Antibacterial Activity of an Antibiotic (K-681) from Streptomyces sp. 681 against Staphylococcus aureus

The antimicrobial agents reduced infectious diseases significantly. However, antibiotic resistance has followed for almost every antimicrobial agent. Especially, Staphylococcus aureus was one of the most notorious for the multidrug resistance. Streptomyces sp. 681 has been selected for antibiotic-producing strain against methicillin-resistant Staphylococcus aureus (MRSA) from 1,000 strains of Actinomycetales which had been isolated from soil. In antimicrobial susceptibility test, all of the test strains were susceptible to vancomycin. However, most strains of Staphylococcus aureus were found to be resistant to methicillin. Ninety eight (75%) strains out of 129 strains showed multiple resistance pattern to more than 5 antimicrobial agents. The MIC values of the purified antibiotic (K-681) were 1-32 ug/ml against Gram-positive bacteria compared to >128 ug/ml against Grarn-negative bacteria or fungi. The MIC was 8 ug/ml for 90% of the 129 clinical isolates of S. aureus. The antibiotic showed no cytotoxicity against P 388, HeLa, and S180 at the concentration of 500 ug/ml.

Biological Properties of a Polyene Antifungal Substance(AF1) Produced from Streptomyces sp. WCM-9 / 대한의진균학회지

BACKGROUND: Pathogenic fungi infect humans, especially immunocompromised patients, with superficial or deeply invasive pattern. In the past 20 years, fungal infections have been increased dramatically resulted by increment of organ transplantation, cancer, AIDS patients, or use of broad-spectrum antibacterial agents. Fungal infections are now important causes of morbidity and mortality of hospitalized patients. but there is no effective antifungal antibiotics as well as antibacterial antibiotics OBJECTIVE: Effective new antifungal antibiotics are needed for the treatment of mycosis. So in an effort to develop effective antifungal antibiotics, we screened over 600 isolates of Streptomyces sp. from soil. METHODS: Antifungal producing strain was selected using disk diffusion method, An antifungal substance (AF1) was purified with ethyl acetate extraction, silica gel column chromatography and reverse phase HPLC. MICs of AF1 were detected by agar dilition method. RESULTS: The compound showed UV maxima of 307, 321, 340, 359 nm indicating methylpentaene. Minimum inhibitory concentrations of the AF1 were 3.7 microgram/ml against mold, and 3.7 - 7.4 microgram/ml against Candida species. AFI was also active against Crytococcus neoformans, with MIC of 0.9 microgram/ml. The concentration of AF1 for K+ ion release from human red blood cell and hemolysis were 5 microgram/ml. CONCLUSION: The antibiotic purified from culture broth of Streptomyces sp. WCM-9 was a polyene antifungal antibiotic which have broad spectrum antifungal activity.