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I isolated the actinomycete strain KH223 from soil samples collected from the Kye Ryong mountain area. This strain is antagonistic to the multidrug-resistant Acinetobacter baumannii. KH223 was confirmed as belonging to the genus Streptomyces based on the scanning electronmicroscopy(SEM) observations of the diaminopimelicacid(DAP) type and morphological and physiological characteristics. Comparison of the 16S rDNA nucleotide sequences revealed that KH223 has a relationship with Streptomyces galbus. Production of antibiotics by KH223 was most favorable when cultured on a glucose, polypeptone, and yeast extract(PY) medium for 6 days at 27oC. The supernatant was found to exhibit an antimicrobial effect on various kinds of bacteria and fungi. Particularly, butanol and ethylacetate extracts of KH223 and cyclo(trp-trp) exhibited significant activity against A. baumannii at concentration ranges of 0.8-12.5 μg/mL, 5.0-25 μg/mL and 12.5→100 μg/mL, respectively. Moreover, in contrast to cyclo(trp-trp) had shown to activity against Micrococcus luteus JCM 1464 at the concentration of 12.5 μg/mL, the butanol extract of KH223 showed significant activity against Bacillus subtilis IAM 1069 and Micrococcus luteus JCM 1464 at the concentration of 0.4 and 0.8 μg/mL, respectively. These results suggest that KH223 may have a great potential in the production of new antibiotics to combat multidrug-resistant pathogens and further studies may be warranted for the same.
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