Identification and characterisation of a Streptomyces sp. isolate exhibiting activity against methicillin-resistant...

A soil-borne bacterium exhibiting broad antimicrobial activity, including activity against MRSA, was investigated. The bacterium was identified using morphological, biochemical and genetic techniques. The 16S rDNA sequence of the isolate indicated that it was most closely related to Streptomyces lavendulae and Streptomyces globosus. DNA-DNA hybridisation revealed 80% homology with S. globosus DSM41122. The antibiotic was partially purified from the culture supernatant using a combination of precipitation, charcoal and ion exchange. The antibiotic was found to be water-soluble and highly thermally stable at acidic pH. It inhibited the growth of S. lavendulae but not Streptomyces tenebrarius. Significantly, the partially purified antibiotic displayed activity towards clinical isolates of methicillin-resistant Staphylococcus aureus, representative of the major clonal complexes.