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Biomedical subjects

M W Mittelman

Publications and source records attributed to M W Mittelman.

24 records · Page 2Linked to original sources
PubMed1994

Investigation of ciprofloxacin penetration into Pseudomonas aeruginosa biofilms.

Bacterial infections associated with indwelling medical devices often demonstrate an intrinsic resistance to antimicrobial therapies. In order to explore the possibility of transport limitation to biofilm bacteria as a contributing factor, the penetration of a fluoroquinolone antibiotic, ciprofloxacin, through Pseudomonas aeruginosa biofilms was investigated. Attenuated total reflection Fourier transform infrared (ATR/FT-IR) spectrometry was employed to monitor bacterial colonization of a germanium substratum, transport of ciprofloxacin to the biofilm-substratum interface, and interaction of biofilm components with the antibiotic in a flowing system. Transport of the antibiotic to the biofilm-substratum interface during the 21-min exposure to 100 micrograms/ml was found to be significantly impeded by the biofilm. Significant changes in IR bands of the biofilm in regions of the spectrum associated with RNA and DNA vibrational modes appeared following exposure to the antibiotic, indicating chemical modification of biofilm components. These results suggest that transport limitations may be an important factor in the antimicrobial resistance of biofilm bacteria and that ATR/FT-IR spectrometry may be used to follow the time course of antimicrobial action in biofilms in situ.

Biofilms↗
PubMed1987

Evaluation of slime-producing bacteria in oil field core flood experiments.

Epifluorescence microscopy and carbohydrate determinations indicated that the decrease in permeability of oil reservoir sand to reclaimed sewage water was partially the result of biological plugging. Filtration and biocide addition studies demonstrated that the increase in bacterial densities and slime concentrations in flooded oil field cores appeared to be due to both deposition from the reclaimed water and in situ microbial growth and slime production. Although these biological components increased throughout the cores during flooding, the region where the water entered the core exhibited the highest cell densities and slime concentrations. The approach described in this report should be useful in predicting the potential of a water source to induce biological plugging of oil reservoir sand.

Journal Article↗
PubMed1985

Copper-binding characteristics of exopolymers from a freshwater-sediment bacterium.

Copper-binding activity by exopolymers from adherent cells of a freshwater-sediment bacterium was demonstrated by a combination of equilibrium dialysis and flameless atomic absorption spectrometry. Crude, cell-free exopolymer preparations containing protein and polysaccharide components bound up to 37 nmol of Cu per mg (dry weight). A highly purified exopolysaccharide preparation bound up to 253 nmol of Cu per mg of carbohydrate. The conditional stability constant for the crude exopolymer-Cu complex was 7.3 X 10(8). This value was similar to those obtained for Cu complexes formed with humic acids and xanthan, an exopolysaccharide produced by Xanthomonas campestris. Studies conducted at copper concentrations, pHs, and temperatures found in sediments from which the bacterium was isolated indicated that the exopolymers were capable of binding copper under natural conditions.

Adhesiveness↗
PubMedDate not supplied

Biocompatibility of silver-coated peritoneal dialysis catheter in a porcine model.

OBJECTIVE: Previous studies have shown that silver formulations coated onto implantable materials retard bacterial colonization and reduce the incidence of catheter-related infections. The objective of this study was to assess the histologic effects of sputter-coated silver/ silicone implants on host tissue. DESIGN: Sputter silver-coated silicone peritoneal dialysis catheter segments with and without Dacron cuffs were implanted in the subcutaneous fat and muscle in 4 pigs. Noncoated implants served as controls. The specimens were retrieved at 1, 2, 3, 4, 7, 8, 9, 10, 12, and 27 weeks. EXPERIMENTAL ANIMALS: Four 6-week-old male Yorkshire-Landrace pigs (5-6 kg) were used. MAIN OUTCOME MEASURES: Histologic parameters evaluated included the degree of inflammation, the number of giant cells, the extent of silver particulate inclusions, and the thickness of the capsules. All specimens were evaluated by a single blinded pathologist. Microbiologic analyses were also performed. RESULTS: The silver-coated catheters were associated with less inflammation than were the noncoated catheters, both in fat and muscle (p = 0.04). The number of giant cells was also lower around the silver-coated than the non-coated catheters, which were implanted in subcutaneous fat (p < 0.05). Particulate inclusions compatible with silver or silver oxide were observed only in tissue around silver-coated implants (p < 0.0001). The thickness of the capsules and the extent of the inflammatory zones were not significantly different. There was no evidence of infection-related changes. CONCLUSIONS: These data suggest that the sputter silver coating does not act as a significant tissue irritant.

Animals↗
PubMedDate not supplied

Bacterial cell size and surface charge characteristics relevant to filter validation studies.

There are two recognized mechanisms whereby organisms are retained by liquid filters; namely, sieve-retention and adsorption. The efficiency of each may be influenced by the organism, suspending milieu, and by the filtration conditions. Validations of sterilizing filtrations require the use of organism suspensions in product-specific media. However, where the product is bactericidal to the challenge organism(s), surrogate solutions may be required. The ideal surrogate solution would minimize adsorptive retention, ensuring that the sterilizing action of the filter under consideration is the consequence of sieve-retention. This review explores the impact that various physicochemical factors may have on bacterial cell size and cell surface characteristics. An understanding of interactions among challenge bacteria, suspending fluid, and filter medium is essential for the development of surrogate solutions that provide a "worst case" mileu for filter validation studies or a "placebo," non-inhibitory challenge solution.

Adsorption↗