Abstract
Summary and Discussion
The tests reported here show that penicillin in amounts varying between 0.0039 and 0.0625 Oxford units sterilized an inoculum containing 1,000 to 10,000 cells of all the strains tested belonging to serological groups A through N with the exception of group D strains which required 2.0 to 5.0 units to inhibit completely the growth of a similar sized inoculum. Group M strains were the most sensitive; group A, C, G, H, and L strains were next; and group B, E, F, K, and N strains were the least sensitive of those found susceptible to the action of penicillin in small amounts.
From our experience as well as that of others, 11 , 12 it appears that with the doses and methods of administration currently used in patients, concentrations of more than 1 Oxford unit per cc of blood would be difficult to maintain for an appreciable length of time. It, therefore, seems unlikely that human infections with group D streptococci that requiresystemic treatment would respond readily to penicillin therapy in amounts commonly used now. Possibly localized infections, where higher concentrations of penicillin could be maintained, might respond favorably to this drug. On the other hand, infections with strains of groups A, B, C, E, F, G, H, L, K, M, and N would be expected to respond favorably to penicillin since they are susceptible in concentrations that can be readily maintained in either the circulation or locally.
By the methods used, no penicillinase or inhibitor of penicillin could be demonstrated in either the extracted cells or filtrate of a broth culture of a resistant group D strain, although with similar methods an inhibitor which was destroyed or inactivated by heat (65°C for 30 min.) was demonstrated in both the cells and filtrate of a broth culture of a strain of E. coll. No attempts were made to further identify this inhibitor.
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