential oil (lemongrass, LGEO) against 17 spoilage microorganisms (bacteria, yeasts and fungi) were evaluated. Additionally, its chemical composition, and antioxidant and antibiofilm activities were investigated. The LGEO exhibited a strong antioxidant activity (84.0 ± 0.1%), and its main constituents were citral (61.5%), geraniol (6.6%) and 1,8-cineole (6.4%). An in vitro antimicrobial evaluation revealed the lowest inhibition zone (1.00 ± 0.00 mm) in Pseudomonas fluorescens, and the highest inhibition zone (18.00 ± 2.46 mm) in Candida krusei. The values for the minimal inhibitory concentration were determined to be the lowest for Salmonella enteritidis and the highest for C. albicans. Furthermore, the concentration of ≥250 µL/L of LGEO suppressed the growth of Penicillium aurantiogriseum, Penicillium expansum, Penicillium chrysogenum and Penicillium italicum. The changes in the molecular structure of the biofilms produced by Pseudomonas fluorescens and Salmonella enteritidis, after their treatment with LGEO, confirmed its action on both biofilm-forming bacteria. Moreover, an in situ antimicrobial activity evaluation displayed the most effective inhibitory effectiveness of LGEO against Micrococcus luteus, Serratia marcescens (250 µL/L) and Penicillium expansum (125, 250 and 500 µL/L) growing on a carrot. Our results suggest that LGEO, as a promising natural antimicrobial agent, can be applied in the innovative packaging of bakery products and different types of vegetables, which combines commonly used packing materials with the addition of LGEO. Full article

Infectious diseases caused by microbial biofilms are a major clinical problem, and new antimicrobial agents that can inhibit biofilm formation and eradicate pre-formed biofilms are urgently needed. Pomegranate extracts are a well-established folkloric medicine and have been used in the treatment of infectious diseases since ancient times, whilst the addition of metal ions, including zinc (II), has enhanced the antimicrobial activity of pomegranate. Micrococcus luteus is generally a non-pathogenic skin commensal bacterium, although it can act as an opportunistic pathogen and cause serious infections, particularly involving catheterization and comorbidities. The aims of this study were to evaluate the holistic activity of pomegranate rind extract (PRE), Zn (II), and PRE/Zn (II) individually and in combination against M. luteus under both planktonic and biofilm conditions. Antimicrobial activity was detected in vitro using the broth dilution method, and synergistic activity was determined using checkerboard and time-kill assays. Effects on biofilm formation and eradication were determined by crystal violet and BacLight^TM Live/Dead staining. PRE and Zn (II) exerted antimicrobial activity against M. luteus under both planktonic and biofilm conditions. After 4 h, potent synergistic bactericidal activity was also found when PRE and Zn (II) were co-administered under planktonic conditions (log reductions: PRE 1.83 ± 0.24, Zn (II) 3.4 ± 0.08, and PRE/Zn (II) 6.88 ± 1.02; p < 0.0001). In addition, greater heterogeneity was induced in the structure of M. luteus biofilm using the PRE/Zn (II) combination compared to when PRE and Zn (II) were applied individually. The activity of PRE and the PRE/Zn (II) combination could offer a novel antimicrobial therapy for the treatment of disease-associated infections caused by M. luteus and potentially other bacteria. Full article

The aims of this article are to characterize: the quantity of culturable bacterial aerosol (QCBA) and the quality of culturable bacterial aerosol (QlCBA) in an office building in Southern Poland during the spring. The average concentration of culturable bacterial aerosol (CCBA) in this building ranged from 424 CFU m⁻³ to 821 CFU m⁻³, below Polish proposals for threshold limit values. Size distributions were unimodal, with a peak of particle bacterial aerodynamic diameters less than 3.3 μm, increasing potentially adverse health effects due to their inhalation. The spring office exposure dose (SPED) of bacterial aerosol was estimated. The highest value of SPED was in April (218 CFU kg⁻¹), whereas the lowest was in June (113 CFU kg⁻¹). Analysis was undertaken to determine the antibiotic resistance of isolated strains and their ability to form biofilms, which may facilitate the spread of antibiotic resistance genes. In the course of the study, it was found that Staphylococcus xylosus had the greatest ability to form biofilms, while the strains with the highest antibiotic resistance were Micrococcus luteus D and Macrococcus equipercicus. Given that mainly antibiotic-sensitive bacteria from bioaerosol were isolated, which transfers resistance genes to their plasmids, this shows the need for increased monitoring of indoor air quality in workplaces. Full article

Monohexosylceramides (CMHs) are highly conserved fungal glycosphingolipids playing a role in several cellular processes such as growth, differentiation and morphological transition. In this study, we report the isolation, purification and chemical characterization of CMHs from Rhizopus stolonifer and R. microspores. Using positive ion mode ESI-MS, two major ion species were observed at m/z 750 and m/z 766, respectively. Both ion species consisted of a glucose/galactose residue attached to a ceramide moiety containing 9-methyl-4,8-sphingadienine with an amidic linkage to a hydroxylated C16:0 fatty acid. The antimicrobial activity of CMH was evaluated against Gram positive and Gram negative bacteria using the agar diffusion assay. CMH from both Rhizopus species inhibited the growth of Bacillus terrae, Micrococcus luteus (M. luteus) and Pseudomonas stutzeri (P. stutzeri) with a MIC₅₀ of 6.25, 6.25 and 3.13 mg/mL, respectively. The bactericidal effect was detected only for M. luteus and P. stutzeri, with MBC values of 25 and 6.25 mg/mL, respectively. Furthermore, the action of CMH on the biofilm produced by methicillin-resistant Staphylococcus aureus (MRSA) was analyzed using 12.5 and 25 mg/mL of CMH from R. microsporus. Total biofilm biomass, biofilm matrix and viability of the cells that form the biofilm structure were evaluated. CMH from R. microsporus was able to inhibit the MRSA biofilm formation in all parameters tested. Full article