Selection of Streptomyces isolates from Turkish karstic caves against antibiotic resistant microorganisms

In this work, actinomycetes isolates were isolated from rock wall and speleothem surfaces and soil samples of 19 karstic caves in Turkey. Out of 290 isolates isolated, 180 isolates (62%) exhibited antimicrobial activity against a panel of four bacteria, two yeasts and four filamentous fungi in the screening program. One of them, Streptomyces sp. 1492, was examined for antibiotic production in batch culture. The maximum of antimicrobial activity was shown at 5th day. Antimicrobial activity of the extracted active compound was recorded as dose dependent bacteriostatic or bactericidal against antibiotic resistant clinical bacteria strains; methicillin-resistant Staphylococcus aureus (MRSA), vancomycin resistant Enterobacter faecium (VRE), and Acinetobacter baumanii. Minimum inhibitor concentration and minimum bactericidal concentrations were determined as lower than standard antibiotic streptomycin; 125 microg/ml and 250-1000 microg/ml, respectively. Active component was found as heat-stable.