Minimum Inhibitory Dose Research Articles

Purification and characterization of lipopeptides produced by Bacillus subtilius and their antibacterial effects on Escherichia coli and Staphylococcus aureus

Lipopeptides have favorable biological activity and thus have great potential to serve as replacements. Whole genome sequencing was used in this work to pinpoint the gene clusters in Bacillus subtilis that code for secondary metabolites that have antibacterial qualities. Afterwards, the metabolic pathways responsible for the production of these compounds were clarified, and the lipopeptides were separated and identified using a combination of chromatography and spectroscopy methods, such as High-Performance Liquid Chromatography (HPLC), Fourier Transform Infrared Spectroscopy (FTIR), and Liquid Chromatography-Mass Spectrometry (LC-MS). Bacillus subtilis mainly synthesized surfactin homologs with carbon chain lengths ranging from C13 to C16 ([M+H]+: 994.6418; 1008.6586; 1022.6730; 1036.6896) and fengycin homologs with carbon chain lengths of C15 and C16 ([M+H]+: 1449.7937, 1463.8046). The isolated lipopeptides exhibited strong inhibitory effects against Escherichia coli and Staphylococcus aureus, with minimum inhibitory doses of 12.50 mg/L and 6.25 mg/L, respectively. Furthermore, lipopeptides demonstrated a dose-dependent inhibition of E. coli and S. aureus. The findings from SEM and SYTO 9/PI staining demonstrate that lipopeptides function by compromising the integrity of bacterial cell membranes. The results demonstrate the effectiveness of lipopeptides as antibacterial agents against foodborne pathogens, indicating their potential as substitutes for traditional antibiotics.

Metabolite profiling and bioactivity guided fractionation of Lactobacillaceae and rice bran postbiotics for antimicrobial-resistant Salmonella Typhimurium growth suppression.

Probiotic-fermented supplements (postbiotics) are becoming increasingly explored for their activity against antibiotic-resistant enteropathogens. Prebiotics are often incorporated into postbiotics to enhance their efficacy, but due to strain differences in probiotic activity, postbiotic antimicrobial effects are poorly understood. To improve postbiotic antimicrobial efficacy, we investigated and compared metabolite profiles of postbiotics prepared with three lactic acid bacteria strains (L. fermentum, L. paracasei, and L. rhamnosus) cultured with and without rice bran, a globally abundant, rich source of prebiotics. At their minimum inhibitory dose, L. fermentum and L. paracasei postbiotics + rice bran suppressed S. Typhimurium growth 42-55% more versus their respective probiotic-alone postbiotics. The global, non-targeted metabolome of these postbiotics identified 109 metabolites increased in L. fermentum and L. paracasei rice bran postbiotics, including 49 amino acids, 20 lipids, and 12 phytochemicals metabolites. To identify key metabolite contributors to postbiotic antimicrobial activity, bioactivity-guided fractionation was applied to L. fermentum and L. paracasei rice bran-fermented postbiotics. Fractionation resulted in four L. fermentum and seven L. paracasei fractions capable of suppressing S. Typhimurium growth more effectively versus the negative control. These fractions were enriched in 15 metabolites that were significantly increased in the global metabolome of postbiotics prepared with rice bran versus postbiotic alone. These metabolites included imidazole propionate (enriched in L. fermentum + rice bran, 1.61-fold increase; L. paracasei + rice bran 1.28-fold increase), dihydroferulate (L. fermentum + rice bran, 5.18-fold increase), and linoleate (L. fermentum + rice bran, 1.82-fold increase; L. paracasei + rice bran, 3.19-fold increase), suggesting that they may be key metabolite drivers of S. Typhimurium growth suppression. Here, we show distinct mechanisms by which postbiotics prepared with lactic acid bacteria and rice bran produce metabolites with antimicrobial activity capable of suppressing S. Typhimurium growth. Probiotic strain differences contributing to postbiotic antimicrobial activity attract attention as adjunctive treatments against pathogens.

IN VITRO ANTIFUNGAL EFFECT OF TWELVE ESSENTIAL OILS ON PENICILLIUM EXPANSUM GROWTH

The questionable safety of food spoiled by microorganisms is and should be the subject of attention and investigation. Pathogens such as Penicillium expansum are more difficult to control due to their resistance and ubiquity. Awareness of plant essential oils (EOs) as alternative natural preservatives is increasing because of their significant antimicrobial activity. The aim of this research work was therefore to contribute to this topic with new results. The antifungal activity of twelve EOs was tested in vitro against five strains of Penicillium expansum, using the vapour-phase diffusion method. Three EOs, from bergamot, star anise and rosaline, inhibited colony growth during two-week cultivation with a partial efficacy, all other EOs showed complete (100%) inhibitory activity at a concentration of 625 μL.L-1. These (EOs from clove, cinnamon, cinnamon bark, laurel, lemongrass, peppermint, Mitcham mint, spearmint, and lavender) were included in the second part of the trial, the aim of which was to determine their minimum inhibitory doses (MIDs). In the case of peppermint, Mitcham mint, spearmint and lavender EOs, some strains of P. expansum grew already at a concentration of 500 μL.L-1. Clove EO stopped the fungal growth of two strains at 250 μL.L-1. Laurel EO was 100% effective at MID 250 μL.L-1 throughout the cultivation period. EOs from lemongrass and cinnamon bark had similar efficacy on the strains. Both EOs were able to inhibit one strain at a MID of 125 μL.L-1, cinnamon bark EO inhibited the remaining strains at 250 μL.L-1, lemongrass EO inhibited three strains at 250 μL.L-1 and one at 500 μL.L-1. The lowest MID was recorded for cinnamon EO, which effectively inhibited two strains at 125 μL.L-1, two strains at 62.5 μL.L-1 and one strain even at 31.25 μL.L-1. The sensitivity of the strains used in this study varied according to the EOs used.

Antifungal and toxicological evaluation of the alkaloids fraction from Neltuma nigra leaves

The use of synthetic fungicides for control soybean crop diseases has been cuestionated because of its impacts on human health and the environment. This work evaluated the composition, antifungal activity and toxicity of the alkaloids fraction obtained from Neltuma nigra leaves and compared its effect with the fungicide difenoconazole on Sclerotium rolfsii, Cercospora kikuchii, and C. sojina. Alkaloids fraction was extracted from leaves of N. nigra and its composition was analyzed by gas-chromatography coupled to mass spectrometry (GC-MS). The antifungal effect was recorded by measuring diameters of halos of inhibition of the growth of the different evaluated fungis. The toxicity of the alkaloids fraction was carried out using the method of Caenorhabditis elegans toxicity test. The extracted alkaloids fraction contained the alkaloids tryptamine (63.9%), tetrahydroxyharman (13.8%), phenethylamine (11.1%), cassine (10.4%), and N-formylphenylethylamine (0.8%). The alkaloids fraction was as effective against S. rolfsii as on the Cercospora strains, with minimum inhibitory doses of 25.0 μg disc-1 and inhibitory halos in the range of 8.5-13.0 mm, while difenoconazole had no effect on S. rolfsii. The toxicity of the alkaloid fraction (30.4-68.8 mg L-1) and difenoconazole (0.1-2.8 mg L-1) was tested on the reproduction, body length, and fertility of C. elegans. The fraction reduced the reproductive rate by 28.8-72.4% whereas difenoconazole did it from 12.2% to complete suppression. Neither of them affected the fertility of C. elegans. These findings suggest that the alkaloids fraction of N. nigra leaves is less toxic than difenoconazole and is a promising botanical fungicide against pathogenic soybean fungi.

Essential oil-loaded starch/cellulose aerogel: Preparation, characterization and application in cheese packaging

Novel antimicrobial emitting aerogels based on starch/cellulose/Thymus daenensis Celak essential oil (SC-TDEO) were developed and optimized for antimicrobial packaging of Koopeh cheese. An aerogel formulation containing cellulose (1 %; extracted from sunflower stalks) and starch (5 %) in a 1:1 ratio was selected for in vitro antimicrobial assay and subsequent cheese application. The minimum inhibitory dose (MID) of TDEO in the vapor phase against Escherichia coli O157:H7 was determined by loading various concentrations of TDEO onto the aerogel, and an MID of 256 μL/Lheadspace was recorded. Aerogels containing TDEO at 25 × MID and 50 × MID were then developed and used for cheese packaging. During a 21-day storage period, cheeses treated with SC-TDEO50 MID aerogel exhibited a significant 3-log reduction in psychrophile counts and a 1-log reduction in yeast-mold counts. Moreover, significant changes in the population of E. coli O157:H7 were observed in cheese samples. After 7 and 14 days of storage with SC-TDEO25 MID and SC-TDEO50 MID aerogels, the initial bacterial count became undetectable, respectively. Sensory evaluations indicated that the samples treated with SC-TDEO25 MID and SC-TDEO50 aerogels received higher scores compared to the control group. These findings demonstrate the potential of the fabricated aerogel to develop antimicrobial packaging suitable for cheese applications.

Use of Melaleuca alternifolia essential oil as an efficient strategy to extend the shelf life of banana fruits

Banana anthracnose is one of the main postharvest diseases economically compromising the fruit production chain. Fruit treatment with natural products can reduce postharvest pathogen infestation and increase protection during storage. For natural control of this disease, the activity of the essential oil of Melaleuca alternifolia (MAEO) was investigated in Colletotrichum musae. The aim of this study was to evaluate the in vitro antifungal activity of the MAEO on C. musae by of different concentrations and to evaluate the effect of MAEO on the incidence and severity of anthracnose. The essential oil (EO) was characterized by gas chromatography (GC-FID and GC-MS). The relative percentage of monoterpenes was 96.94%, and terpinen-4-ol was the main component (47.08%). The minimum inhibitory dose (EC100) of the mycelial growth of C. musae was reached at a concentration of 2.15 μg mL−1. Bananas were treated with water emulsions MAEO into at different concentrations (0.50, 1.00, 2.00, 3.00, 4.00 and 5.00 μg mL−1) for 08 days of storage at 25 ± 2 °C. MAEO showed fungistatic action from the concentration of 2.0 μg mL−1 (p < 0.05). The results showed that, after storage, MAEO at 0.50, 1.00, 2.00, 3.00, 4.00 and 5.00 μg mL−1 reduced area under the disease-progress curve (AUDPC) by 80%, 90%, 95%, 96%, 97% and 98%, respectively. MAEO reduces the severity of anthracnose after fruits treatment, without causing phytotoxic action, maybe a promising candidate for Biorational pesticides, in preservation and increment shelf life fruits banana.

Development and Evaluation of Bacteriophage Cocktail to Eradicate Biofilms Formed by an Extensively Drug-Resistant (XDR) Pseudomonas aeruginosa.

Extensive and multiple drug resistance in P. aeruginosa combined with the formation of biofilms is responsible for its high persistence in nosocomial infections. A sequential method to devise a suitable phage cocktail with a broad host range and high lytic efficiency against a biofilm forming XDR P. aeruginosa strain is presented here. Out of a total thirteen phages isolated against P. aeruginosa, five were selected on the basis of their high lytic spectra assessed using spot assay and productivity by efficiency of plating assay. Phages, after selection, were tested individually and in combinations of two-, three-, four-, and five-phage cocktails using liquid infection model. Out of total 22 combinations tested, the cocktail comprising four phages viz. φPA170, φPA172, φPA177, and φPA180 significantly inhibited the bacterial growth in liquid infection model (p < 0.0001). The minimal inhibitory dose of each phage in a cocktail was effectively reduced to >10 times than the individual dose in the inhibition of XDR P. aeruginosa host. Field emission-scanning electron microscopy was used to visualize phage cocktail mediated eradication of 4-day-old multi-layers of XDR P. aeruginosa biofilms from urinary catheters and glass cover slips, and was confirmed by absence of any viable cells. Differential bacterial inhibition was observed with different phage combinations where multiple phages were found to enhance the cocktail's lytic range, but the addition of too many phages reduced the overall inhibition. This study elaborates an effective and sequential method for the preparation of a phage cocktail and evaluates its antimicrobial potential against biofilm forming XDR strains of P. aeruginosa.

Enhancement of anti-bactericidal and anti-biofilm activities of silver nanoparticles against multidrug-resistant enteric pathogens isolated from children with diarrhea

Background: Gastroenteritis has a significant mortality andmorbidity incidence in children globally. Antimicrobial resistance in Enterobacteriaceaeis a serious public health problem, especially in developing countries.Objective: The present study aimed to evaluate the anti-bacterial and anti-biofilmactivities of AgNPs alone and in combination with kanamycin against multidrug-resistant Enterobacteriaceae and P. aeruginosa isolated from diarrheal children.Materials and methods: 90 Enterobacteriaceae and P. aeruginosa isolates fromdiarrheal children were evaluated against 10 antibiotics. Minimum inhibitory doses ofAgNPs and kanamycin were determined using broth microdilution, synergistic wasdetermined using Checkerboard dilution tests, and the Calgary technique was used toanalyze biofilm development.Results: A total of 90 stool cultures were conducted for bacteria associated withdiarrhea among children attending some Baghdad hospitals. The findings revealed thatbacterial diarrhea was most often caused by E. coli 31 (34.5%), followed by S. typhi 19(21.1%), K. pneumoniae 14 (15.5%), P. aeruginosa 11 (12.2%) and S. sonnei 6 (6.7%),and significant variations between the strain&amp;#39;s species were discovered using statisticalanalysis (P &amp;lt; 0.05). The present study&amp;#39;s findings revealed that bacteria isolated fromchildren with diarrhea were spread significantly in age groups of 37–48 months andsignificantly different between age groups (P &amp;lt; 0.05), with a male/female ratio of0.57/1. Imipenem and amikacin were the most active antibiotics compared to penicillin,which was the least effective antibiotic. The combination of sublethal doses of AgNPswith sub-MIC (½MIC) of kanamycin exhibited substantial synergistic bactericidaleffects against MDR-Enterobacteriaceae. AgNPs inhibited biofilm formation by55%–65% for diarrhea-causing bacteria, while the combination of AgNPs withkanamycin demonstrated the strongest biofilm inhibition of around 80%–90% againstMDR-Enterobacteriaceae with a highly significant variation (P &amp;lt; 0.05).Conclusions: The outcomes of the research shows that the combination of AgNPs withkanamycin has remarkable synergistic bactericidal and anti-biofilm effectivenessagainst MDR-Enterobacteriaceae isolated from diarrheal children.

SELECTED PLANT ESSENTIAL OILS OF THE LAMIACEEAE AND APIACEAE FAMILY AS THE ANTIFUNGAL AGENTS IN THE VAPOUR PHASE AGAINST RHIZOPUS STOLONIFER AND RHIZOPUS ORYZAE ISOLATED FROM MOULDING BREADS

Species of the Rhizopus genus are often involved in the moulding of bread and bakery products. Essential oils (EOs) are a suitable alternative to extend the shelf life of food. This research was focused on testing the effect of selected EOs on the growth of Rhizopus species. Tested strains were isolated from mouldy breads. The antifungal activity of EOs against R. stolonifer and R. oryzae strains was determined by micro-atmospheric method (625 μL EO/L air) during 7 days of cultivation. Eight EOs, thyme, red thyme, savory, caraway, marjoram, wild thyme, and oregano 100% inhibited the growth of all strains. Basil, sage, and anise EOs only partially inhibited the growth of strains. Subsequently, the minimum inhibitory doses were determined using micro-atmospheric method. Minimal inhibition doses were 250 μL/L for thyme and red thyme EO, 250 and 500 μL/L for savory EO, 250 and 500 μL/L for oregano EO, 500 and ˃500 μL/L for wild thyme EO, ˃500 μL/L for caraway and marjoram EOs. Strains of the genus Rhizopus reacted differently to the presence of EOs. Thyme and red thyme were evaluated as the most effective EOs in this study.

ANTIFUNGAL ACTIVITY OF SELECTED ESSENTIAL OILS AGAINST RHIZOPUS STOLONIFER

Nowadays, it is very important to find out the protection of plant products as an alternative to synthetic fungicides. The promising alternative is the use of the essential oils (EOs). The aim of our research was to evaluate the antifungal effect of angelica (Angelica archangelica L.), anise (Pimpinella anisum L.), fennel (Foeniculum vulgare Miller.), camphore (Cinnamonum camphorum Nees &amp; Eberm), litsea (Litsea deccanensis L.), cumin (Carum carvi L.), dill (Anethum graveolens L.), thyme (Thymus vulgaris L.), mint (citrate) (Mentha citrata L.), mint (piperita) (Mentha piperita L.), laurel (Laurus nobilis L.), cinnamon (Cinnamomum zeylanicum L.) EOs against three isolates of the genus Rhizopus obtained from moldy plants source the chemical composition of selected EOs was determined by gas chromatography coupled with mass spectrometry (GC – MS) and by gas chromatography with flame ionization detector (GC – FID). The antifungal activity of EOs against the growth of Rhizopus spp. was investigated by gas diffusion method (625 μL/L of air). The mycelium growth inhibition was measured on the 2nd, 4th, and 7th days of cultivation. Six EOs: litsea, mint (citrata), mint (piperita), cumin, thyme and cinnamon completely inhibited the growth of all tested fungi. For these EOs the minimum inhibitory doses were determined. According to probit analyses, the most effective tested EO was thyme and the least effective was cumin. Our results indicated that EOs are effective in the vapor phase and had a potential antifungal activity against Rhizopus stolonifer strains. So, they could be utilized in novel biological fungicide development.

Antibacterial activity of medicinal plants against Streptococcus agalactiae

Streptococcus agalactiae, group B Streptococcus (GBS), infects and causes severe diseases in humans and numerous animal species, including fish, given its ability to cross the host-specific barrier. The emergence of antibiotic resistant GBS strains makes it necessary to look for alternatives to treat and prevent infections that it produces. The aim of the present study was to determine the antibacterial activity of ethanolic and aqueous extracts of medicinal plants from Misiones province, northeast Argentina, against GBS from humans and fish. We used human Streptococcus agalactiae ATCC® BAA-611™ and tilapia Streptococcus agalactiae ATCC® 51487™ strains. Minimum Inhibitory Dose (MID) was determined by the disc diffusion method. Minimum Inhibitory Concentration (MIC), Minimum Bactericidal Concentration (MBC), MBC/MIC ratio, drug synergism with commercial antibiotics, and resistance assays were determined with extracts that showed antibacterial activity. Medium Lethal Dose 50 (LD50) was determined by the Artemia salina assay. For ethanolic and aqueous Eugenia uniflora L. extracts, we obtained a MID = 0.5 mg.disc-1. For both extracts of Eugenia uniflora L., the MIC and MBC values were 1 mg.mL-1 and 5 mg.mL-1, respectively. The MICI (MBC/MIC ratio) = 5 qualified the action of these extracts as bacteriostatic. The drug synergism assay with ampicillin, erythromycin, and clindamycin combination and extracts showed indifference. The LD50 of the aqueous extract was 0.82 mg.mL-1 indicating moderate toxicity. This work is a first step to identify chemical compounds in native medicinal plants of Misiones, Argentina, that could mean an alternative for the treatment of Streptococcus agalactiae infections.

Efficacy of Amikacin and Meropenem on Colistin-Induced Klebsiella pneumoniae Persisters

Colistin-based antibiotic therapies have been recommended for the treatment of multidrug-resistant Klebsiella pneumoniae infections. During colistin treatment, persister cells that tolerate antibiotics may arise. Here we designed an in vitro study to assess the killing activity of colistin, meropenem, and amikacin on colistin-induced K. pneumoniae persisters in comparison with starvation-induced persisters. Colistin-induced persisters were generated under exposure to 10 × minimum inhibitory concentration dose of colistin, whereas starvation-induced persisters were produced by limitation of nutrients. In colistin-induced persisters, amikacin totally inhibited cell growth in 6 hours, whereas 98% of the cell population was inhibited by meropenem, and total eradication with meropenem was observed after 24 hours. Both antibiotics also inhibited metabolic activity >88%. The lack of killing effect under colistin exposure suggested to us that these cells could protect themselves from further colistin stress. There was no significant permeabilization change in the cellular membrane with all antibiotics. There was no killing effect on starvation-induced persister cells with the exposure to all antibiotics. In 6 hours, the metabolic activity of the persisters with meropenem and colistin increased 99% and 40%, respectively, whereas there was no increase with amikacin. The sustained inhibition with amikacin was an important finding for antipersister effect of amikacin. Amikacin had rapid and sustained antipersister activity on colistin-induced persister cells. During the colistin treatment of K. pneumoniae infection, the addition of amikacin to the regimen seems to be an effective approach to prevent a recurrence.

Antioxidant and antifungal properties of essential oils of oregano (Origanum vulgare) and mint (Mentha arvensis) against Aspergillus flavus and Penicillium commune for use in food preservation

This study determined the chemical composition and evaluated the antioxidant activity and antifungal properties of essential oils of oregano (Origanum vulgare) and mint (Mentha arvensis) against the fungi Aspergillus flavus and Penicillium commune as possible alternatives for food preservation. The antimicrobial activity of both oils is shown by their minimum inhibitory concentration (4 mg/mL) for oregano oil, and (8 mg/mL) for mint oil, and minimum inhibitory dose (< 110 µl/L) for oregano oil, and (< 1500 µL/L) for mint oil. In addition, both oils presented antioxidant activity superior to 70% at the concentrations of 0.5 mg/mL for oregano oil and 30 mg/mL for mint oil after 360 min of reaction. As a control, the oils were evaluated for their cytotoxic potential using cells in culture and the method based on mitochondrial activity. Both oils were cytotoxic to both cell lines tested, with cells' survival rates less than 20% when in contact with 25 μg/mL of oils concentrations. Overall, the essential oils have activity against Aspergillus flavus and Penicillium commune, and their volatile components expressed high antifungal activity that expands their use for situations in which direct contact with the liquid is undesired. However, both essential oils showed high cytotoxicity.

English

The genome engineering methods have gained much appreciation for hitting plant disease resistance panorama since the last decade. The in vitro regeneration system is the foundation part of any research related to genetic engineering in plants. Hence, we established a tissue culture regime for efficient in vitro regeneration response of potato cultivar Lady Rosetta tagged with low to no resistance to late blight on foliage and medium to low resistance to late blight on tubers in potato. In this study, five callus induction media and seven regeneration media were investigated to get the best in vitro regeneration response in Lady Rosetta. Based on a statistical analysis of recorded data, the selected combination was CIM2-28 days old calli-RM7. The genetic fidelity of in vitro regenerated plants on a selected combination was assessed using the SSR markers. The wild-type and in vitro regenerated plants showed the same DNA profile. Moreover, a minimal inhibitory dose of basta was optimized for selecting genetically transformed plants in potato, and a 9mg /L basta dose was selected.

Biological Activity and Antibiofilm Molecular Profile of Citrus aurantium Essential Oil and Its Application in a Food Model.

The main aim of the study was to investigate the chemical composition, antioxidant, antimicrobial, and antibiofilm activity of Citrus aurantium essential oil (CAEO). The biofilm profile of Stenotrophonomonas maltophilia and Bacillus subtilis were assessed using the mass spectrometry MALDI-TOF MS Biotyper and the antibiofilm activity of Citrus aurantium (CAEO) was studied on wood and glass surfaces. A semi-quantitative composition using a modified version was applied for the CAEO characterization. The antioxidant activity of CAEO was determined using the DPPH method. The antimicrobial activity was analyzed by disc diffusion for two biofilm producing bacteria, while the vapor phase was used for three penicillia. The antibiofilm activity was observed with the agar microdilution method. The molecular differences of biofilm formation on different days were analyzed, and the genetic similarity was studied with dendrograms constructed from MSP spectra to illustrate the grouping profiles of S. maltophilia and B. subtilis. A differentiated branch was obtained for early growth variants of S. maltophilia for planktonic cells and all experimental groups. The time span can be reported for the grouping pattern of B. subtilis preferentially when comparing to the media matrix, but without clear differences among variants. Furthermore, the minimum inhibitory doses of the CAEO were investigated against microscopic fungi. The results showed that CAEO was most active against Penicillium crustosum, in the vapor phase, on bread and carrot in situ.

The in vitro and in situ effect of selected essential oils in vapour phase against bread spoilage toxicogenic aspergilli

The major objective of this study was to determine the antifungal, anti-toxicogenic and anti-sporulation effect of selected essential oils in the control growth of Aspergillus spp. by contact vapour method in in vitro and in situ condition. In continue, the effect of the essential oils treatment on the sensory profile of the bread was evaluated. In this study, ten essential oils (EOs), namely: thyme, clove, laveder, cumin, oregano, cinnamon, basil, rosemary, sage and lemongrass were tested against four strains of Aspergillus [Aspergillus flavus (SLO-B-201), Aspergillus parasiticus (SLO-B-219), Aspergillus ochraceus (SLO-B-245) and Aspergillus westerdijkiae (SLO-B-249)] isolated from bread samples. The Aspergillus strains were tested for potential production of mycotoxins by thin layer chromatography (TLC). The chemical composition of all tested EOs was identified by GC-MS and by gas chromatography with flame ionization detector (GC-FID). The antifungal activity, the minimum inhibitory doses (MIDs), anti-toxicogenic and antisporulation effect of the selected EOs were investigated by gas diffusion method in both, in vitro and in situ analyses. The results indicated that the thyme, clove, oregano, cinnamon and lemongrass were highly effective against tested toxigenic Aspergillus species in vapour phase. A treated bread sample with EOs does not have negative effect on the sensory properties of the breads, with exception of oregano and lemongrass. In this context, application EOs in vapour phase seems to be an effective, sustainable and safe method and promising alternative to the use of chemical inhibitors for bread preservation.

Incubation period induced biogenic synthesis of PEG enhanced Moringa oleifera silver nanocapsules and its antibacterial activity

Human pathogenic diseases are on the rage in the list of enfeebling diseases globally. The endless quest to salvage these drug-resistant pathogens ravaging our system through various therapies still posts serious challenge. This study engaged a biogenic synthesis that is benign, facile, biocompatible, cost-effective and eco-friendly to synthesized silver nanocapsule (AgNCs) via Moringa oleifera aqueous extract under incubation control. The flavonoid-kaempferol, phenolic-chlorogenic acid and tannin components of MO acted as the potential stabilizing and reducing agent in the formation of AgNCs. The formulated AgNCs was further functionalized with PVA, PVP and PEG for biocompatibility and dispersion enhancement. Various characterization techniques were used to determine the properties of AgNCs formulated. The absorbance due to the color change was observed by the UV-Visible spectroscopy with surface plasmons resonance peak between 425 and 455 nm. The Fourier transform infrared spectroscopy (FTIR) shows the various functional group responsible for the biogenic synthesis of AgNCs. The X-ray spectroscopy analysis shows a single phase cubic structure of AgNCs formed. The Scanning electron microscopy (SEM) image shows a rod-like nanocapsule of uniform grains. The antibacterial potency of AgNCs was proven against gram-positive (Staphylococcus aureus) and Gram-negative (Escherichia coli and Coliform). The AgNCs inhibited the growth of the three human pathogens with Coliform showing the highest activity to the AgNCs with a minimum inhibitory dose of 15 μg/mL. It is noteworthy that the bacterial strains show functional susceptibility to the AgNCs at lower concentrations compared to the conventional antibacterial drugs. Consequently, AgNCs serve as an enhanced substitute for the conventional antibacterial drugs in therapeutic biomedical field sequel to its pharmacodynamics against the bacterial strains.

One-pot facile synthesis of silk sericin-capped gold nanoparticles by UVC radiation: Investigation of stability, biocompatibility, and antibacterial activity.

Herein, an easy one-pot synthesis method for gold nanoparticles (AuNPs), involving only gold salt and sericin extracted from silkworm cocoon in the presence of ultraviolet C (UVC) radiation, was developed. Nanoparticle formation was confirmed by characteristic surface plasmon resonance peaks at 520-540 nm wavelengths, and the influence of silk sericin on enhancing the colloidal stability of AuNPs was confirmed. Transmission electron microscopy examination showed the average size (<10 nm) and size distribution decreased significantly with higher sericin concentration. No antibacterial activity was observed on Gram-positive Bacillus subtilis or Gram-negative Escherichia coli for sole AuNPs (0.065-0.26 mg/ml), but the conjugation of AuNPs with streptomycin antibiotic decreased significantly the required minimum inhibitory concentration doses, as also confirmed with agar plating, Scanning Electron Microscopy and Atomic Force Microscopy analyses. Furthermore, sericin-capped AuNPs showed high cell viabilities (>100%) and no sign of any detectable apoptosis or necrosis in 1-day incubation. Also, high real-time cell proliferation results of AuNPs competitive with positive control groups implied excellent in vitro biocompatibility. These results evidenced that sericin enhanced the colloidal stability of AuNPs and the biological activities of sericin-capped AuNPs reported here could render them suitable nanoscale vehicles for biomedical applications.

Effect of essential oils of Myrtaceae plants on the Penicillium commune

The aim of this research was to determine the inhibitory effect of vapor phase of five essential oils (EOs) on the growth of seven strains of Penicillium commune isolated from moldy milk products. Another objective was to determine the minimum inhibitory doses (in vitro and probit analyses) of EOs, which at concentration 625 μL.L-1 of air completely inhibited the growth of all strains. The antifungal activity was evaluated by the micro-atmosphere method. The essential oils used in this study were extract of plants from family Myrtaceae. Only one essential oil – clove (from Syzygium aromaticum L.; leaves) completely inhibited the growth of all strains during cultivation at 25 °C and 5 °C. Eucalyptus essential oil (from Eucaliptus globulus; leaves), tea tree essential oil (from Melaleuca alternifolia Cheel; leaves), cajeput essential oil (from Melaleuca leucadendra L.; leaves and twigs), niaouli essential oil (from Melaleuca quinquenervia (Cav.) S.T.Blake; leaves) have different effects on the growth of P. commune strains. The order of tested essential oils according to the inhibition effect on the growth of the strains of P. commune (from the strongest to the weakest effect) was: clove &gt; tea tree &gt; cajeput &gt; niaouli &gt; eucalyptus. Clove EO that completely inhibited the growth of all strains was used to determine minimum inhibitory doses (MIDs). The MIDs were 125 µL.L-1 of air for two strains of P. commune and 250 µL.L-1 of air for five strains of P. commune on the 7th and 14th day of cultivation, also. Using probit analysis, predicted MIDs90 and MIDs50 were calculated. The MIDs90 were determined from 104.93 to 301.37 µL.L-1 of air.

Acibenzolar-S-methyl against Botrytis mold on table grapes in vitro and in vivo

The objective of this work was to investigate the effect of the resistance inducer Acibenzolar-S-methyl (ASM), against Botrytis mold on table grapes in vitro and in vivo. To assess the effect of ASM on mycelial growth Botrytis cinerea, different concentrations (0.125, 0.25, 0.5, 1.0, 2.0 and 3% w:v) were tested. Treatments were set up in triplicate, in a completely randomized experimental design, and replicated twice. Results were expressed in minimum inhibitory concentrations and effective dose per 50% response of mycelial growth. Healthy table grapes (cvs. Italia and Benitaka) were harvested at full ripe to evaluate the ASM 1% effect against gray mold under artificial conditions. Bunches were split into two groups in order to perform two types of experiments (spray or immersion). For both trials, treated bunches were arranged in carton boxes and stored at 2±1 °C, for one month, followed by one week of shelf-life at 22±2 °C. In order to evaluate the ASM effect against gray mold under field conditions, ASM 1% was sprayed on both cultivars one week before harvest. Grapes treated with iprodione 0.2% with three applications during the season were included as a standard chemical control. Bunches were harvested at full ripe, arranged in carton boxes and submitted to a cold storage process as described previously. Results for the in vitro experiments showed that the minimum inhibitory concentration of ASM was achieved by 3% and the ED50 was 0.04%. Under artificial conditions, for both cultivars, the efficacy of ASM was higher when the grapes were immersed than sprayed. A significant difference was observed for ASM as compared with control. Regarding the effect of ASM against gray mold in the field, the incidence of gray mold was recorded for both cultivars. For ‘Italia’ and ‘Benitaka’ grapes, ASM, iprodione and sulfur dioxide pad reduced the incidence of gray mold by 85, 79 and 77%, and by 80.5, 73 and 82%, respectively. As for the physico-chemical berry properties, none of the treatments were significantly different from the control for total soluble solids, titratable acidity and color index. A single ASM treatment applied one week before harvest is effective for controlling gray mold in ‘Italia’ and ‘Benitaka’ table grapes.