Flow microcalorimetric assay of antibiotics--II. Neomycin sulphate and its combinations with polymyxin B sulphate and zinc bacitracin on interaction with Bacillus pumilus (NCTC 8241).
A flow microcalorimetric assay for Neomycin has been developed which is monitored through interaction of the antibiotic with Bacillus pumilus as the test organism. The assay has better reproducibility (relative standard deviation 2.3%) and is more sensitive than conventional microbiological bioassay (0.5-2 micrograms ml-1). The effects of combinations with zinc bacitracin, with polymyxin B sulphate, and with both zinc bacitracin and polymyxin B sulphate (both in equimolar proportions), and in those proportions present in the commercial preparation TrisepR (ICI, Macclesfield, UK) have also been investigated. Synergy was observed for the combinations of Neomycin with the other two antibiotics in binary mixtures at the relative proportions found in TrisepR. The addition of all three antibiotics at the levels used in TrisepR did not show synergy. However, addition of all three antibiotics at equimolar concentrations did show synergy. It is suggested that microcalorimetry may be useful in in vitro experiments for exploring the relative proportions required for maximal effect in antibiotic combinations.
Joslin Kjeldsen
N
N
Department of Chemistry, Chelsea College, University of London, UK.
Beezer
A E
AE
Miles
R J
RJ
D001407:Bacillus / Q000187:drug effects*; D001414:Bacitracin / Q000032:analysis* / Q000494:pharmacology; D001681:Biological Assay; D002151:Calorimetry / Q000379:methods; D004357:Drug Synergism; D004359:Drug Therapy, Combination / Q000032:analysis / Q000494:pharmacology; D008826:Microbial Sensitivity Tests; D009355:Neomycin / Q000032:analysis* / Q000494:pharmacology; D011112:Polymyxin B / Q000032:analysis* / Q000494:pharmacology
D001414:Bacitracin; D009355:Neomycin; D011112:Polymyxin B