Flow microcalorimetric assay of antibiotics--IV. Polymyxin B sulphate, neomycin sulphate, zinc bacitracin and their combinations with Escherichia coli suspended in buffer plus glucose medium.
Flow microcalorimetric assays for polymyxin B sulphate and neomycin sulphate have been developed using Escherichia coli as the test organism, suspended in a glucose plus buffer medium. These assays have a better reproducibility (relative standard deviations 3.2 and 2.0%, respectively), and require a shorter time (1 h including time required for preparation of the calorimeter) than do conventional microbiological assays, but are not as sensitive. It is suggested that a screening programme might produce a small group of more suitable (i.e. more sensitive) test organisms, which could be used to develop rapid and reproducible flow microcalorimetric assays for a wide range of antibiotics by the procedure described. The effect of combinations of polymyxin B sulphate, neomycin sulphate and zinc bacitracin (the antibiotic components of the commercial preparation Trisep, ICI, Macclesfield, UK) on the power output of cells suspended in glucose plus buffer medium is also reported. In defined combinations, the effects of neomycin sulphate appeared to be exerted before those of polymyxin B sulphate.
Joslin Kjeldsen
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N
Department of Chemistry, Chelsea College, University of London, UK.
Beezer
A E
AE
Miles
R J
RJ
Sodha
H
H
D001414:Bacitracin / Q000032:analysis* / Q000494:pharmacology; D002021:Buffers; D002151:Calorimetry / Q000379:methods; D003470:Culture Media / Q000494:pharmacology; D004359:Drug Therapy, Combination / Q000032:analysis / Q000494:pharmacology; D004926:Escherichia coli / Q000187:drug effects*; D005947:Glucose / Q000494:pharmacology; D008826:Microbial Sensitivity Tests; D009355:Neomycin / Q000032:analysis* / Q000494:pharmacology; D011112:Polymyxin B / Q000032:analysis* / Q000494:pharmacology
D002021:Buffers; D003470:Culture Media; D001414:Bacitracin; D009355:Neomycin; D005947:Glucose; D011112:Polymyxin B