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Agar Surfaces (agar + surface)
Selected AbstractsRAPA: a novel in vitro method to evaluate anti-bacterial skin cleansing productsINTERNATIONAL JOURNAL OF COSMETIC SCIENCE, Issue 2 2010S. A. Ansari Synopsis Development of efficacious anti-bacterial skin cleansing products has been limited by the availability of a pre-clinical (in vitro) method to predict clinical efficacy adequately. We report a simple and rapid method, designated as rapid agar plate assay (RAPA), that uses the bacteriological agar surface as a surrogate substrate for skin and combines elements of two widely used in vivo (clinical) methods (Agar Patch and Cup Scrub). To simulate the washing of the human hand or forearm skin with the test product, trypticase soy agar plates were directly washed with the test product and rinsed under running tap water. After air-drying the washed plates, test bacteria (Staphylococcus aureus or Escherichia coli) were applied and the plates were incubated at 37°C for 18,24 h. Using S. aureus as the test organism, anti-bacterial bar soap containing triclocarbanilide showed a strong linear relationship (R2 = 0.97) between bacterial dose and their per cent reduction. A similar dose-response relationship (R2 = 0.96) was observed for anti-bacterial liquid hand soap against E. coli. RAPA was able to distinguish between anti-bacterial products based on the nature and level of actives in them. In limited comparative tests, results obtained by RAPA were comparable with the results obtained by clinical agar patch and clinical cup scrub methods. In conclusion, RAPA provides a simple, rugged and reproducible in vitro method for testing the relative efficacy of anti-bacterial skin cleansing products with a likelihood of comparable clinical efficacy. Further testing is warranted to improve the clinical predictability of this method. Résumé Le développement des produits de nettoyage de peau antibactérienne efficace a été limité par la disponibilité d'une méthode (in vitro) préclinique pour prévoir en juste proportion l'efficacité clinique. Nous rapportons une méthode simple et rapide, indiquée comme analyse rapide de plat d'agar (RAPA) ce des utilisations la surface bactériologique d'agar comme substrat de remplacement pour la peau et combinons des éléments de deux méthodes (cliniques) in vivo employées couramment (correction d'agar et la tasse frottent). Pour simuler le lavage de la peau humaine de main ou d'avant-bras avec le produit d'essai, des plats de l'agar de soja de trypticase ont été directement lavés avec le produit d'essai et rincés sous l'eau du robinet courante. Après l'air séchant les plats lavés, les bactéries d'essai (S. doré Ou Escherichia coli) étaient appliquées et des plats ont été incubées au °C 37 pendant 18,24 heures. Utilisant S. doré Comme organization d'essai, le triclocarbanilide contenant du savon de barre antibactérienne a montré un rapport linéaire fort (R2 = 0.97) entre la dose bactérienne et leur réduction de pour cent. On a observé un rapport semblable de réponse à dose donnée (R2 = 0.96) pour le savon liquide antibactérien de main contre E. coli. RAPA pouvait distinguer les produits antibactériens basés sur la nature et le niveau des actives dans eux. Dans les essais comparatifs limités, résultats obtenus par RAPA étaient comparables aux résultats obtenus par la correction clinique d'agar et la tasse clinique frottent des méthodes, en conclusion, RAPA fournit à une méthode in vitro simple, raboteuse et reproductible pour examiner l'efficacité relative des produits de nettoyage de peau antibactérienne la probabilité de l'efficacité clinique comparable. Davantage d'essai est justifié pour améliorer la prévisibilité clinique de cette méthode. [source] DIRECT PLATING: A METHOD FOR DETECTING FUNGAL CONTAMINATION IN PAPERBOARD CARTONSJOURNAL OF FOOD SAFETY, Issue 3 2001JAN A. NARCISO ABSTRACT Contamination of refrigerated juice products in gable-top cartons can occur by filamentous fungi that are present in the paperboard. A method was developed to assay the mycoflora of paperboard carton material used in beverage packaging. This method involved direct plating on an agar surface of 1 cm2 carton pieces rather than disintegration of carton material in a blender prior to plating. When compared to the standard disintegration method traditionally used for monitoring contamination of paperboard, the new method is less cumbersome, more efficient, and reduces opportunities for contamination. The number of colonies produced by the direct plating method was greater than or equal to the modified standard disintegration method. Direct plating also resulted in a larger number of different genera isolated. [source] Phenotypic diversity of Flo protein family-mediated adhesion in Saccharomyces cerevisiaeFEMS YEAST RESEARCH, Issue 2 2009Sebastiaan E. Van Mulders Abstract The Saccharomyces cerevisiae genome encodes a Flo (flocculin) adhesin family responsible for cell,cell and cell,surface adherence. In commonly used laboratory strains, these FLO genes are transcriptionally silent, because of a nonsense mutation in the transcriptional activator FLO8, concealing the potential phenotypic diversity of fungal adhesion. Here, we analyse the distinct adhesion characteristics conferred by each of the five FLO genes in the S288C strain and compare these phenotypes with a strain containing a functional copy of FLO8. Our results show that four FLO genes confer flocculation, but with divergent characteristics such as binding strength, carbohydrate recognition and floc size. Adhesion to agar surfaces, on the other hand, largely depended on two adhesins, Flo10 and Flo11. Expression of any FLO gene caused a significant increase in cell wall hydrophobicity. Nevertheless, the capacity to adhere to plastic surfaces, which is believed to depend on hydrophobic interactions, differed strongly between the adhesins. Restoring Flo8 yielded both flocculation and cell,surface adherence, such as invasive growth, a phenotype not observed when any of the single FLO genes was overexpressed. Taken together, this study reveals how S. cerevisiae carries a small reservoir of FLO genes that allows cells to display a wide variety of adhesive properties. [source] Investigation of critical inter-related factors affecting the efficacy of pulsed light for inactivating clinically relevant bacterial pathogensJOURNAL OF APPLIED MICROBIOLOGY, Issue 5 2010H.P. Farrell Abstract Aims:, To investigate critical electrical and biological factors governing the efficacy of pulsed light (PL) for the in vitro inactivation of bacteria isolated from the clinical environment. Development of this alternative PL decontamination approach is timely, as the incidence of health care,related infections remains unacceptably high. Methods and Results:, Predetermined cell numbers of clinically relevant Gram-positive and Gram-negative bacteria were inoculated separately on agar plates and were flashed with ,60 pulses of broad-spectrum light under varying operating conditions, and their inactivation measured. Significant differences in inactivation largely occurred depending on the level of the applied lamp discharge energy (range 3·2,20 J per pulse), the amount of pulsing applied (range 0,60 pulses) and the distance between light source and treatment surface (range 8,20 cm) used. Greater decontamination levels were achieved using a combination of higher lamp discharge energies, increased number of pulses and shorter distances between treatment surface and the xenon light source. Levels of microbial sensitivity also varied depending on the population type, size and age of cultures treated. Production of pigment pyocynanin and alginate slime in mucoid strains of Pseudomonas aeruginosa afforded some protection against lethal action of PL; however, this was evident only by using a combination of reduced amount of pulsing at the lower lamp discharge energies tested. A clear pattern was observed where Gram-positive bacterial pathogens were more resistant to cidal effects of PL compared to Gram negatives. While negligible photoreactivation of PL-treated bacterial strains occurred after full pulsing regimes at the different lamp discharge energies tested, some repair was evident when using a combination of reduced pulsing at the lower lamp discharge energies. Strains harbouring genes for multiple resistances to antibiotics were not significantly more resistant to PL treatments. Slight temperature rises (,4·2°C) were measured on agar surfaces after extended pulsing at higher lamp discharge energies. Presence of organic matter on treatment surface did not significantly affect PL decontamination efficacy, nor did growth of PL-treated bacteria on selective agar diminish survival compared to similarly treated bacteria inoculated and enumerated on nonselective agar plates. Conclusions:, Critical inter-related factors affecting the effective and repeatable in vitro decontamination performance of PL were identified during this study that will aid further development of this athermal process technology for applications in health care and in industry. Very rapid reductions (c. 7 log10 CFU cm,2 within ,10 pulses) occurred using discharge energy of 20 J for all tested clinically relevant bacteria under study when treated at 8 cm distance from xenon light source. While no resistant flora is expected to develop for treatment of microbial pathogens on two-dimensional surfaces, careful consideration of scale up factors such as design and operational usage of this PL technique will be required to assure operator safety. Significance and Impact of the Study:, Findings and conclusions derived from this study will enable further development and optimization of this decontamination technique in health care and in food preparation settings, and will advance the field of nonthermal processing technologies. [source] Dormant ascospores of Talaromyces macrosporus are activated to germinate after treatment with ultra high pressureJOURNAL OF APPLIED MICROBIOLOGY, Issue 1 2004J. Dijksterhuis Abstract Aims:, Ascospores of Talaromyces macrosporus are constitutively dormant and germinate after a strong external shock, classically a heat treatment. This fungus is used as a model system to study heat resistance leading to food spoilage after pasteurization. This study evaluates the effect of high pressure on the germination behaviour of these spores. Methods and Results:, Ascospore containing bags were subjected to ultra high pressure and spores were plated out on agar surfaces. Untreated suspensions showed invariably very low germination. Increased germination of ascospores occurred after short treatments at very high pressure (between 400 and 800 MPa). Activation is partial compared with heat activation and did not exceed 6·9% (65 times that of untreated suspensions) of the spore population. Maximum activation was attained shortly (10 s,3 min) after the pressure was applied and accompanied by cell wall deformations as judged by scanning electron microscopy. The spores observed in this study were harvested from cultures that were 39,58 days old. The maturity of spores at similar developmental stages was measured by assessing the heat resistance of ascospores. Between 20 and 40 days heat resistance increased 2·4-fold, but only an additional increase of 1·3-fold was observed at later stages (40,67 days). Conclusions:, Our investigations show that high pressure constitutes a second type of shock that can activate heat-resistant ascospores to germinate. Activation is maximal after very short treatments and accompanied with changes in the cell wall structure. High-pressure activation is not the result of immaturity of the ascospores. Significance and Impact of the Study: These observations are relevant for the application of high pressure as a novel pasteurization method. [source] WVD2 is a novel microtubule-associated protein in Arabidopsis thalianaTHE PLANT JOURNAL, Issue 6 2007Robyn M. Perrin Summary Arabidopsis WAVE-DAMPENED 2 (WVD2) was identified by forward genetics as an activation-tagged allele that causes plant and organ stockiness and inversion of helical root growth handedness on agar surfaces. Plants with high constitutive expression of WVD2 or other members of the WVD2-LIKE (WDL) gene family have stems and roots that are short and thick, have reduced anisotropic cell elongation, are suppressed in a root-waving phenotype, and have inverted handedness of twisting in hypocotyls and roots compared with wild-type. The wvd2-1 mutant shows aberrantly organized cortical microtubules in peripheral root cap cells as well as reduced branching of trichomes, unicellular leaf structures whose development is regulated by microtubule stability. Orthologs of the WVD2/WDL family are found widely throughout the plant kingdom, but are not similar to non-plant proteins with the exception of a C-terminal domain distantly related to the vertebrate microtubule-associated protein TPX2. in vivo, WVD2 and its closest paralog WDL1 are localized to interphase cortical microtubules in leaves, hypocotyls and roots. Recombinant glutathione- S -transferase:WVD2 or maltose binding protein:WVD2 protein bind to and bundle microtubules in vitro. We speculate that a C-terminal domain of TPX2 has been utilised by the WVD2 family for functions critical to the organization of plant microtubules. [source] | ||||||||||