Minimum Growth Inhibitory Concentration Research Articles

Toxicity of commercial and pure forms of three nonsteroidal anti-inflammatory drugs in Xenopus laevis embryos before and after ozonation

In this study, the toxic and teratogenic effects of three commercial drugs and their active ingredients on Xenopus laevis embryos before and after ozonation were evaluated using the Frog Embryos Teratogenesis Assay–Xenopus (FETAX). First, the median lethal concentration (LC50) and, if data were available, the median effective concentration, teratogenic index and minimum growth inhibitory concentration were determined for each drug substance without ozonation. Then, the active substance amounts of three selected nominal concentrations (LC50/2, LC50, and LC50×2) of each test substance before ozonation were measured by HPLC analysis and the toxicity of these substances was evaluated after 2, 3, 4, and 5 h of ozonation. In addition, degradation products that may occur during ozonation were evaluated by LC-MS analysis. The 96-h LC50s of Dolphin–diflunisal, Dichloron–diclofenac sodium, and Apranax–naproxen drug–active substance pairs were determined to be 22.3 and 11.1, 25.7 and 18.7, and 47.8 mg active substance/L and 45.3 mg/L, respectively. According to the FETAX test results, the Dolphin–diflunisal drug–active ingredient pair did not cause growth retardation in exposed embryos. Dichloron–diclofenac sodium and Apranax–naproxen drug–active ingredient pairs were both teratogenic and growth inhibitory. In the second stage of the study, in which the effectiveness of ozonation in eliminating the toxic effects of drugs is evaluated, it is seen that ozonation is partially successful in eliminating the toxic effects of Dolphin–diflunisal and Dichloron–diclofenac sodium pairs, but insufficient for eliminating the effects of the Apranax–naproxen pair.

A novel defensin-like peptide C-13326 possesses protective effect against multidrug-resistant Aeromonas schubertii in hybrid snakehead (Channa maculate ♀ × Channa argus ♂).

The purpose of this study was to investigate whether a defensin-like antimicrobial peptide (C-13326 peptide) identified in Hermetia illucens could possess protective effect against multidrug-resistant Aeromonas schubertii in hybrid snakehead (Channa maculate ♀ × Channa argus ♂). The cDNA of C-13326 peptide comprised 243 nucleotides encoding 80 amino acids, with six conserved cysteine residues and the classical CSαβ structure. The recombinant expression plasmid pPIC9K-C-13326 was constructed and transformed into GS115 Pichia pastoris, and the C-13326 peptide was expressed by induction with 1% methanol. The crude extract of C-13326 peptide was precipitated by ammonium sulfate, assayed by Braford method, detected by tricine-SDS-PAGE, evaluated by BandScan software and identified by liquid chromatography-mass spectrometry. The C-13326 peptide was shown to have inhibitory activity against the growth of multidrug-resistant A. schubertii DM210910 by using the minimum growth inhibitory concentration and Oxford cup method. In addition, scanning electron microscopy analysis suggested that C-13326 peptide inhibited the growth of A. schubertii DM210910 by damaging the bacterial cell membrane. To explore the role of peptide C-13326 invivo, hybrid snakehead was fed with peptide C-13326 as feed additives for 7 days. The results revealed that C-13326 peptide could significantly down-regulate the expression levels of IL-1β, IL-8, IL-12 and TNF-α (p < .05), and significantly improved the survival rate of hybrid snakehead after challenging with A. schubertii DM210910. Therefore, the C-13326 peptide is a promising antimicrobial agent for A. schubertii treatment in aquaculture.

MIC Determination of Silver Nanoparticles on Nystatin-Resistant Candida albicans in Patients with Denture Stomatitis: An In Vitro Study

Background: Denture stomatitis (DS) is a chronic mucosa inflammation that supports removable dentures. Candida albicans is the most critical factor in the pathogenesis of DS. Systemic antifungal drugs such as nystatin are effective in people with acute candidiasis. Yet, in cases of predisposing factors such as a denture, nystatin cannot completely control the infection, and recurrences are common. Objectives: In this study, the resistance and sensitivity of oral C. albicans species to nystatin were evaluated, and the effect of silver nanoparticles (AgNPs) was investigated on the nystatin-resistant specimens. Methods: This in vitro study was performed on 20 C. albicans specimens isolated from patients with denture stomatitis. After confirmation of C. albicans and in vitro biofilm preparation, nystatin was applied to the biofilm. The results were recorded as minimum growth inhibitory concentration (MIC) using Clinical &amp; Laboratory Standards Institute (CLSI) standard protocol, and the specimens with MIC of more than 1 µg/mL were categorized as resistant. Then, biofilms were re-formed for nystatin-resistant specimens exposed to AgNPs, and MIC results were reported. Results: This study revealed that 8 C. albicans specimens (40%) represented a MIC of more than 1 µg/mL when exposed to nystatin. The results of AgNPs exposure to this group showed significantly higher efficiency of AgNPs than nystatin (P &lt; 0.05). AgNPs can reduce the MIC of 6 nystatin-resistant specimens (75% of all resistant specimens). Conclusions: Both nystatin and AgNPs are effective against Candida biofilms formed on denture surfaces. However, AgNPs seem more effective in the case of resistant species.

Antibacterial potential of biosynthesized silver nanoparticles using Nepeta sessilifolia Bunge and Salvia hydrangea DC. ex Benth. extracts from the natural habitats of Iran's Rangelands

BackgroundNowadays, the use of herbal extracts for the production of nanoparticles has attracted a lot of attention due to the fast reaction, economy, and compatibility with the environment. The aim of the present study is the biosynthesis of silver nanoparticles from the extracts of Nepeta sessilifolia Bunge and Salvia hydrangea DC. ex Benth. and their antibacterial activity was measured.MethodsFor this purpose, the flowering branch of N. sessilifolia and the flower of S. hydrangea were randomly collected from three places, respectively, from the rangelands of Aqdash Mountain and Biabe in Isfahan province, Iran in May 2021. After extracting aqueous extracts by hot method, silver nanoparticles were synthesized by the biological method. Green synthesized silver nanoparticles were analyzed by UV–Vis spectroscopy, XRD, FTIR, and FESEM-EDAX. The antibacterial effect was evaluated by diffusion method in agar and determination of minimum growth inhibitory and lethal concentration (MIC and MBC) by dilution method in liquid culture medium.ResultsBased on the results of UV–Vis spectroscopy, silver nanoparticles synthesized from N. sessilifolia and S. hydrangea had distinct absorption peaks at wavelengths of 407 to 424 nm and 414 to 415 nm, respectively. The crystalline nature of these synthetic silver nanoparticles was confirmed by XRD. FESEM analysis showed that the size of biosynthesized silver nanoparticles from N. sessilifolia and S. hydrangea extracts were 10–50 nm and 10–80 nm, respectively, and were cubic. The results of diffusion in agar showed that the largest diameter of the growth inhibition zone belonging to the synthetic silver nanoparticles from both extracts of N. sessilifolia (~ 26.00 mm) and S. hydrangea (~ 23.50 mm) was against Gram-positive bacteria Staphylococcus aureus. The most vigorous killing activity by synthetic silver nanoparticles from N. sessilifolia extract was against Klebsiella pneumoniae with a value of 250 μg/mL, two times stronger than rifampin.ConclusionTherefore, the studied extracts can be suitable options for fast and safe green synthesis of silver nanoparticles effective against some bacterial strains. These synthetic silver nanoparticles can be used as possible options and have strong potential for the production of natural antibiotics.

Pterostilbene, a Natural Methoxylated Analog of Resveratrol, Exhibits Antifungal Activity Induced by Reactive Oxygen Species Production and Plasma Membrane Injury

Pterostilbene has been shown to exhibit antifungal activities. However, the detailed action mechanism is unknown. Here, we analyzed the antifungal mechanism of pterostilbene against Saccharomyces cerevisiae. The minimum growth inhibitory and fungicidal concentrations of pterostilbene were 120 and 240 µM in a YPD medium, respectively. Although pterostilbene produced reactive oxygen species (ROS), resveratrol did not. This effect was maximized at 120 µM. Furthermore, α-tocopherol acetate inhibited ROS production and reversed pterostilbene-induced growth inhibition. At 240 µM, pterostilbene showed fungicidal effects accompanied by the leakage of intracellular potassium ions, suggesting the involvement of membrane injury in addition to oxidative stress in fungicidal action. Nevertheless, the antioxidants gradually reversed the decrease in cell viability caused by pterostilbene, suggesting that ROS production mainly contributed to the lethal effect. As Pterocarpus marsupium extract, mainly containing pterostilbene, is used as a traditional medicine, pterostilbene has great potential for development as a preservative with fewer adverse effects.

Minimum Concentration of Stingless Bee Propolis (Trigona sp.) in Inhibiting the Growth of Dandruff Bacteria

Lack of confidence in men and women, one of which is when there is dandruff on the hair and scalp. Hair loss is a further symptom of the presence of white scales on the scalp that cause itching. The presence of excessive microorganisms can aggravate this dandruff. Ingredients such as ketocanozole, zinc pyrithione, selenium sulfide and sulfur are compounds commonly used in shampoo formulas. Propolis is an alternative natural ingredient to treat dandruff. The purpose of this study was to determine the minimum growth inhibitory concentration (MIC) of propolis against dandruff-causing bacteria. Dandruff-causing microbes were isolated from dandruff hair and with the well method in a petri dish, the minimum growth inhibitory concentration of propolis was determined. The microbial colonies produced were very diverse with a round shape like grapes, yellowish white in color. The concentration of 6.25% is the MIC value of propolis extract against dandruff microbes. The effectiveness values against ketoconazole and propolis X from the tested propolis extract were 223.52% and 99.59%, respectively.&#x0D; &#x0D; Keywords: hair loss, dandruff, propolis, bacteria , Trigona

Hexanoic acid: a new potential substitute for copper-based agrochemicals against citrus canker.

The aim of the study is to evaluate hexanoic acid (HA) as an alternative to manage citrus canker. The minimal growth inhibitory concentration of HA against Xanthomonas citri subsp. citri was determined at 2·15mmoll-1 using a respiratory activity assay. Growth curves at different pH values showed that growth inhibition was not due to media acidification induced by HA. The germination rate and root elongation of Lactuca sativa seeds exposed to different concentrations of HA (varying from 0·86 to 5·16mmoll-1 ) were assessed to screen for phytotoxicity. The acid exhibited low phytotoxicity for L.sativa at 1·29 and 2·58mmoll-1 . To evaluate the ability of HA to protect citrus against X.citri infection, leaves of Citrus sinensis were sprayed with the acid and subsequently challenged with X.citri. HA at 3·44mmoll-1 was able to protect citrus against infection, showing a reduction of three orders of magnitude in the number of citrus canker lesions per cm2 when compared to the untreated negative control. HA is a potential alternative to copper for citrus canker management. HA inhibits X.citri growth, exhibits low phytotoxicity and is an alternative to copper for the protection of citrus plants against bacterial infection.

Antimicrobial Peptides and their Multiple Effects at Sub-Inhibitory Concentrations.

The frequent occurrence of multidrug-resistant strains to conventional antimicrobials has led to a clear decline in antibiotic therapies. Therefore, new molecules with different mechanisms of action are extremely necessary. Due to their unique properties, antimicrobial peptides (AMPs) represent a valid alternative to conventional antibiotics and many of them have been characterized for their activity and cytotoxicity. However, the effects that these peptides cause at concentrations below the minimum growth inhibitory concentration (MIC) have yet to be fully analyzed along with the underlying molecular mechanism. In this mini-review, the ability of AMPs to synergize with different antibiotic classes or different natural compounds is examined. Furthermore, data on microbial resistance induction are reported to highlight the importance of antibiotic resistance in the fight against infections. Finally, the effects that sub-MIC levels of AMPs can have on the bacterial pathogenicity are summarized while showing how signaling pathways can be valid therapeutic targets for the treatment of infectious diseases. All these aspects support the high potential of AMPs as lead compounds for the development of new drugs with antibacterial and immunomodulatory activities.

Antimicrobial Effect of Zataria Essential Oil on the Skin Bacteria in Wistar Rats

Objective: Zataria is one of the native plants of Iran which is widely used for the treatment of diseases among Iranians. In this study, we investigated the antimicrobial effects of Zataria essential oil on the skin bacteria in rats. Methods: Bacterial strains were isolated from the skin of 6 wistar rats and the antimicrobial effects of Zataria essential oil were evaluated by disk diffusion and microbroth dilution methods. In-vivo tests were performed to evaluate the antimicrobial effect of the essential oil by microbial culture as well as allergy tests on the skin of experimental rats compared to controls. Results: Three bacterial strains were isolated from the skin of rats identified as Staphylococcus aureus, Corynebacterium and Staphylococcus epidermidis. Minimum Growth Inhibitory Concentration (MIC) and Minimum Bactericidal Concentration (MBC) for the two strains of Staphylococcus aureus and Corynebacterium were obtained 0.39 and 0.78 mg/ml, while for Staphylococcus epidermidis, they were 0.195 and 0.39 mg/ml, respectively. In-vivo test results showed the antibacterial effect of the essential oil on the skin bacteria and no inflammatory effects were observed under the allergy test. Conclusion: Zataria essential oil has antimicrobial effects on the skin infections in lower concentrations. The use of this essential oil as an antiseptic and preservative in cosmetics is recommended instead of chemical preservatives that generally have skin side effects.

Synthesis and characterization of novel antibacterial Sol-gel derived TiO2/Zn2TiO4/Ag nanocomposite as an active agent in Sunscreens

The application of zinc oxide (ZnO) nanoparticles in sunscreen formulations has two advantages: protection against harmful rays of sun and cosmetic attractiveness. Furthermore, in recent years Ag–TiO2 nanoparticles have gained a great in cosmetics and hygiene industry due to its stronger antibacterial effect compared to pure TiO2. In the present study, nanocomposite composed of titanium dioxide, zinc oxide and silver nanoparticles (TiO2/Zn2TiO4/Ag) were synthetized via sol-gel method and characterized using XRD, (FT-IR) and (SEM). Antibacterial properties of nanocomposite was determined using minimum growth inhibitory concentration test against E. coli and Staphylococcus aureus bacteria and toxicity in a sunscreen cream were also investigated. Cytotoxicity of nanocomposite was also assessed qualitatively and quantitatively. The nanocomposite had an average size of 20–29 nm. The analytical results, XRD, FT-IR and SEM confirmed the presence of ZnO, TiO2 and Ag in nanocomposite structure after sintering at 400 °C. MIC results demonstrated the strong anti-bacterial activity of nanocomposite against both gram-positive and gram-negative bacteria. Qualitative and quantitative toxicity tests showed that the toxicity of nanocomposite was very low and it was dose dependent. It could be concluded that this novel TiO2/Zn2TiO4/Ag nanocomposite could be beneficial in development of sunscreen cream with high protection.

Inhibition of Pseudomonas aeruginosa biofilm formation and expression of virulence genes by selective epimerization in the peptide Esculentin-1a(1-21)NH2.

Pseudomonas aeruginosa is a pathogenic bacterium known to cause serious human infections, especially in immune-compromised patients. This is due to its unique ability to transform from a drug-tolerant planktonic to a more dangerous and treatment-resistant sessile life form, called biofilm. Recently, two derivatives of the frog skin antimicrobial peptide esculentin-1a, i.e. Esc(1-21) and its D-amino acids containing diastereomer Esc(1-21)-1c, were characterized for their powerful anti-Pseudomonal activity against both forms. Prevention of biofilm formation already in its early stages could be even more advantageous for counteracting infections induced by this bacterium. In this work, we studied how the diastereomer Esc(1-21)-1c can inhibit Pseudomonas biofilm formation in comparison to the parent peptide and two clinically-used conventional antibiotics, i.e. colistin and aztreonam, when applied at dosages below the minimal growth inhibitory concentration. Biofilm prevention was correlated to the peptides' ability to inhibit Pseudomonas motility and to reduce the production of virulent metabolites, for example, pyoverdine and rhamnolipids. Furthermore, the molecular mechanism underlying these activities was evaluated by studying the peptides' effect on the expression of key genes involved in the virulence and motility of bacteria, as well as by monitoring the peptides' binding to the bacterial signaling nucleotide ppGpp. Our results demonstrate that the presence of only two D-amino acids in Esc(1-21)-1c is sufficient to downregulate ppGpp-mediated expression of biofilm-associated genes, presumably as a result of higher peptide stability and therefore prolonged interaction with the nucleotide. Overall, these studies should assist efficient design and optimization of new anti-infective agents with multiple pharmacologically beneficial properties.

Antifungal Activities of 4″,6″-Disubstituted Amphiphilic Kanamycins.

Amphiphilic kanamycins derived from the classic antibiotic kanamycin have attracted interest due to their novel bioactivities beyond inhibition of bacteria. In this study, the recently described 4″,6″-diaryl amphiphilic kanamycins reported as inhibitors of connexin were examined for their antifungal activities. Nearly all 4″,6″-diaryl amphiphilic kanamycins tested had antifungal activities comparable to those of 4″,6″-dialkyl amphiphilic kanamycins, reported previously against several fungal strains. The minimal growth inhibitory concentrations (MICs) correlated with the degree of amphiphilicity (cLogD) of the di-substituted amphiphilic kanamycins. Using the fluorogenic dyes, SYTOXTM Green and propidium iodide, the most active compounds at the corresponding MICs or at 2×MICs caused biphasic dye fluorescence increases over time with intact cells. Further lowering the concentrations to half MICs caused first-order dye fluorescence increases. Interestingly, 4×MIC or 8×MIC levels resulted in fluorescence suppression that did not correlate with the MIC and plasma membrane permeabilization. The results show that 4″,6″-diaryl amphiphilic kanamycins are antifungal and that amphiphilicity parameter cLogD is useful for the design of the most membrane-active versions. A cautionary limitation of fluorescence suppression was revealed when using fluorogenic dyes to measure cell-permeation mechanisms with these antifungals at high concentrations. Finally, 4″,6″-diaryl amphiphilic kanamycins elevate the production of cellular reactive oxygen species as other reported amphiphilic kanamycins.

Antimicrobial Activity of NCR Plant Peptides Strongly Depends on the Test Assays.

The symbiosis specific NCR247 and NCR335 cationic plant peptides of Medicago truncatula have been shown to exert antimicrobial activity against a wide range of microbes. However, their antimicrobial efficiency is clearly limited by divalent cations. Here, the antibacterial and antifungal activities of NCR247 and NCR335 peptides were compared to those of the well-characterized peptide antibiotics polymyxin B and the aminoglycoside streptomycin on three model microbes, Escherichia coli, Bacillus subtilis and Saccharomyces cerevisiae as representatives of Gram-negative and Gram-positive bacteria as well as eukaryotic fungi. The aim of the study was to assess how the killing efficiency of these peptides depends on various, widely used antimicrobial susceptibility assays. Validated resazurin microdilution assay was used to determine minimal growth inhibitory concentrations in three general test media (MHB, MHBII and low-salt medium LSM). Bactericidal/fungicidal activities were determined by the commonly used drop plate assay. The natural plant peptides showed distinct characteristics, NCR247 had a generally high sensitivity for Ca2+ and Mg2+ in the medium, while NCR335 proved to be a robust and strong antimicrobial agent with comparable efficiency values to polymyxin B. Activity data were confirmed visually, both NCR247 and NCR335 treatments at minimal bactericidal concentrations induced complete disruption of the membranes and provoked cell lysis on all tested microorganisms as observed by scanning electron microscopy.

Antifungal Activity of Diglycerin Ester of Fatty Acids against Yeasts and Its Comparison with Those of Sucrose Monopalmitate and Sodium Benzoate

The antifungal activities of diglycerin monoester of fatty acids (DGCs), which have been employed as food emulsifiers, were examined against three yeasts, Saccharomyces cerevisiae, Candida albicans and Candida utilis and were compared with those of sucrose monoester of palmitic acid (SC16) as another type of emulsifier and sodium benzoate (SB) as a weak acid food preservative. When the minimum growth inhibitory concentrations (MICs) of diglycerin monolaurate (DGC12) against these yeasts were determined 2 d after incubation in YM broth at pH5.0, they were relatively low, being 0.01% (w/v), for both S. cerevisiae and C. utilis, whereas was high, being 4.0% (w/v), for C. albicans. On the contrary, the MICs of sucrose monopalmitate (SC16) were high, being 3.0 and 4.0% (w/v), for the former two yeasts, respectively, but 0.6% (w/v) for the last yeast. In contrast to these emulsifiers, the MICs of sodium benzoate (SB) were similar independently upon the yeast strain, being in order 0.4, 0.3 and 0.5% (w/v), for the above yeasts, respectively. The anti-yeast activities of DGC12 and SC16 were gradually increased with a decrease in pH, in a manner similar to that of SB, except for the action of SC16 on C. albicans, for which the activity was more effective at pHs 5.0 and 6.0 than at pHs 4.0 and 7.0. Among DGCs tested having different fatty acid moieties in the molecule, lauroyl ester (DGC12) was more effective than myristoyl and palmitoyl esters against S. cerevisiae and C. utilis. The inhibitory effect of DGC12 on the yeast growth depended upon both the cell density and the strength of aeration during the treatment. Further, DGC12 was found to kill S. cerevisiae and C. utilis cells at a rather low concentration of 0.005% (w/v) in 50mM acetate buffer at pH5.0, although, against C. albicans cells, only slight fungicidal activity was demonstrated at a high concentration of 0.5% (w/v). The results obtained support the effectiveness of practical application of DGC12 to acidic foods for the control of growth and survival of general yeasts such as S. cerevisiae and C. utilis.

Sustainable Preparation of Copper Particles Decorated Carbon Microspheres and Studies on Their Bactericidal Activity and Catalytic Properties

Cu particles decorated carbon composite microspheres (CCMs) with a unique sesame ball structure have been prepared by combining the mass-producible spray drying technique with calcinations. The conventional cuprammonium cellulose complex solution obtained by dissolving cellulose in a cuprammonia solution has been applied as raw materials for the preparation of Cu(NH3)42+/cellulose complex microspheres via a spray drying process. The resulted Cu(NH3)42+/cellulose complex microspheres are then transformed into the Cu particles homogeneously decorated porous carbon spheres in situ by calcinations at 450 or 550 °C. The coordination effect between the Cu(NH3)42+ species and the hydroxyl groups of the cellulose macromolecules has been exploited for directing the dispersion of the Cu particles in the resultant composite CCMs. The antimicrobial effects of the CCMs are evaluated by determining the minimum growth inhibitory concentrations using Staphylococcus aureus and Escherichia coli as representatives, respecti...

Anti-Salmonella Activity of Volatile Compounds of Vietnam Coriander.

Essential oil derived from the fresh leaves of Polygonum odoratum Lour was tested for their effects on a foodborne bacterium Salmonella choleraesuis subsp. choleraesuis ATCC 35640 using a broth dilution method. This essential oil showed a significant antibacterial activity against S. choleraesuis at the concentration of 200 µg/mL. Twenty-five volatile compounds were characterized from this essential oil by GC-MS, and aldehyde compounds were found abundant and accounted for more than three-fourths of the essential oil. Among the compounds characterized, dodecanal (C12 ) was the most abundant (55.5%), followed by decanal (C10 ) (11.6%). Both alkanals were effective against S. choleraesuis with the minimum growth inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) values of 100 µg/mL. The most potent antibacterial activity against this bacterium was found with two minor compounds, dodecanol (lauryl alcohol) and 2E-dodecenal, both with each MBC of 6.25 µg/mL. Their primary antibacterial action against S. choleraesuis provably comes from their ability to function as nonionic surface-active agents (surfactants), disrupting the native function of integral membrane proteins nonspecifically. Thus, the antibacterial activity is mediated by biophysical processes. In the case of 2E-alkenals, a biochemical mechanism is also somewhat involved, depending on their alkyl chain length.

Visible light driven photocatalysis and antibacterial activity of AgVO3 and Ag/AgVO3 nanowires

Ag/AgVO3 nanowires and AgVO3 nanorods were synthesized in aqueous media via a facile sonochemical route. The as-synthesized products were characterized by X-ray diffraction, Brunauer–Emmett–Teller surface area analysis, scanning electron microscopy together with an energy dispersion X-ray spectrum analysis, transmission electron microscopy and UV–vis diffuse reflectance spectroscopy. The results revealed that inert atmosphere promotes the formation of Ag/AgVO3 nanowires. The photocatalytic studies revealed that the Ag/AgVO3 nanowires exhibited complete photocatalytic degradation of Rhodamine B within 45min under visible light irradiation. The antibacterial activity of Ag/AgVO3 nanowires was tested against Escherechia coli and Bacillus subtilis. The minimum growth inhibitory concentration value was found to be 50 and 10 folds lower than for the antibiotic ciprofloxacin for E. coli and B. subtilis, respectively. The antibacterial properties of the β-AgVO3 nanorods prove that in case of the Ag dispersed Ag/AgVO3 nanowires, the enhanced antibacterial action is also due to contribution from the AgVO3 support.

Morphological Changes of the Filamentous Fungus Mucor Mucedo and Inhibition of Chitin Synthase Activity Induced by Anethole

trans-Anethole (anethole), a major component of anise oil, has a broad antimicrobial spectrum with antimicrobial activity relatively weaker than those of well-known antibiotics, and significantly enhances the antifungal activity of polygodial and dodecanol against the baker's yeast Saccharomyces cerevisiae and human pathogenic yeast Candida albicans. However, the antifungal mechanism of anethole is unresolved. Anethole demonstrated antifungal activity against the filamentous fungus, Mucor mucedo IFO 7684, accompanied by hyphal morphological changes such as swollen hyphae at the tips. Its minimum growth inhibitory concentration was 0.625 mM. A hyperosmotic condition (1.2 M sorbitol) restricted the induction of morphological changes, while hypoosmotic treatment (distilled water) induced bursting of hyphal tips and leakage of cytoplasmic constituents. Furthermore, anethole dose-dependently inhibited chitin synthase (CHS) activity in permeabilized hyphae in an uncompetitive manner. These results suggest that the morphological changes of M. mucedo could be explained by the fragility of cell walls caused by CHS inhibition.

ChemInform Abstract: Structure-Activity Relationships of a New Antifungal Imidazole, AFK-108, and Related Compounds.

Fungicidal activity of widely used imidazole antifungal drugs in topical applications is not so strong in spite of their potent fungistatic activities against dermatophytes and pathogenic yeasts. In order to improve fungicidal activity of imidazole antifungal agents, a series of novel imidazole derivatives having a hydrophobic substituent derived from isoprenoid were synthesized. The efficacy of these compounds was evaluated with respect to direct cell-membrane damaging activity, ergosterol biosynthesis inhibition, minimum growth-inhibitory concentration (MIC) and therapeutic effect for experimental dermatophytosis of guinea pigs. Among the newly synthesized compounds, the geranyl derivative named AFK-108 (2a) showed the highest in vivo fungicidal activity with both cell membrane damaging activity and ergosterol biosynthesis inhibition in vitro.

Effect of Chitosan Acetate on Bacteria Occurring on Neungee Mushrooms, Sarcodon aspratus

Minimal growth inhibitory concentrations (MICs) of chitosan acetate (M.W. 60 kDa) on heterotrophic bacteria (strains MK1, S, and R) isolated from the soft-rotten tissues of Neungee mushroom (Sarcodon aspratus) were measured. The slimy substance produced by the MK1 strain was responsible for the diseased mushroom’s appearance. The S and R strains were members of the Burkholderia cepacia complex. These strains showed different levels of susceptibility toward chitosan acetate. The MIC of chitosan acetate against the MK1 and S strains was 0.06%. The MIC against the R strain was greater than 0.10%. Survival fractions of the MK1 and S strains at the MIC were 3 × 10−4 and 1.4 × 10−3 after 24 h, and 2 × 10−4 and 7 × 10−4 after 48 h, respectively. Survival fractions of the R strain after 24 and 48 hr at 0.1% chitosan acetate were 1 × 10−2 and 6.9 × 10−3, respectively. Compared to the MK1 and S strains, the low susceptibility of the R stain towards chitosan acetate could be due to the ability of the R strain to utilize chitosan as a carbon source. Thirty-eight percent of Neungee pieces treated in a 0.06% chitosan acetate solution for 2~3 second did not show any bacterial growth at 4 days, whereas bacterial growth around untreated mushroom pieces occurred within 2 days. These data suggest that chitosan acetate is highly effective in controlling growth of indigenous microorganisms on Neungee. The scanning electron micrographs of the MK1 strain treated with chitosan revealed a higher degree of disintegrated and distorted cellular structures.