Relative Effectiveness of Antibiotics in Rats Given Limiting B Vitamins by Mouth or by Injection

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Abstract
Limiting amounts of thiamine, riboflavin, and pantothenic acid were administered to rats either by inclusion in the diet or by subcutaneous injection, and the effectiveness of dietary antibiotics on growth determined. Penicillin and aureomycin consistently increased growth under both conditions, but the magnitude of the increase was usually greater when the limiting B vitamin was in the diet than when it was injected. This was true in 5 of 6 experiments with thiamine, 6 of 6 with pantothenic acid, and three of 5 with riboflavin. The results suggest that the antibiotics stimulate an increased intestinal synthesis of these vitamins, but leave the question open whether this is the only mechanism involved. Streptomycin was relatively ineffective in diets containing limiting amounts of these vitamins, but it seemed to improve the effectiveness of the injected vitamins.