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Biomedical subjects

S P Gorman

Publications and source records attributed to S P Gorman.

At least 19 recordsLinked to original sources
PubMed1994

Incidence and nature of peritoneal catheter biofilm determined by electron and confocal laser scanning microscopy.

Thirty-two Tenckhoff catheters retrieved from continuous ambulatory peritoneal dialysis patients with a history of peritonitis were examined for microbial biofilm. Confocal laser scanning microscopy was successfully employed to visualize bacteria in biofilm occluded from view by scanning electron microscopy. Occluded but viable microbial biofilm was associated with 17 (81%) catheters from patients free from infection following renal transplant. Mixed isolate biofilm with two or more isolates of coagulase-negative staphylococci or Staphylococcus aureus was found on 41% of these catheters. Clearly visible viable biofilm consisting exclusively of Pseudomonas aeruginosa occurred on all four catheters removed due to recurrent peritonitis. Five (71%) catheters retrieved from patients transferred to haemodialysis had viable biofilm. Antibiotic sensitivities of the biofilm isolates were similar in profile to those reported for non-biofilm isolates from infected dialysate. Persistence of catheter biofilm despite direct contact with therapeutic levels of antibiotics in peritoneal dialysate requires that attention be directed towards improving antibiotic efficacy against peritonitis-causing bacteria in biofilm form.

Bacterial Adhesion↗
PubMed1994

Characterization of biofilm and encrustation on ureteric stents in vivo.

OBJECTIVE: To examine the relationship between encrustation and microbial biofilm formation on indwelling ureteric stents. PATIENTS AND METHODS: Ureteric stents from 40 patients were examined for the presence of a microbial biofilm and encrustations. Bacteria in stent biofilms were isolated and identified. RESULTS: A profuse biofilm (> 10(4) c.f.u. cm-3) was identified on 11 (28%) stents. Enterococcus faecalis was the most common biofilm organism identified and Proteus spp. were not present. Encrustation was seen in 23 (58%) of stents and was not associated with the level of urinary calcium. The major risk factor for stent encrustation was the presence of urolithiasis. Importantly, there was no causative link between stent biofilm formation and encrustation. Both biofilm formation and encrustation increased with the duration of stenting. CONCLUSION: The results indicate that polyurethane is readily encrusted and colonized by bacteria in vivo despite antibiotic prophylaxis. Newer materials must be sought if effective long-term stenting is to be achieved.

Adult↗
PubMed1993

Selective decontamination of the digestive tract (SDD) does not prevent the formation of microbial biofilms on endotracheal tubes.

The purpose of selective decontamination of the digestive tract (SDD) is to eradicate potentially disease-producing micro-organisms from the oropharynx and gastro-intestinal tract of intensive care unit (ICU) patients, thereby reducing the incidence of nosocomial sepsis, particularly pneumonia. Microbial biofilms form on endotracheal (ET) tubes even when SDD is being administered and may represent a persistent focus for infection. The aim of this investigation was to determine the susceptibilities of organisms adherent to ET tubes to SDD antibiotics (amphotericin B, tobramycin and polymyxin) and to measure the concentrations of these agents in the tracheal aspirates of 11 patients who were being mechanically ventilated. Following extubation, a section was cut from the tip of each ET tube and any adherent microorganisms subsequently isolated were identified and their MICs determined. Samples of tracheal aspirate were obtained three hours after administration of the SDD regimen and the concentrations of the constituent antimicrobials were measured. Enterobacteriaceae were not recovered from any of the tubes but six strains of Staphylococcus aureus, three Pseudomonas spp., three enterococci and four yeasts were isolated. Wide variations in the concentrations of all antibiotics were observed and in many cases they were below the MICs for the organisms isolated. In particular, tobramycin concentrations were uniformly less than the median MIC for the S. aureus isolates and this may account for the predominance of Gram-positive bacteria adherent to the ET tubes. Microbial biofilms attached to these tubes may have a role in the pathogenesis of nosocomial pneumonia in ICU patients.

Amphotericin B↗
PubMed1993

Interaction of sucralfate with antibiotics used for selective decontamination of the gastrointestinal tract.

The interactions of sucralfate with colistin sulfate, with tobramycin sulfate, and with amphotericin B were studied. Sucralfate 500 mg was added to 40 mL of distilled water adjusted to pH 3.5 with hydrochloric acid. Stock solution of one of the three antibiotics was added to give a final colistin concentration of 50 mg/L (as the sulfate salt), final tobramycin concentration of 50 mg/L (as the sulfate salt), and final amphotericin B concentration of 25 mg/L. Samples were removed from each sucralfate-antibiotic mixture at 0, 5, 10, 15, 30, 45, 60, and 90 minutes and analyzed for antibiotic concentration by high-performance liquid chromatography (colistin), enzyme immunoassay (tobramycin), and spectrophotometry (amphotericin B). To determine if any interaction was reversible, the mixtures were stored for 90 minutes without sampling, the pH was adjusted to 6.5-7.0, and samples were removed and analyzed. All tests were performed in triplicate, and the temperature was maintained at 25 degrees C. Significant drug loss was observed starting at five minutes for each antibiotic-sucralfate mixture. This effect was not reversible in the less acidic environment. The concentrations of colistin, tobramycin, and amphotericin B declined rapidly when each drug was combined separately with sucralfate.

Amphotericin B↗
PubMed1992

Stability of ciprofloxacin in peritoneal dialysis solution.

The long-term stability of ciprofloxacin in dialysis fluid was studied. Ciprofloxacin was added to nine 2-L bags of dialysis solution containing 1.3% dextrose to yield a nominal concentration of 25 mg/L. Three bags each were stored at 4, 20, and 37 degrees C; three 20-mL samples were removed from each bag after 0, 0.5, 1, 2, 5, 7, 10, 14, 21, 28, and 42 days and analyzed in triplicate by high-performance liquid chromatography. Additional samples were removed from each bag on day 42 and analyzed by microbiological assay with Pseudomonas aeruginosa (nine samples tested for each storage temperature studied). The net percentage of change in ciprofloxacin concentration was 0.76% after storage at 4 degrees C, 1.02% after storage at 20 degrees C, and 0.75% after storage at 37 degrees C. Antimicrobial activity after storage at all three temperatures was confirmed by microbiological assay. Ciprofloxacin 25 mg/L was stable for 42 days when stored in dialysis fluid containing 1.36% dextrose at 4, 20, and 37 degrees C.

Chromatography, High Pressure Liquid↗
PubMed1991

The effects of three non-antibiotic, antimicrobial agents on the surface hydrophobicity of certain micro-organisms evaluated by different methods.

The effects of three non-antibiotic, antimicrobial agents (taurolidine, chlorhexidine acetate and providone-iodine) on the surface hydrophobicity of the clinical strains Escherichia coli, Staphylococcus saprophyticus, Staphylococcus epidermidis and Candida albicans were examined. Three recognized techniques for hydrophobicity measurements, Bacterial Adherence to Hydrocarbons (BATH), the Salt Aggregation Test (SAT) and Hydrophobic Interaction Chromatography (HIC) were compared. At concentrations reported to interfere with microbial-epithelial cell adherence, all three agents altered the cell surface hydrophobicity. However, these effects failed to exhibit a uniform relationship. Generally, taurolidine and povidone-iodine treatments decreased the hydrophobicity of the strains examined whereas chlorhexidine acetate effects depended upon the micro-organism treated. Subsequently, the exact contribution of altered cell surface hydrophobicity to the reported microbial anti-adherence effects is unclear. Comparison of the three techniques revealed a better correlation between the results obtained with the BATH test and HIC than the results obtained with the BATH and SAT or SAT and HIC. However, these differences may be due to the inaccuracy associated with the visual assessment of results employed by the SAT.

Anti-Bacterial Agents↗
PubMed1987

On the statistical evaluation of adherence assays.

Parametric (unpaired t-test) and non-parametric (Mann-Whitney U-test) methods have been used in the evaluation of adherence assays on the non-antibiotic antimicrobial agent, Taurolin. In all but one case, where the anti-adherence effect was known to be marginal, both statistical methods gave similar results although there were some minor differences in the levels of significance achieved. The effect of the agent on the deviation of adherence data from normality was quantified by calculation of the skewness coefficient for each data set. A significant anti-adherence effect appears to result in a decrease in the skewness of the adherence assay data. It was concluded that either parametric or non-parametric statistical evaluation of adherence assay data is valid for large numbers of observations. In future studies of this type it is suggested that attention should also be given to the effect of the anti-adherence agent on the deviation of adherence data from normality as denoted by the skewness coefficient.

Adhesiveness↗
PubMed1987

The sporicidal activity and inactivation of chlorhexidine gluconate in aqueous and alcoholic solution.

The sporicidal activity of chlorhexidine gluconate in aqueous and alcoholic solution against spores of Bacillus subtilis was examined over a broad temperature range. Activity was not observed at 20 degrees C even with concentrations as high as 10% chlorhexidine. Temperatures of 37 degrees-70 degrees C in combination with such high concentrations were required for reductions in spore viability. No viable spores were recoverable after 4 h contact at 55 degrees C with 10% aqueous chlorhexidine and none after 3 h contact with the alcoholic solution. Because of the high concentrations necessary for activity and the possibility of sporostasis occurring from inefficient chlorhexidine inactivation, existing inactivation systems were examined and modified to obtain satisfactory results. The spores of other Bacillus species examined (B. cereus, B. megaterium and B. stearothermophilus) proved to be considerably less resistant than those of B. subtilis. Presence of organic matter had little effect on the activity.

Bacillus subtilis↗
PubMed1987

Reduced adherence of micro-organisms to human mucosal epithelial cells following treatment with Taurolin, a novel antimicrobial agent.

Taurolin, a non-antibiotic antimicrobial agent, significantly reduced the adherence of buccal and vaginal strains of Candida albicans blastospores and urine isolates of Escherichia coli and Staphylococcus saprophyticus to epithelial cells. Light microscopy and radio-isotopic counting methods were used to quantify the adherence of the micro-organisms to either uroepithelial or buccal epithelial cells. A maximum reduction in adherence of approximately 65% was obtained. The anti-adherence capacity was time-dependent, requiring a contact time of 30 min to achieve maximum effect. Taurolin at sub-minimum inhibitory concentrations (MIC) significantly reduced the adherence of Candida and E. coli. A concentration slightly higher than the MIC was required for Staph. saprophyticus. Treatment of either epithelial cells or micro-organisms with Taurolin resulted in reduced adherence of microorganisms.

Anti-Bacterial Agents↗
PubMed1987

A comparative study of the microbial antiadherence capacities of three antimicrobial agents.

The antimicrobioal agents, taurolidine, chlorhexidine and povidone-iodine were examined for microbial anti-adherence activity. Two adherence systems were investigated using light microscopic and radio-isotopic assay methods: that of an oral isolate of Candida albicans to human buccal epithelial cells and of a urine isolate of Escherichia coli to human uroepithelial cells. Each of the three agents exhibited significant anti-adherence activity which was concentration dependent. The activity was expressed at subminimum inhibitory concentrations of the agents. Treatment of either the microbial or epithelial cells resulted in significant reductions in adhering micro-organisms. Consideration of the data in respect of the skewness coefficient and percentage clear epithelial cells indicated that the agents exhibited a broadly based anti-adherence capacity.

Anti-Bacterial Agents↗
PubMed1986

Effect of miconazole and clotrimazole on K+ release and inhibition of ergosterol biosynthesis in Trichophyton mentagrophytes and related ultrastructural observations.

Measurement of K+ ions in extracellular fluids was used to provide evidence of direct membrane damage induced by miconazole and clotrimazole in Trichophyton mentagrophytes mycelium. K+ release from mycelium treated with high concentrations of drug was extensive, although leakage occurred more rapidly and to a greater extent with miconazole than with clotrimazole. Cells treated with fungicidal concentrations of drug were completely necrotic. The effect of miconazole was concentration dependent. A reduction in ergosterol levels was evident after 5 h treatment with miconazole. Further reduction in ergosterol concentration was demonstrated after 24 h with fungistatic concentrations of drug and was a concentration dependent effect. Fungistatic concentrations of miconazole also induced ultrastructural changes in mycelium, which were apparent within 5 h of treatment and became more pronounced after 24 h. Clotrimazole also reduced ergosterol levels and affected ultrastructure of mycelium. The plasma membrane in particular was affected by both these drugs.

Cell Membrane Permeability↗
PubMed1986

Decrease in adherence of bacteria and yeasts to human mucosal epithelial cells by noxythiolin in vitro.

Adherence of buccal and vaginal isolates of Candida albicans to buccal epithelial cells and the adherence of urine isolates of Escherichia coli and Staphylococcus saprophyticus to uroepithelial cells was quantified by light microscopy. The antimicrobial agent noxythiolin reduced the adherence of these micro-organisms in both exponential and stationary growth phases. Adherence of both the blastospore and pseudohyphal forms of C. albicans was reduced. Treatment of epithelial cells and/or micro-organisms with noxythiolin resulted in decreased adherence. No anti-adherence effect was observed with formaldehyde and N-methylthiourea, the degradative products of noxythiolin.

Adhesiveness↗
PubMed1986

Inhibition of hyphal development and kill of Candida albicans blastospores by noxythiolin in vitro.

The cidal activity of the antimicrobial agent, noxythiolin, was investigated against a laboratory strain and a fresh isolate of Candida albicans. The order of resistance to noxythiolin was hyphal form (isolate) greater than or equal to 25 degrees C-grown blastospores (isolate) greater than 37 degrees C-grown blastospores (isolate) greater than laboratory strain blastospores. Noxythiolin activity was superior to that of 'equivalent' formaldehyde concentrations. Mycelial transformation in C. albicans was examined by light and scanning electron microscopy and measured in terms of percentage germination and hyphal extension. Noxythiolin, 2.5%, in contact for 30 min prevented germination of the blastospore population whereas the decomposition products, formaldehyde and N-methylthiourea, showed no appreciable effect in the expected concentrations. The implications of these results are discussed in relation to the observed clinical efficacy of noxythiolin.

Candida albicans↗
PubMed1986

An assessment of the fungicidal activity of antimicrobial agents used for hard-surface and skin disinfection.

Trichophyton mentagrophytes and Aspergillus niger conidia and Candida albicans blastospores were employed to assess the fungicidal activity of a range of antimicrobial agents used for hard-surface and skin disinfection in hospitals in the U.K. The antimicrobials were tested at in-use concentrations. The time taken to give greater than 99.99% kill was determined by estimating the number of survivors (cfu/ml) at a variety of time intervals after exposure of washed suspensions of spores to the disinfectants. At equivalent times the recovery in the broth was investigated. An alcoholic solution of chlorhexidine gluconate (0.02%) (Hibitane), iodine in Industrial Methylated Spirit (IMS) and a phenolic (0.36% phenols, Stericol) produced a 99.99% kill of all species within 2 min, alcoholic and aqueous solutions (10%) of povidone-iodine (Betadine) and hypochlorite (0.2%) required 10 min to give a 99.99% kill of all species tested. The preparations which contained cetrimide (Cetavlon), aqueous solutions of chlorhexidine gluconate (Hibitane) and combinations of these (Savloclens and Savlodil) were only slowly fungicidal, particularly against T. mentagrophytes spores, which was the most resistant of the three fungal species to disinfection.

Anti-Infective Agents, Local↗
PubMed1985

Ultrastructure of protoplasts from mycelium and microconidia of Trichophyton mentagrophytes.

Protoplast formation from mycelium and microconidia of Trichophyton mentagrophytes was achieved with Novozym 234. Pretreatment procedures with dithiothreitol or urea mercaptoethanol sodium lauryl sulphate before digestion with Novozym 234 greatly reduced protoplast yield from mycelium. Snail gut enzyme did not protoplasts in good yield. Scanning electron microscopy of mycelium protoplasts showed the acquired spherical shape. The plasma membrane appeared finely granular although remnants of cell wall could sometimes be observed. Transmission electron microscopy showed the cell interior of these protoplasts was plasmolysed. Microconidia treated with Novozym 234 displayed a range of cell wall digestion, with intact protoplasts showing distinct cytoplasmic organelles.

Enzymes↗
PubMed1985

Inhibition of hyphal development in Trichophyton mentagrophytes arthroconidia by ketoconazole and miconazole.

In the presence of 0.5 mg/l ketoconazole and miconazole, arthroconidia from three isolates of Trichophyton mentagrophytes produced germ tubes, which continued to grow for 12 h before further elongation ceased. Lower concentrations reduced the rate of elongation, but did not halt the process. Higher concentrations had no greater effect than 0.5 mg/l. The inhibitory effect of ketoconazole was independent of time of addition of drug during the first six hours of germination. Ketoconazole inhibition was reversible after 12 h contact, whereas miconazole inhibition was not. Morphological effects of drug treatment were investigated by scanning electron microscopy. In the absence of imidazoles, hyphae were straight and regular; ketoconazole treated hyphae were short, irregular and branching; miconazole treatment produced extensive debris and spores forming within the hyphae were visible.

Ergosterol↗