Minimum Inhibitory Concentration Values Research Articles

Optimizing the green synthesis of antibacterial TiO2 - anatase phase nanoparticles derived from spinach leaf extract

Titanium dioxide nanoparticles, renowned for their abundance, non-toxicity, and stability, have emerged as indispensable components in various fields such as air purification, healthcare, and industrial processes. Their applications as photocatalysts and antibacterial agents are particularly prominent. The synthesis methods significantly influence the properties and subsequent applications of these nanoparticles. While several techniques exist, the biological approach using plant extracts offers advantages such as simplicity, biocompatibility, and cost-effectiveness. This study focused on the green synthesis of titanium dioxide nanoparticles utilizing spinach leaf extract. Within the scope of this investigation, the green synthesis of titanium dioxide nanoparticles through spinach leaf extract were synthesized and optimized, followed by a comprehensive examination of their morphological, structural, and chemical attributes with UV-visible spectroscopy, FTIR spectroscopy, XRD, FESEM, and EDX. The minimum inhibitory concentration (MIC) against E. coli and S. aureus was determined to evaluate their antibacterial potential. Optimal synthesis conditions were identified at 50 °C, using a 1/30 concentration and 20 ml of spinach leaf extract. Spherical anatase nanoparticles, ranging from 10 to 40 nm, were produced under these conditions. The change in the color of the extract, absorption at 247 nm, change and increase of the peak at 800 − 400 wavelengths, and the maximum intensity of X-ray diffraction at the angle of 25.367 with the crystal plane 101 were indications of the synthesis of these nanoparticles. Notably, the synthesized nanoparticles exhibited antibacterial activity with MIC values of 0.5 mg/ml against E. coli and 2 mg/ml against S. aureus. This research presents a novel, eco-friendly approach to synthesizing titanium dioxide nanoparticles with promising antibacterial properties.

Genetic identification of methicillin resistant Staphylococcus aureus (MRSA) isolated from diabetic foot ulcers and evaluating the inhibition activity of reuterin against this bacteria.

To genetically diagnose the isolates of methicillin-resistant staphylococcus aureus taken from patients with severe diabetic foot infections, and to test the inhibitory effect of reuterin on the growth of these bacteria. The experimental study was conducted from June to November 2021 at the Diabetes Unit of Al-Faihaa General Hospital, Basrah, Iraq, and comprised 62 foot ulcer swabs from the necrotic lesions of patients with type 2 diabetes. The swabs were cultivated first in brain heart infusion broth media, and then streaked on Mannitol salt agar and staphylococcus chromogeneic agar media for phenotypic and genetic analysis. The genetic identification of bacteria was confirmed by deoxyribonucleic acid extraction, and methicillin-resistant staphylococcus aureus was confirmed by the presence of plasmid mecA gene. The inhibition activity of reuterin towards methicillin-resistant staphylococcus aureus was determined using the minimum inhibitory concentration test. All data was analyzed with SPSS version 23. A total of 62 swabs were taken from the necrotic lesions of type 2 diabetes mellitus (T2DM) patients with diabetic foot ulcers. Of the total isolates, 9(14.5%) gave mauve to purple colour on staphylococcus chromogeneic agar, which was then genetically confirmed as methicillin-resistant staphylococcus aureus. The minimum inhibitory concentration value of these bacteria was 10μl/ml at 16mm inhibition zone diameter. There was no cytotoxicity of reuterin to human red blood cells. Reuterin was found to be a natural antimicrobial substance suitable for use to disinfect diabetic foot wounds from bacterial contamination and infection, especially those caused by methicillin-resistant staphylococcus aureus.

Antifungal Activity of Tea Tree (Melaleuca alternifolia Cheel) Essential Oils against the Main Onychomycosis-Causing Dermatophytes.

Onychomycosis is a common fungal infection that affects the nails and accounts for approximately 50% of all nail diseases. The main pathogens involved include dermatophytes, such as Trichophyton rubrum, members of the T. mentagrophytes complex, and emerging pathogens in this infection, T. schoenleinii and T. tonsurans. Tea tree (Melaleuca alternifolia Cheel) essential oil (EO) has been proposed as a promising natural alternative to traditional treatments due to its antimicrobial properties. Among its more than 100 compounds, terpinen-4-ol is one of the main contributors to the antifungal action of this EO. To determine the antifungal activity of tea tree EO against dermatophytes, we designed an in vitro study using EUCAST-AFST protocols to obtain the values of MIC (minimum inhibitory concentration) and MFC (minimum fungicidal concentration) of several commercial M. alternifolia Cheel EOs against three species of dermatophytes isolated from clinical samples with suspected toenail onychomycosis. The results showed that the microorganism most sensitive to the action of the EO was T. rubrum, which had an MIC value more than 13 times lower than the value obtained for T. schoenleinii (0.4% v/v), the most resistant isolate. No differences in antifungal activity were observed by the analysed EOs or between the MIC and MFC values. These in vitro results suggest that tea tree EO is a viable option for the alternative treatment of onychomycosis, although clinical studies are needed to confirm the long-term antifungal activity, safety and efficacy of the oils studied in a clinical context.

Dissecting the Simultaneous Extracellular/Intracellular Contributions to Cr(VI) Reduction under Aerobic and Anaerobic Conditions Using the Newly Isolating Cr(VI)-Reducing Bacterium of Pseudomonas sp. HGB10.

Quantifying extracellular and intracellular contributions to Cr(VI) reduction is crucial for understanding bacterial Cr(VI)-reduction mechanisms. However, this contribution under different oxygen conditions remains largely unexplored. This study quantified the extracellular/intracellular contribution to aerobic and anaerobic Cr(VI) reduction using Pseudomonas sp. HGB10, an isolated Cr(VI)-reducing bacterium, as the experimental model. Interestingly, it was found that the lower anaerobic minimum inhibitory concentration (MIC) does not necessarily imply a lower anaerobic Cr(VI)-reduction rate for HGB10. For the initial Cr(VI) concentration of 20 mg L-1, the maximum anaerobic Cr(VI)-reducing rate reached 100%, while the aerobic counterpart was only 75%, even though the value of the aerobic MIC (400 mg L-1) is twice that of the anaerobic (200 mg L-1). Additionally, the calculated extracellular contributions to aerobic and anaerobic Cr(VI) reduction were 10.76% and 55.71%, respectively, while the intracellular contributions were 68.29% and 40.38%. The sum of extracellular and intracellular contributions to Cr(VI) reduction (79.05% and 96.09%) under aerobic and anaerobic conditions was nearly balanced with the corresponding maximum values despite minor relative errors. These results indicated that anaerobic Cr(VI) reduction mainly occurred extracellularly rather than intracellularly, which differs from the existing result. Overall, our findings provide new insights into bacterial Cr(VI) reduction.

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.

Cryptophytes as potential source of natural antimicrobials for food preservation.

Cryptophytes are a promising source of bioactive compounds that have not been fully explored. This research investigated the antimicrobial activity of total phenolic compounds (TPC) and exopolysaccharides (EPS) extracted from several cryptophytes against a range of harmful foodborne bacteria and fungi. To measure the minimum inhibitory concentration (MIC) value, the broth microdilution method was used. In the antibacterial evaluation of TPC, the MIC ranged between 31.25 and 500 μg/mL, while for the antifungal activity test, it varied from 31.25 to 125 μg/mL. In the antibacterial activity test of EPS, the MIC values ranged from 125 to 1,000 μg/mL, whereas in the antifungal susceptibility test, it ranged between 62.5 and 1,000 μg/mL. The most resistant pathogen against TPC was Escherichia coli, while Campylobacter jejuni was the most susceptible. In the case of EPS, the most resistant pathogen was Salmonella Typhimurium, while Aspergillus versicolor exhibited the highest susceptibility. Overall, in terms of antimicrobial activity, TPC was more effective than EPS. Finally, the tolerance level (TL) for TPC and EPS was ≤4 in all tested samples, indicating their bactericidal/fungicidal mechanism of action. In conclusion, TPC and EPS isolated from cryptophytes demonstrated remarkable antimicrobial properties and ability to fully eradicate pathogens, and could be considered as natural preservatives in the food industry.

Protein‐Based Polymeric Metal–Nanocomposite Derived From Egg Albumin: A Highly Effective Antimicrobial Agent Against Bacteria

ABSTRACTThe synthesis of four distinct protein‐based metal nanocomposites has been fabricated by employing egg albumin and zinc metal through a simple, straightforward two‐step method. The Fourier transform infrared (FTIR), X‐ray diffraction (XRD), and scanning electron microscopy (SEM) analyses confirmed the successful incorporation of zinc nanoparticles into the protein matrix and revealed an irregular microporous structure with average crystallite sizes of less than 100 nm. Thermal stability was assessed via thermogravimetric (TG) and derivative thermal gravimetry (DTG) analysis, revealing a notable increase in thermal stability in a high‐temperature range (300°C°C–700°C), suggesting remarkable stability at elevated temperatures. Antimicrobial efficacy against both gram‐positive (B. cereus and Lactobacillus spp.) and gram‐negative bacteria (E. coli and K. pneumoniae) was evaluated using paper disk diffusion, pour plate, and minimum inhibitory concentration (MIC) methods. All samples exhibited antibacterial efficacy, with zone of inhibition (ZOI) diameters ranging from 12 to 35 mm, and demonstrated a bactericidal effect by eliminating 93 to 98% of bacteria within 8 to 20 h at their MICs. Notably, protein–ZnO–PANI exhibited potent antimicrobial activity against all four bacterial strains and among all the samples, demonstrated higher antimicrobial activity than the unpolymerized nanocomposites. The disk diffusion study confirmed that a concentration of 25 μg/mL of protein–ZnO–PANI resulted in ZOI measurements of 25 mm and 35 mm, whereas MIC values of 300 μg/mL and 200 μg/mL were observed against Bacillus cereus and E. coli, respectively, and killed 95% of B. cereus and 98% of E. coli within 24 h. Based on the obtained results, a plausible mechanism was also proposed.

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.

Antibacterial synergistic effect of sea cucumber extract and kelulut honey combination

Natural products remain one of the major sources of new drug molecules today. The combination of sea cucumber extract with stingless bee honey holds great potential for health supplement. However, the specific results of the combination have yet to be determined. In this study, the antibacterial activity of kelulut honey and Phyllophorus spiculata sea cucumber extract samples individually and in combination were assessed with disk-diffusion assays and broth dilution method. Most of the samples exhibit small or absence of inhibitory activity using disk-diffusion assay method. Only kelulut honey sample with 100% concentration has a positive antagonism effect against Escherichia coli and Staphylococcus epidermidis. For the broth dilution method, Gram-positive bacteria were found to be more susceptible as compared to Gram-negative bacteria species, with lower minimum inhibitory concentration (MIC) value of kelulut honey, sea cucumber or combination sample. The growth of gram-positive S. epidermidis is inhibited by sea cucumber extract at MIC value of 0.031 mg/mL, kelulut honey at MIC value of 0.063 mg/ mL and combination sample at MIC value of 0.063 mg/mL, all of which are of lower MIC value as compared to E. coli inhibition. The absorbance at optical density (OD) 600nm wavelength was also measured to monitor the growth of bacteria in solution. From the results, broth dilution proves to be a more effective method to assess the antibacterial activity in the combination samples. Two combinations showed the best antibacterial synergy (OD600 value of 0.000) against both Gram-positive and Gram-negative bacteria, which were (1) ½ sea cucumber: ½ kelulut honey combination and (2) ¾ sea cucumber: ¼ kelulut honey combination. This preliminary evidence on their antibacterial synergistic activities is promising and shows possible commercialization potential.

Identification of Cercospora spp. on corn in North America and baseline flutriafol fungicide sensitivity.

Gray leaf spot (GLS) is an important corn disease reportedly caused by Cercospora zeae-maydis and C. zeina. Recently, flutriafol, a demethylation inhibitor (azole) fungicide received EPA registration as Xyway® LFR®, a product that is applied at planting for management of fungal diseases in corn, including suppression of GLS. In this study, 448 Cercospora spp. isolates were collected in 2020 and 2021 from symptomatic corn leaf samples submitted from the United States and Ontario, Canada. The Cercospora spp. were identified using multi-locus genotyping of the internal transcribe spacer (ITS), elongation factor 1-α (EF1), calmodulin (CAL), histone H3 (HIS), and actin (ACT) gene. Based on the multi-locus phylogenetic analyses, six species were identified; C. cf. flagellaris (n = 77), C. kikuchii (n = 4), C. zeae-maydis (n = 361), Cercospora sp. M (n = 2), Cercospora sp. Q (n = 1), and Cercospora sp. T (n = 3). In subsequent pathogenicity tests using selected isolates from each of these species, only C. zeae-maydis resulted in symptoms on corn with no disease symptoms observed after inoculation with C. cf. flagellaris, C. kikuchii, Cercospora sp. M, Cercospora sp. Q, and Cercospora sp. T. While disease symptoms were observed on soybean following inoculation with C. cf. flagellaris, C. kikuchii, and Cercospora sp. Q, but not the other three species. Fungicide sensitivity of Cercospora spp. to flutriafol was assessed using a subset of 340 isolates. The minimum inhibitory concentration (MIC) to inhibit the growth of Cercospora spp. completely was determined based on growth of each species on flutriafol-amended clarified V8 agar at nine concentrations. The EC50 was also calculated from the same trial by measuring relative growth as compared to the non-amended control. Cercospora zeae-maydis was sensitive to flutriafol with mean MIC values of 2.5 µg/mL and EC50 values ranging from 0.016 to 1.020 µg/mL with a mean of 0.346 µg/mL. Cercospora cf. flagellaris, C. kikuchii, Cercospora sp. M, Cercospora sp. Q, and Cercospora sp. T had mean EC50 values of 1.25 µg/mL, 7.14 µg/mL, 2.48 µg/mL, 1.81 µg/mL, and 2.24 µg/mL respectively. These findings will assist in monitoring the sensitivity to the flutriafol fungicide in Cercospora spp. populations.

First Confirmed Description of Acremonium egyptiacum from Greece and Molecular Identification of Acremonium and Acremonium-like Clinical Isolates.

Acremonium and the recently separated acremonium-like genera, such as Sarocladium, are emerging causes of opportunistic disease in humans, mainly post-traumatic infections in immunocompetent hosts, but also invasive infections in immunocompromised patients, such as those undergoing transplantation. Acremonium egyptiacum has emerged as the major pathogenic Acremonium species in humans, implicated mainly in nail but also in disseminated and organ specific infections. In this first study of acremonium-like clinical isolates in Greece, 34 isolates were identified and typed by sequencing the internal transcribed spacer, and their antifungal susceptibility was determined by a modified CLSI standard M38 3rd Edition method for filamentous fungi. A. egyptiacum was the primary species (18 isolates) followed by Sarocladium kiliense (8), Acremonium charticola, Gliomastix polychroma, Proxiovicillium blochii, Sarocladium terricola, Sarocladium zeae, and Stanjemonium dichromosporum (all with one isolate). Two isolates, each with a novel ITS sequence, possibly represent undescribed species with an affinity to Emericellopsis. All three A. egyptiacum ITS barcode types described to date were identified, with 3 being the major type. Flutrimazole, lanoconazole, and luliconazole presented the lower minimum inhibitory concentration (MIC) values against A. egyptiacum, with a geometric mean (GM) MIC of 2.50, 1.92, and 1.57 μg/mL, respectively. Amphotericin B, itraconazole, posaconazole, voriconazole, terbinafine, amorolfine, and griseofulvin MICs were overall high (GM 12.79-29.49 μg/mL). An analysis of variance performed on absolute values showed that flutrimazole, lanoconazole, and luliconazole were equivalent and notably lower than those of all the other drugs tested against A. egyptiacum. Antifungal susceptibility of the three different A. egyptiacum genotypes was homogeneous. Overall, the high MICs recorded for all systemically administered drugs, and for some topical antifungals against the tested A. egyptiacum and other acremonium-like clinical isolates, justify the routine susceptibility testing of clinical isolates.

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.

Optimization of the Central α-Amino Acid in Cystobactamids to the Broad-Spectrum, Resistance-Breaking Antibiotic CN-CC-861.

Cystobactamids have a unique oligoarylamide structure and exhibit broad-spectrum activity against Gram-negative and Gram-positive bacteria. In this study, the central α-amino acid of the cystobactamid scaffold was modified to address the relevance of stereochemistry, hydrogen bonding and polarity by 33 derivatives. As demonstrated by three matched molecular pairs, l-amino acids were preferred over d-amino acids. A rigidification to a six-membered system stabilized the bioactive conformation for the on-target Escherichia coli gyrase, but did not improve antimicrobial activity. Compound CN-CC-861, carrying a propargyl side chain, had more than 16-fold lower minimal inhibitory concentration (MIC) values against Enterococcus faecalis, Staphylococci and Acinetobacter strains, compared to known analogues. Moreover, CN-CC-861 retained activity against multidrug-resistant enterococci, displayed strong bactericidal activity, moderate-low frequencies of resistance and in vivo efficacy in a neutropenic thigh infection model with E. coli. Overall, the findings will guide the design of new promising structures with higher activities and broader spectrum.

Phosphorus-Nitrogen Compounds: Part 76. Design and Syntheses of Dispiro- and Trispiro(N/N)cyclotriphosphazenes: Conformational and Structural Analyses, Chirality, Electrochemical, Dye-Sensitized Solar Cells, and Bioactivity Studies.

The reactions of monospirocyclotriphosphazenes (1 and 2) with N-methyl-1,3-diaminopropane gave unsymmetrical cis-(3 and 5) and trans-(4 and 6) dispirocyclotriphosphazenes. Trans-cis-trans (tct) (7 and 11), cis-cis-cis (ccc) (8 and 12), trans-trans-cis (ttc) (9 and 13), and cis-trans-trans (ctt) (14) trispirocyclotriphosphazenes were obtained from the reactions of 3 and 5 and 4 and 6 with N-methyl-1,3-diaminopropane. cis-Dispirocyclotriphosphazenes (3 and 5) exist as "pseudomesoracemates", while trans-dispirocyclotriphosphazenes (4 and 6) are in "racemates". The existences of cis-3 and trans-4 as "pseudomesoracemate" and "racemate" were confirmed by 31P NMR spectra recorded by the addition of "chiral solvating agent (CSA)". X-ray crystallography proved that the absolute configurations of each enantiomer of cis-5 and trans-6 are SS' and RS'. Trispirocyclotriphosphazenes tct, ttc, ccc, and ctt exist as racemates, pseudomesoracemate, and meso forms. Furthermore, Hirshfeld surface analysis of the crystal structures of cis-5 and trans-6 revealed that the most significant contribution to crystal packing comes from H···H (58.2 and 57.6%, respectively). An oxidation-reduction wave was detected in the reversible cyclic voltammograms of the phosphazenes. The highest power conversion efficiency in dye-sensitized solar cell studies was obtained with cis-5. Additionally, trans-6 exhibited the lowest minimal inhibitory concentration value (78.1 μM) against Candida tropicalis, and it was observed to cleave pBR322 plasmid DNA.

Characterization and applications of iron oxide nanoparticles synthesized from Phyllanthus emblica fruit extract

Nanotechnology is a treasure trove of diversified themes which are endowed with broad applications. Herein, iron oxide (Fe2O3) nanoparticles were synthesized using Phyllanthus emblica aqueous fruit extract. The UV-Visible spectrum exhibited a surface plasmon resonance peak at 295nm. Fourier Transform Infrared Spectroscopy provided insight into the functional groups responsible for capping. X-ray diffraction analysis authenticated the crystalline nature of nanoparticles, while energy dispersive X-ray spectroscopy divulged that iron and oxygen comprised 54% of the nanoparticles’ weight. Scanning electron microscopy established irregular morphology and agglomeration of nanoparticles. The Fe2O3 nanoparticles validated potent antimicrobial activity against 11 bacterial and 1 fungal isolates. The biggest zone of inhibition (23mm) was measured against S. enterica, whereas the smallest zone of inhibition (12mm) was documented against C. albicans and E. coli. The values for minimum inhibitory concentration ranged between 10 and 15μg/ml for all microbes. Nevertheless, no synergy was exhibited by the nanoparticles with any of the selected antibiotics (Fractional Inhibitory Concentration Index > 1). The photocatalytic dye degradation capability of Fe2O3 nanoparticles was assessed and the observations implied a significant increase in degradation of methyl red although, not of methylene blue. Furthermore, the nanoparticles were in possession of substantial antioxidant (34–38%) and anti-inflammatory (31–38%) capacities. Consequent upon the robust activities of P. emblica-mediated nanoparticles, these can be scrutinized for biomedical and environmental implementations in future.

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.

Phenotypic antimicrobial resistance associated with different <em>bla</em> genotypes and their combinations in Enterobacterales

Introduction: Varying combinations of β-lactamase genes (bla) in Enterobacterales manifest different resistant phenotypes.Objectives: This study aimed to identify bla gene types and combinations resulting in variations in phenotypic antimicrobial resistance.Methods: Minimum inhibitory concentrations (MICs) of 75 extended spectrum β-lactamase (ESBL), AmpC β-lactamase and carbapenemase-producing Entero-bacterales isolates from a variety of clinical specimens were determined by Vitek micro-broth dilution. Bla genes were detected by 16-plex tandem PCR panel and Xpert Carba-R assay. BlaCTX-M group-1 and blaOXA-48 were the most common ESBL and carbapenemase genes, respectively.Results: Majority of the isolates (92%, 69/75) had bla gene combinations. Thirty-eight isolates (51%) carried ESBL, AmpC genes and/or narrow spectrum bla genes without any carbapenemase genes. The common bla gene combination in these isolates was blaCTX-M group-1 + blaOXA1 which is known to confer decreased susce-ptibility to piperacillin-tazobactam. Antibiotics with potential activity against ESBL-producing bacteria such as fourth generation cephalosporins, β-lactam/β-lactam-inhibitor combinations, quinolones and gentamicin also showed low rates of susceptibility. Highest susceptibility rates were to meropenem (92%) and amikacin (92%). Thirty-seven isolates (49%) carried carbapenemase genes as well. These isolates showed even higher resistance rates to all antibiotics, except amikacin (92%susceptible). Significantly higher MIC values for cefoxitin, ceftazidime, ceftriaxone, cefepime, meropenem, amikacin, tobramycin and trimethoprim-sulfamethoxazole were seen in isolates carrying blaNDM than blaOXA-48. However, a higher MIC for norfloxacin was seen in isolates with blaOXA-48.Conclusions: In conclusion, this study showed that Enterobacterales with different bla gene combinations manifest variations in phenotypic resistance to both β-lactam and non-β-lactam antibiotics.

Synergistic photocatalytic and antibacterial efficacies of Ag/rGO and Ag/Ag2O/rGO nanocomposites: The impact of oxide formation and ternary heterojunction

This study explores the efficient solvothermal integration of Ag/rGO and Ag/Ag2O/rGO nanocomposites using various solvents and employs thorough characterization procedures. The primary focus is on understanding the nuanced effects resulting from the combination of Ag nanoparticles with rGO nanosheets, particularly in the context of Ag2O formation. For a quantitative assessment of their photocatalytic and antibacterial properties, graphene oxide and silver nitrate (AgNO3) were introduced to create Ag/rGO and Ag/Ag2O/rGO nanocomposites. The results demonstrate a significant enhancement in photocatalytic performance for the Ag/Ag2O/rGO nanocomposite, achieving a rapid degradation of 99.99 % of methylene blue dye within 30 minutes under simulated solar light irradiation. This heightened efficiency is attributed to improved separation and transfer efficiency, as well as the substantial generation of photoinduced carriers due to the incorporation of visibly active Ag2O nanoparticles. Moreover, the Ag/Ag2O/rGO nanocomposite exhibits an enhanced antibacterial activity, reflected in Minimum Inhibitory Concentration (MIC) values of 50 μg/ml for Bacillus cereus and 300 μg/ml for Escherichia coli. The nanocomposite's higher antimicrobial activity against Gram-positive bacteria, particularly Bacillus cereus, is underscored, revealing its potential as an effective antibacterial agent. The formation of a ternary heterojunction in the Ag/Ag2O/rGO nanocomposite results in a notable increase in the production of free radicals, enhancing charge carrier migration and separation efficiency. This quantitative evidence emphasizes the versatile nature of the nanocomposite, highlighting its potential across diverse fields through augmented antibacterial and photocatalytic properties.

Evaluation of Totarol for Promoting Open Wound Healing in Dogs.

This study investigates the susceptibility of common pathogens to totarol and assesses its clinical effectiveness in promoting wound healing in client-owned dogs with open wounds. Twenty-three client-owned dogs with open wounds were divided into two groups: (1) the treatment group (T-group) and (2) the control group (C-group). Clinical samples were collected from the wounds for the bacterial identification and determination of the minimum inhibitory concentrations (MICs) of totarol. In the T-group, wounds were treated with standard wound care together with the application at a dosage of 0.3 mL (two sprays) of commercial totarol product per 25 cm2 of the wound area. The C-group received only standard wound care. This in vitro study found that totarol exhibited antimicrobial activity against both standard pathogens and clinical wound pathogens. The MIC values of totarol dissolved in absolute ethyl alcohol were 4 µg/mL for Gram-positive pathogens and ranged from 256 to 512 µg/mL for Gram-negative pathogens. However, the MIC values of the commercial totarol product ranged from 512 to 1024 for both Gram-positive and Gram-negative pathogens. Clinically, the use of a commercial totarol product as an adjunctive therapy significantly improved wound healing, as indicated by a greater percentage of wound area reduction (p < 0.05). From day 2 to day 7 of the treatment, the percentage of wound area reduction differed significantly between the T-group and the C-group. At the end of the study, the average percentage of wound area reduction was 69.18% ± 18.12 and 41.50% ± 20.23 in the T-group and C-group, respectively. The finding of this study illustrates the antimicrobial properties of totarol and its product against prevalent wound pathogens. These results suggest the potential of totarol as an adjunctive option for canine wound care.

In Vitro Antiproliferative, Antibacterial, and Anti-Angiogenic Studies of Triethanolamine-Based Salts

The triethanolammonium (TEA) cation associated with the anion cyclopropanecarboxylate, mercaptoacetate, trichloroacetate, and 4-dodecylbenzenesulfonate led to the formation of TEA-based salts. The antibacterial activity of the TEA salts was examined against some bacteria and the obtained results were used to calculate minimal inhibitory concentrations (MICs) values. Additionally, the antiproliferative activities of TEA salts were examined in vitro on breast cancer cell line. Furthermore, in vitro scratch assay was performed by HUVECs (human vascular endothelial cell line) to assess the anti-angiogenic effect of these salts. These compounds did not dramatically differentiate the cell viability of cancer cells. On the other hand, it was demonstrated that TEA salts blocked human endothelial cell migration slightly. Therefore, these compounds were determined to have a limited ability to inhibit angiogenesis.