Tulita F. Lenert

THE EVALUATION OF NEOMYCIN AND OTHER ANTIMICROBIAL AGENTS OF BACTERIAL AND FUNGAL ORIGIN, AND SUBSTANCES FROM HIGHER PLANTS

The extensive literature on antibiotics indicates the ease with which apparently new antimicrobial agents may be detected. The differentiation, however, between many of these readily detected and apparently new antibiotics and those already known to microbiologists is less readily accomplished. The evaluation of the toxicity and chemotherapeutic activity of new antimicrobial substances is often slow, and the inherent toxicity of many new products frequently becomes apparent only after intensive study. The complete evaluation of the toxicity of a potential chemotherapeutic agent is highly important prior to clinical trial. In a disease such as tuberculosis, in which prolonged administration is necessary, this is particularly essential. In the present report, methods for the evaluation of new chemotherapeutic agents will be discussed with reference to tuberculosis, and a few of the new antimicrobial agents will be mentioned.

Observations on the Action of Streptomycin in vitro (I).

Summary 1. A standardized procedure for determination of sensitivity of microorganisms to streptomycin is described. 2. The sensitivity of an organism to streptomycin is influenced by age of culture, concentration of organisms, growth phase of culture, and constituents of medium used. Providing these factors are held constant, the sensitivity of a given strain will remain constant from day to day. 3. The action of streptomycin is bacterio-static rather than bactericidal. Its action is inhibited by certain growth stimulating substances such as peptone, as well as by certain reducing substances. 4. The sensitivity of 84 strains belonging to 7 species is described. Marked variation in sensitivity exists between different strains within a single species and at times between different cells within a given strain. 5. The sensitivity of 9 strains belonging to 8 species is essentially the same when tested against crude streptomycin sulfate (453 /xg/mg), against 3 preparations of the crys talline CaCl2 double salt of streptomycin (685 to 708 /xg/mg) and against a preparation of streptomycin sulfate (802 /xg/mg) prepared from a crystalline salt. 6. The sensitivity of 4 strains of E. typhosa to certain preparations of impure streptomycin sulfate is greater than to highly purified streptomycin sulfate.

Biological Activity of a Residual Form of Streptomycin against Eberthella typhosa.

Summary The sensitivity of E. typhosa to a residual fraction of streptomycin obtained during the purification process is at least 2 to 5 times greater than to the crystalline CaCl2 double salt of streptomycin. By the Oxford cup plate method, the E. typhosa-Be. subtilis (or E. colt) differential ratio of this material is approximately 2.0-3.0. This residual streptomycin is active in vivo as well as in vitro. Its activity in vivo is not as great, however, as might be anticipated from the in vitro results.