- Volume 28, Issue 4, 1989
Volume 28, Issue 4, 1989
- Articles
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- Review Article
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Adherence of staphylococci to intravascular catheters
More LessSummaryAdherence of seven strains of Staphylococcus epidermidis and three strains of S. aureus to three types of intravascular catheters was assessed by ATP bioluminescence, by culture after ultrasonication and by scanning electronmicroscopy. The catheter materials studied were silicone elastomer, thermoplastic polyurethane and polyurethane and polyurethane coated with Hydromer®, a coating which absorbs water and provides a hydrophilic sheath around the catheter. The adherence assays were performed in phosphate-buffered saline on a rotary shaker at 37°C, with the catheters precoated with serum and uncoated, and the results were correlated with bacterial hydrophobicity. There was wide strain-to-strain variation in bacterial adherence; S. aureus and slime-producing S. epidermidis strains adhered better than did non-slime-producing strains. Overall, there was less bacterial adherence to Hydromer®-coated catheters than to polyurethane and silicone catheters but it was unrelated to bacterial hydrophobicity. Serum coating of catheters resulted in marked reduction of bacterial adherence.
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Establishment of an experimental model of a Staphylococcus aureus abscess in mice by use of dextran and gelatin microcarriers
More LessSummaryStaphylococcus aureus UC®9271 mixed with dextran or gelatin microcarrier beads and injected subcutaneously into mice resulted in the formation of reproducible, sustained abscesses with as few as 2 × 103 cfu. Without microcarrier beads, 4 × 107 cfu were required to produce an abscess. The abscesses that developed with microcarriers attained a diameter of up to 1.5 cm and persisted for several days before discharging through the skin. The pH of the abscesses fell from 7.1 to 6.6 within 24 h. Histological and microscopic examination of the abscesses revealed an influx of phagocytic cells, mostly polymorphonuclear leucocytes, within 1-2 h after injection. Cell debris accumulated and the abscess became encapsulated 24-48 h after infection. Enzymatic digestion of the abscess contents allowed analysis of the host and bacterial cell populations and treatment with lysostaphin permitted differentiation between phagocytosed and free bacterial populations of S. aureus. Phagocytosed but viable S. aureus comprised c. 50% of the total bacterial population after 24 h; however, by 96 h the phagocytosed population was only 1-5% of the total population, primarily because of an increase in extracellular bacterial numbers. Prevention of abscess formation by antibiotic treatment based upon the minimal inhibitory concentration (MIC) of an antibiotic for S. aureus was not always predictable. Tetracycline did not prevent abscess formation even though it possessed a low MIC for S. aureus; methicillin had a borderline MIC value but was quite active. However, the MIC values were quite predictive of antibiotic cures in a systemic-lethal S. aureus infection in mice.
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Immunochemistry of the cell surfaces of Bacteroides bivius and Bacteroides disiens
More LessSummaryOuter membranes were extracted from seven strains of Bacteroides bivius and six strains of B. disiens by the Sarkosyl method. Lipopolysaccharides (LPS) were extracted from the same strains by the Proteinase K method, and from three strains of each species by an aqueous phenol method. Analysis of the outer-membrane proteins by SDS-PAGE demonstrated that, within a species, very similar patterns with many shared or common bands were produced, but there were sufficient differences between species to allow separation. Immunoblotting with antisera raised against whole cells of each of the type strains showed that many antigens were shared between species. Smooth LPS was present in both species. By immunoblotting, the O-antigen of B. disiens was shown to be common to all six strains, and there was no cross-reaction between the B. disiens antiserum and B. bivius LPS. The O-antigen of B. bivius was not detected by immunoblotting with homologous antiserum, but antiserum to B. bivius reacted with a series of common low molecular mass antigens that were present in LPS preparations from strains of both species.
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A physiological classification of viridans streptococci by use of the API-20STREP system
More LessSummaryPhysiological reactions of viridans streptococci were examined by the API-20STREP system and a selection of conventional tests. Cluster analysis of these results produced a classification similar to a taxonomic scheme based on that of Colman and Williams. The organisms could be divided into the six recognised species—Streptococcus mutans, S. bovis, S. mitior, S. sanguis, S. salivarius and S. milleri. Analysis confirmed that S. mitior and S. sanguis can be distinguished in the API-20STREP test by hydrolysis of arginine but not by dextran production. Although S. mutans, S. mitior and S. sanguis can be divided into two further subgroups, the taxonomic significance of this is unclear. With this means of classification, most organisms could be identified easily by a small number of tests. API-20STREP is convenient for performing physiological tests on viridans streptococci, but the information provided by the manufacturers in regard to identification and nomenclature is in need of revision.
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Bacterial growth and toxin production in ileostomy effluents
More LessSummaryEscherichia coli (2), Vibrio cholerae (2) and Aeromonas sobria (1) strains were examined for their ability to grow and produce toxins in samples of ileostomy fluid. Three categories of response were observed: no detectable growth, growth without detectable toxin, and growth with detectable toxin. Clear differences were apparent between samples of ileostomy fluid obtained from different individuals and between samples obtained from the same individual at different times. The patterns of response were unique for each of the five test strains. We propose that the procedure developed forms a basis for investigating the host-parasite relationship in diarrhoeal disease.
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