Biomedical subjects
Publications and source records attributed to A E Beezer.
The proposed flow microcalorimetric method for the diagnosis of bacteriuria has been extended to include antibiotic sensitivity testing. Sensitive organisms rapidly (4-8 min) show thermal responses to the added antibiotics over the normal range of concentrations (1 x, 2x, MIC value).
The use of microcalorimetry in the routine identification of microorganisms is critically discussed and assessed. By use of flow microcalorimetric studies on Saccharomyces cerevisiae and Kluyveromyces fragilis the role of physical parameters and that of oxygen tension are discussed. The conclusion reached is that identification of microorganisms by microcalorimetry and subsequent discussion of metabolic events revealed by the thermogram, except under restrictive conditions, is inappropriate. However flow microcalorimetry, in contrast to batch microcalorimetry which has been used in the published material on microorganism identification, may allow characterization of yeasts suitable for particular industrial processes.
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Improvements in the reproducibility of nystatin agar diffusion assays have been achieved by the use of liquid nitrogen stored inocula and deep frozen standard stock solutions. The overall percentage variability of the assay has been reduced from over 5% with daily prepared standards and inocula to around 1% with a frozen inocula and to 0.6% with a combination of frozen inocula and standards. The implications of these improvements in the standardization of nystatin assays, and microbiological assays generally are discussed.
The classical agar diffusion and turbidimetric methods of assay for nystatin are compared with the more recently documented assays for this antibiotic which depend upon physicochemical measurement of the response of micro-organisms. Liquid nitrogen stored inocula were used throughout. It is concluded that the newer methods of assay are as reproducible and reliable as the agar diffusion and turbidimetric methods and that they are generally more sensitive. The choice between the assay methods compared can thus be based on speed, cost and sample through-put.
The clinically important polyene antibiotic amphotericin B, in combination with two antifungal imidazole compounds, clotrimazole and miconazole, was studied in vitro. With use of results of cytoplasmic leakage, metabolic heat output, and minimal inhibitory concentration studies, a definite antagonistic response was demonstrated. It is suggested that, if combined antifungal drug therapy is clinically indicated, the drug combination be tested against the isolate by the simple technique of measuring cytoplasmic leakage or by the more elaborate method of flow microcalorimetry.
The growth of Kluyveromyces fragilis in a complex medium under anaerobic and aerobic growth conditions has been conducted using a flow microcalorimeter. Growth under defined conditions is characterized by an initial exponential rise in heat output rate to a maximum, followed by a decline to a baseline deflection. Inadequate oxygenation can result in a more structured thermogram. The results are used to illustrate the deficiencies of some calorimetric incubations, and observations reported by other authors are critically discussed.
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Explore the source record for details and available documents.
Explore the source record for details and available documents.
Explore the source record for details and available documents.