Abstract
An antibiotic substance B44P identical with streptovaricin showed a strong inhibitory activity in vitro, mainly against Gram positive bacteria including Mycobact. tuberculosis. It also inhibited the growth of Sh. sonnei, Sh. boydii and Salm. enteritidis at small doses, but exhibited no activity against fungi. The antibacterial activity was not virtually influenced by the inoculum number of test cells, the medium pH within the range of 5.0-8.5, or human blood serum added to the medium. The mode of activity was considered to be mainly bacteriostatic, while partly bactericidal. Gram negative bacteria such as Sh. boydii and Salm. enteritidis could readily be made resistant to the substance B44P by being transferred through medium containing this antibiotic. On the other hand, Staph. aureus developed resistance slowly step by step. The frequency of naturally resistant mutants were nil in S. enteritidis and Sh. boydii and 1.0-4.6×10-6 in Staph. aureus. No cross resistance was found between the substance B44P and other antibiotics. The substance B44P exhibited low toxicity in mice by single or long-term administration. A dog showed practically no pathologic signs by oral administration of 200 mg/kg/day of the drug for 33 successive days. Another dog, however, which received 500 mg/kg/day, developed some symptoms. Liver, kidney and bone marrow were not considered to be damaged by oral administration of this antibiotic. When orally given, the substance B44P was absorbed and appeared in the blood and the urine quite rapidly. Excretion continued for about a day. Relatively dense distributions of the antibiotic were observed in the livers and stomachs of mice after oral administration.
