926 research outputs found
Exopolysaccharide Matrix Of Developed Candida Albicans Biofilms After Exposure To Antifungal Agents
No full textThis study aimed to evaluate the effects of fluconazole or nystatin exposure on developed Candida albicans biofilms regarding their exopolysaccharide matrix. The minimal inhibitory concentration (MIC) against fluconazole or nystatin was determined for C. albicans reference strain (ATCC 90028). Poly(methlymethacrylate) resin (PMMA) specimens were fabricated according to the manufacturer's instructions and had their surface roughness measured. Biofilms were developed on specimens surfaces for 48 h and after that were exposed during 24 h to fluconazole or nystatin prepared in a medium at MIC, 10 x MIC or 100 x MIC. Metabolic activity was evaluated using an XTT assay. Production of soluble and insoluble exopolysaccharide and intracellular polysaccharides was evaluated by the phenol-sulfuric method. Confocal laser scanning microscope was used to evaluate biofilm architecture and percentage of dead/live cells. Data were analyzed statistically by ANOVA and Tukey's test at 5% significance level. The presence of fluconazole or nystatin at concentrations higher than MIC results in a great reduction of metabolic activity (p0.05). The exposure to nystatin also did not alter the exopolysaccharide matrix at all the tested concentrations (p>0.05). Biofilm architecture was not affected by either of the antifungal agents (p>0.05). Nystatin promoted higher proportion of dead cells (p<0.05). It may be concluded that fluconazole and nystatin above the MIC concentration reduced the metabolic activity of C. albicans biofilms; however, they were not able to alter the exopolysaccharide matrix and biofilm architecture.236716722Gendreau, L., Loewy, Z.G., Epidemiology and etiology of denture stomatitis (2011) J Prosthodont, 20, pp. 251-260Tobudic, S., Kratzer, C., Lassnigg, A., Presterl, E., Antifungal susceptibility of Candida albicans in biofilms (2012) Mycoses, 55, pp. 199-204Chaffin, W.L., Candida albicans cell wall proteins (2008) Microbiol Mol Biol Rev, 72, pp. 495-544Seneviratne, C.J., Jin, L., Samaranayake, L.P., Biofilm lifestyle of Candida: A mini review (2008) Oral Dis, 14, pp. 582-590Ramage, G., Rajendran, R., Sherry, L., Williams, C., Fungal biofilm resistance (2012) Int J Microbiol, , 528-521Chandra, J., Kuhn, D.M., Mukherjee, P.K., Hoyer, L.L., McCormick, T., Ghannoum, M.A., Biofilm formation by the fungal pathogen Candida albicans: Development, architecture, and drug resistance (2001) J Bacteriol, 183, pp. 5385-5394Konopka, K., Dorocka-Bobkowska, B., Gebremedhin, S., Duzgunes, N., Susceptibility of Candida biofilms to histatin 5 and fluconazole (2010) Antonie Van Leeuwenhoek, 97, pp. 413-417Baillie, G.S., Douglas, L.J., Effect of growth rate on resistance of Candida albicans biofilms to antifungal agents (1998) Antimicrob Agents Chemother, 42, pp. 1900-1905Niimi, M., Firth, N.A., Cannon, R.D., Antifungal drug resistance of oral fungi (2010) Odontology, 98, pp. 15-25Ramage, G., Mowat, E., Jones, B., Williams, C., Lopez-Ribot, J., Our current understanding of fungal biofilms (2009) Crit Rev Microbiol, 35, pp. 340-355Baillie, G.S., Douglas, L.J., Matrix polymers of Candida biofilms and their possible role in biofilm resistance to antifungal agents (2000) J Antimicrob Chemother, 46, pp. 397-403Seneviratne, C.J., Jin, L.J., Samaranayake, Y.H., Samaranayake, L.P., Cell density and cell aging as factors modulating antifungal resistance of Candida albicans biofilms (2008) Antimicrob Agents Chemother, 52, pp. 3259-3266da Silva, W.J., Seneviratne, J., Samaranayake, L.P., Del Bel Cury, A.A., Bioactivity and architecture of Candida albicans biofilms developed on poly (methyl methacrylate) resin surface (2010) J Biomed Mater Res B Appl Biomater, 94, pp. 149-156(2008) Reference Method For Broth Dilution Antifungal Susceptibility Testing of Yeasts, Approved Standard, , CLSI, CLSI Document M27-A3, Wayne, PA:CLSIda Silva, W.J., Seneviratne, J., Parahitiyawa, N., Rosa, E.A., Samaranayake, L.P., Del Bel Cury, A.A., Improvement of XTT assay performance for studies involving Candida albicans biofilms (2008) Braz Dent J, 19, pp. 364-369Tenuta, L.M., Ricomini, F.A.P., Del Bel Cury, A.A., Cury, J.A., Effect of sucrose on the selection of mutans streptococci and lactobacilli in dental biofilm formed in situ (2006) Caries Res, 40, pp. 546-549Dubois, M., Gilles, K., Hamilton, J.K., Rebers, P.A., Smith, F., A colorimetric method for the determination of sugars (1951) Nature, 28, p. 167. , 168Heydorn, A., Nielsen, A.T., Hentzer, M., Sternberg, C., Givskov, M., Ersboll, B.K., Quantification of biofilm structures by the novel computer program COMSTAT (2000) Microbiology, 146, pp. 2395-2407Force, R.W., Nahata, M.C., Salivary concentrations of ketoconazole and fluconazole: Implications for drug efficacy in oropharyngeal and esophageal candidiasis (1995) Ann Pharmacother, 29, pp. 10-15Gomes, P.N., da Silva, W.J., Pousa, C.C., Narvaes, E.A., Del Bel Cury, A.A., Bioactivity and cellular structure of Candida albicans and Candida glabrata biofilms grown in the presence of fluconazole (2011) Arch Oral Biol, 56, pp. 1274-1281Ellepola, A.N., Samaranayake, L.P., Oral candidal infections and antimycotics (2000) Crit Rev Oral Biol Med, 11, pp. 172-198Ellepola, A.N., Samaranayake, L.P., The postantifungal effect (PAFE) of antimycotics on oral C. albicans isolates and its impact on candidal adhesion (1998) Oral Dis, 4, pp. 260-267Nett, J.E., Sanchez, H., Cain, M.T., Andes, D.R., Genetic basis of Candida biofilm resistance due to drug-sequestering matrix glucan (2010) J Infect Dis, 202, pp. 171-175Mores, A.U., Souza, R.D., Cavalca, L., de Paula e Carvalho, A., Gursky, L.C., Rosa, R.T., Enhancement of secretory aspartyl protease production in biofilms of Candida albicans exposed to subinhibitory concentrations of fluconazole (2011) Mycoses, 54, pp. 195-201Goncalves, L.M., Del Bel Cury, A.A., Sartoratto, A., Garcia, R.V.L., Silva, W.J., Effects of undecylenic acid released from denture liner on Candida biofilms (2012) J Dent Res, 91, pp. 985-98
Levorotatory carbohydrates and xylitol subdue Streptococcus mutans and Candida albicans adhesion and biofilm formation
No full textDietary carbohydrates and polyols affect the microbial colonization of oral surfaces by modulating adhesion and biofilm formation. The aim of this study was to evaluate the influence of a select group of l-carbohydrates and polyols on either Streptococcus mutans or Candida albicans adhesion and biofilm formation in vitro. S. mutans or C. albicans suspensions were inoculated on polystyrene substrata in the presence of Tryptic soy broth containing 5% of the following compounds: d-glucose, d-mannose, l-glucose, l-mannose, d- and l-glucose (raceme), d- and l-mannose (raceme), l-glucose and l-mannose, sorbitol, mannitol, and xylitol. Microbial adhesion (2h) and biofilm formation (24h) were evaluated using MTT-test and Scanning Electron Microscopy (SEM). Xylitol and l-carbohydrates induced the lowest adhesion and biofilm formation in both the tested species, while sorbitol and mannitol did not promote C. albicans biofilm formation. Higher adhesion and biofilm formation was noted in both organisms in the presence of d-carbohydrates relative to their l-carbohydrate counterparts. These results elucidate, hitherto undescribed, interactions of the individually tested strains with l- and d-carbohydrates, and how they impact fungal and bacterial colonization. In translational terms, our data raise the possibility of using l-form of carbohydrates and xylitol for dietary control of oral plaque biofilms
Fungal species in endodontic infections : A systematic review and meta-analysis
No full textFungal infections are common on oral mucosae, but their role in other oral sites is ill defined. Over the last few decades, numerous studies have reported the presence of fungi, particularly Candida species in endodontic infections, albeit in relatively small numbers in comparison to its predominant anaerobic bacteriome. Here, we review the fungal biome of primary and secondary endodontic infections, with particular reference to the prevalence and behavior of Candida species. Meta-analysis of the available data from a total of 39 studies fitting the inclusion criteria, indicate the overall weighted mean prevalence (WMP) of fungal species in endodontic infections to be 9.11% (from a cumulative total of 2003 samples), with 9.0% in primary (n = 1341), and 9.3% in secondary infections (n = 662). Nevertheless, WMP for fungi in primary and secondary infections which were 6.3% and 7.5% for culture-based studies, increased to 12.5% and 16.0% in molecular studies, respectively. The most prevalent fungal species was Candida spp. The high heterogeneity in the reported fungal prevalence suggests the need for standardized sampling, and speciation methods. The advent of the new molecular biological analytical platforms, such as the next generation sequencing (NGS), and matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF), that enables identification and quantitation of a broad spectrum of hitherto unknown organisms in endodontic infections should radically alter our understanding of the endodontic mycobiome in the future. Candida spp. appear to be co-pathogens with bacteria in approximately one in ten patients with endodontic infections. Hence, clinicians should comprehend the importance and the role of fungi in endodontic infections and be cognizant of the need to eradicate both bacteria and fungi for successful therapy
Analysis of the secondary endodontic lesions focusing on the extraradicular microorganisms : an overview
No full textThe present study aimed at reviewing the literature on extraradicular infections of endodontically treated teeth, summarizing the main hypotheses on etiopathogenesis and describing the most suitable techniques to identify the composition of pathogenic extraradicular microorganisms. Medline database was searched using the keywords “Apical biofilm,” “extraradicular infection,” “secondary endodontic lesion,” “endodontic retreatment,” “biofilm” either alone or combined with AND. A further hand search was performed on the main endodontic journals. The most frequent bacterial species identified in different studies and with different techniques may vary considerably. Although the presence of some species of microorganisms seems to be determinant, the true origin of extraradicular infection is still undetermined. The literature analysis showed marked differences in methodology, materials, aims, and techniques adopted, which led to highly heterogeneous outcomes. The picture emerging from this review is that extraradicular infection is likely a multifactorial disease that requires further systematic investigation using standardized technique
Severe Acute Respiratory Syndrome (SARS): An interim information paper for dental health care workers
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The destiny of a person in L.P. Karsavin’s philosophy of history
No full textIn the article analyses L.P. Karsavin’s concept of a person in his philosophy of history. Opens the specificity of Karsavin’s understanding of a person in the framework of Vl. Solovyov’s All-Unity and differences from Berdyaev’s personalism. The author comes to conclusion that Karsavin’s philosophy of history has personalistic character and in it reproduced the most systematic in Russian metaphysics experience of studying and understanding forms and types of personality in history of world and Russian culture
Advanced GPR data processing algorithms for detection of anti-personnel landmines
No full textGround Penetrating Radar (GPR) is seen as one of several promising technologies aimed to help mine detection. GPR is sensitive to any inhomogeneity in the ground. Therefore any APM regardless of the metal content can be detected. On the other hand, all the inhomogeneities, which do not represent mines, show up as a clutter in GPR images. Moreover, it is known that reflectivity of APM is often weaker than that of stones, pieces of shrapnel and barbed wire, etc. Altogether these factors cause GPR to produce unacceptably high false alarm rate whilst it reaches the 99.6% detection rate which is prescribed by an UN resolution as a standard for humanitarian demining. The main goal of the work presented in the thesis is reduction of the false alarm rate while keeping the 99.6% detection rate intact. To reach this goal a set of data processing algorithms is developed and organized into an unsupervised target detection scheme. These algorithms are dedicated to clutter suppression and simultaneous detection of APM signatures in both GPR raw data and images resulting from them. The developed algorithms constitute together the following achievements: - An unsupervised generalized likelihood ratio test-based feature fusion framework; - A waveform based target detection/clutter suppression; - Advanced methods for construction of GPR maps The unsupervised generalized likelihood ratio test based feature fusion framework, which has been suggested in this thesis, takes as input an arbitrary amount of confidence maps corresponding to training and testing sites. The output of the framework is a list of target locations. The framework uses training data which can come from independent and non-coincident measurements with different radars and even sensors. The data from each of the sensors are processed independently to result in several detection lists. Every detection in these lists is accompanied with one or several features each represented by a scalar number. A decision level fusion is applied to reconcile the lists i.e. to associate the detections in them with the appropriate physical locations. Then the binary hypothesis testing is executed for the reconciled locations separating them on clutter and target lists. The generalized likelihood ratio test is employed to this end. The feature pre-normalization via Johnson's transform in suggested by the author to be used prior the testing. It is shown in the thesis that such approach outperforms the direct generalized likelihood ratio testing ad. hoc. based fusion techniques. The waveform based target detection/clutter suppression algorithm, which detects disc-shaped APM in heavy clutter with low false alarm rate, has been developed by the author. The algorithm detects a class of low-metal APM with a cylindrical shape (such as PMN2, M14, and NR22 etc.) using just a single reference target return. It suppresses clutter responses from friendly objects while marking the presence of targets with sharp monopulses and preserving the spatial pattern inherent to localized objects. The algorithm is insensitive to the reflectivity and physical diameter of the target and also tolerates certain volatility in the properties of the hosting soil. This algorithm is superimposed with a focusing technique to further improve the mine detectability. A number of improved projection techniques, which allow better detection of APM in focused GPR images is also developed by the author. These utilize the prior knowledge on the character of the spatial correlation properties of target images and allow detection of the burial depth of the target. The algorithms suggested in the thesis were tested on the data acquired during two separate measurement campaigns held at the special facilities for testing of mine detection systems. It has been shown, that the fused multi-feature detection that uses the algorithms reported in this thesis, significantly decreases the false alarm rate in comparison to the previously published studies for the same minefields.Electrical Engineering, Mathematics and Computer Scienc
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