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Biomedical subjects

D Stickler

Publications and source records attributed to D Stickler.

16 recordsLinked to original sources
PubMed2005

Reduced adherence of Candida to silane-treated silicone rubber.

Silicone rubber is widely used in the construction of medical devices that can provide an essential role in the treatment of human illness. However, subsequent microbial colonization of silicone rubber can result in clinical infection or device failure. The objective of this study was to determine the effectiveness of a novel silane-treated silicone rubber in inhibiting microbial adherence and material penetration. Test material was prepared by a combination of argon plasma discharge treatment and fluorinated silane coupling. Chemicophysical changes were then confirmed by X-ray photoelectron spectroscopy, contact-angle measurement, and atomic force microscopy. Two separate adherence assays and a material penetration assay assessed the performance of the new material against four strains of Candida species. Results showed a significant reduction (p < 0.01) of Candida albicans GDH 2346 adherence to silane-treated silicone compared with untreated controls. This reduction was still evident after the incorporation of saliva into the assay. Adherence inhibition also occurred with Candida tropicalis MMU and Candida krusei NCYC, although this was assay dependent. Reduced penetration of silane-treated silicone by Candida was evident when compared to untreated controls, plaster-processed silicone, and acrylic-processed silicone. To summarize, a novel silicone rubber material is described that inhibits both candidal adherence and material penetration. The clinical benefit and performance of this material remains to be determined.

Argon↗
PubMed2003

Polymer surface properties and their effect on the adhesion of Proteus mirabilis.

A problem encountered in patients undergoing long-term catheterization of the urinary tract is that of encrustation and blockage of the catheter by crystalline bacterial biofilms. This is principally caused by the action of the urease-producing pathogen Proteus mirabilis. A major aim of this work is to develop materials resistant to encrustation. Here, the effects of polymer surface properties on the adhesion of P. mirabilis are examined. Spin-coated polymer films were characterized through contact angle measurements to give the Lifschitz-van der Waals, electron acceptor and electron donor terms of the surface free energy, gamma(s)LW, gamma(s)+ and gamma(s)- respectively. A parallel-plate flow cell was used to assess adhesion to these polymer films of P. mirabilis suspended in an aqueous phosphate buffer, pH 7.4, ionic strength 0.26 mol/kg. P. mirabilis was found to adhere significantly less (p < 0.02) to films of agarose, poly(2-hydroxyethylmethacrylate) and cross-linked poly(vinyl alcohol) than to more hydrophobic materials. These polymer films were found to be strongly electron donating, i.e. possessing large gamma(s)-. Films examined using scanning electron microscopy mostly showed no evidence of roughness down to a scale of 1-10 microm. The better performance is thought to be due to a repulsive interaction with the bacterial surface caused by acid/base-type interactions.

Bacterial Adhesion↗
PubMed2002

Surface modification of an experimental silicone rubber aimed at reducing initial candidal adhesion.

Silicone rubber, which is a widely used biomaterial, is often used to make soft liners for permanent denture. Colonization of denture soft lining materials by Candida albicans can result in clinical problems. The aim of this study was to chemically modify the surface of an experimental silicone rubber in order to produce a silicone that was less susceptible to candidal colonization. Surface modification was carried out with the use of argon-plasma bombardment followed by silane treatment, which caused the incorporation of either hydrophilic or hydrophobic functional groups onto the surface. Changes in water contact angles and chemical analysis of the materials with scanning ion mass spectroscopy confirmed surface changes. In vitro assays were carried out using C. albicans to measure levels of adherence to the surface-modified silicone after 1 h. C. albicans exhibited very low adherence to all silane-treated surfaces, whether hydrophobic or hydrophilic. This led to the conclusion that incorporated long-chain functional groups were inhibiting the adherence of the yeast, possibly by the formation of a barrier between the surface of the material and the yeast. In conclusion, silane surface treatment of an experimental silicone rubber has been successful in reducing candidal adherence.

Biocompatible Materials↗
PubMed1999

Ability of Proteus mirabilis to swarm over urethral catheters.

The aim of this study was to investigate the ability of Proteus mirabilis to swarm over various types of urinary catheters. The test strain was found to swarm over catheters for distances of up to 10 cm within 24 h. Migration was significantly more rapid over hydrogel-coated latex catheters than over all-silicone or silicone-coated latex catheters. Scanning electron micrographs revealed discrete rafts of typically elongated swarmer cells on catheter surfaces. Migration of swarmers along catheters into the bladder could thus initiate Proteus mirabilis catheter-associated infections.

Catheters, Indwelling↗
PubMed1999

Biofilms.

Outside of the laboratory, most microbes grow as organised biofilm communities on surfaces. The past year has seen important advances in our understanding of how cells initiate biofilm formation. We have also begun to appreciate how cells can co-ordinate their activities and build the complex structures of mature biofilms that afford protection for their inhabitants.

Bacteria↗
PubMed1998

Studies on the formation of crystalline bacterial biofilms on urethral catheters.

A model of the catheterised bladder was used to test the ability of urease-producing urinary tract pathogens to encrust urethral catheters. Encrustation was assessed by determining the amounts of calcium and magnesium deposited on the catheters and visualised by scanning electron microscopy. Urease-positive Morganella morganii, Klebsiella pneumoniae, and Pseudomonas aeruginosa failed to raise the urinary pH and form crystalline biofilms. In contrast, strains of Proteus mirabilis, Proteus vulgaris, and Providencia rettgeri generated alkaline urine (pH 8.3-8.6) and extensive catheter encrustation within 24 h.

Biofilms↗
PubMed1993

Proteus mirabilis biofilms and the encrustation of urethral catheters.

Bacterial biofilms were observed on 69 of 75 catheters taken from patients undergoing long-term bladder management. Ten catheters were colonized by pure cultures of Proteus mirabilis. In each of these cases the bacteria formed layers on the catheter surface, underlying encrustations of struvite and hydroxyapatite which partially or completely occluded the catheter lumen. Encrustation was also apparent on catheters colonized by P. mirabilis plus other species, but was rarely seen on catheters colonized by non-urease-producing species. These observations support the hypothesis that catheter encrustation is brought about by the activity of urease-producing biofilms and confirms that the main target in the control of catheter encrustation should be P. mirabilis.

Catheterization↗
PubMed1992

Scanning electron microscopy of bacterial biofilms on indwelling bladder catheters.

Fifty Foley bladder catheters that had been indwelling for periods ranging from 3 to 83 days (mean 35 days) were examined for the presence of bacterial biofilm. Scanning electron microscopy on freeze-dried cross-sections and fixed, critical point-dried longitudinal sections revealed biofilm formation on the luminal surfaces of 44 of the catheters. Culture of urine samples and sonicates from catheters revealed that the prevalence of bacteriuria was less than that of catheter colonization. A wide range of nosocomial species were found colonizing the catheters, Escherichia coli being most often isolated. The bacterial composition of the biofilms ranged from single species to mixed communities containing up to four species. There was no relationship between the length of time that the catheter had been in situ and the extent of biofilm formation. The biofilms varied in thickness from 3 to 490 microns and were visible as layers of bacterial cells up to about 400 cells deep, embedded in a matrix.

Bacterial Adhesion↗
PubMed1992

Virulence factors in Escherichia coli from urinary tract infections in patients with spinal injuries.

A collection of 70 strains of Escherichia coli from urinary tract infections in spine-injured patients undergoing long-term bladder catheterization were tested for characteristics that have been associated with the ability to produce pyelonephritis. The incidence of the virulence factors were: mannose-resistant haemagglutinins (30%), P-fimbriae (17%), haemolysin (27%), K-antigens (28%) and aerobactin (by bioassay 33%, by gene probe 39%). Only 54% of the strains belonged to the O-serotypes usually associated with urinary tract infections. E. coli carrying the full complement of virulence factors were rare in the urinary tract of the spinal patients and were not associated with episodes of symptomatic pyelonephritis. It is clear that the neuropathic bladder and the presence of the catheter permits a wide variety of bacterial types to colonize the urinary tract and cause infection of the kidney. The identification of host markers rather than bacterial factors is suggested as a more fruitful approach to the early detection of cases likely to progress to pyelonephritis in this group of patients.

Cross Infection↗
PubMed1991

Activity of antiseptics against biofilms of mixed bacterial species growing on silicone surfaces.

As part of a programme to establish the relative merits of antiseptics that are used as bladder instillations to control urinary tract infections in patients with indwelling catheters, the activity of five such formulations were tested against dense (10(9) cfu/cm2) mixed biofilms composed of Citrobacter diversus, Pseudomonas aeruginosa and Enterococcus faecalis growing on silicone discs. All three species were resistant to chlorhexidine (200 mg/l) and povidone-iodine (1% v/v) in the biofilm mode of growth, whereas these agents rapidly eliminated viable cells from urine suspensions of the mixed community. Lactic acid (1% v/v) produced a 1 log reduction of the biofilm population within 30 min of exposure. The mandelic acid (1% w/v) and mandelic acid (0.5% w/v)/lactic acid (0.5% v/v) mixture proved to be the most effective in eliminating the biofilm organisms. It is suggested that these latter solutions should now be tested for efficacy in bladder washouts against urinary tract infections in catheterized patients.

Anti-Infective Agents, Urinary↗
PubMed1991

Activity of some antiseptics against urinary tract pathogens growing as biofilms on silicone surfaces.

The activity of chlorhexidine, mandelic acid and a mandelic/lactic mixture were tested against biofilms of four species of gram-negative nosocomial organisms that commonly infect the catheterized urinary tract. Cells growing on silicone discs were exposed to concentrations of agents used in bladder instillation. Citrobacter diversus biofilms proved to be sensitive to all three agents. Pseudomonas aeruginosa, Proteus mirabilis and Klebsiella pneumoniae all survived well in chlorhexidine but their viability was significantly reduced by the mandelic acid formulations. These results suggest that bladder instillations of mandelic acid or mandelic/lactic acids would be more effective than chlorhexidine in eliminating biofilms from catheter surfaces.

Anti-Infective Agents, Urinary↗
PubMed1991

Activity of antiseptics against biofilms of mixed bacterial species growing on silicone surfaces.

As part of a programme to establish the relative merits of antiseptics that are used as bladder instillations to control urinary tract infections in patients with indwelling catheters, the activity of five such formulations were tested against dense (10(9) cfu/cm2) mixed biofilms composed of Citrobacter diversus, Pseudomonas aeruginosa and Enterococcus faecalis growing on silicone discs. All three species were resistant to chlorhexidine (200 mg/l) and povidone-iodine (1% v/v) in the biofilm mode of growth, whereas these agents rapidly eliminated viable cells from urine suspensions of the mixed community. Lactic acid (1% v/v) produced a 1 log reduction of the biofilm population within 30 min of exposure. The mandelic acid (1% w/v) and mandelic acid (0.5% w/v)/lactic acid (0.5% v/v) mixture proved to be the most effective in eliminating the biofilm organisms. It is suggested that these latter solutions should now be tested for efficacy in bladder washouts against urinary tract infections in catheterized patients.

Anti-Infective Agents, Local↗
PubMed1989

Racial differences in optic nerve head parameters.

Results of previous studies have strongly indicated that the prevalence of elevated intraocular pressure is greater in blacks than in whites and that blacks are more susceptible than whites to glaucomatous damage at any given level of pressure. It has also been suggested that a larger disc area might predispose an eye to glaucomatous damage. We investigated the possibility that clinically quantifiable differences might exist in optic disc parameters between normotensive white and black patients. Disc area, cup-to-disc ratio, and cup volume measured with a video-ophthalmograph (Rodenstock Optic Disc Analyzer) were significantly larger in blacks than in whites, while there was no difference in the disc rim area between the two groups. We derived a mathematical model of the optic disc that relates posterior displacement of the lamina cribrosa to the disc area, distensibility of the disc, and intraocular pressure.

Adolescent↗
PubMed1989

Activity of antiseptics against Escherichia coli growing as biofilms on silicone surfaces.

The activity of chlorhexidine, acetic, lactic and mandelic acids were examined against biofilms of Escherichia coli established on silicone discs and against the test strain growing in suspension in urine. The results showed that the concentrations of chlorhexidine and acetic acid normally used for bladder instillations to control infections in patients with indwelling catheters failed to eliminate cells from the biofilm in exposure periods of up to 2 h. Lactic acid (1% v/v) had a bactericidal effect on planktonic cells but poor activity against cells in the biofilm. Mandelic acid (1% v/v), and mandelic (1% v/v) and lactic acid (1% v/v) mixtures eliminated organisms from both suspensions and biofilms. It is suggested that these solutions be considered as alternatives to acetic acid and chlorhexidine for the washing of catheterized bladders.

Acetates↗
PubMed1981

Outcome of intensive care. An application of a predictive model.

The development of a scoring system to estimate equivalency of illness between individuals has been undertaken. A model has been formulated to calculate probability of survival from each of 225 potential "conditions" apt to occur in patients admitted to intensive care areas. The presence or absence of each factor was noted on admission to a university hospital ICU. The relation between conditions noted in observations on a sample of patients, and survival allows assignment of a weight to each complication on the basis of which a "Condition Index Score" (CIS) or prognosis index can be objectively calculated. Potential uses of CIS are to: (1) establish objective criteria for admission to and discharge from intensive care, and for transfer to tertiary care centers; (2) compare quality of care (outcome vs. CIS) between different intensive care facilities; (3) serve as basis for multi-institutional studies concerning critically ill patients; (4) compare outcomes in groups of patients with equal CIS who are and are not treated in ICUs; and (5) establish appropriate numbers of critical care beds for any hospital or area by CIS criteria.

Critical Care↗