Anti-Methicillin Resistant Staphylococcus aureus Activity and Optimal Culture Condition of Streptomyces sp SUK 25

Background: The potential of secondary metabolites extracted from Slreptomyces sp. to treat bacterial infections including infections with Staphylococcus aureas is previously documented. The current study showed significant antimicrobial activities associated with endophytic Streptomyces sp. isolated from medicinal plants in Peninsular Malaysia. Objectives: The current study aimed to determine anti-methicillin-resistant-Staphylococcus aureus (MRSA) activities of Streptowyces sp. isolates. Materials and Methods: Disc diffusion and Minimum Inhibitory Concentration (MIC) assay were used to determine the antibacterial activity of Streptornyces sp. isolates. Optimization of fermentation parameters for the most potent anti-MRSA extract in terms of medium type, pH, aeration rate, and culture period was also carried out. Lastly, toxicity of the extract against Chang liver cells was determined employing the MIT, 2-(3, 5- diphenyltetrazol-2-ium-2-yl)-4, 5-d imethyl-1,3-thiazole; bromide assay. Results: The results indicated Streptomyces sp. SUK25 isolates showed the most potent anti-MRSAactivity. Disc diffusion assay revealed that spread plate technique was more efficient in screening anti-MRSA activity compared to pour plate (P < 0.05).To determine anti-MRSA MIC of Streptomyces sp. SUK 25, Thronton media was used. Therefore, MIC was determined as 2.44 0.01 mu g/mL, and accordingly, the lowest MIC was 1.95 pgjrnL based on a seven-day culture, pH7, and aeration rate of 140 rpm. The crude extract was not toxic against Chang liver cells (IC50 = 43.31 +/- 1 24 mu g/mL). Conclusions: The Streptomyces sp. SUK 25 culturing was optimized using Thronton media, at pH 7 and aeration of 140 rpm. Further isolation and identification of bioactive compounds will develop anti-MRSA therapeutics.