Minimum Bactericidal Concentration Research Articles

Effects of antimicrobials over sessile and planktonic microbiota associated with an industrial cooling water system

The bacterial community from a cooling water system was investigated through culture-dependent and independent strategies, and the responses of planktonic and sessile bacteria (grown in glass slides and stainless-steel coupons) to antimicrobials of industrial and clinical use were assessed. The morphotypes with higher biofilm-forming potential were Pseudoxanthomonas sp., Rheinheimera sp., Aeromonas sp. and Staphylococcus sp., and the first also exhibited lower susceptibility to all antibiotics and biocides tested. 16S rRNA high throughput sequencing indicated that Pseudomonadota (77.1% on average, sd 11.1%), Bacteroidota (8.4, sd 5.7%), and Planctomycetota (3.0, sd 1.3%) were the most abundant phyla. KEGG orthologs associated with antibiotics and biocide resistance were abundant in all samples. Although the minimum inhibitory and bactericidal concentrations were generally higher for biofilms, morphotypes in planktonic form also showed high levels of resistance, which could be associated with biofilm cells passing into the planktonic phase. Overall, monochloramine was the most effective biocide.

Influence of critical micelle concentration of choline-based long chain fatty acid soaps on their antibacterial activity against Methicillin resistant Staphylococcus aureus

HypothesisAntimicrobial resistance (AMR) is a pressing global health concern. ESKAPEE pathogens, such as Methicillin-resistant Staphylococcus aureus (MRSA) are notable of concern in healthcare settings due to their resistance to critical antibiotics. To combat AMR, the development of alternatives such as bacterial membrane-active agents is crucial. Fatty acids (FAs) have emerged as a sustainable, antibiotic-free solution with inherent antibacterial activity. However, long chain saturated fatty acids (LCFAs) sodium soaps exhibit poorly antibacterial properties in comparison to short chain FAs, believed to be linked to limited solubility in aqueous media. ExperimentsWe employed choline as a chaotropic organic counter-ion to enhance the solubility of LCFAs and investigated their antibacterial effects against MRSA. The optimal medium conditions for micelle formation for LCFAs was first investigated. Then, we determined the critical micelle concentration (CMC), micellar morphology, and aggregation number through surface tension measurements and small angle neutron scattering experiments. Antimicrobial activity was assessed using minimum bactericidal concentration (MBC) assays and time-kill experiments. FindingsWe have identified conditions where LCFAs are effective against MRSA for the first time, providing valuable insights for developing new antibacterial agents to fight AMR. LCFAs need to be used above their Krafft temperatures and CMC to exhibit antibacterial efficacy.

Chitosan-coated PLGA microemulsion loaded with tannic acid against Escherichia coli in vitro and in vivo

The overuse of antibiotics has resulted in a surge of drug-resistant bacteria, making the pursuit of natural antimicrobials an urgent and significant trend. Encapsulation and nanoparticulation are effective ways to enhance the antibacterial properties of natural drugs. In this study, we encapsulated tannic acid (TA) with chitosan (CS) and poly (lactide-co-glycolide) (PLGA) using the emulsion-solvent evaporation method to enhance the antimicrobial effect of TA. We prepared a bilayer membrane spherical nanoemulsion of TA-PLGA-CS (TPC) with uniform size of 559.87 ± 1.16 nm, and zeta potential of 59.53 ± 1.07 mV. TPC could be stably stored for 90 days at 4°C without affecting the properties of the emulsion, and the minimum bactericidal concentration against four strains of Escherichia coli (E. coli) remained unchanged for 60 d. The results indicated that TPC enhanced the inhibitory effect of TA against E. coli. Scanning electron microscope images revealed that TPC treatment caused damage to the bacterial cell membrane. In addition, in vivo experiments indicated that TPC exhibited a superior therapeutic effect on artificial colibacillosis in chickens infested with Avian pathogenic Escherichia coli, as evidenced by the changes in body weight and a reduction bacterial load in heart. Furthermore, TPC reversed the down-regulation of catalase, glutathione peroxidase1 (GPX1), and GPX7 gene expression levels in intestinal tissues. Compared to the model group, TPC treatment elevated serum glutathione peroxidase activities and lowered myeloperoxidase and lactate dehydrogenase levels, offering antioxidant protection that was slightly better than that of doxycycline hydrochlorid group. In summary, we prepared a novel TA antimicrobial preparation with significant antioxidant potential and inhibitory effect against E. coli both in vitro and in vivo.

Prokaryotic Expression, Purification, and Biological Properties of a Novel Bioactive Protein (PFAP-1) from Pinctada fucata.

Pinctada fucata meat is the main by-product of the pearl harvesting industry. It is rich in nutrition, containing a lot of protein and peptides, and holds significant value for both medicine and food. In this study, a new active protein was discovered and expressed heterogeneously through bioinformatics analysis. It was then identified using Western blot, molecular weight, and mass spectrometry. The antibacterial activity, hemolysis activity, antioxidant activity, and Angiotensin-Converting Enzyme II (ACE2) inhibitory activity were investigated. An unknown functional protein was screened through the Uniprot protein database, and its primary structure did not resemble existing proteins. It was an α-helical cationic polypeptide we named PFAP-1. The codon-optimized full-length PFAP-1 gene was synthesized and inserted into the prokaryotic expression vector pET-30a. The induced expression conditions were determined with a final isopropyl-β-d-thiogalactoside (IPTG) concentration of 0.2 mM, an induction temperature of 15 °C, and an induction time of 16 h. The recombinant PFAP-1 protein, with low endotoxin and sterility, was successfully prepared. The recombinant PFAP-1 protein exhibited strong antibacterial activity against methicillin-resistant Staphylococcus aureus (MRSA) in vitro, and the diameter of the inhibition zone was 15.99 ± 0.02 mm. Its minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) were 37.5 μg/mL and 150 μg/mL, respectively, and its hemolytic activity was low (11.21%) at the bactericidal concentration. The recombinant PFAP-1 protein significantly inhibited the formation of MRSA biofilm and eradicated MRSA biofilm. It also demonstrated potent 1,1-diphenyl-2-picryl-hydrazyl radical (DPPH) scavenging activity with a half-maximal inhibitory concentration (IC50) of 40.83 μg/mL. The IC50 of ACE2 inhibition was 5.66 μg/mL. Molecular docking results revealed that the optimal docking fraction of PFAP-1 protein and ACE2 protein was -267.78 kcal/mol, with a confidence level of 0.913. The stable binding complex was primarily formed through nine groups of hydrogen bonds, three groups of salt bridges, and numerous hydrophobic interactions. In conclusion, recombinant PFAP-1 can serve as a promising active protein in food, cosmetics, or medicine.

Multidrug-Resistance of Vibrio Species in Bivalve Mollusks from Southern Thailand: Isolation, Identification, Pathogenicity, and Their Sensitivity toward Chitooligosaccharide-Epigallocatechin-3-Gallate Conjugate.

Vibrio spp. is a Gram-negative bacteria known for its ability to cause foodborne infection in association with eating raw or undercooked seafood. The majority of these foodborne illnesses are caused by mollusks, especially bivalves. Thus, the prevalence of Vibrio spp. in blood clams (Tegillarca granosa), baby clams (Paphia undulata), and Asian green mussels (Perna viridis) from South Thailand was determined. A total of 649 Vibrio spp. isolates were subjected to pathogenicity analysis on blood agar plates, among which 21 isolates from blood clams (15 isolates), baby clams (2 isolates), and green mussels (4 isolates) showed positive β-hemolysis. Based on the biofilm formation index (BFI) of β-hemolysis-positive Vibrio strains, nine isolates exhibited a strong biofilm formation capacity, with a BFI in the range of 1.37 to 10.13. Among the 21 isolates, 6 isolates (BL18, BL82, BL84, BL85, BL90, and BL92) were tlh-positive, while trh and tdh genes were not detected in all strains. Out of 21 strains, 5 strains showed multidrug resistance (MDR) against amoxicillin/clavulanic acid, ampicillin/sulbactam, cefotaxime, cefuroxime, meropenem, and trimethoprim/sulfamethoxazole. A phylogenetic analysis of MDR Vibrio was performed based on 16s rDNA sequences using the neighbor-joining method. The five MDR isolates were identified to be Vibrio neocaledonicus (one isolate), Vibrio fluvialis (one isolate) and, Vibrio cidicii (three isolates). In addition, the antimicrobial activity of chitooligosaccharide-epigallocatechin gallate (COS-EGCG) conjugate against MDR Vibrio strains was determined. The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of COS-EGCG conjugate were in the range of 64-128 µg/mL. The antimicrobial activity of the conjugate was advocated by the cell lysis of MDR Vibrio strains, as elucidated by scanning electron microscopic images. Vibrio spp. isolated from blood clams, baby clams, and Asian green mussels were highly pathogenic, exhibiting the ability to produce biofilm and being resistant to antibiotics. However, the COS-EGCG conjugate could be used as a potential antimicrobial agent for controlling Vibrio in mollusks.

Wild Vitis Species as Stilbenes Sources: Cane Extracts and Their Antibacterial Activity against Listeria monocytogenes.

Grapevines (Vitis spp.) produce several valuable polyphenol-type secondary metabolites including various stilbenoids. Although the potential application of stilbenes may offer alternative solutions to food safety or health challenges, only little information is available on their antibacterial activity against foodborne pathogens. In this work, high-performance liquid chromatography was used to analyze the stilbenoid profile of various wild Vitis species, including V. amurensis, V. davidii, V. pentagona, and V. romanetii, selected from the gene bank for grapes at the University of Pécs, Hungary. We found that the stilbene profile of cane extracts is strongly genotype-dependent, showing the predominant presence of ε-viniferin with a wide concentration range ≈ 320-3870 µg/g dry weight. A novel yet simple and efficient extraction procedure was developed and applied for the first time on grape canes, resulting in ε-viniferin-rich crude extracts that were tested against Listeria monocytogenes, an important foodborne pathogen. After 24 h exposure, V. pentagona and V. amurensis crude extracts completely eliminated the bacteria at a minimum bactericidal concentration of 42.3 µg/mL and 39.2 µg/mL of ε-viniferin, respectively. On the other hand, V. romanetii extract with 7.8 µg/mL of ε-viniferin resulted in 4 log reduction in the viable bacterial cells, while V. davidii extract with 1.4 µg/mL of ε-viniferin did not show significant antibacterial activity. These findings indicate that the ε-viniferin content was directly responsible for the antibacterial effect of cane extract. However, pure ε-viniferin (purity > 95%) required a higher concentration (188 µg/mL) to eradicate the bacteria under the same conditions, suggesting the presence of other antibacterial compounds in the cane extracts. Investigating the onset time of the bactericidal action was conducted through a kinetic experiment, and results showed that the reduction in living bacterial number started after 2 h; however, the bactericidal action demanded 24 h of exposure. Our results revealed that the canes of V. pentagona and V. amurensis species are a crucial bio-source of an important stilbene with antimicrobial activity and health benefits.

Controlling Staphylococcus aureus Biofilm on Food Contact Surfaces: The Efficacy of Oliveria decumbens Essential Oil and its Implications on Biofilm-Related Genes.

This study aimed to investigate the effect of Oliveria decumbens essential oil (Od-EO) on the phenotypic properties and gene expression of Staphylococcus aureus biofilm on commonly used food contact surfaces. The minimum inhibitory concentration and minimum bactericidal concentration of Od-EO on Staphylococcus aureus ATCC25923 were determined to be 0.5 and 1µl/mL, respectively. Crystal violet staining, scanning electron microscopy (SEM), biofilm metabolic activity evaluation and Real-time PCR analysis were used to assess the anti-biofilm properties of Od-EO. The results demonstrated that Od-EO exhibited significant anti-biofilm properties against S. aureus and effectively reduced the metabolic activity of biofilm cells. Furthermore, the inhibitory effects of Od-EO on biofilm formation were more pronounced on Stainless Steel (SS) compared to High Density Polyethylene (HDPE) surfaces. Real-time PCR analysis revealed that Od-EO downregulated the expression of biofilm-related genes (icaA, icaD, clfA, clfB, FnbA, FnbB, hld) in S. aureus grown on SS, while the expression levels of all studied genes except hld in the biofilm formed on HDPE remained unchanged or increased. One of the main anti-biofilm mechanisms of the Od-EO on the HDPE is related to the disturbance in the QS of the cells. These findings highlight the potential of Od-EO as an effective agent for controlling and inhibiting S. aureus biofilm in the food industry and its potential use in disinfectant compounds.

Postbiotic mediators derived from Lactobacillus species enhance riboflavin-mediated antimicrobial photodynamic therapy for eradication of Streptococcus mutans planktonic and biofilm growth

BackgroundStreptococcus mutans has been implicated as a primary causative agent of dental caries and one of its important virulence properties is an ability to form biofilm on tooth surfaces. Thus, strategies to prevent and control S. mutans biofilms are requested. The present study aimed to examine the eradication of S. mutans planktonic and biofilm cells using riboflavin (Rib)-mediated antimicrobial photodynamic therapy (aPDT) enhanced by postbiotic mediators derived from Lactobacillus species.Materials and methodsMinimum inhibitory concentration (MIC) and the minimum bactericidal concentration (MBC) of Rib and postbiotic mediators were determined. The antimicrobial and anti-biofilm effects of Rib-mediated aPDT (Rib plus blue light), Rib-mediated aPDT in combination with postbiotic mediators derived from Lactobacillus casei (LC) (aPDT+ LC), and Rib-mediated aPDT in combination with postbiotic mediators derived from Lactobacillus plantarum (LP) (aPDT+ LP) were evaluated. The anti-virulence potential of Rib-mediated aPDT, aPDT+ LC, and aPDT+ LP were assessed by measuring the expression of the gtfB gene using quantitative real-time polymerase chain reaction (qRT-PCR) at the highest concentrations of Rib, LC, and LP, at which the S. mutans had proliferation as the same as in the control (non-treated) group.ResultsAccording to the results, the MIC doses of LC, LP, and Rib were 64 µg/mL, 128 µg/mL, and 128 µg/mL, respectively, while the MBC values of LC, LP, and Rib were 128 µg/mL, 256 µg/mL, and 256 µg/mL, respectively. Rib-mediated aPDT, aPDT+ LP, and aPDT+ LC showed a significant reduction in Log10 CFU/mL of S. mutans compared to the control group (4.2, 4.9, and 5.2 Log10 CFU/mL, respectively; all P < 0.05). The most destruction of S. mutans biofilms was observed after treatment with aPDT+ LC followed by aPDT+ LP and Rib-mediated aPDT (77.5%, 73.3%, and 67.6%, respectively; all P < 0.05). The concentrations of 31.2 µg/mL, 62.5 µg/mL, and 62.5 µg/mL were considered as the highest concentrations of LC, LP, and Rib, respectively, at which S. mutans replicates as same as the control group and were used for gtfB gene expression assay using qRT-PCR during Rib-mediated aPDT, aPDT+ LP, and aPDT+ LC treatments. Gene expression results revealed that aPDT+ LP and aPDT+ LC could decrease the gene expression level of gtfB by 6.3- and 5.7-fold, respectively (P < 0.05), while only 5.1-fold reduction was observed after Rib-mediated aPDT (P < 0.05).ConclusionOur findings indicate that aPDT+ LP and aPDT+ LC hold promise for use as a treatment to combat S. mutans planktonic and biofilms growth as well as anti-virulence as a preventive strategy to inhibit biofilms development via reduction of gtfB gene expression.

Antibacterial and antioxidant activities of Chlorella vulgaris and Scenedesmus incrassatulus using natural deep eutectic solvent under microwave assisted by ultrasound

Microalgae are increasingly recognized as promising sources of natural bioactive compounds. However, traditional extraction methods using volatile organic solvents (VOCs) pose environmental risks. This study explores renewable deep eutectic solvents (DES) as sustainable alternatives for extracting bioactive compounds from microalgae biomass, focusing on Chlorella vulgaris and Scenedesmus incrassatulus. Four DES systems, comprising choline chloride (ChCl) and glycerol, citric acid, urea, and glucose, were compared with three conventional solvents (ethanol, methanol, and water). Extraction efficiency was assessed based on total phenolic content (TPC), flavonoid content, and tannin content, followed by antioxidant activity evaluation using DPPH, CAT, and FRAP assays. Additionally, antibacterial activity of the DES extracts was determined against Escherichia coli (ATCC 25922), Pseudomonas aeruginosa (ATCC 27853), Staphylococcus aureus (ATCC 29213), and Bacillus subtilis (ATCC 3366) using disc diffusion and microplate dilution methods to determine minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC). Results reveal that DES, particularly choline chloride: citric acid, outperform conventional solvents in terms of polyphenol extraction efficiency, antioxidant activity, and antibacterial activity against both Gram-negative and Gram-positive bacteria. For instance, the citric acid-based DES (SIDES2) showed a TPC of 4.98 mg/g, while the conventional solvent ethanol exhibited a TPC of 3.27 mg/g. Additionally, SIDES2 exhibiting the highest DPPH scavenging activity of 75 %, compared to 60 % for ethanol. Furthermore, SIDES2 showed an MIC of 0.5 mg/ml against Staphylococcus aureus. This study underscores the potential of DES for sustainable extraction of natural antioxidants from microalgae biomass, contributing to the development of environmentally friendly extraction processes in various industries.

Phytofabrication, characterization of silver nanoparticles using Hippophae rhamnoides berries extract and their biological activities.

Fabrication of plant-based metal nanoparticles has yielded promising results, establishing this approach as viable, sustainable, and non-toxic in the biomedical sector for targeted drug delivery, diagnostic imaging, biosensing, cancer therapy, and antimicrobial treatments. The present work demonstrates the suitability of Hippophae rhamnoides berries for the instant green synthesis of silver nanoparticles to check their antioxidant, lipid peroxidation, and antimicrobial potential. The preliminary characterization of Hippophae rhamnoides-mediated AgNPs was validated by monitoring the color shift in the solution from pale yellow to reddish brown, which was further confirmed by UV-vis spectroscopy and the plasmon peaks were observed at 450 nm. Field Emission Scanning Electron Microscopy (FESEM) and X-ray diffraction (XRD) were used to evaluate the surface topography and structure of AgNPs. Herein, the antioxidant potential of synthesized AgNPs was investigated using DPPH free radical assay and the antimicrobial efficacy of similar was checked against E. coli and S. aureus by following MIC (minimum inhibitory concentration) and MBC (Minimum bactericidal concentration) assay. Along with the inhibitory percentage of lipid peroxidation was analysed by following TBARS (Thiobarbituric acid reactive species) assay. The results revealed that the AgNPs were spherical in shape with an average size distribution within the range of 23.5-28 nm and a crystalline structure. Negative zeta potential (-19.7 mV) revealed the physical stability of synthesized AgNPs as the repulsive force to prevent immediate aggregation. The bioactive functional moieties involved in reducing bulk AgNO3 into AgNPs were further validated by FTIR. TBARS was adapted to test lipid peroxidation, and Hippophae rhamnoides-mediated AgNPs showed a 79% inhibition in lipid peroxidation compared to Hippophae rhamnoides berries extract as 65%. Furthermore, the antibacterial tests showed 37 ± 0.01 mm and 35 ± 0.0132 mm, zones of inhibition against E. coli MTCC 1698 and S. aureus MTCC 3160 with MIC and MBC values of 1 mg/mL, respectively.

Green Synthesis of Silver Nanoparticle Using Black Mulberry and Characterization, Phytochemical, and Bioactivity.

Synthesis of silver nanoparticles (AgNPs) using plant extracts has been proposed as a more advantageous and environmentally friendly alternative compared to existing physical/chemical methods. In this study, AgNPs were synthesized from silver nitrate using black mulberry (BM) extract. The biosynthesized AgNPs were characterized through an UV-visible spectrometer, X-ray diffraction, and transmission electron microscopy. Additionally, BM-AgNPs were subjected to antioxidant, antibacterial, anti-inflammatory, and anticancer activities. AgNPs biosynthesized from BM extract were dark brown in color and showed a strong peak at 437 nm, confirming that AgNPs were successfully synthesized. The size of AgNPs was 170.17 ± 12.65 nm, the polydispersity index was 0.281 ± 0.07, and the zeta potential value was -56.6 ± 0.56 mV, indicating that the particles were stable. The higher total phenol, flavonoid, and anthocyanin content of BM-AgNPs compared to BM extract indicates that the particles contain multiple active substances due to the formation of AgNPs. The DPPH and ABTS assays showed decreased IC50 values compared to BM extract, demonstrating improved antioxidant activity. AgNPs inhibited the growth of S. aureus and E. coli at 600 μg/mL, with minimum bactericidal concentrations determined to be 1000 and 1200 μg/mL, respectively. The anti-inflammatory activity was 64.28% at a BM-AgNPs concentration of 250 μg/mL. As the concentration increased, the difference from the standard decreased, indicating the inhibitory effect of AgNPs on bovine serum albumin denaturation. The viability of MCF-7 cells treated with BM-AgNPs was found to be significantly lower than that of cells treated with BM extract. The IC50 value of BM-AgNPs was determined to be 96.9 μg/mL. This study showed that BM-AgNPs have the potential to be used in the pharmaceutical industry as antioxidant, antibacterial, anti-inflammatory, and anticancer agents.

Nanobiological synthesis of silver oxide-doped titanium oxide bionanocomposite targeting foodborne and phytopathogenic bacteria

Fungi possess remarkable capabilities for metal speciation, dissolution, and mineral formation, which contribute to the production of mycogenic nanostructures. This study explores a green chemistry approach for synthesizing silver oxide-doped titanium oxide (Ag2O-doped TiO2) bionanocomposite utilizing Trichoderma virens. The light yellowish fungal filtrate transformed into a dark brownish colloidal suspension after reacting with silver nitrate and rutile titanium (IV) oxide. X-ray diffractometry (XRD) unveiled the crystalline structure of Ag2O-doped TiO2 bionanocomposite (22.15 nm), showing the coexistence of cubic and rutile tetragonal phases of Ag2O and TiO2, respectively. Fourier-transform infrared spectroscopy (FTIR) showed the presence of functional groups of alcohols, phenols nitro compounds, and aromatic amines derived from the cultural filtrate of T. virens. Raman analysis revealed vibrational modes corresponding to Ag2O and TiO2 nanoparticles. Distinct sharp emission peaks characteristic to Ti, Ag, and O were depicted using energy dispersive X-ray analysis (EDX) analysis. X-ray photoelectron spectroscopy (XPS) confirmed the presence of elemental valence states and binding energies of Ag, Ti, and O in the mycogenic nanocomposite. Field emission scanning electron microscopy (FESEM) revealed aggregation of polydispersed Ag2O-doped TiO2 bionanocomposite, displaying spherical- and cuboctahedron-shaped nanostructures with rough surfaces. High-resolution transmission electron microscopy (HRTEM) showed the presence of circular-, semi-spherical-, hexagonal-, and polygonal-shaped monodispersed Ag2O NPs, with defined boundaries. The Ag2O NPs were obviously deposited on the sheet-like TiO2 NPs. Selected area electron diffraction pattern implied the polycrystallinity of the as-synthesized bionanocomposite. A broad antibacterial spectrum of the prepared bionanocomposite was attained against foodborne pathogenic bacteria; Escherichia coli (12.05 mm), Salmonella enterica (11.26 mm), and Staphylococcus aureus (11.44 mm) and phytopathogenic bacteria; Clavibacter michiganensis subsp. michiganensis (15.72 mm), C. michiganensis subsp. capsici (10.80 mm), streptomycin-sensitive and -resistant Xanthomonas citri pv. citri (14.11 and 14.53 mm, respectively), and streptomycin-sensitive and -resistant Pectobacterium carotovorum subsp. carotovorum (11.36 and 11.07 mm, respectively) using in vitro Kirby-Bauer method. Minimum inhibitory and minimum bactericidal concentrations were determined via a broth micro-dilution assay. FESEM revealed significant morphological alterations in bacterial cells upon treatment with the Ag2O-doped TiO2 bionanocomposite, including deformed shape, rough surface, cell thinning, wrinkled cell wall, protrusions, cavitations, and cracks. These findings signify the successful mycosynthesis of Ag2O-doped TiO2 bionanocomposite, which acted a potent antibacterial agent against a variety of foodborne and phytopathogenic bacteria, which could be employed for environmental, biomedical, agricultural, food bio-processing applications.

Chirality and pH Influence the Self-Assembly of Antimicrobial Lipopeptides with Diverse Nanostructures.

Chirality plays a crucial role in the self-assembly of biomolecules in nature. Peptides show chirality-dependent conformation and self-assembly. Lipidation of peptides occurs in vivo and has recently been exploited in designed conjugates to drive self-assembly and enhance bioactivity. Here, a library of pH-responsive homochiral and heterochiral lipidated tripeptides has been designed. The designed lipopeptides comprise homochiral C16-YKK or C16-WKK (where all the amino acids are l-isomers), and two heterochiral conjugates C16-Ykk and C16-Wkk (where the two lysines are d-isomers). The self-assembly of all the synthesized lipopeptides in aqueous solution was examined using a combination of spectroscopic methods along with cryogenic-transmission electron microscopy (cryo-TEM) and small-angle X-ray scattering (SAXS). Interestingly, it was observed that at acidic pH all the lipopeptides self-assemble into micelles, whereas at basic pH the homochiral lipopeptides self-assemble into nanofibers, whereas the heterochiral lipopeptides self-assemble into nanotapes and nanotubes. A pH switch was demonstrated using a thioflavin T fluorescence probe of β-sheet structure present in the extended structures at pH 8. We demonstrate that both chirality and pH in lipopeptides influence the self-assembly behavior of the model tripeptides, which also show promising bioactivity. Good cytocompatibility is observed in hemolytic assays and antimicrobial activity against both Gram-negative and Gram-positive bacteria is shown through the determination of minimum inhibition concentration (MIC) and minimum bactericidal concentration (MBC) values and live/dead bacteria staining assay.

5-aminolevulinic acid photodynamic therapy for chronic wound infection in rats with diabetes

Recent research indicated that ulcers and peripheral vascular disease resulting from drug-resistant bacterial infections are the main causes of delayed healing in chronic diabetic wounds. 5-Aminolevulinic acid (ALA) is a second-generation endogenous photosensitizer. The therapeutic effect and mechanism of ALA-mediated photodynamic therapy (ALA-PDT) on methicillin-resistant Staphylococcus aureus (MRSA)-infected wounds in diabetic rats were investigated in this study. The results revealed the promising antibacterial effects of ALA-PDT MRSA in vitro, with a minimum inhibitory concentration and minimum bactericidal concentration of 250 and 500 μM, respectively. ALA-PDT also changed the permeability and structural integrity of bacterial cell membranes by producing reactive oxygen species. Meanwhile, ALA-PDT accelerated wound healing in MRSA-infected diabetic rats, with 5 % ALA-PDT achieving complete sterilization in 14 days and wound closure in 21 days. Treatment with 5 % ALA-PDT additionally improved the histopathological appearance of skin tissue, as well as fibrosis, inflammatory cytokine release, and angiogenesis-related protein expression. These findings indicated that ALA-PDT significantly promoted the healing of MRSA-infected wounds in diabetic rats by eliminating bacteria, inhibiting inflammation, generating granulation tissues, promoting neovascularization, and restoring damaged nerves. In addition, the healing mechanism was related to the activation of inflammatory and angiogenesis pathways through the regulation of tumor necrosis factor-alpha and interleukin-6 expression and upregulation of CD206, CD31, and VEGF. These findings underscored the potential role of ALA-PDT in promoting the healing of chronic diabetic wounds.

Antibacterial Activity of Ethanolic Extract of Torch Ginger (Etlingera elatior) Towards Enterococcus faecalis: A Preliminary Research to the Alternative of Root Canal Irrigant of Primary Teeth

Enterococcus faecalis is a notable pathogen found in the root canals of primary teeth with endodontic infections, often resistant to conventional root canal irrigation solutions, leading to treatment failure. Torch ginger or kecombrang (Etlingera elatior), a spice plant, is reported to contain bioactive compounds with antibacterial properties. This study investigates the antibacterial efficacy of ethanolic extract of torch ginger against Enterococcus faecalis, evaluating its potential as an alternative irrigant based on minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC), and effective concentration. Samples included Enterococcus faecalis ATCC® 29212™ and 70% ethanol extract of torch ginger, tested in eight concentrations (80%, 75%, 65%, 50%, 25%, 12.5%, 6.25%, and 3.125%) obtained through maceration, alongside two control groups (NaOCl and saline). The Kirby-Bauer disc diffusion method was employed to determine MIC, while the streaking method from MIC testing identified MBC. Data analysis for MIC and MBC values was conducted using the One-Way ANOVA parametric test (p &lt; 0.05). Torch ginger extract demonstrated antibacterial activity against Enterococcus faecalis, with inhibition observed at a minimum concentration of 3.125% with average inhibition zone diameter of 9.63 ± 0.25 mm and reaching up to 80% concentration with average inhibition zone diameter of 15.03 ± 0.21 mm. The MIC was established at 3.125%, and the MBC among the tested concentrations was 80%. The study concludes that the ethanolic extract of torch ginger shows significant antibacterial activity against Enterococcus faecalis. An 80% concentration is identified as the most effective for inhibiting and killing the pathogen, suggesting its potential as an alternative root canal irrigant of primary teeth.

Isolation and antimicrobial activity of secondary metabolites of pothos tener wall

The Pothos genus is extensively utilised in traditional medicine in China and India. An underexplored species of Pothos tener Wall was identified in Sulawesi, Indonesia. Antimicrobial activity was assessed using microdilutions and streak plates against Staphylococcus aureus, Eschericia coli, Aeromonas hydrophila, Aspergillus niger, and Candida albicans. Significant effectiveness was observed in the methanol extract, as indicated by the Minimum Inhibitory Concentration (MIC) and Minimum Bactericidal Concentration (MBC) values for three different extracts (methanol, ethyl acetate, and n-hexane) of P. tener. The isolates obtained were structurally analysed using Ultraviolet (UV)-spectroscopy, Fourier-transform Infra Red-Spectroscopy (FT-IR), Mass Spectroscopy (MS), Nuclear Magnetic Resonance (NMR), and antimicrobial testing after undergoing fractionation and subfractionation. The isolate obtained was stigmasterol with moderate antimicrobial activity against A. niger and A. hydrophila, with MIC equivalent to MBC of 500 µg/ml. The first report of stigmasterol from P. tener has potent antimicrobial properties, bolstering empirical data in this field.

Determination of bactericidal activity against 3HC-2-Tre-labelled Mycobacterium abscessus (Mycobacteroides abscessus) by automated fluorescence microscopy

The minimum bactericidal concentration (MBC) of antibiotics is an important parameter for the potency of a drug in eradicating a bacterium as well as an important measure of the potential of a drug candidate in research and development. We have established a fluorescence-based microscopy method for the determination of MBCs against the non-tuberculous mycobacterium Mycobacterium abscessus (Mycobacteroides abscessus) to simplify and accelerate the performance of MBC determination compared to counting colony forming units on agar. Bacteria are labelled with the trehalose-coupled dye 3HC-2-Tre and analysed in a 96-well plate. The results of the new method are consistent with MBC determination by plating on agar. The method was used to evaluate the bactericidality of the antibiotics rifabutin, moxifloxacin, amikacin, clarithromycin and bedaquiline. Bactericidal effects against M. abscessus were observed, which are consistent with literature data.

Inhibitory potential of natural antimicrobial compounds against histamine-forming lactic acid bacteria

This work evaluated the potential of natural antimicrobial compounds to prevent histamine formation by inhibiting the microbial growth of Lentilactobacillus parabuchneri and Limosilactobacillus reuteri, bacteria selected for their ability to produce histamine in cheese. Of the evaluated compounds, eugenol, carvacrol, thymol and cinnamaldehyde were the most effective in inhibiting histamine-forming lactic acid bacteria and, therefore, in reducing histamine generation, even at concentrations below the minimum bactericidal concentration (MBC). Carvacrol significantly impacted both microbial viability and the metabolism of bacteria with the inhibition of decarboxylase activity. In the case of L. parabuchneri, the use of 0.7 mg/mL carvacrol (MBC/2) resulted in an 88% reduction in histamine content, and for L. reuteri a 96% reduction was observed by using 0.65 mg/(MBC/2). Therefore, using essential oil components during food processing and preservation would be a good strategy to prevent histamine accumulating in cheese and to, consequently, mitigate its adverse effects.

Evaluation of anti-microbial activity of biotite and biotite composite based on crystallographic parameters: Estimation of crystallite size employing X-ray diffraction data

This study dealt with naturally occurring biotite from the river sediment to synthesize biotite based composite to evaluate antimicrobial activities against gram positive bacteria, negative bacteria and fungi. Biotite mineral, and synthesized carbon aerogel –biotite (CBt) composite and carbon aerogel-biotite –ZnO (CBtZ) composites were considered for the antimicrobial study. The samples were characterized by X-ray diffraction technique and different crystallographic parameters were computed applying X-ray diffraction data. Also, FESEM was performed to understand the surface morphology of the samples. Crystal size of the biotite, CBt and CBtZ were computed 103.215, 57.567, and 36.496 nm respectively. Tabulated microstrain are 0.175, 0.499 and 0.935 for the biotite, CBt and CBtZ respectively. Various models and equations were used to justify crystallite size, including the Williamson-Hall plot, linear straight line model, Scherrer equation, Monshi-Scherrer model, Size-strain plot (SSP) model, Halder-Wagner method and Sahadat-Scherrer model. For the both composite samples, following models confirmrd the presence of nanocrystal with a range of 50.789–97.777 nm (CBt) and 36.496–105.843 nm(CBtZ). However, for the biotite, all mentioned models were proved invalid except scherrer equation, SSP model and Monshi-Scherrer model. Linear straight line model was found invalid to calculate crystallite size of the three samples. Moreover, different crystal parameters like dislocation density, volume of the unit cell, lattice parameters were computed. Zone of inhabitation estimation method was employed to estimate antimicrobial activity against Listeria monocytogenes, Staphylococcus aureus, Salmonella abony, Escherichia coli and Candida albicans. Required minimum inhibitory concentration (MIC) together with minimum bactericidal concentration (MBC) also estimated in this study. Crystal size effect on the antimicrobial activities of the samples were evaluated in this study.

Bioactive compound from marine seagrass Streptomyces argenteolus TMA13: combatting fish pathogens with time-kill kinetics and live-dead cell imaging.

Actinobacteria, pervasive in aquatic and terrestrial environments, exhibit a filamentous morphology, possess DNA with a specific G + C content and production of numerous secondary metabolites. This study, focused on actinobacteria isolated from marine seagrass, investigating their antibacterial activity against fish pathogens. Among 28 isolates, Streptomyces argenteolus TMA13 displayed the maximum zone of inhibition against fish pathogens-Aeromonas hydrophila (10mm), Aeromonas caviae (22mm), Edwardsiella tarda (17mm), Vibrio harveyi (22mm) and Vibrio anguillarum (12mm) using the agar plug method. Optimization of this potent strain involved with various factors, including pH, temperature, carbon source and salt condition to enhance both yield production and antibacterial efficacy. In anti-biofilm assay shows the maximum percentage of inhibition while increasing concentration of TMA13 extract. Minimal Inhibitory Concentration (MIC) and Minimal Bactericidal Concentration (MBC) assays with TMA13 crude extract demonstrated potent activity against fish pathogens at remarkably low concentrations. Time-kill kinetics assay showcased growth curve variations over different time intervals for all fish pathogens treated with a 100µg/ml concentration of crude extract, indicating a decline in cells viability and progression into the death phase. Additionally, fluorescence microscopic visualization of bacterial cells exposed to the extracts emitting green and red fluorescence, enabling live-dead cell differentiation was also studied. Further characterization of the crude extract through GC-MS and FT-IR analyses performed and identified secondary metabolites with functional groups exhibiting significant antibacterial activity. This study elucidates the capacity of Streptomyces argenteolus TMA13 to enhance the production of antibiotic compounds effective against fish pathogens.