The antibacterial activity of a new 3-azinomethyl-rifamycin.

The new 3-azinomethyl-rifamycin, SPA-S-565, was shown to exert an effective antibacterial activity in vitro comparable to that of rifampicin. In fact, the antibacterial activity of SPA-S-565 against numerous Gram-positive cocci belonging to Staphylococcus and Streptococcus species as well as against 20 strains of Mycobacterium tuberculosis, was similar to that of rifampicin. In Swiss albino mice intraperitoneally infected with Staphylococcus aureus Oxford strain or Streptococcus pyogenes, the protective activity of SPA-S-565 and rifampicin was quite remarkable, and no significant difference was noted between the two antibiotics. In M. tuberculosis-infected mice treated with the antibacterial agents every seven days, the protection exerted by SPA-S-565 was significantly greater than that exerted by rifampicin.