Paper disk-agar diffusion assay of penicillin in the presence of streptomycin.
Microbiological assay of individual antibiotics in mixtures of antibiotics depends on the use of selective inactivation and/or of test bacteria with differential susceptibility. Controlled experiments revealed that streptomycin in concentrations of 20 and 40 mug/ml did not influence a disk diffusion assay of penicillin with Sarcina lutea (ATCC 9341) as the test organism. In the case of penicillin concentrations less than or equal to 1 IU/ml, addition of 80 mug of streptomycin per ml influenced the penicillin assay significantly. Clinical use of streptomycin resulting in levels above 40 mug/ml usually did not occur; therefore penicillin could be assayed as though streptomycin were not present. We observed additionally that S. lutea was unable to grow on agar plates prepared with semicarbazide hydrochloride.
Raahave
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D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D004058:Diffusion; D004305:Dose-Response Relationship, Drug; D008826:Microbial Sensitivity Tests; D010406:Penicillins / Q000494:pharmacology*; D012505:Sarcina / Q000187:drug effects; D013307:Streptomycin / Q000494:pharmacology*
D000900:Anti-Bacterial Agents; D010406:Penicillins; D013307:Streptomycin