Antibacterial and antibiofilm activities from soil Streptomyces spp. isolated from Muna Island, Indonesia against multidrug-resistant clinical isolates.

Abstract

The global increase in multidrug-resistant (MDR) bacterial infection has rapidly been gaining concern and leading for investigating new strategies to tackle this problem. In this study, the antibacterial potential of 25 soil actinomycetes strain has been evaluated by initial screening against MDR bacterial strains including Escherichia coli strain M19, Pseudomonas aeruginosa strain M19, Klebsiella pneumoniae strain M19, Bacillus subtilis strain M19, and Methicillin Resistant Staphylococcus aureus (MRSA). Among them, three actinomycetes isolates encoded APM-7, APM-11, and APM-21 exhibited strong and a broad antibacterial spectrum, hence there were selected for further study to extract its secondary metabolites following antibacterial, and antibiofilm assessment. The ethyl acetate extract of those three selected actinomycetes were evaluated for its antibacterial spectrum, and the minimum inhibitory concentration (MIC) ranged from 78 to 10000 µg/mL. Those extracts also displayed significant biofilm inhibition values ranging from 6.06 to 72.4%. Based on the results, APM-21 extract showed the best antibacterial and antibiofilm activities with the strongest values. Further, nucleotide sequencing of the 16S rRNA gene showed that these three potential strains APM-7, APM-11, and APM-21 to have identity with Streptomyces cyaneus, Streptomyces coerulescens, and Streptomyces panayensis, respectively. Moreover, based on Liquid Chromatography Tandem-Mass Spectrometry (LC-MS/MS) analysis, two antibacterial compounds namely rancimanycin III, and enteromycin were detected in all those three extracts. Interestingly, APM-21 extract also contains two prominent antibacterial substances including paramagnetoquinone C, and caerulomycin I, suggesting their contribution to the most potential activities recorded in this study. Ultimately, our study provides new insights into a promising candidate for use in an active compound combating strategy to prevent MDR bacterial strains infection.