Antifungal activity of silver nanoparticles prepared using Aloe vera extract against Candida albicans.

Background and Aim: Resistance to antifungal agents is a serious public health concern that has not been investigated enough because most studies on antimicrobials are dedicated to antibacterial resistance. This study aimed to synthesize silver nanoparticles (AgNPs) using Aloe vera extract, and to assess its antifungal activity against Candida albicans. Materials and Methods: Silver nanoparticles were synthesized by reducing Ag nitrate with aqueous A. vera extracts. Physicochemical properties of synthesized AgNPs were determined by ultraviolet-visible spectrophotometry, photon cross-correlation spectroscopy, energy-dispersive X-ray fluorescence spectrometry, X-ray diffraction analysis, and Fourier-transform infrared spectroscopy. An antifungal investigation was performed against four clinical C. albicans (C1, C2, C3, and C4) and a reference strain, C. albicans ATCC 10321. Results: Cubic AgNPs with a mean X50 hydrodynamic diameter of 80.31 ± 10.03 nm were successfully synthesized. These AgNPs exhibited maximum absorbance at 429.83 nm, and X-ray fluorescence (XRF) confirmed the presence of Ag in AgNPs solution by a characteristic peak in the spectrum at the Ag Kα line of 22.105 keV. Infrared spectra for AgNPs and A. vera extract indicated that the compounds present in the extract play an essential role in the coating/capping of synthesized AgNPs. Different concentrations (200, 100, 50, 25, 10, and 5 µg/mL) of AgNPs were tested. The antifungal activity was shown to be dose-dependent with inhibition zones ranging from 10 mm to 22 mm against C. albicans ATCC 10231, 0 mm to 15 mm against C1, 0 mm to 16 mm against C2 and C3, and 0 mm to 14 mm for C4. Minimum inhibitory concentration ranged from 16 µg/mL to 32 µg/mL against clinical C. albicans (C1, C2, C3, and C4) and was 4 µg/mL against C. albicans ATCC 10231. Conclusion: This study showed the ability of A. vera to serve as an efficient reducing agent for the biogenic synthesis of AgNPs with excellent antifungal activity.

Evaluation of the Microbiological Effect of Colloidal Nanosilver Solution for Root Canal Treatment.

BACKGROUND: The goal of endodontic treatment, along with the preparation of the root canal and giving it a shape corresponding to the obturation technique, is the drug treatment of the canal. The aim of this study was to determine the antibacterial effect of a colloidal solution of nanosilver at its various dilutions on root canal microorganism. MATERIALS AND METHODS: A solution of silver nanoparticles at a concentration of 10,000 ppm (1.0%) was diluted in various concentrations (10 solutions from 1% to 0.0025%). Cultures used for research: Str. agalacticae ATCC 3984, E. faecalis ATCC 323, St. aureus ATCC 4785, C. albicans ATCC 10231. After thawing, cultures of microorganisms were introduced into a liquid nutrient medium: cerebral heart broth for bacterial cultures and Sabouraud broth for C. albicans. The cultivation was carried out at a temperature of 37 °C for 24 h. A bacterial suspension for inoculation was prepared from a microbial sediment according to a turbidity standard of 0.5 McFarland in saline. Then, 100 µL of the obtained suspension of microorganisms was inoculated by the "lawn" method using a spatula on the Muller-Hinton medium. Solutions of silver nanoparticles were introduced into wells prepared in agar with a sterile metal punch. Further incubation was carried out for 24 h at 37 °C. RESULTS: colloidal solution of silver nanoparticles at concentrations of 1%, 0.75%, 0.5% inhibited the growth of Str. agalacticae ATCC 3984 with a growth retardation zone of 6-7 mm. The E. faecalis ATCC 29212 strain was sensitive to solutions of silver nanoparticles at concentrations of 1%, 0.75%, 0.5% with a growth inhibition zone of 6-7 mm. Strain St. aureus 4785 demonstrated sensitivity to solutions of silver nanoparticles at concentrations of 1%, 0.75%, 0.5%, 0.1%, 0.05% with a growth retardation zone of 6-8 mm. CONCLUSION: colloidal solutions of silver nanoparticles have antimicrobial action against gram-positive bacteria (Str.agalacticae ATCC 3984, St. aureus ATCC 4785, E. faecalis ATCC 29212) and yeast-like fungi of the genus Candida (C. albicans ATCC 10231, C. albicans 672 and C. albicans D-225M), but this action is strain-specific and depends on the concentration of the solution.

In vitro antimicrobial activity, antibioresistance reversal properties, and toxicity screen of ethanolic extracts of Heracleum mantegazzianum Sommier and Levier (giant hogweed), Centaurea jacea L. (brown knapweed), and Chenopodium album L. (Pigweed): Three invasive plants.

Background: Plants, including invasive ones, can play a significant role in the fight against antibiotic resistance and the search for new antimicrobials. Aims: The present study aimed at assessing the antimicrobial activity, antibioresistance reversal properties, and toxicity of four samples from invasive plants, namely, Heracleum mantegazzianum (leaves and flowers), Chenopodium album (leaves), and Centaurea jacea (flowers). Methods: The extraction of active compounds was done with ethanol (80%, v/v) and the extraction yields were calculated. Antimicrobial activity was studied using the agar-well diffusion method against Escherichia coli ATCC 25922, Staphylococcus aureus ATCC 6538, and Candida albicans ATCC 10231. Minimum inhibitory concentrations (MIC) and minimum bactericidal concentrations (MBC) were determined using the mircodilution method. The antibioresistance reversal properties were assessed using the checkerboard method and the toxicity of the extracts was studied using the larval form of the Greater Wax Moth (Galleria mellonella). Results: The mass yields were 11.9, 15.0, 18.2, and 21.5, respectively, for C. jacea flower (CJF), H. mantegazzianum flower (HMF), H. mantegazzianum leaf (HML), and C. album leaf (CAL). The highest inhibition diameters (ID) were found with HMF, CAL, CJF, and HML against S. aureus with 26.6, 21.6, 21.0, and 20.0 mm, respectively. Only CJF and HMF were active against E. coli with respective ID of 15.3 and 19.0 mm. Except HMF (ID = 13.6 ± 2.0 mm), no other extract was active against C. albicans. Moreover, HMF exhibited the lowest MIC (0.5 mg/ml) and the lowest MBC (1 and 4 mg/ml) against both S. aureus and E. coli. Regarding the synergy test, an additional effect [0.5 ≤ fractional inhibitory concentration (FIC) ≤ 1] was found in almost all the combinations antibiotics + extracts excepted for HMF + (Kanamycin or Ampicillin) against S. aureus and CJF + Ampicillin against E. coli where we found synergy effect (FIC ≤0.5). The median lethal doses (LD50s) of HMF, HML, CAL, and CJF were 20.2, 0.58, 13.2, and 4.0 mg/ml, respectively. Conclusion: Only the ethanolic extract of HMFs showed noteworthy broad spectrum antimicrobial activity.

Enhancement of the antifungal activity of some antimycotics by farnesol and reduction of Candida albicans pathogenicity in a quail model experiment.

Background and Aim: Clinical strains of microorganisms, including pathogenic yeast-like fungi (YLF), are resistant to currently used antifungal agents. Thus, it is relevant to study the combinations of existing antimicrobial drugs and a medicinal extract of plant origin (farnesol). In previous studies, farnesol showed a relatively strong anti-biofilm effect against Candida albicans. This study aimed to determine how much the resistance profile of non-biofilm microorganisms can change. Materials and Methods: Six clinical isolates of C. albicans and one reference strain were used to study the interaction of farnesol with the most used antimycotics. To determine the sensitivity of YLF to antimycotic drugs, such as nystatin (50 µg), amphotericin B (10 µg), ketoconazole (10 µg), clotrimazole (10 µg), voriconazole (10 µg), fluconazole (25 µg), miconazole (10 µg), and intraconazole (10 µg), the classic disk diffusion method was used. In the second stage, one of the six strains was used to simulate candidiasis of the gastrointestinal tract in an in vivo quail model. As an unusual experimental design, this study investigated the effects of pretreated C. albicans in quails, not the in vivo pathogenicity of C. albicans, after treatment with farnesol. Results: The resistance profiles of Candida strains did not improve with farnesol in all strains. All concentrations of farnesol (100, 50, and 25 µM) demonstrated a fungistatic effect (i.e., an increase in drug sensitivity) in 23 of 56 (7×8) cases (41%). The remaining 54% demonstrated no changes in the resistance to antifungal drugs or deterioration of the indicators in rare cases (5%). At 100 µM farnesol, sensitivity improved in 33 of 56 cases (59%). Candidiasis or the severity of clinical disease of the quail digestive tract developed to a lesser extent if fungi were treated with farnesol. Conclusion: Farnesol does not always show a positive result on single cells without biofilm in the laboratory. However, in a biofilm or an in vivo model with biofilms, farnesol can be considered a new antimycotic drug or an additive to existing antimycotics.