Colistin and Isavuconazole Interact Synergistically In Vitro against Aspergillus nidulans and Aspergillus niger

The in vitro interactions of isavuconazole in combination with colistin were evaluated against 55 clinical Aspergillus species isolates belonging to the five most important species (Aspergillus flavus, Aspergillus fumigatus, Aspergillus nidulans, Aspergillus niger, and Aspergillus terreus) responsible for human aspergillosis by a microdilution checkerboard technique based on the European Committee on Antimicrobial Susceptibility Testing (EUCAST) reference method for antifungal susceptibility testing. Selected isolates (A. nidulans, n = 10; A. niger, n = 15) were additionally evaluated by an agar diffusion assay using isavuconazole gradient concentration strips with or without colistin incorporated Roswell Parc Memorial Institute (RPMI) agar. Interpretation of the checkerboard results was done by the fractional inhibitory concentration index. Using the checkerboard method, combination isavuconazole–colistin was synergistic for 100% of the 15 A. nidulans isolates and for 60% of the 20 A. niger isolates. No interactions were found for any of the other isolates. By agar diffusion assay, minimal inhibitory concentrations (MICs) in combination decreased compared to isavuconazole alone for 92% of the isolates. No interactions were found for any A. nidulans isolates, but synergy was observed for 40% of the A. niger isolates. A poor essential agreement of EUCAST and gradient concentration strip MICs at ± 2 log2 dilutions with 0% was obtained. Antagonistic interactions were never observed regardless of the technique used.

Geraniol and Linalool Loaded Nanoemulsions and Their Antimicrobial Activity

Geraniol and linalool have been found to be effective against foodborne microorganisms in vitro. However, due to their hydrophobic nature, it is difficult to achieve an even dispersion in foods with high water content resulting in dramatic loss of activity. The aim of the study was to fabricate geraniol or linalool nanoemulsions and investigate their effect against Escherichia coli K12, Listeria innocua and Pseudomonas lundensis in a meat simulation medium. The agar diffusion assay revealed that both geraniol and linalool had a potent antimicrobial activity against all bacteria. Dynamic light scattering showed that geraniol and linalool nanoemulsions had a mean diameter of 68.22±2.46 and 173.59±4.15 nm, respectively. Killing assay results showed that both nanoemulsions were able to significantly reduce E. coli and L. innocua counts by approx. 3 log CFU/ml. Ps. lundensis proved to be more resistant to both nanoemulsions showing a reduction of approx. 1.2 log CFU/ml,. Overall, this study showed that nanoemulsions loaded with geraniol or linalool represent a promising antimicrobial system to improve food preservation and food safety.

Short microwave-assisted modular synthesis of naturally occurring oxygenated bibenzyls

The naturally occurring oxygenated bibenzyls lunularin and m-O-methyllunularin were prepared in a modular synthesis in four steps from two appropriate iodophenols and trimethylsilylacetylene utilizing microwave-assisted Sonogashira couplings as the crucial steps. The antimicrobial activity of the resulting natural products was evaluated in an agar diffusion assay.

Antimicrobial activity of crude extracts and fractions of Vernonia polyanthes Less (assa-peixe) flowers

ABSTRACT Vernonia polyanthes, known as “assa-peixe”, is a plant native to Brazil, and the decoction or infusion of its flowers, roots and leaves are used in folk medicine, being considered sources of diuretic, balsamic, anti-rheumatic substances, and are used in cases of bronchitis and persistent cough. The aim of the study was to evaluate the antimicrobial activity of the extract/fractions obtained by methanol maceration and infusion of V. polyanthes flower, also including qualitative identification of flower compounds, through phytochemical evaluation, using colorimetric tests. Identification tests for the presence of anthraquinones, tannins, flavonoids, saponins and alkaloids were performed. Microbiological evaluation was made through agar diffusion assay, using Escherichia coli, Staphylococcus aureus and Pseudomonasaeruginosa as test organisms. From the performed colorimetric tests it was possible to verify the presence of tannins and flavonoids in both extracts. Alkaloids were also observed in the macerated extract. The ethyl acetate fraction from the agar diffusion assay, from both extracts, presented microbial activity over Staphylococcus aureus. It was possible to qualitatively identify the floral compounds, and to show the differences between extraction methods, being methanol considered the best solvent to the extraction.

Clinical and Microbiological Evaluation of the Carious Dentin Before and After Application of Papacarie Gel

Objective: To evaluate clinically and microbiologically the efficacy of Papacarie® in the removal of carious dentin in both permanent and primary teeth. Study design: Thirty permanent and primary molars with dentinal carious lesions were excavated and subjected to clinical and microbiological assessment before and after application of Papacarie®. The gel was further tested for in vitro antimicrobial efficacy against standard cariogenic micro-organisms using agar diffusion assay. Results: Papacarie® was able to differentiate between infected and affected dentin clinically along with high patient comfort during caries excavation. The mean time taken for caries removal and restoration was observed to be 4.17 ± 0.40 min. and 8.57 ± 0.45 min. for permanent teeth and 4.21 ± 0.36 min. and 9.24 ± 0.58 min. for primary teeth. There was a significant reduction in the total viable colony forming units from the dentin samples before and after application of Papacarie®. It was also observed that Papacarie® had no inhibitory effect on standard cariogenic microorganisms in the agar diffusion assay. Conclusions: Papacarie® is an effective caries removal method clinically in both permanent and primary teeth. The number of viable microorganisms after complete caries excavation using Papacarie® still appears to be high and this bacterial count should be tackled by a suitable restorative material with potent antimicrobial activity.

Steroids and Ceramide from the Stem Bark of Odyendyea gabonensis

Two new steroids, 22E, 24R-stigmast-22-ene-3,6,11-trione (1) and 22E, 24R-3-acetylstigmasta- 5,22-diene-7,11-dione (2), and one new ceramide, (2S,3S,4R,5R) N-(1,3,4,5-tetrahydroxyundecan- 2-yl)tetradecanamide (7), together with eleven known compounds were isolated from the CH2Cl2 extract of the stem bark of Odyendyea gabonensis. The structures of all compounds were determined by comprehensive analyses of their 1D and 2D NMR, mass spectral (EI and ESI) data, chemical reactions, and comparison with previously known analogs. Pure compounds were tested for their activity against the bacteria Bacillus subtilis, Staphylococcus aureus and Escherichia coli, the fungi Mucor miehei and Candida albicans, and the plant pathogen oomycetes Aphanomyces cochlioides, Pythium ultimum and Rhizoctonia solani using the paper disk agar diffusion assay. For active compounds, MICs were determined by the broth microdilution assay. Cytotoxic activity against the human lung adenocarcinoma cell line A 549 was evaluated by the MTT assay. All compounds delivered low to missing antimicrobial activities in the agar diffusion assay and MICs > 1 μg mL-1. The alkaloids 10 and 11 displayed cytotoxic activity against the human lung adenocarcinoma cell line A549 with IC50 2.5 and 4:5 μm respectively.