Increasing cases of penicillin allergy and drug-resistant staphylococcus infections led us to further attempts of finding new antibiotics effective against gram-positive organisms. In the series of screening tests of our laboratory a neutral antibiotic, slightly soluble in water, but soluble in various organic solvents, was isolated from a streptomyces culture and was designated mikamycin1),2). This substance appears to belong to the same group as streptogramin3), PA 1145),6) and staphylomycin4),7),8).
In this publication some of biological studies in the laboratory evaluation of this antibiotic will be reported.
During the course of screening the strains of streptomyces for tumor inhibitory activity, purified powders or culture filtrates which possessed a destructive activity on tumor cells, were frequently found to inhibit the development of ascaris ova. Further detailed studies have suggested some correlation between these two activities. The following experiments were carried out to elucidate these phenomena.
An antiviral and antibacterial antibiotic was produced by Streptomyces No. 290 collected from the premises of National Institute of Agricultural Science, Animal Husbandry Division at Chiba City in 1952. This substance was obtained as crystalline picrate and named virocidin.
The present paper deals with the characteristics of virocidin-producing strain and extraction, purification and properties of virocidin.
Streptomyces No. 4738 strain isolated from the soil of Cambodia produced two kinds of antibiotic, A- and B-substances. The investigation proved that A-substance belonged to aureothricin-thiolutin group and B- substance was a new antibiotic, deep blue needle-like crystals which change the color with pH. The B-substance was named cyanomycin.
In 1956, it was reported by Aiso and his coworkers that a crude powder obtained from culture broth of a new streptomyces strain indicated a clear antitumor activity against Ehrlich cancer cells. It was named Gancidin1).
In its further purification study of gancidin we could isolate several basic and neutral fractions from the crude complex.
But in antitumor animal test of these isolated fractions, any clear antitumor activity as reported by Aiso, et al. formerly was not recognized, though a certain fraction indicated an extraordinary high activity against microbes and some other fraction prolongation effect on survival periods of tumor bearing animals.
The problem of viability duration of Mycobacterium tuberculosis appears to be very important in a correlation to the chemotherapeutic effect of antituberculous drugs. If a subinhibitory concentrations of a drug could produce a reduction of viability duration of the organism, it would be indicated that even such low concentrations of the drug may be effective for the therapy of tuberculos is and may be effective in retarding the emergence of drug resistance. Since blood levels of drugs in human body are not always inhibitory for the growth of the organism, it appears very important to know whether the above possibility exists or not. It is the purpose of the present paper to study the viability duration of M. tuberculosis grown on subinhibitory concentrations of antituberculous drugs.