Thiolactomycin, a new antibiotic. IV. Biological properties and chemotherapeutic activity in mice.

The new thiolactone antibiotic, thiolactomycin, is rapidly absorbed in rats when administered either orally or by intramuscular injection. A peak in concentration of the drug is reached in the blood and in various visceral organs within 15 minutes after administration. The concentration decreases rather rapidly and about 51-69% of the drug is excreted in urine during the first 24 hours. Though the in vitro effect of thiolactomycin is moderate, it effectively protected mice challenged intraperitoneally with several strains of S. marcescens and K. pneumoniae and more effective than carbenicillin in treating experimental acute urinary tracts infected with S. marcescens. Also, in mice whom immunodefense was decreased by treatment with cyclophosphamide, thiolactomycin was more effective than carbenicillin against S. marcescens challenge.