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Biomedical subjects

J Johnsson

Publications and source records attributed to J Johnsson.

191 records · Page 11Linked to original sources
PubMed1985

Gas chromatographic fatty acid profiles for characterisation of mycobacteria: an interlaboratory methodological evaluation.

Three species of mycobacteria were cultured and processed for cellular fatty acid analysis by capillary gas chromatography in three laboratories to study interlaboratory variations of the resulting chromatographic profiles. Largely consistent and characteristic fatty acid profiles were obtained, although there were minor quantitative variations in the patterns due to methodological differences (cultivation, hydrolysis, derivatization, gas chromatographic conditions etc.). The following points were important for achieving informative and reproducible results. A chemically defined growth medium (e.g., Proskauer-Beck) provides more consistent profiles than the lipid-rich Löwenstein-Jensen medium. Harvesting directly into the digesting solution (NaOH or HCl in methanol) followed by heating or autoclaving is a simple and reliable way of releasing fatty acids. Care should be taken to ensure reproducible detection of long-chain alcohols either by using acid methanolysis or including a base-wash step in the procedure following alkaline hydrolysis. The temperature of the gas chromatographic injector should be at least 325 degrees C. A capillary column of a minimum length of 10 m coated with a methyl silicone is adequate. Our results indicate the possibility of recommending a practical and reproducible gas chromatographic procedure for mycobacterial characterisation.

Chromatography, Gas↗
PubMed1983

Influence of beta-lactamase-producing strains of Branhamella catarrhalis and Haemophilus influenzae on certain beta-lactam antibiotics.

Ampicillin, benzylpenicillin, cefaclor and cefuroxime were exposed to strains of Branhamella catarrhalis and Haemophilus influenzae with and without ability to produce beta-lactamase. The antibiotics were dissolved in phosphate buffer at pH 6, 7 and 8 and the mean enzyme activity was calculated from decrease in peak heights by the HPLC technique. Cefuroxime was the most stable drug regardless of pH. For the other antibiotics, changes in pH influenced the results. In infectious processes factors like pH and pCO2 show some variation. This fact may influence the interaction between beta-lactams and beta-lactamases.

Anti-Bacterial Agents↗
PubMed1979

Comparison between agar and broth minimum inhibitory concentrations of cefamandole, Cefoxitin, and cefuroxime.

The in vitro susceptibility to cefamandole, cefoxitin, and cefuroxime of clinical isolates of Streptococcus faecalis, Klebsiella, and indole-positive Proteus was assayed using minimum inhibitory concentration (MIC) determinations in broth and on solid media. It could be demonstrated that the agar dilution MICs obtained when S. faecalis was tested against cefuroxime and when indole-positive Proteus strains were tested against cefamandole tended to be considerably lower than those obtained with the broth dilution technique. The Klebsiella strains tested did not show any major differences with regard to MICs in broth or on solid media. Using an animal experimental infection model it could be demonstrated that with indole-positive Proteus the higher broth MIC correlated better to the observed data than the lower agar MIC when a beta-lactamase-producing strain was tested. The data obtained indicated that the beta-lactamase of the indole-positive Proteus strain was inducible. The results of the study gave evidence for a risk of false susceptibility of some bacterial species against cefamandole when agar techniques, e.g. paper disk diffusion, are used. For cefuroxime, the same phenomenon can be expected with S. faecalis and to some extent with indole-positive Proteus. In this study, cefoxitin seemed considerably less affected by the technique used for susceptibility testing.

Bacteria↗
PubMedDate not supplied

Lactate levels in the rabbit cornea and aqueous humor subsequent to non-gas permeable contact lens wear.

The validity of using the aqueous humor lactate concentration as an indicator of corneal lactate production was tested. For this purpose, ten rabbits wore non-gas permeable contact lenses on one eye for 12 hours. Aqueous humor and corneal extracts were assayed for lactate by means of an enzymatic technique. The contact lens wear caused a limited increment in the corneal lactate concentration, but no change was recorded in the aqueous humor. We therefore conclude that the corneal lactate production has a negligible effect on the lactate concentration in aqueous humor. However, significant individual variations in lactate levels were recorded in the present study, as in earlier ones. Insufficient specificity in the currently used techniques for lactic acid concentration determination may in part explain this.

Animals↗