ABSTRACT
As-IBBR is a metabolite isolated from the fermented broth of Streptomyces IBBR. The pure antibiotic was analyzed and the physico-chemical and biological properties were appraised. The antibiotic could be classified as a member of the polypeptide antibiotics [according to Berdy, 1972]. The mechanism of action of the antibiotic on Staph. aureus cells was studied. As-IBBR exerted a strong inhibitory effect on the protein and RNA syntheses, while exerted a moderate effect on DNA synthesis. Table [I]: Antimicrobial Activity of AS-IBBR. Test organism: Staphylococcus aureus Smith, MIC mcg/ml: 6.25. Test organism: Staphylococcus aureus 252-R, MIC mcg/ml: 6.25. Test organism: Staphylococcus aureus 199-R, MIC mcg/ml: 3.13. Test organism: Staphylococcus epidermidis [R-25], MIC mcg/ml: 3.13. Test organism: Streptococcus faecalis [N-478], MIC mcg/ml: 6.25. Test organism: Escherichia coli 1346, MIC mcg/ml: 100. Test organism: Klebsiella Pneumoniae 5075, MIC mcg/ml: 100. Test organism: Serratia marcescens 7006, MIC mcg/ml: 100. Test organism: Pseudomonas aeruginosa 12, MIC mcg/ml: 100. Test organism: Proteus vulgaris 6028, MIC mcg/ml: 100. MIC was determined on heart infusion agar