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Agar Diffusion Method (agar + diffusion_method)
Selected AbstractsComparative study on the antimicrobial activities of different sandalwood essential oils of various originFLAVOUR AND FRAGRANCE JOURNAL, Issue 3 2006Leopold Jirovetz Abstract In total, eight samples of different sandalwoods [Amyris balsamifera L., Santalum album L. and Santalum spicatum (R.Br.) A.DC.] and a mixture of , - and , -santalols, as well as eugenol as reference compound, were tested by an agar dilution and agar diffusion method for their antimicrobial activities against the yeast Candida albicans, the Gram-positive bacterium Staphylococcus aureus and the Gram-negative bacteria Escherichia coli, Pseudomonas aeruginosa and Klebsiella pneumoniae. The main compounds of each essential oil were investigated by gas chromatographic,spectroscopic (GC-FID and GC,MS) and ,olfactory methods to obtain information about the inßuence of these volatiles on the observed antimicrobial effects. For the santalol mixture, as well as for one S. album and one S. spicatum sample with moderate concentrations of santalols, antimicrobial activity was found against all the strains used. The A. balsamifera sample, containing only a small quantity of , -santalol and nearly no , -santalol, showed high effects only against Klebsiella pneumoniae, while against the other strains weak or no activity was observed. Therefore, santalols in medium and/or high concentrations in sandalwood oils show a significant inßuence on antimicrobial potential in such natural products. Copyright © 2006 John Wiley & Sons, Ltd. [source] Composition and antimicrobial activity of essential oil of Stachys plumosa Griseb.FLAVOUR AND FRAGRANCE JOURNAL, Issue 2 2006Silvana Petrovi Abstract The essential oil of Balkan endemic Stachys plumosa Griseb. obtained by steam distillation was analysed by GC and GC,MS. Essential oil yield was 0.15% (v/w) and 45 components were identified (86.9% of the total amount). Dehydroabietane was identified as the most prominent component (61.2%), while other constituents were present in much lower quantity, predominantly diterpenes kaurene and biformene (3.2% and 3.0%, respectively). The antimicrobial activity was tested on six bacterial strains and two fungal strains, using the agar diffusion method. Diameters of growth inhibition zones were measured. The most sensitive microorganisms were, in order: Pseudomonas aeruginosa > Bacillus subtilis > Enterococcus faecalis > Klebsiella pneumoniae > Candida albicans (ATCC 10259) > Candida albicans (ATCC 24433) > Escherichia coli > Staphylococcus aureus. Copyright © 2005 John Wiley & Sons, Ltd. [source] INHIBITION OF HELICOBACTER PYLORI BY PHENOLIC EXTRACTS OF SPROUTED PEAS (PISUM SATIVUM L.)JOURNAL OF FOOD BIOCHEMISTRY, Issue 1 2006CHIA-YU HO ABSTRACT Infection by Helicobacter pylori is associated with gastric and duodenal ulcers. Conventional treatments to eradicate it have side-effects such as diarrhea and dizziness. The excessive use of antibiotics could also lead to antibiotic-resistant bacteria. The use of plant phenolic phytochemicals can be an alternative because of their health benefits due to both antioxidant activity and antimicrobial activity. The pea (Pisum sativum), the world's second most important pulse crop, produces phenolic phytochemicals with antimicrobial potential. Because the synthesis of phenolic compounds increases with stress, we investigated the anti- H. pylori effectiveness of extracts from pea sprouts, germinated in the dark condition following treatment with either distilled water or acetyl salicylic acid. The peas were germinated for 8 days and the sprouted samples were measured for total soluble phenolic content, antioxidant and guaiacol peroxidase activity. Subsequently, the sprout extracts were tested for anti- H. pylori activity using the agar diffusion method and the effective dose was determined based on phenolic content. The results showed that both acetyl salicylic acid-treated and untreated pea sprouts at days 5 and 8 had anti- H. pylori activity. The minimum volume for inhibition was 50 ,L of extracts. The inhibitory effects were dose dependent. From this study, the potential to use natural phenolic phytochemicals from pea sprouts to control H. pylori was found to be promising. This provides a strategy and foundation to design legume phenolics as functional ingredients against H. pylori. [source] INHIBITION OF FOODBORNE PATHOGENS AND SPOILING BACTERIA BY ESSENTIAL OIL AND EXTRACTS OF ERIGERON RAMOSUS (WALT.) B.S.P.JOURNAL OF FOOD SAFETY, Issue 2 2009ATIQUR RAHMAN ABSTRACT The antibacterial potential of essential oil and methanolic extracts of Erigeron ramosus (Walt.) B.S.P. was evaluated. Thirty-one components representing 95.3% of the total oil were identified, of which ,-caryophyllene (24.0%), ,-humulene (14.5%), 1,8-cineole (9.0%), eugenol (7.2%), globulol (7.1%), caryophyllene oxide (5.2%), ,-cadinene (5.0%), ,-copaene (4.9%) and widdrol (2.0%) were the major components. The antibacterial activity of essential oil and methanolic extracts of E. ramosus was determined in vitro using the agar diffusion method and minimum inhibitory concentration determination test against 14 (seven gram-positive and seven gram-negative) foodborne bacteria. The essential oil (5 µL/mL, corresponding to 1,000 ppm/disc), methanol extract and its different organic subfractions (7.5 µL/mL, corresponding to 1500 ppm/disc) of E. ramosus displayed a great potential of antibacterial activity against all gram-positive bacteria: Staphylococcus aureus (ATCC 6538 and KCTC 1916), Listeria monocytogenes (ATCC 19116, ATCC 19118, ATCC 19166 and ATCC 15313) and Bacillus subtilis ATCC 6633 and four gram-negative bacteria: Pseudomonas aeruginosa KCTC 2004, Enterobacter aerogenes KCTC 2190 and Escherichia coli (0157:H7 ATCC 43888 and ATCC 8739). The zones of inhibition of different concentrations of essential oil and methanolic extracts against the tested bacteria were found in the range of 10.1,22.3 mm, and MIC values were recorded between 62.5 and 500 µg/mL. PRACTICAL APPLICATIONS The use of essential oil and organic extracts of Erigeron ramosus (Walt.) B.S.P. as antibacterial agents will be suitable for applications on the food industry as natural preservatives or flavoring to control foodborne pathogens. They can be used as growth inhibitors of Listeria monocytogenes, Staphylococcus aureus, Bacillus subtilis, Escherichia coli, Enterobacter aerogenes and Pseudomonas aeruginosa, some important foodborne pathogens and spoiling bacteria. The main reason for their suitability is their natural origin, which consumers find comforting and which is beneficial for the environment, and the very low risk that pathogens will develop resistance to the mixture of components that make up the oil and extracts with their apparent diversity of antibacterial mechanisms. These beneficial characteristics could increase food safety and shelf life. [source] Heterogeneity in antifungal susceptibility of clones of Candida albicans isolated on single and sequential visits from a HIV-infected southern Chinese cohortJOURNAL OF ORAL PATHOLOGY & MEDICINE, Issue 6 2001Y. H. Samaranayake Abstract: The increased frequency and severity of candidal infections in human immunodeficiency virus (HIV)-infected individuals has prompted the wide use of antifungals, such as amphotericin B, ketoconazole, and fluconazole, resulting in the emergence of drug-resistant strains of Candida albicans. To study this phenomenon in an ethnic Chinese cohort, we isolated multiple colonies of Candida from the oral cavities of 16 HIV-infected patients on single and subsequent sequential visits over a period of 12 months. Ten of the 16 patients had sporadic episodes of oropharyngeal candidiasis (Group A), while the remainder were asymptomatic with respect to this condition (Group B). Oral rinses were collected and immediately processed in the laboratory for the isolation of C. albicans in a standard manner. A total of 433 C. albicans isolates were tested for their susceptibility to amphotericin B, ketoconazole and fluconazole by an agar diffusion method using the commercially available E-test. All tested isolates demonstrated variable susceptibility to amphotericin B, ketoconazole and fluconazole. The minimum inhibitory concentration (MIC) of the isolates for amphotericin B, ketoconazole and fluconazole ranged from <0.002,1.5 ,g/ml, <0.002,4.0 ,g/ml and <0.016,32 ,g/ml, respectively. Sequential isolates of a few patients demonstrated variable susceptibility to all the antifungals, and no discernible MIC pattern emerged either in group A or B over time. Interestingly, significant variation in antifungal susceptibility was also noted in isolates obtained from the same patient on a single visit. Sequential yeast isolates in 9 of 16 patients (56%) demonstrated significant differences in MIC within and between visits for both amphotericin B and ketoconazole, while a lower percentage , 44% (7/16) , exhibited this trait for fluconazole. Our study demonstrates the diversity in antifungal susceptibility in either commensal or "infective" oral strains of C. albicans in HIV disease, and shows the need for vigilance for the emergence of resistant strains, and for frequent antifungal susceptibility studies. [source] In vitro anti- Helicobacter pylori potential of methanol extract of Allium ascalonicum Linn. (Liliaceae) leaf: susceptibility and effect on urease activityPHYTOTHERAPY RESEARCH, Issue 5 2004Bolanle A. Adeniyi Abstract The crude methanol extract of the leaf of Allium ascalonicum was screened in vitro against ,ve strains of Helicobacter pylori (Hp) (ATCC 24376, UCH 97001, UCH 97009, UCH 98026 and UCH 99039) for antibacterial activity by the agar diffusion method in Mueller-Hinton agar supplemented with de,brinated horse blood. All the strains were inhibited by the extract to varying degrees. The minimum inhibitory concentrations (MICs) of the extract against all the tested strains ranged from 6.25 to 12.5 mg/mL. The effects of increasing concentrations of the extract on the urease activity of three of the Helicobacter pylori strains were investigated further. The results showed that increasing the concentration of the extract decreased the urease activity of all the strains tested. Phytochemical screening of the plant showed that it contains alkaloids, cardiac glycosides and saponins. The anti-Hp activity observed is discussed in relation to the chemical constituents reportedly isolated from these plants and their traditional uses. The result of this work suggests that Allium ascalonicum has some therapeutic potential against Helicobacter pylori infection, which could be explored for patients with gastroduodenal disorders. Copyright © 2004 John Wiley & Sons, Ltd. [source] Evaluations of lactic acid bacteria as probiotics for juvenile seabass Lates calcariferAQUACULTURE RESEARCH, Issue 2 2008Sirirat Rengpipat Abstract Lactic acid bacteria (LAB) were isolated from adult, wild-caught and farmed seabass (Lates calcarifer) intestines for evaluation as possible probiotics using the well agar diffusion method. Five LAB isolates (designated as LAB-1,5) were found to inhibit Aeromonas hydrophila, a known seabass pathogen. Median lethal concentrations (LC50) of A. hydrophila on juvenile seabass were measured in aquaria. Median lethal concentration values of 7.76, 7.47 and 7.26 log10 CFU mL,1 for 72, 96 and 120 h, respectively, were found. Juvenile seabass (0.6±0.2 g) were cultured in aquaria and fed individual LAB-1,5 fortified feeds with 7 log10 CFU g,1 LAB. Seabass fed LAB-4 fortified feed had significantly greater growth (P<0.05) than fish fed other feeds. Seabass fed LAB-4 also had greater survival, but this was non-significant (P<0.05). Challenge tests of LAB-4 fed seabass with A. hydrophila at ,7 log10CFU mL,1 yielded significantly greater survival compared with control seabass (P<0.05). Aeromonas hydrophila infections in seabass were confirmed by observing disease manifestation and by immunohistochemistry techniques. LAB-4 was preliminarily identified using lactic acid analysis, biochemical and physical characteristics. It was further identified using 16S rDNA sequencing. LAB-4 was identified as Weissella confusa (identity of 99%). GenBank accession number for the 16S rDNA sequence for LAB-4 was AB023241. [source] | |||||||||||||