Bactericidal Concentration Research Articles

Microencapsulation of <i>Chromolaena odorata</i> Leaf Extract with Cellulose Esters for the Application as an Eco-Friendly Antibacterial Agent

The aim of this work is to develop an eco-friendly antibacterial agent in the form of microcapsules containing extract from Chromolaena odorata leaves using the solvent evaporation method. The wall materials for encapsulating were tested with various cellulose esters including cellulose acetate (CA), cellulose acetate butyrate (CAB), and cellulose acetate propionate (CAP). The evaluation of microcapsules containing C. odorata leaf extract was focused on their encapsulation efficiency, size, shape, thermal stability, and antimicrobial activities. The results showed that CAB was a suitable wall material for the encapsulation of C. odorata leaf extract. The CAB microcapsules exhibited the highest encapsulation efficiency, which was 65.82 ± 3.07. The size of CAB microcapsules was the smallest, at 1013.3 ± 66.5 nm. According to the thermogravimetric analysis, the prepared microcapsules were able to protect the extract of C. odorata leaves from the environment. Moreover, the CAB microcapsules containing C. odorata leaf extract showed the best antibacterial activities against Escherichia coli ATCC 25922 and Stapphylococcus aureus ATCC 25923. The minimum bactericidal concentration of the microcapsules was 25.6 mg/mL in both bacteria. This study proved the potential application of C. odorata leaf extract as a biomaterial in diverse industries in the future.

Novel antibacterial pullulan derivatives modified with quaternary phosphonium salts for infected wound treatments

The development of novel antibacterial agents is urgently needed to tackle bacterial infection, the major global issue menacing human health. Among them, polymeric quaternary phosphonium salts are worth noticing owing to their strong antibacterial activities and other merits including low bacterial drug resistance. Herein, pullulan modified with quaternary phosphonium salts (PQP) was synthesized using esterification reactions of pullulan and (5-carboxypentyl)triphenylphosphonium bromide (CPTPPB) mediated by N,N′‑carbonyldiimidazole (CDI), and was evaluated as novel antibacterial agents for treating wound infection for the first time. The chemical structures, chemical bonding, elemental compositions, crystalline properties and thermostability of PQP were systematically investigated. PQP exhibited in vitro antibacterial activities against Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli), which were unveiled by the spread plate method and possibly resulted from the damage of bacterial cell walls/membranes mediated by electrostatic and hydrophobic interactions according to preliminary mechanism studies. Weak cytotoxicity and excellent hemocompatibility of PQP at the effective bactericidal concentration were observed. Moreover, in the infected wound model of mice, PQP was capable of disinfecting the wound and accelerating the healing. We opine PQP in this work is promising for antibacterial applications and will inspire the synthesis of novel antibacterial agents derived from natural polymers.

Environmental Monitoring of Nebraska Ready-to-eat Meat Processing Establishments Resulted in the Isolation of Listeria Alongside Pseudomonas Highly Resistant to Quaternary Ammonia Sanitizer

Robust environmental monitoring for Listeria monocytogenes often may not be feasible for small and very small meat processors in the United States due to the limitations in finances, staffing, or expertise. Three small/very small processors in Nebraska were sampled using sponge applicators in nonfood contact surface areas to determine if biofilm and sanitizer resistance behaviors of Pseudomonas could relate to the prevalence of L. monocytogenes and Listeria spp. in ready-to-eat meat processing environments. Samples were 3.3% (3/90) positive for L. monocytogenes, and 12.2% (11/90) of samples were positive for Listeria spp. Pseudomonas spp. were also isolated. When Listeria spp. and Pseudomonas spp. were assayed for biofilm production and resistance to a quaternary ammonia sanitizer, multiple isolates belonging to both genera capable of forming biofilms were identified. Four Pseudomonas spp. isolates resisted the 200 ppm manufacturer-recommended sanitizer concentration for food contact surface sanitation, and one Pseudomonas spp. isolated from a drain sample that was also positive for L. monocytogenes demonstrated a sanitizer minimum bactericidal concentration of 1000 ppm. These findings further support the need for monitoring of small and very small meat processors for L. monocytogenes as well as highlight the need to identify other bacteria in these processing environments, like Pseudomonas, that are resistant to environmental stressors.

Chemical Composition, Antioxidant and Antimicrobial Activities of Anacyclus maroccanus Ball. and Anacyclus radiatus Loisel. Essential Oils Against Multidrug Resistant Microbial Pathogens

Objective: The present study aimed to characterize the phytochemical composition, the antioxidant and antimicrobial potencies of two essential oils obtained from the Moroccan ecotypes A. maroccanus and A. radiatus. Methods: The chemical composition of EOs was analysed by means of Gas Chromatography-Mass Spectroscopy analysis (GC-MS); moreover, 2,2-diphenyl-1-picrylhydrazyl (DPPH) and reducing power assays ware made to evaluate the antioxidant activity. In addition, disk diffusion method, minimum inhibitory concentration (MIC), and minimum bactericidal concentration (MBC) were employed to evaluate the antimicrobial activities against some resistant and pathogenic microorganism strains. Results: Results showed that the Anacyclus maroccanus and Anacyclus radiatus EOs were characterized by high amounts of oxygenated monoterpenes and sesquiterpenes, along with radical scavenging and reducing properties. Furthermore, EOs exhibited marked antimicrobial effects against all the tested bacterial and fungal strains. Conclusion: The current findings suggest that EOs from Anacyclus maroccanus and Anacyclus radiatus Moroccan ecotypes are a promising source of natural antioxidants that could be used in the pharmaceutical industry, particularly against drug-resistant microbial strains.

Ag quantum dots-doped poly (vinyl alcohol)/chitosan hydrogel coatings to prevent catheter-associated urinary tract infections

The prevention of catheter-associated urinary tract infections (CAUTIs) significantly impacts the reduction of morbidity and mortality associated with the use of indwelling urinary catheters. This study focused on developing an antibacterial double network hydrogel coating for latex urinary catheters, which incorporated Ag quantum dots (Ag QDs) in a polyvinyl alcohol (PVA)-chitosan (CS) double network hydrogel matrix. The PVA-CS-Ag QDs, referred to as the PCA hydrogel coating exhibited excellent mechanical and physiochemical properties with controlled release of Ag QDs. The antibacterial properties of the PCA hydrogel-coated urinary catheters were studied against both gram-negative Escherichia coli (E. coli, ATCC25922) and gram-positive Staphylococcus aureus (S. aureus, ATCC29213). The continuous release of CS oligomers and Ag QDs from the hydrogel coating contributed to the synergistic antibacterial and antiadhesion effects. Measurements of the Ag release rate revealed that even after 30 days, the concentration of Ag QDs from the PCA hydrogel-coated urinary catheters remained significantly higher than the effective antibacterial concentration of the total Ag (0.1 μg·L−1). These results indicated that the PCA hydrogel coating not only efficiently prevented bacteria attachment, but also exhibited long-term antibacterial activity, thereby inhibiting biofilm formation. Furthermore, the PCA hydrogel-coated urinary catheter demonstrated excellent biocompatibility and hemocompatibility. Overall, this novel PCA hydrogel-coated urinary catheter, with its exceptional antibacterial properties, holds great potential in reducing the incidence of CAUTIs.

Determination of Biological Activity of Hylocereus polyrhizus Methanol Extracts: Antimicrobial Activity, Probiotic-Promoting Effect, Photoprotective Activity

In our study, the biological activity of Hylocereus polyrhizus obtained from Türkiye was determined. Firstly, antimicrobial activity of methanol extracts obtained from H. polyrhizus against test microorganisms was determined by disc diffusion susceptibility assay, minimum inhibition concentration (MIC) and minimum fungicidal or bactericidal concentration (MFC or MBC) tests. Then, viable cell counting against Limosilactobacillus fermentum MA-7 using the macro-dilution method was used to determine the probiotic-promoting effect of the fruit extracts. Finally, the photo-protective activity of the extracts and extract-cream mixtures was obtained spectrophotometrically. The inhibition zone diameter of the peel extract against the test microorganisms is in the range of 9.60-12.37 mm and the fruit extract is in the range of 7.85-12.00 mm. MBC values ranged from 40 µg/µl to 80 µg/µl in peel extract and between 10 µg/µl and >80 µg/µl in the fruit extract. The inhibition zone diameters of the extracts against probiotics were determined as 6.10 -10.25 mm. As a result of the viable cell count, the viability rate of L. fermentum MA-7 increased as the fruit methanol extract concentration and time increased. The photoprotective activities of the peel and fruit extracts were determined as 13.17 and 12.26. It was determined that the extracts increased sun protection factor (SPF) value of the cream. The results indicated that H. polyrhizus extracts may have potential for use in the nutraceutical products, cosmetic and pharmaceutical industries.

Discovery and characterization of cyclotides, plant-based peptides from <i>Viola dalatensis</i> Gadnep

Cyclotides demonstrate remarkable stability due to their unique characteristic - the cyclic cystine knot motif. Cyclotides exhibit a wide range of biological activities. This study aims to explore the presence of cyclotides in Viola dalatensis Gadnep, a plant indigenous to Vietnam, through the utilization of LC-MS and LC-MS/MS techniques. We conducted a comprehensive analysis of three extraction methods: 50% acetonitrile with 1% formic acid, 70% ethanol, and 50% methanol. The initial method is extremely efficient for cyclotide extraction when utilizing LC-MS analysis. An ammonium sulfate salt concentration of 30% is used to enhance the cyclotide content and optimize the RP-HPLC purification procedure. The precipitates demonstrate a notable advantage in terms of antibacterial properties compared to the extracts, particularly when the antibacterial concentration is decreased by a factor of four in comparison to the extracts. The combination of cyclotides demonstrated potent antimicrobial activity against Bacillus subtilis and Pseudomonas aeruginosa. The impact was most noticeable when the concentration of the cyclotide mixture was ten times lower than the precipitates. The inhibition zones for these bacteria measured 17.17 ± 2.24 mm and 20.23 ± 0.84 mm, respectively. The identification of the primary structure of nine cyclotides through LC-MS/MS analysis was successfully achieved.

Biological Activity, Cytotoxicity, and Phytochemical Content of Leaf Extracts of Matoa (Pometia pinnata) and Pulasan (Nephelium ramboutan-ake) From the Sapindaceae Family

This study sought to assess the leaf extracts of matoa (Pometia pinnata) and pulasan (Nephelium ramboutan-ake) for antimicrobial, antifungal, antioxidant, and cytotoxic activities, besides phytochemical content. Four extracts (hexane, ethyl acetate, ethanol, and water) were obtained from each plant via sequential extraction. The antimicrobial activities were evaluated using colorimetric broth microdilution methods. The antioxidant activities were studied using 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging and ferric-reducing antioxidant power (FRAP) assays. The cytotoxicity was examined using mouse fibroblasts NIH/3T3 while the phytochemical content was detected using various chemical tests. Among the extracts, only the water extract of matoa and ethyl acetate extract of pulasan exerted bactericidal effects on Bacillus cereus (minimum bactericidal concentration (MBC): 0.63 mg/mL) and Staphylococcus aureus (MBC: 1.25 mg/mL), respectively. In contrast, all extracts, except hexane extract, of both plants exhibited fungicidal effects with minimum fungicidal concentrations of 0.31-1.25 mg/mL. All extracts of matoa leaves displayed higher DPPH radical scavenging activity and FRAP than the extracts of pulasan leaves. Notably, the water extract of matoa showed the lowest half-maximal inhibitory concentration (IC50) value of 9.88 ± 1.70 µg/mL and the highest FRAP value of 6.11 ± 0.51 mmol Fe2+ equivalent/g extract (n=3). These antioxidant activities were significantly correlated (p<0.01) with the amounts of phenolic compounds in the extracts. All extracts of both plants, except water extracts, showed significant toxicities (p<0.05) towards NIH/3T3 cells. Alkaloids, terpenoids, saponins, and glycosides were detected in the leaves of both plants. The matoa and pulasan leaves contained bioactive compounds with antibacterial, antifungal, and antioxidant activities.

Antimicrobial and Anti-Inflammatory Potential of Euphorbia paralias (L.): a bioprospecting study with phytoconstituents analysis.

The phytochemicals in the aerial parts of Euphorbia paralias (also known as Sea Spurge) and their anti-inflammatory and antimicrobial activities were investigated. The methanolic extract was characterized using GC-MS and HPLC techniques. The anti-inflammatory feature was estimated through a Human Red Blood Cell (HRBC) membrane stabilization technique, while the antimicrobial feature was evaluated by the disc diffusion agar technique, minimum bactericidal concentration, and minimum inhibitory concentration (MIC) via micro-broth dilution method. The GC/MS results demonstrated the existence of various phytochemicals, such as n-hexadecenoic acid, cis-11-eicosenoic acid, and methyl stearate, recognized for their anti-inflammatory and antibacterial features. The similarity of the phytochemical composition with other Euphorbia species emphasizes the genus-wide similarity. The anti-inflammatory activity exhibited a noteworthy inhibitory effect comparable to the reference drug indomethacin. The extract's antimicrobial potential was tested against a range of microorganisms, demonstrating significant action against Gram-positive bacteria and Candida albicans. The quantification of total phenolics and flavonoids further supported the therapeutic potential of the extract. The methanolic extract from E. paralias emerges as a successful natural source of important active constituents with potential applications as anti-inflammatory and antimicrobial agents. This research provides a first step to valorize Euphorbia paralias insights as a source of worthwhile phytochemicals that have potential applications in the pharmaceutical industry.

Antibacterial Potentials and Phytochemical Screening of Eucalyptus globulus Leaves Extract against Selected Isolates

In recent decades, medicinal plants have been of great interest as they have been the sources of natural products. As a result, there is a need to analyse the phytochemical and antibacterial properties of Eucalyptus globulus against Escherichia coli, Bacillus cereus, Staphylococcus aureus and Pseudomonas aeruginosa. This study was carried out to determine the percentage yield, phytochemical properties, antibacterial activity, minimum inhibitory and minimum bactericidal concentration (MIC/MBC) of the crude extracts using the reflux extraction, qualitative phytochemical, agar well diffusion and broth dilution method respectively; while aqueous, normal hexane and ethyl acetate were used as extraction solvents. Aqueous extract has the highest yield of 16.08%, ethyl acetate extract (8.76%) while n-hexane extract had 3.84%. Phytochemicals such as tannins, alkaloids, and phenols were present in all three solvent extracts; while terpenoids, glycosides and steroids were absent. Saponins and flavonoids were present in water extract, flavonoids were present only in the ethyl acetate extract. The most active with mean inhibition zone (MIZ) diameter of 13.33±0.58mm and 10.33±0.58mm against Bacillus cereus and Staphylococcus aureus respectively at 50mg/mL while the lowest activity of MIZ diameter of 8.00±2.00mm was obtained with same extract and concentration against Escherichia coli. N-hexane and ethyl acetate extracts show no activity against the test organisms. The lowest MIC of 15.6mg/mL and MBC of 31.3mg/mL were obtained against Escherichia coli. Based on these results, it can be concluded that Eucalyptus globulus leaf extracts possess antibacterial activity against some of the test organisms and can be considered for drug development.

The antimicrobial peptide Microcin C7 inhibits the growth of Porphyromonas gingivalis and improves the perodontal status in a rat model.

This study aimed to investigate the antibacterial and anti-inflammatory effects of the antimicrobial peptide Microcin C7 for Porphyromonas gingivalis-associated diseases. Reverse-phase high-performance liquid chromatography revealed that Microcin C7 could remain 25.5% at 12 hours in saliva. At a concentration of <10mg mL-1, Microcin C7 showed better cytocompatibility, as revealed by hemolysis test and subchronic systemic toxicity test. Moreover, the minimum inhibitory concentration and minimum bactericidal concentration of Microcin C7 were analyzed using a broth microdilution method, bacterial growth curve, scanning electron microscopy, and confocal laser microscopy and determined to be 0.16mg mL-1 and 5mg mL-1, respectively. Finally, in a rat model, 5mg mL-1 Microcin C7 showed better performance in decreasing the expression of inflammatory factors (IL-1β, IL-6, IL-8, and TNF-α) and alveolar bone resorption than other concentrations. Microcin C7 demonstrated favorable biocompatibility, antibacterial activity, anti-inflammatory effect, and could decrease the alveolar bone resorption in a rat model, indicating the promising potential for clincal translation and application on P. gingivalis-associated diseases.

Impact of Microencapsulation on Ocimum gratissimum L. Essential Oil: Antimicrobial, Antioxidant Activities, and Chemical Composition

Ocimum gratissimum (OG) is a species rich in essential oils (EO), which is known for its antimicrobial and antioxidant properties. This study aimed to encapsulate the essential oil of Ocimum gratissimum (OGE), determine its chemical composition, and evaluate its antioxidant and antimicrobial activities against six pathogenic bacteria, comparing it with the free essential oil (OGF). The EO was extracted by hydrodistillation using a Clevenger-type apparatus, and an oil-in-water emulsion was prepared using a combination of biopolymers: maltodextrin (MA), cashew gum (CG), and inulin (IN). The chemical profile was identified using gas chromatography–mass spectrometry (GC–MS). Antioxidant activity was assessed using the Oxygen Radical Absorbance Capacity with fluorescein (ORAC-FL) method, while the Minimum Inhibitory Concentrations (MIC) and Minimum Bactericidal Concentrations (MBC) were determined by the microdilution method. Microparticles were formed using the spray-drying method, achieving an encapsulation efficiency of 45.2%. The analysis identified eugenol as the main compound both before and after microencapsulation. The OGE microparticles demonstrated high inhibitory and bactericidal effects against S. aureus, S. choleraesuis, and E. coli, with MIC values of 500 µg·mL−1 and MBC values of 1000 µg·mL−1, as well as antioxidant activity of 1914.0 µmol-TE·g−1. Therefore, it can be inferred that the EO of OG maintained its antimicrobial and antioxidant effects even after microencapsulation by spray-drying, making it a promising natural ingredient.

Extraction of Bio Oil from Jordanian Biomass Resources via Pyrolysis and its Antibacterial Effect

This study explores the potential of pyrolytic oil extracted from Jordanian biomass resources as an antibacterial agent. Pyrolysis, a transformative thermal decomposition process, offers a promising avenue for converting biomass into valuable products. Pyrolytic oil, derived from biomass via pyrolysis, presents a complex composition and inherent antibacterial properties, making it a candidate for addressing antibiotic resistance and promoting sustainable solutions. Five biomass feed stocks were subjected to pyrolysis and their product distributions were analyzed. Pyrolytic oil yields were investigated and antibacterial activities against four bacterial strains were evaluated using disc diffusion, minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) assays. Results indicate varying levels of antibacterial activity among the biomass extracts, highlighting their potential as eco-friendly antibacterial agents.

Synergistic Effect of Metronidazole and Chlorhexidine against Porphyromonas gingivalis Growth: An In Vitro Study.

Aim: To evaluate the potential synergistic activity of metronidazole (MTZ) and chlorhexidine (CHX) against Porphyromonas. gingivalis (P. gingivalis) growth. Methods: Antimicrobial susceptibility tests of P. gingivalis to MTZ and CHX were performed on in vitro serial 2-fold dilutions of MTZ (from 1 mg/mL to 0.015 mg/mL) and CHX (from 1 mg/mL to 0.03 mg/mL) in thioglycollate medium broth in a 96-well plate. The turbidity of each sample was analyzed by absorbance spectrophotometry at 450 nm wavelengths by using an enzyme-linked immunosorbent assay (ELISA) reader. The MIC50 (minimum inhibitory concentration) and MBC (minimum bactericidal concentration) were assessed. To investigate the potential synergism between MTZ and CHX, bacterial cells were treated with MTZ or CHX, as described above, either alone or in combination. Results: The MIC50 of MTZ was 0.03 mg/mL while that of CHX ranged from 0.12 to 0.06 mg/mL. MTZ and CHX exerted a significant inhibitory effect on P. gingivalis growth in a dose-dependent manner. MTZ at a low and ineffective concentration of 0.015 mg/mL, associated with a suboptimal concentration of CHX (0.03 mg/mL), exhibited a significant synergistic inhibitory effect on bacterial growth (50% inhibition vs. control) (p < 0.001), and the effect was more remarkable with 0.06 mg/mL CHX (75% inhibition vs. control). Conclusions: CHX and MTZ showed a significant synergistic effect against P. gingivalis growth. A non-effective concentration of MTZ (0.015 mg/mL) combined with suboptimal concentrations of CHX (0.03 mg/mL and 0.06 mg/mL) were related to a 50% growth in the inhibition and 99.99% death of P. gingivalis, respectively. The applicability of the clinical use of these concentrations should be tested in randomized controlled trials.

Enhancing Antibacterial Efficacy: Synergistic Effects of Citrus aurantium Essential Oil Mixtures against Escherichia coli for Food Preservation

Essential oils (EOs) from various medicinal and aromatic plants are known for their diverse biological activities, including their antimicrobial effects. Citrus aurantium EO is traditionally used for therapeutic benefits due to its high content of bioactive compounds. Therefore, this study focuses on its potential use as a food preservative by investigating the combined antibacterial properties of EOs from leaves (EO1), flowers (EO2), and small branches (EO3) of Citrus aurantium against six bacterial strains by the agar disk diffusion, minimum inhibitory concentration (MIC), and minimum bactericidal concentration (MBC) methods. The chemical compositions of the EOs were analysed by gas chromatography–mass spectrometry (GC-MS) and revealed the presence of numerous compounds responsible for their antimicrobial properties. The MIC values for the EOs were 3.12 mg/mL, 4.23 mg/mL, and 1.89 mg/mL, for EO1, EO2 and EO3, respectively, while the MBC values were 12.5 mg/mL, 6.25 mg/mL, and 6.25 mg/mL, respectively. A simplex centroid design was created to analyse the effect of the individual and combined EOs against E. coli. The combined EOs showed enhanced antibacterial activity compared to the individual oils, suggesting a synergistic effect (e.g., trial 9 with an MIC of 0.21 mg/mL), allowing the use of lower EO concentrations and reducing potential negative effects on food flavour and aroma. Additionally, the practical application of investigated EOs (at concentrations twice the MIC) was investigated in raw chicken meat stored at 4 °C for 21 days. The EOs, individually and in combination, effectively extended the shelf life of the meat by inhibiting bacterial growth (total bacterial count of less than 1 × 104 CFU/g in the treated samples compared to 7 × 107 CFU/g in the control on day 21 of storage). The study underlines the potential of C. aurantium EOs as natural preservatives that represent a sustainable and effective alternative to synthetic chemicals in food preservation.

Physicochemical Characterization, Rheological Properties, and Antimicrobial Activity of Sodium Alginate-Pink Pepper Essential Oil (PPEO) Nanoemulsions.

Essential oils (EOs) have antimicrobial properties, but their low solubility in water and strong flavor pose challenges for direct incorporation into food, as they can negatively impact organoleptic properties. To overcome these issues, strategies such as oil-in-water (O/W) nanoemulsions have been developed to improve EO dispersion and protection while enhancing antimicrobial efficacy. The objective of this study was to create sodium alginate-pink pepper essential oil (PPEO) nanoemulsions using microfluidization. Various formulations were assessed for physicochemical, physical, and antimicrobial properties to evaluate their potential in food applications. The microfluidized emulsions and nanoemulsions had droplet sizes ranging from 160 to 443 nm, polydispersity index (PdI) ranging from 0.273 to 0.638, and zeta potential (ζ) ranging from -45.2 to 66.3 mV. The nanoemulsions exhibited Newtonian behavior and remarkable stability after 20 days of storage. Antimicrobial testing revealed effectiveness against Staphylococcus aureus and Listeria monocytogenes, with minimum inhibitory concentrations (MIC) of 200 µg/mL for both microorganisms and minimum bactericidal concentrations (MBC) of 800 µg/mL and 400 µg/mL, respectively, proving that encapsulation of PPEO in nanoemulsions significantly increased its antibacterial activity. These results present the possibility of using PPEO nanoemulsions as a more effective natural alternative to synthetic preservatives in food systems.

Antimicrobial Activity of Anionic Bis(N-Heterocyclic Carbene) Silver Complexes

The antimicrobial properties of a series of anionic bis(carbene) silver complexes Na3[Ag(NHCR)2] were investigated (2a–2g and 2c′, where NHCR is a 2,2′-(imidazol-2-ylidene)dicarboxylate-type N-heterocyclic carbene). The complexes were synthesized by the interaction of imidazolium dicarboxylate compounds with silver oxide in the presence of aqueous sodium hydroxide. Complexes 2f,g were characterized analytically and spectroscopically, and the ligand precursor 1f and complexes 2c and 2g were structurally identified by X-ray diffraction methods. The anions of 2c and 2g, [Ag(NHCR)2]3−, showed a typical linear disposition of Ccarbene-Ag-Ccarbene atoms and an uncommonly eclipsed conformation of carbene ligands. The antimicrobial properties of complexes 2a–g, which contains chiral (2b–2e and 2c′) and non-chiral derivatives (2a,f,g), were evaluated against Gram-negative bacteria, Escherichia coli and Pseudomonas aeruginosa, and a Gram-positive bacterium, Staphylococcus aureus. From the observed values of the minimal inhibitory concentration and minimal bactericidal concentration, complexes 2a and 2b showed the best antimicrobial activity against all strains. An interesting chirality–antimicrobial relationship was found, and eutomer 2c′ showed better activity than its enantiomer 2c against the three bacteria. Furthermore, these complexes were investigated experimentally and theoretically by 109Ag nuclear magnetic resonance, and the electronic and steric characteristics of the dianionic carbene ligands were also examined.

Coaggregation dynamics in drinking water biofilms and implications for chlorine disinfection

Biofilms in drinking water (DW) systems persistently challenge traditional disinfection methods due to intricate microbial interactions, with coaggregation playing a crucial role in forming multispecies biofilms. This study examined the implications of coaggregation on tolerance towards sodium hypochlorite (NaOCl) disinfection. Dual-species biofilms were formed for seven days on polyvinyl chloride coupons, comprising a strain of the emerging pathogen Stenotrophomonas maltophilia and the coaggregating strain Delftia acidovorans 005 P. For comparison, dual-species biofilms were also formed with a non-coaggregation strain (D. acidovorans 009 P). The minimum bactericidal concentration (MBC) for each planktonic strain varied (D. acidovorans: 1 mg/L, S. maltophilia: 1.5 mg/L) below the safe DW treatment limits. However, high NaOCl doses (10 ×MBC and 100 ×MBC,) showed low efficacy against dual-species biofilms, indicating significant biofilm tolerance to disinfection. Membrane damage occurred at sub-MBC without culturability loss, underscoring biofilm resilience. The biofilm analysis revealed a complex interplay between the composition of extracellular polymeric substances and the architecture, which was influenced by the presence of the coaggregating strain. Overall, coaggregation significantly influenced biofilm formation and resilience, impacting NaOCl disinfection. These findings underscore the challenges of microbial interactions in biofilms, emphasizing the need for improved disinfection strategies to control biofilms in drinking water systems.

Biological characteristics of marine Streptomyces SK3 and optimization of cultivation conditions for production of compounds against Vibiriosis pathogen isolated from cultured white shrimp (Litopenaeus vannamei).

Antibiotic resistance in shrimp farms has emerged as an extremely serious situation worldwide. The main aim of this study was to optimize the cultural conditions for producing new antibiotic agents from marine Streptomyces species. Streptomyces SK3 was isolated from marine sediment and was identified by its 16S rDNA as well as biochemical characteristics. This microbe produced the highest concentration of bioactive secondary metabolites (BSMs) when cultured in YM medium (YM/2). It produced the maximum total protein (41.8 ± 6.36 mg/ml) during the late lag phase period. The optimum incubation temperature was recorded at 30 °C; BSMs were not produced at ≤10 °C within an incubation period of 3-4 days. The suitable agitation speed was found to be 200 rpm with pH 7.00. The proper carbon, nitrogen, and trace elements supplementation consisted of starch, malt extract, calcium carbonate (CaCO3), and magnesium sulfate (MgSO4). The ethyl acetate extract was found to act strongly against three vibriosis pathogens, Vibrio harveyi, Vibrio parahaemolyticus, and Vibrio vunificus, as indicated by the inhibition zones at 34.5, 35.4, and 34.3 mm, respectively. The extract showed the strongest anti-V. harveyi activity, as indicated by minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) values of 0.101 ± 0.02 and 0.610 ± 0.04 mg/ml, respectively. Basic chemical investigation of the crude extract using thin layer chromatography (TLC), bioautography, liquid chromatography tandem mass spectrometry (LC‒MS/MS), Fourier transform infrared spectroscopy (FTIR), and proton nuclear magnetic resonance (1H-NMR) revealed that the active components were the terpenoid and steroid groups of compounds. They showed carboxylic acid and ester functions in their molecules.

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.