Minimum Bactericidal Concentration Research Articles

Comparative Evaluation of Antimicrobial Efficacy of Silver Nanoparticles Infused with Azadirachta indica Extract and Chlorhexidine Against Red-complex Pathogens.

The present study aimed to evaluate the antimicrobial efficacy of silver nanoparticles infused with Azadirachta indica extract and chlorhexidine against red-complex periopathogens. Neem leaf extraction was done followed by standardization to the synthesis of neem-infused silver nanoparticles and fractionation of compounds done by using thin layer chromatography to separate the mixture of neem leaf extract. Characterization of neem-infused silver nanoparticles was done by scanning electron microscopy and UV-Visible spectroscopy. The compound identified in neem-infused silver nanoparticles was gedunin which was confirmed by Fourier transform infrared spectroscopy and nuclear magnetic resonance spectroscopy. Determination of antibacterial activity done by disc diffusion, minimum inhibitory concentration (MIC), and minimum bactericidal concentration (MBC) methods. Group I-99% ethanolic extract, group II-neem-infused silver nanoparticles (NAgNPs), group III-chlorhexidine. The relative inhibitory zone value for Tannerella forsythia (180) in neem-infused silver nanoparticles (group II) was greater when compared with other periopathogens Porphyromonas gingivalis (133) and Treponema denticola (160) than 99% ethanolic extract (group I), chlorhexidine (group III). Neem-infused silver nanoparticles (group III) showed superior antimicrobial activity against T. forsythia (19.3 ± 31.1547) and T. denticola (18±0) when compared with P. gingivalis (17.6 ± 0.5774). On evaluating MIC and minimum bacterial concentrations, P. gingivalis is more resistant than other pathogens in neem-infused silver nanoparticles (group III). Neem-infused silver nanoparticles exhibited superior antibacterial activity as compared with gold-standard chlorhexidine against red-complex periodontal pathogens. For MIC and MBC all the three periopathogens were effective but P. gingivalis was more resistant. Antibiotics are effective against many drug-resistant bacteria. As a ready-made medicine, they can be used to treat many infections. Silver nanoparticles in drug delivery systems generally increase solubility, stability, and biodistribution, thereby increasing their effectiveness. Green synthesis using plant extracts as precursors to synthesize nanoparticles has proven to be environmentally non-hazardous combined with remarkably improved efficacy against bacterial and viral diseases. So neem-infused silver nanoparticles can be utilized as a drug delivery system. Hence, it can be used as a potential antibacterial ingredient in formulations for periodontal use like mouthwashes and gels for local drug delivery. How to cite this article: Krishnappan S, Ravindran S, Balu P, et al. Comparative Evaluation of Antimicrobial Efficacy of Silver Nanoparticles Infused with Azadirachta indica extract and Chlorhexidine Against Red-Complex Pathogens. J Contemp Dent Pract 2024;25(6):547-553.

Evaluation of Antibacterial Activities of Clove Bud Oil and Extract on Bacterial Isolates from Dental Caries

Dental caries remains one of the most prevalent oral health issues worldwide, primarily caused by bacterial activity w ithin the oral cavity. This study investigates the antibacterial activities of clove oil bud against bacteria associated with dental caries. The clove buds were collected, identified, and processed for ethanol extraction of bioactive compounds. Also, 30 samples of dental caries were obtained using swab sticks and cultured on nutrient agar, MacConkey agar, and Mannitol salt agar, then incubated for 24 hours and identified using biochemical tests and molecular analysis. Qualitative and quantitative phytochemical analysis confirmed the presence of alkaloids (5.033%), saponins (3.50%), flavonoids (0.407%), phenols (0.4545%), tannins (5.227%), and glycosides (2.1285%) in the ethanol extract, while the clove oil contained saponins (8.70%) and a small amount of glycosides (0.0375%). The extracted compounds underwent Gas Chromatography-Mass Spectrometry (GC-MS) analysis, which identified key constituents such as eugenol, Caryophyllene oxide, and 9,12-Octadecadienoic acid. The characterization of the clove oil revealed a density of 0.86 g/cm³, viscosity of 113.59 mm²/s, refractive index of ≥36% Brix, saponification value of 39.19 mg KOH, iodine value of 21.488 g/ml, peroxide value of 13.4 mEq/kg, and a free fatty acid content of 1.37%. Biochemical tests on the bacterial isolates from dental caries samples identified several species, including Actinomyces spp., Streptococcus spp., Lactococcus spp., Lacticaseibacillus paracasei, Staphylococcus aureus strain CIB, Bifidobacterium spp., Veillonella spp., and Bacillus subtilis. Antimicrobial activity assay shows that clove oil exhibited significant inhibition of microbial growth at higher concentrations: B.subtilis had inhibition zones of 12 mm at 100 mg/ml, 6 mm at 50 mg/ml, and 2 mm at 25 mg/ml. Similarly, Lacticaseibacillus agile 1365 showed inhibition zones of 14 mm at 100 mg/ml, 8 mm at 50 mg/ml, and 3 mm at 25 mg/ml. S.aureus strain B3A22 had inhibition zones of 10 mm at 100 mg/ml and 6 mm at 50 mg/ml. In contrast, L. paracasei showed minimal inhibition, indicating lower susceptibility to clove oil. On the other hand, the result also illustrates that clove extract was more effective at lower concentrations compared to clove oil. B.subtilis had inhibition zones of 14 mm at 100 mg/ml, 8 mm at 50 mg/ml, and 5 mm at 25 mg/ml. L.paracasei demonstrated inhibition zones of 16 mm at 100 mg/ml, 11 mm at 50 mg/ml, and 8 mm at 25 mg/ml. S.aureus strain B3A22 had inhibition zones of 10 mm at 100 mg/ml and 6 mm at 50 mg/ml. The Minimum Inhibitory Concentration (MIC) of clove oil was found to be 25 mg/ml for B.subtilis, 100 mg/ml for L.paracasei, 25 mg/ml for L.agile 1365, and 25 mg/ml for both S.aureus strain CIB and strain B3A22 respectively. In comparison, clove extract demonstrated lower MIC values: 12.5 mg/ml for B.subtilis, 12.5 mg/ml for L.paracasei, 12.5 mg/ml for L.agile 1365, 25 mg/ml for S.aureus strain CIB, and 25 mg/ml for S.aureus strain B3A22. The Minimum Bactericidal Concentration (MBC) of clove oil was 50 mg/ml for B.subtilis, for L.paracasei, 25 mg/ml for L.agile 1365, 50 mg/ml for S.aureus strain CIB, and 100 mg/ml for S.aureus strain B3A22. In contrast, clove extract showed an MBC of 25 mg/ml for B.subtilis, 50 mg/ml for L.paracasei, 25 mg/ml for L.agile 1365, 50 mg/ml for S.aureus strain CIB, and 25 mg/ml for S.aureus strain B3A22. These results underscore the significant antibacterial activity of clove extract, particularly due to its higher potency at lower concentrations compared to clove oil, supporting its potential use in developing alternative treatments for dental caries.

Jellein-I-conjugated gold nanoparticles: Insights into the antibacterial, antibiofilm activities against MRSA, and anticancer properties

Antimicrobial peptides (AMPs) and their conjugation with nanoparticles hold promise for targeting Methicillin-resistant Staphylococcus aureus (MRSA). In this study, Jellein-I peptide, with a cysteine at the C-terminus, was conjugated to gold nanoparticles (GNPs) to enhance its antibacterial, antibiofilm, and anticancer activities. The GNPs were synthesized and then conjugated to Jellein-I, forming Jellein-I-Cys-GNPs. The nanoparticles were characterized using UV–visible spectroscopy, transmission electron microscopy (TEM), dynamic light scattering (DLS), and Fourier transform infrared (FTIR) spectroscopy. UV–visible spectroscopy, DLS, and TEM confirmed the formation of GNPs with an average size of 5.5 nm. The UV–visible spectroscopy and FTIR results indicated the presence of peptide functional groups on the surface of the GNPs. To assess antibacterial activity, minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) assays were performed against MRSA strains. The conjugated Jellein-I exhibited lower MIC and MBC values (94 μM) compared to the free peptide (512 μM) against both clinical and standard MRSA strains. Additionally, GNP-conjugated Jellein-I demonstrated antibiofilm activity, inhibiting and removing biofilms while reducing metabolic activity by more than 82 %, 44 %, and 72 %, respectively. Cell viability studies on rat dermal fibroblast (RDF) cells showed over 80 % viability across all treatment concentrations. Furthermore, a clonogenic assay on the metastatic melanoma cell line (A375) demonstrated that GNP-conjugated Jellein-I had significantly better anticancer effects than the free peptide, even at a concentration as low as 9 μM. Our findings suggest that the conjugation of Jellein-I-Cys to GNPs could be a promising formulation for enhancing the antibacterial, antibiofilm, and anticancer activities of peptides. Further in vivo studies may establish this new nanoformulation as a potential therapeutic candidate for MRSA infections and cancer treatment.

Antibacterial effect of Cu2O/TiO2 visible-light photocatalytic composite on Xanthomonas campestris.

In this study, a Cu2O/TiO2 (CuTi) visible-light photocatalytic composite was employed for the treatment of Xanthomonas campestris and X. campestris-infected Brassica napus seedlings. The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) values against X. campestris were determined to be 8 and 32 μg ml-1, respectively. Transmission electron microscopy analysis demonstrated a direct correlation between the extent of bacterial cell damage and the concentration of CuTi. Noteworthily, a bactericidal rate of 100% was achieved at a concentration of 150 μg ml-1 over a treatment duration of 120 min. Moreover, alterations in active oxidants and antioxidants, including reactive oxygen species, glutathione reductase, superoxide dismutase, peroxidase, and catalase within the bacterial cells, were examined to elucidate the underlying mechanism of inhibition by the CuTi. The B. napus infected by X. campestris was treated with CuTi, and the efficacy was validated through determination of plant resistance indexes. The combined data confirmed that the CuTi is characterized by a low dose, fast onset, good effect, and higher safety for killing X. campestris, and it is expected to be developed as an antimicrobial agent for vegetables.

Antimicrobial Activity of Bacillus Coagulans Supernatant Against Human Enteric Pathogens

Background: Chronic bacterial diarrheas are common intestinal infections that have been treated with antibiotics for many years. However, the excessive use of antibiotics has led to the development of resistance in the bacteria that cause these infections. As a result, there has been growing interest in using probiotics with antibacterial effects and a greater ability to survive stomach acidity to help control antibiotic-resistant bacteria. Objectives: In the current study, the antimicrobial activity of Bacillus coagulans (a probiotic bacterium) against four different enteric pathogens (Escherichia coli, Salmonella typhi, Shigella flexneri, and Bacillus cereus), which play a significant role in the prevalence of bacterial diarrhea, has been investigated. Methods: The antimicrobial effect of the cell-free supernatant of Bacillus coagulans against pathogens (E. coli, S. typhi, Sh. flexneri, and B. cereus) was studied using agar well-diffusion, agar disc-diffusion, as well as minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) methods. In the MIC test, the concentrations of B. coagulans cell-free supernatant examined were 100, 50, 25, 12.5, 6.25, and 3.1 µg per mL. Each bacterial strain was tested in four replicates. Results: The antimicrobial activity of B. coagulans supernatant was not observed in either the agar well-diffusion or agar disc-diffusion results. However, MIC results showed that different concentrations of B. coagulans supernatant significantly inhibit the growth of E. coli (MIC = 25 µg/mL, P < 0.0001), S. typhi (MIC = 50 μg/mL, P < 0.0001), S. flexneri (MIC = 3.1 μg/mL, P < 0.0001), and B. cereus (MIC = 100 µg/mL, P < 0.0001). Conclusions: The MBC results showed that the minimum inhibitory concentration of the supernatant had no bactericidal effects and did not completely prevent the growth of all four pathogens. Although the MIC results indicated the antibacterial activity of B. coagulans against all four pathogens, further studies are required to draw more accurate conclusions.

Antibacterial activity and mechanism of Stevia extract against antibiotic-resistant Escherichia coli by interfering with the permeability of the cell wall and the membrane.

Natural plant-derived compounds with broad-spectrum antimicrobial activity have become an effective strategy against multidrug-resistant bacteria. The present study was designed to compare the antibacterial activity of six chlorogenic acid (CA) isomers extracted from stevia and investigated the underlying antibacterial mechanisms involved. The results indicated that isochlorogenic acid C (ICAC) exhibited the strongest antibacterial activity against the tested bacteria, especially E. coli, at a 2 mg/mL minimum inhibitory concentration (MIC) and 8 mg/mL minimum bactericidal concentration (MBC). At the MBC, ICAC inhibited 72.66% of the clinical multidrug-resistant strains. Scanning electron microscopy (SEM) revealed that ICAC induced considerable morphological alterations in E. coli ATCC25922 and C4E2. The significant increase in the activity of extracellular alkaline phosphatase (AKP) indicated that ICAC damages the permeability of the bacterial cell wall. Additionally, the intracellular membrane (IM) permeability and the content of lipopolysaccharide (LPS), a main component of the outer membrane (OM), were determined. The significant decrease in LPS content and increased leakage of intracellular proteins and K+ from E. coli indicated that ICAC could induce the exfoliation of OM and disrupt IM permeability, resulting in the loss of barrier function. The uptake of propidium iodide (PI), a compromised cell membrane nucleic acid stain, and confocal laser scanning microscopy (CLSM) further demonstrated that ICAC disrupted IM integrity. Moreover, the bactericidal effect and damage to bacterial microstructural function occurred in a dose-dependent manner. These data demonstrate that ICAC has excellent antibacterial activity and is a promising approach for overcoming the antibiotic resistance of pathogenic bacteria.

Tannic acid and Gallic Acid as Alternative Compounds for the Application as Preservatives in Cosmetic Products

Introduction: Tannic acid and gallic acid have been known as natural compounds with antibacterial activity. In this work, the antimicrobial efficiency of tannic acid (TA) and gallic acid (GA), as well as their mixtures, was tested. Method: During the research, the minimal inhibitory concentration, minimal bactericidal concentration, and fractional inhibitory concentration were defined. Based on them, for further study, mixtures of TA/GA in ratios 50:50 and 80:20 were chosen as a preservation mixture applied to the cosmetic emulsion. Results: The obtained cosmetics emulsions were analyzed for the total mesophilic aerobic bacteria count and the total combined yeast count. The preservation efficiency test was performed according to the ISO 11930 standard. A stability test for cosmetics formulation was also carried out. Conclusion: The preservation mixture of TA/GA in an 80:20 ratio incorporated in the cosmetics formulation showed good preservation efficiency and could be considered a natural origin preservative.

Developing a novel calcium silver zeolite for caries management

ObjectiveTo develop a novel calcium silver zeolite (Ca-Ag-Zeo) and assess its biocompatibility, physiochemical properties and antimicrobial effects.MethodsCa-Ag-Zeo was synthesized using ion-exchange method with calcium chloride, silver nitrate and Zeolite X (Zeo). Silver zeolite X (Ag-Zeo) and Zeo were set as control. The chemical structure, morphology, crystal structure and elemental composition of Ca-Ag-Zeo was characterized by X-ray diffraction spectrum, scanning electron microscopy, transmission electron microscopy and energy dispersive spectroscopy, respectively. Its biocompatibility on the human gingival fibroblasts was assessed by cell counting kit-8 assay. Its physiochemical properties were determined by the released calcium and silver ion using Inductive Coupled Plasma Emission Spectrometry for up to 12 weeks. The antimicrobial properties on Streptococcus mutans, Lactobacillus acidophilus, Lactobacillus casei, and Candida albicans were assessed by minimum bactericidal concentration (MBC) or minimum fungicidal concentration (MFC) assay.ResultsCa-Ag-Zeo with a hexagonal cage structure was synthesized. As for biocompatibility, the half-maximal inhibitory concentration (± SD in mg/mL) of Ca-Ag-Zeo, Ag-Zeo and Zeo in human gingival fibroblasts were 0.52 ± 0.05, 0.15 ± 0.01 and 3.35 ± 0.58, respectively (Zeo > Ca-Ag-Zeo > Ag-Zeo; p < 0.05). As for physiochemical properties, the accumulated ion release (± SD in mg) of Ca-Ag-Zeo, Ag-Zeo and Zeo were 0.011 ± 0.003, 0 and 0 for calcium ion, respectively (Ca-Ag-Zeo > Ag-Zeo, Zeo; p < 0.001), and 0.213 ± 0.032, 0.209 ± 0.019 and 0 for silver ion, respectively (Ca-Ag-Zeo, Ag-Zeo > Zeo; p < 0.001). As for anti-microbial ability, the MBC/MFC (mg/mL) of Ca-Ag-Zeo, Ag-Zeo and Zeo were 32, 16 and > 256 against Streptococcus mutans; 32, 16, > 256 against Lactobacillus acidophilus; 16, 16, and 256 against Lactobacillus casei; 0.25, 0.125; and 2, 1, > 256 against Candida albicans, respectively.ConclusionA novel Ca-Ag-Zeo was developed. It presented better biocompatibility compared to Ag-Zeo. It released calcium and silver ions sustainably, and it could inhibit the growth of common cariogenic microorganisms.

Antibacterial Properties of Cinamaldehyde and its Impact on Biofilm Formation by Respiratory Isolates of Corynebacterium Propinquum

Objective: Analyze the antibacterial properties of cinnamaldehyde (CN) and its effect on biofilm formation by Corynebacterium propinquum. Theoretical Framework: C. propinquum can form biofilm and be multiresistant. In the context of advancing resistance and the need for new and more effective drugs, constituents extracted from cinnamon, such as CN, stand out as they have proven antimicrobial activity. Method: It was investigated whether CN essential oil (EO) was hemolytic for sheep erythrocytes. The antibacterial activity against nasopharyngeal C. propinquum strains was evaluated by determining the minimum inhibitory concentrations (MIC) and minimum bactericidal concentrations (MBC), and by analyzing the combinatorial effect with chloramphenicol (CL). Biofilm formation on a hydrophobic surface (polystyrene), in the presence or absence of subinhibitory concentrations (SubMIC) of CN, was also evaluated. Results and Discussion: The results demonstrated that CN was not hemolytic. Despite the MIC being higher than that of CL, the antibacterial action was strong for both strains, but it was impossible to determine the MBC. The combinatorial antibacterial effect of CN+CL demonstrated partial synergy or indifference. Weak biofilm formation was observed for the strains and the presence of CN SubMIC, although it did not change the pattern, increased its production. Research Implications: This research's practical and theoretical implications suggest promising antibacterial properties of CN on emerging pathogen C. propinquum. Originality/Value: This study is relevant not only because it demonstrates aspects of virulence of a pathogen that has been little studied, but also because it shows the antibacterial action of CN, a constituent of an easily accessible spice. It highlighted the possibility of future research into the treatment of infections caused by a microorganism that is often multi-resistant.

In vitro and In silico Antibacterial Evaluation of N-Methyl-2-phenylmaleimides

Background: Novel antibiotics are needed to stem the rise of antimicrobial resistance. N-Methyl-2-phenylmaleimide (NMP) compounds previously synthesised by our research group are structural analogues of 2,3,5-substituted perhydropyrrolo[3,4-d]isoxazole-4,6-diones found by others to have antibacterial activity. Objectives: This study aims to explain the significance of NMPs and their antibacterial activity. The antibacterial activity of the NMPs was determined against Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, and Pseudomonas aeruginosa. The partition coefficient of the NMPs and a pharmacophore model were used to explain their antibacterial activity. Methods: The Kirby Bauer Disc diffusion method was used to screen the NMPs for activity, while the broth microdilution method was used to determine the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of the active NMPs. Using the in vitro antibacterial activity of 2,3,5-substituted perhydropyrrolo[3,4-d]isoxazole-4,6-diones, a common feature pharmacophore model was constructed and validated. The rank score, fit value, enrichment factor (EF20%), and receiver operating characteristic area under the curve (ROC-AUC) were used as validation metrics. Results: The NMPs were only active against S. aureus, with compound 3 (4 µg/ml) being the most active. The majority of NMPs were bacteriostatic. A common feature pharmacophore model was validated (rank score: 120.5; fit value: 4; EF20%: 4.3; ROC-AUC: 0.9 ± 0.03) and showed that three hydrogen bond acceptors and a ring aromatic region are important for activity. Comparing the partition coefficient of the NMPs to their MIC a statistically significant correlation was found. Conclusion: NMPs can be used as lead compounds in future studies. The validated pharmacophore model and partition coefficient can be used to develop more active compounds.

Antimicrobial Activity of Composite Preparations Based on Biosurfactants and Heterocyclic Amino-Containing 1,4-Naphtoquinone Derivativesantimicrobial Activity of Composite Preparations Based on Biosurfactants and Heterocyclic Amino-Containing 1,4-Naphtoquinone Derivatives

Background. The development of highly effective and environmentally safe composite drugs with antimicrobial properties is an important challenge in biotechnology and pharmacy. Objective. To determine the antimicrobial activity of new composite preparations based on rhamnolipids combined with heterocyclic amine-containing derivatives of 1,4-naphthoquinone against the test-bacteria Escherichia coli B-906, Staphylococcus aureus 209-P, Mycobacterium luteum B-917, and fungi Candida tenuis UCM Y-70 and Aspergillus niger UCM F-1119. Methods. The in vitro antimicrobial activity of heterocyclic amine-containing derivatives of 1,4-naphtho­quinone, biosurfactants, and composite preparations based on them was tested against cultures of Escherichia coli B-906, Staphylococcus aureus 209-P, Mycobacterium luteum B-917, and fungi Candida tenuis UCM Y-70 and Aspergillus niger UCM F-1119 using the agar diffusion method on solid nutrient media, as well as the serial dilution method (minimum inhibitory and bactericidal concentrations). The toxicity of the heterocyclic amine-containing derivatives of 1,4-naphthoquinone was predicted using in silico methodology via the ProTox-II software. Results. It was found that 2-chloro-3-((1-methyl-1H-pyrazol-3-yl)amino)naphthalene-1,4-dione 3.2 and 2-chloro-3-((3-(n-tolyl)- 1H-pyrazol-5-yl) amino) naphthalene-1,4-dione 3.3 exhibit antimicrobial activity. Their composite preparations, due to the combination with rhamnolipids, demonstrated improved solubility and enhanced antimicrobial effects. Based on the results of the calculated assessment, the studied heterocyclic amine-containing derivatives of 1,4-naphthoquinone are predicted to fall into toxicity class IV. Conclusions. The antimicrobial activity of 2-chloro-3-((1-methyl-1H-pyrazol-3-yl)amino)naphthalene-1,4-dione 3.2 and 2-chloro-3-(3-( 3-(p-tolyl)-1H-pyrazol-5-yl)amino)naphthalene-1,4-dione 3.3 is enhanced. This suggests the potential of the proposed biotechnological approaches in the development of new biocidal preparations.

Antibacterial and Anticancer Properties of Endophenazines from Streptomyces prasinus ZO16, an Endophyte in Zingiber officinale Rosc.

&lt;b&gt;Background and Objective:&lt;/b&gt; This study investigated a bacterial strain, ZO16, isolated from ginger (&lt;i&gt;Zingiber officinale&lt;/i&gt;) roots. Analysis of its 16S ribosomal DNA (rDNA), along with chemical and physical properties, revealed it to be &lt;i&gt;Streptomyces prasinus&lt;/i&gt;. This study aimed to isolate and characterize the main bioactive compounds from ZO16, evaluating their antibacterial and anticancer properties. &lt;b&gt;Materials and Methods:&lt;/b&gt; Techniques like column chromatography and thin-layer chromatography (TLC) were used to purify the key compounds from ZO16's culture extract. Nuclear Magnetic Resonance (NMR) spectroscopy and mass spectrometry were utilized to confirm the identities of the purified compounds as endophenazine A (compound 1) and endophenazine B (compound 2). The antibacterial and anticancer properties of these compounds were then evaluated. &lt;b&gt;Results:&lt;/b&gt; The isolated compounds displayed antibacterial activity against &lt;i&gt;Staphylococcus aureus&lt;/i&gt; ATCC 25923 and Methicillin-Resistant &lt;i&gt;Staphylococcus aureus&lt;/i&gt; (MRSA). The minimum inhibitory concentration (MIC) of the isolated compounds against bacteria ranged from 8 to 32 μg/mL, while the minimum bactericidal concentration (MBC) was between 32 and 128 μg/mL. These compounds exhibited effectiveness against tested cancer cells with IC&lt;sub&gt;50&lt;/sub&gt; values ranging from 30.40 to 32.51 μg/mL for cervical cancer (HeLa), 78.32 to 86.45 μg/mL for liver cancer (HepG2) and 23.41 to 28.26 μg/mL for breast cancer (MDA-MB-231) cells. However, these compounds also showed moderate toxicity towards non-cancerous Vero cells (IC&lt;sub&gt;50&lt;/sub&gt; = 317.44-328.63 μg/mL). &lt;b&gt;Conclusion:&lt;/b&gt; The findings of this study suggest that &lt;i&gt;Streptomyces prasinus&lt;/i&gt; strain ZO16 produces compounds with antibacterial and anticancer properties. Further investigation of these compounds has the potential to contribute to the development of improved methods for controlling and treating bacterial infections and some cancers.

Antimicrobial effect of lactoferrin and glycerol monolaurate on selected bacteria associated with newborn infections

Human breast milk contains a rich array of bioactive substances, such as immunoglobulins, lactoferrin antimicrobial peptides, and glycerol monolaurate, which play a crucial role in providing immune protection to infants. Infant formula manufacturers strive to match mother's milk's nutritional makeup, including immune-boosting ingredients. Lactoferrin and glycerol monolaurate (GML) are important antibacterial compounds in human milk. The study aimed to investigate the effect of bovine lactoferrin (bLf) and GML in preventing the growth of inoculated bacteria into infant formula. The study examined both individual and combined use of these components. The bacteria that were tested included: 1) Gram-negative bacteria: Cronobacter sakazakii strains 12868 and 29004, Pseudomonas aeruginosa, Salmonella enterica Typhimurium, and 2) Gram-positive bacteria: Methicillin-resistant Staphylococcus aureus (MRSA), and Listeria monocytogenes. The result of the agar diffusion assays showed that bLf, at a concentration of 16 mg/disc, exhibited strong inhibition (≥20 mm) of all the selected bacterial strains. On the other hand, GML at a concentration of 8 mg/disc showed strong inhibition of all strains; however, Gram-positive bacteria were more susceptible, so a concentration of 5 mg/disc was enough to achieve strong inhibition of these strains. The minimal bactericidal concentrations (MBC) analysis aimed to achieve a >3-log reduction in the growth of various bacterial strains. The results showed that S. enterica Typhimurium and L. monocytogenes were more susceptible to bLf than the other strains (MBC: 7 and 4.8 mg/ml, respectively, vs. 14.9–18.4 mg/ml for the other strains). In contrast, MRSA and L. monocytogenes were more susceptible to GML (MBC: 6 and 10 mg/ml, respectively, vs. 16–18 mg/ml for Gram-negative strains). The results of reconstituted powdered infant formulas (RPIF), with the addition of bLf, GML, or both at pathogen-specific MBC, showed significant log reductions in the growth of experimentally inoculated bacteria compared to the control at different time intervals. All bacterial strains exposed to bLf and GML exhibited >3-log reduction within 72 h, with Gram-positive strains showing >7-log reduction. GML and bLf combined had a stronger anti-bacterial activity than individual components, indicating the potential of combining GML and bLf as natural agents against specific pathogenic bacteria. Future studies are needed to understand the potential use of these compounds in different food matrices and clinical settings.

Inhibitory effect and mechanism of violacein on planktonic growth, spore germination, biofilm formation and toxin production of Bacillus cereus and its application in grass carp preservation

Bacillus cereus is a ubiquitous foodborne pathogen commonly found in various foods. Its ability to form spores, biofilms and diarrhoeal and/or emetic toxins further exacerbates the risk of food poisoning. Violacein is a tryptophan derivative with excellent antibacterial activity. However, the knowledge on the antibacterial action of violacein against B. cereus was lacking, and thus this study aimed to investigate the antibacterial activity and mechanism. The antibacterial results demonstrated that minimum inhibitory concentration and minimum bactericidal concentration of violacein were 3.125 mg/L and 12.50 mg/L, respectively. Violacein could effectively inhibit planktonic growth, spore germination and biofilm formation of B. cereus (P < 0.001). Meanwhile, violacein significantly downregulated the expression of toxin genes, including nheA (P < 0.05), nheB (P < 0.001), bceT (P < 0.01), cytK (P < 0.001), hblC (P < 0.001) and hblD (P < 0.001). Results of extracellular alkaline phosphatase, nucleotide and protein leakage assays and scanning and transmission electron microscopy observation tests showed violacein destroyed cell walls and membranes of B. cereus. In addition, 6.25 mg/kg of violacein could significantly inhibit B. cereus in grass carp fillets (P < 0.05). These results demonstrate that violacein has great potential as an effective natural antimicrobial preservative to control food contamination and poisoning events caused by B. cereus.

The Effects of Blue Vitriol and Brimstone on Etiological Agents of Bacterial Vulvovaginitis

Vulvovaginitis is an inflammation of the vulva and/or the vagina which may be symptomatic or asymptomatic. It is a common public health problem that can affect women and girls of all ages. The study aimed at evaluating the effects of blue vitriol and brimstone on etiological agents of bacterial vulvovaginitis. One hundred high vaginal swab specimens were aseptically and properly collected from suspected cases of vulvovaginitis. Plates of nutrient agar and blood agar were inoculated and incubated aerobically at 25 oC for 24 hours. The isolates were identified based on their morphological, physiological, biochemical and molecular characteristics. The antimicrobial activity of blue vitriol and brimstone was determined using the agar-well diffusion method. Minimal inhibitory concentration (MIC) and minimal bactericidal concentration (MBC) of the test samples were determined using the broth dilution method. The isolates include Staphylococcus epidermidis, Eschericha coli, Lactobacillus spp. and Staphylococcus aureus. The inhibition zone diameter (IZD) of blue vitriol against the isolates ranges from 30.00±0.00mm to 31.50±2.12mm at concentrations of 50mg/ml to 200mg/ml. The IZD of brimstone against the isolates ranges from 29.00±1.41mm to 11.00±0.00mm at concentrations of 50mg to 200mg/ml. The positive control, ciprofloxacin gave IZD of 17.50±2.12mm to 21.50±2.12mm. The MIC of blue vitriol against all the isolates was 12.50mg/ml; while the MBC ranges between 25mg/ml to 50mg/ml. The MIC of brimstone was 25mg/ml to 200mg/ml; while the MBC was 50mg/ml to 200mg/ml. Ciprofloxacin gave MIC and MBC ranging from 25mg/ml to 100mg/ml against all the isolates. The study has shown that natural compounds such as blue vitriol and brimstone are good antimicrobials; and could serve as substitutes to conventional antimicrobial agents in the treatment of bacterial vulvovaginitis. Keywords: Vagina, Vulva, Vulvovaginitis, Blue vitriol, Brimstone, Antimicrobials.

In vitro efficacy of aquaculture antimicrobials and genetic determinants of resistance in bacterial isolates from tropical aquaculture disease outbreaks.

Understanding the efficacy of antimicrobials against pathogens from clinical samples is critical for their responsible use. The manuscript presents in vitro efficacy and antimicrobial resistance (AMR) genes in seven species of fish pathogens from the disease outbreaks of Indian aquaculture against oxytetracycline, florfenicol, oxolinic acid, and enrofloxacin. In vitro efficacy was evaluated by minimum inhibitory concentration and minimum bactericidal concentration. The gene-specific PCR screened AMR genes against quinolones (qnrA, qnrB, and qnrS) and tetracyclines (tetM, tetS, tetA, tetC, tetB, tetD, tetE, tetH, tetJ, tetG, and tetY). The results showed that Aeromonas veronii (45%) showed the maximum resistance phenotype, followed by Streptococcus agalactiae (40%), Photobacterium damselae (15%), Vibrio parahaemolyticus (10%), and Vibrio vulnificus (5%). There was no resistance among Vibrio harveyi and Vibrio alginolyticus against the tested antimicrobials. The positive association between tetA, tetB, tetC, tetM, or a combination of these genes to oxytetracycline resistance and qnrS to quinolone resistance indicated their potential in surveillance studies. The prevalence of resistance phenotypes (16.43%) and evaluated AMR genes (2.65%) against aquaculture antimicrobials was low. The resistance phenotype pattern abundance was 0.143. All the isolates showed susceptibility to florfenicol. The results help with the appropriate drug selection against each species in aquaculture practices.

Investigation of antimicrobial and antioxidant properties of postbiotics produced by lactobacillus rhamnosus and limosilactobacillus reuteri and their potential application in surface decontamination of red meat

This study investigated the antimicrobial properties of postbiotics produced by lactobacillus rhamnosus and limosilactobacillus reuteri in surface decontamination of red meat against pathogenic bacteria (Escherichia coli and Staphylococcus aureus). The study evaluated postbiotic activity using agar well diffusion, minimum inhibitory concentration (MIC mg/mL), minimum bactericidal concentration (MBC mg/mL), antioxidant properties, total phenolic content (TPC), and organic acid content. Among 18 meat samples, the mixed postbiotic (L. rhamnosus and L. reuteri, 100 mL/mg) displayed the strongest effect against E. coli, achieving a 5.54 log CFU/g reduction after 48 h with a well diffusion diameter of 23 mm, MIC of 20, and MBC of 25. A similar trend was observed for S. aureus, with the mixed postbiotic showing a reduction of 6.9 log CFU/g after 48 h, MIC of 25, and MBC of 50. Interestingly, the mixed postbiotic also exhibited the highest TPC (250.8 mL/mg). L. reuteri postbiotic displayed the strongest antioxidant activity (52.3 mL/mg) and highest organic acid content (18.9 mL/mg). These results suggest the potential of Lactobacilli-derived postbiotics as natural antimicrobials for controlling surface pathogens on meat products. Additionally, the observed link between TPC and antimicrobial activity warrants further investigation into the potential role of antioxidants in enhancing biopreservation efficacy.

Antibacterial activity and mechanism of Ag2Cu2O3 mixed-metal oxide

Pure phase Ag2Cu2O3 mixed-metal oxides with homogeneous morphology of short rod-like structure were synthesized through simple co-precipitation methods. The efficacious antibacterial activities of the obtained Ag2Cu2O3 against both Gram positive and Gram negative bacteria were corroborated by the minimum inhibitory concentration (4.88 mg/L for both Escherichia coli and Staphylococcus lentus) and minimum bactericidal concentration (19.53 mg/L for E. coli and 9.76 mg/L for S. lentus). In shake flask inactivation experiments, more than 99 % of bactericidal rate was achieved for both test strains within 30 min using 250 mg/L of the Ag2Cu2O3. From the results of free radical quenching experiments and electron spin resonance spectroscopy, singlet oxygen in suspension played an important role in the sterilization of the Ag2Cu2O3, but some factors other than reactive oxygen species might also make a significant contribution. Through the simulated antibacterial experiments of the leached Cu2+ and Ag+ from Ag2Cu2O3, we found that trace Ag+ exhibits strong bactericidal ability against both strains. While, trace Cu2+ displayed a more pronounced sterilization activity against S. lentus than E. coli, which explains the higher antibacterial activity of Ag2Cu2O3 against Gram positive bacteria compared with Gram negative ones.

Antimicrobial spectrum against wound pathogens and cytotoxicity of star-arranged poly-l-lysine-based antimicrobial peptide polymers.

Introduction. As growing numbers of patients are at higher risk of infection, novel topical broad-spectrum antimicrobials are urgently required for wound infection management. Robust pre-clinical studies should support the development of such novel antimicrobials.Gap statement. To date, evidence of robust investigation of the cytotoxicity and antimicrobial spectrum of activity of antimicrobial peptides (AMP)s is lacking in published literature. Using a more clinical lens, we address this gap in experimental approach, building on our experience with poly-l-lysine (PLL)-based AMP polymers.Aim. To evaluate the in vitro bactericidal activity and cytotoxicity of a PLL-based 16-armed star AMP polymer, designated 16-PLL10, as a novel candidate antimicrobial.Methods. Antimicrobial susceptibilities of clinical isolates and reference strains of ESKAPE (Enterococcus spp., Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, Enterobacter spp.) pathogens, to 16-PLL10 were investigated. Human erythrocyte haemolysis and keratinocyte viability assays were used to assess toxicity. Modifications were made to 16-PLL10 and re-evaluated for improvement.Results. Minimum bactericidal concentration of 16-PLL10 ranged from 1.25 µM to ≥25 µM. At 2.5 µM, 16-PLL10 was broadly bactericidal against ESKAPE strains/wound isolates. Log-reduction in colony forming units (c.f.u.) per millilitre after 1 h, ranged from 0.3 (E. cloacae) to 5.6 (K. pneumoniae). At bactericidal concentrations, 16-PLL10 was toxic to human keratinocyte and erythrocytes. Conjugates of 16-PLL10, Trifluoroacetylated (TFA)-16-PLL10, and Poly-ethylene glycol (PEG)ylated 16-PLL10, synthesised to address toxicity, only moderately reduced cytotoxicity and haemolysis.Conclusions. Due to poor selectivity indices, further development of 16-PLL10 is unlikely warranted. However, considering the unmet need for novel topical antimicrobials, the ease of AMP polymer synthesises/modification is attractive. To support more rational development, prioritising clinically relevant pathogens and human cells, to establish selective toxicity profiles in vitro, is critical. Further characterisation and discovery utilising artificial intelligence and computational screening approaches can accelerate future AMP nanomaterial development.

Antilisterial effect of alkyl polyglycosides biosurfactant and modes of action

Several outbreaks of Listeria monocytogenes originated mainly from contaminated contact surfaces. Thus, this study investigated the antilisterial effect of natural surfactants in terms of their use as a 2-in-1 sanitizing washer on a food contact surface and evaluated their modes of action. The antilisterial activity of alkyl polyglycosides (APGs), namely capryl glucoside (CA), coco glucoside (CG), and decyl glucoside (DG), was evaluated based on the minimum inhibitory concentration (MIC) and the minimum bactericidal concentration (MBC) using broth dilution assay. The results showed that CG had the strongest antilisterial activity. Therefore, CG was selected for further investigation. The time-kill assay showed a lethal effect of 0.5 % (w/w) CG by inactivating 4 Log reduction (99.99 %) of L. monocytogenes within 3 s. Furthermore, 1 % (w/w) CG with slight mechanical force in washing (by shaking) was efficient for sanitizing a stainless-steel coupon surface based on its ability to cause a total reduction of deposited L. monocytogenes (99.9 %) within 10 min. Scanning electron microscopy and applying Fourier-transform infrared spectroscopy revealed that CG chemically disrupted the cell wall and plasma membrane of L. monocytogenes within 5 min after a gentle wash. The results showed it had potent antimicrobial activity and was bactericidal against L. monocytogenes. Overall, our results supported the use of CG as a natural antibacterial surfactant to alter the chemical sanitizer and the possibility of its practical use in the food industry and for household use.