Comparison of biofilms formed by Candida albicans and Candida parapsilosis on bioprosthetic surfaces.
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Little is known about fungal biofilms, which may cause infection and antibiotic resistance. In this study, biofilm formation by different Candida species, particularly Candida albicans and C. parapsilosis, was evaluated by using a clinically relevant model of Candida biofilm on medical devices. Candida biofilms were allowed to form on silicone elastomer and were quantified by tetrazolium (XTT) and dry weight (DW) assays. Formed biofilm was visualized by using fluorescence microscopy and confocal scanning laser microscopy with Calcofluor White (Sigma Chemical Co., St. Louis, Mo.), concanavalin A-Alexafluor 488 (Molecular Probes, Eugene, Oreg.), and FUN-1 (Molecular Probes) dyes. Although minimal variations in biofilm production among invasive C. albicans isolates were seen, significant differences between invasive and noninvasive isolates (P < 0.001) were noted. C. albicans isolates produced more biofilm than C. parapsilosis, C. glabrata, and C. tropicalis isolates, as determined by DW assays (P was <0.001 for all comparisons) and microscopy. Interestingly, noninvasive isolates demonstrated a higher level of XTT activity than invasive isolates. On microscopy, C. albicans biofilms had a morphology different from that of other species, consisting of a basal blastospore layer with a dense overlying matrix composed of exopolysaccharides and hyphae. In contrast, C. parapsilosis biofilms had less volume than C. albicans biofilms and were comprised exclusively of clumped blastospores. Unlike planktonically grown cells, Candida biofilms rapidly (within 6 h) developed fluconazole resistance (MIC, >128 microg/ml). Importantly, XTT and FUN-1 activity showed biofilm cells to be metabolically active. In conclusion, our data show that C. albicans produces quantitatively larger and qualitatively more complex biofilms than other species, in particular, C. parapsilosis. (+info)
Semi-solid surface fluorometric analysis of glucose.
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We describe an enzymatic fluorometric method for determining glucose concentrations in blood samples by analysis on a semi-solid surface (silicone-rubber pads). The method is an adaptation of existing spectrophotometric procedures based on the sequential coupling reactions with glucose-6-phosphate dehydrogenase and NADP+. The rate of appearance of NADPH fluorescence at 460 nm (excitation wavelength, 340 nm) is monitored and related to the glucose concentration in plasma or serum. The calibration curve is linear to 2.50 g/liter. The chief advantages of this method over the spectrophotometric procedure are low cost and rapid response. The results obtained correlate well with those of the o-toluidine method (correlation coefficient, 0.986). (+info)
Silicone foam sponge for pilonidal sinus: a new technique for dressing open granulating wounds.
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A silicone foam sponge has been used to replace the daily packing of deep granulating wounds with moist sterile gauze. In the treatment of pilonidal sinus use of the sponge demands less nursing time and is more comfortable for the patient than the excision and open granulation technique. Patients can usually return to work soon after operation. The method has many applications in surgery, and widespread application of the technique to the management of granulating wounds could result in considerable savings to the NHS in money and skilled nursing time. (+info)
Enterococcus faecalis surface proteins determine its adhesion mechanism to bile drain materials.
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An important step in infections associated with biliary drains is adhesion of micro-organisms to the surface. In this study the role of three surface proteins of Enterococcus faecalis (enterococcal surface protein, aggregation substances 1 and 373) in the adhesion to silicone rubber, fluoro-ethylene-propylene and polyethylene was examined. Four isogenic E. faecalis strains with and without aggregation substances and one strain expressing enterococcal surface protein were used. The kinetics of enterococcal adhesion to the materials was measured in situ in a parallel plate flow chamber. Initial deposition rates were similar for all strains, whereas the presence of surface proteins increased the total number of adhering bacteria. Nearest neighbour analysis demonstrated that enterococci expressing the whole sex-pheromone plasmid encoding aggregation substances 1 or 373 adhered in higher numbers through mechanisms of positive cooperativity, which means that adhesion of bacteria enhances the probability of adhesion of other bacteria near these bacteria. Enterococci with the enterococcal surface protein did not adhere through this mechanism. These findings indicate that the surface proteins of E. faecalis play a key role in the adhesion to bile drains and bile drain associated infections. (+info)
Silicone sleeve of extrusion cannula as an intraocular foreign body.
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An unusual intraocular foreign body--the silicone sleeve of a soft-tipped extrusion cannula left behind accidentally in the vitreous cavity following a vitreoretinal surgical procedure for complex retinal detachment--is reported. The silicone sleeve remained within the eye for a year without causing any problem. (+info)
Ampullary pyogenic granuloma as a complication of lacrimal plug migration.
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We present a patient with ampullary pyogenic granuloma caused by spontaneous migration of a silicone lacrimal plug. A 43-year-old woman with severely dry eyes was treated with non-absorbable silicone punctal plugs insertion in both superior and inferior puncta. Irritation and purulent discharge gradually developed 3 weeks after implantation. A pink, fleshly ampullary lesion over the left superior punctum was noted later. The migrated silicone plug was found close to the common canaliculus during surgery. Histopathologic examination confirmed the diagnosis of pyogenic granuloma. A migrated lacrimal plug resulting in pyogenic granuloma is a rare complication. The treatment of choice is removal of the migrated plug as early as possible. Patients with lacrimal plugs insertions should be informed of possible complications and should be followed up regularly for early detection of plug-related problems. (+info)
In vivo study of bacterial adhesion to five types of intraocular lenses.
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PURPOSE: To determine in vivo behavior of the ability of the Staphylococcus epidermidis strain (American Type Culture Collection [ATCC] 14990) to attach to 120 intraocular lenses (IOLs) made of five different biomaterials: fluorine polymethylmethacrylate (PMMA), heparinized PMMA, silicone, hydrophobic acrylic, and hydrogel. The pig was chosen as an animal model of endophthalmitis, after a bibliographical analysis and a personal study of its aqueous humor composition. METHODS: Crystalline lenses from 90 domestic pigs were removed aseptically and replaced with previously infected IOLs. The animals were killed 24 hours, 72 hours, and 1 week after implantation of the IOLs. The extent of bacterial binding was then measured by counting. Results were compared with a two-factor analysis of variance (ANOVA 2), confirmed by the Kruskal-Wallis nonparametric test. RESULTS: The extent of bacterial binding (expressed as bound bacteria per area unit) was found to range in increasing order from hydrogel, to fluorine PMMA, to hydrophobic acrylic, to heparinized PMMA, to silicone polymer. Comparison of pairs of materials showed statistically significant differences, except between hydrogel and fluorine PMMA. CONCLUSIONS: To the authors' knowledge, no study has been published so far concerning the in vivo evolution of populations of bacteria adhering to different intraocular materials. Bacterial adhesion to the implant surface must therefore depend on the hydrophobicity or hydrophilicity of the biomaterial. Adhesion is also affected by the nature of the surrounding medium. Because of its complexity, the latter appears to be very difficult to model, thus making in vivo studies essential. (+info)
Fenestrations enhance tear mixing under silicone-hydrogel contact lenses.
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PURPOSE: Extended wear of conventional hydrogel soft contact lenses (SCLs) is associated with adverse ocular responses. Some of these ocular events are thought to result from inadequate tear mixing in the postlens tear film (PoLTF). Therefore, strategies to increase tear mixing may improve the safety of extended-wear SCLs. Recently, it has been suggested that placing fenestrations in soft lenses increases tear mixing. In the present study, hydrodynamic modeling and tear-mixing measurements were used to explore the effects of fenestrations on tear exchange under an SCL. METHODS: Tear mixing, expressed as the time to deplete 95% of fluorescent dye from the PoTLF (T(95)), was measured in 20 subjects fitted with two pairs of silicone hydrogel SCLs. The lenses were identical except that one pair was fenestrated (F) with 40 holes each 100 microm in diameter. The effect of fenestrations on improving tear mixing is explained and enhancement of tear mixing is predicted, with the use of hydrodynamic modeling. RESULTS: T(95) estimates were significantly lower (P < 0.001) in the F (mean T(95) = 18.3 minutes) lenses compared with the standard unfenestrated (S-uF) (mean T(95) = 22.6 minutes) lenses (DeltaT(95) = 4.3 minutes, 95% CI = 2.5-6.2) and were in general agreement with the proposed mixing model. Optimization of tear mixing can be achieved by selectively placing fenestrations in the pooling regions before the thinnest regions. The model predictions were sensitive to the distribution of tear-film thickness under the lens. CONCLUSIONS: Fenestrations improve tear-mixing efficiency. Accurate prediction of the effects of lens parameters on tear mixing, however, demands quantitative measurement of the postlens distribution of tear-film thickness. (+info)