Chromatographic fractionation of antibiotic 136 and characterization of its components.
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Anti-Bacterial Agents↗
Biomedical subjects
H S Ragheb
Publications and source records attributed to H S Ragheb.
Effect of volume of solution per cylinder on estimation of antibiotic potency in diffusion assay.
The volume of antibiotic solutions in cylinders used for diffusion assays is assumed to have no significant effect on estimation of potency. The size of zones of inhibition from cylinders containing 0.10, 0.20, and 0.30 mL of sample solution was compared with zones of inhibition from cylinders containing 0.20 mL of standard solutions. For zinc bacitracin, chlortetracycline.HCl, oxytetracycline, lincomycin.HCl, monensin Na, neomycin sulfate, K penicillin, streptomycin sulfate, and tylosin, the percent recovery (95-102) was optimum when both standard and sample cylinders contained the same volume (0.20 mL/cylinder). At 0.30 mL/cylinder for sample and 0.20 mL for standard solutions, there was a positive bias in potency of about 50%. At 0.10 mL/cylinder, there was a negative bias of approximately 25% except for neomycin, monensin, and bacitracin. For these antibiotics, the bias was about -50%. For hygromycin B, variation in volume of solution per cylinder has little effect on assay results. Experiments on commercial feeds and premixes gave essentially the same results as for the standard solutions experiments.
Anti-Bacterial Agents↗
Evaluation of AOAC microbial diffusion procedure for analysis of chlortetracycline in high mineral feeds.
The performance of the AOAC microbial diffusion assay procedure for the analysis of chlortetracycline was evaluated in mixed feeds and premixes as well as laboratory-prepared feeds, all with various mineral contents. In 100 mixed feeds with a calcium content ranging from less than 1 to greater than 22%, no relationship was shown between calcium content and incidence of chlortetracycline deficiency. In 106 premixes, a relationship was shown between chlortetracycline content and adherence to guarantee: below 10 g/lb, the incidence of deficiency was high; in premixes containing 20 g chlortetracycline and above, the incidences of deficiency were less than 5%. In laboratory-prepared feeds containing 12-15% calcium, grinding and storage at both 4 degrees C and at room temperature (20 degrees C) caused no decrease in the chlortetracycline concentration. Only storage of the ground feed at 37 degrees C caused a distinct loss of activity. The temperature-related loss was attributed to the epimerization of chlortetracycline.
Animal Feed↗