title: Anti-Methicillin Resistant Staphylococcus aureus Activity and Optimal Culture Condition of Streptomyces sp. SUK 25.
abstract: BACKGROUND
  The potential of secondary metabolites extracted from Streptomyces sp. to treat bacterial infections including infections with Staphylococcus aureus is previously documented. The current study showed significant antimicrobial activities associated with endophytic Streptomyces sp. isolated from medicinal plants in Peninsular Malaysia.
  
  
  OBJECTIVE
  The current study aimed to determine anti-methicillin-resistant-Staphylococcus aureus (MRSA) activities of Streptomyces sp. isolates.
  
  
  METHODS
  Disc diffusion and Minimum Inhibitory Concentration (MIC) assay were used to determine the antibacterial activity of Streptomyces 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 MTT, 2- (3, 5- diphenyltetrazol-2-ium-2-yl) -4, 5-dimethyl -1, 3 - thiazole; bromide assay.
  
  
  RESULTS
  The results indicated Streptomyces sp. SUK 25 isolates showed the most potent anti-MRSA activity. 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 µg/mL, and accordingly, the lowest MIC was 1.95 µg/mL 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 µg/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.
authors.affiliation: School of Diagnostic and Biomedical Sciences, Faculty of Medicine and Health Sciences, University Sultan Zainal Abidin, Kuala Terengganu, Terengganu, Malaysia.
authors.forename: Ahmad
authors.initials: A
authors.lastname: Siti Junaidah
authors.affiliation: School of Bioscience and Biotechnology Study, Faculty of Science and Technology, University Kebangsaan Malaysia, Selangor, Malaysia.
authors.forename: Sudi
authors.initials: S
authors.lastname: Suhaini
authors.affiliation: School of Bioscience and Biotechnology Study, Faculty of Science and Technology, University Kebangsaan Malaysia, Selangor, Malaysia.
authors.forename: Hasidah
authors.initials: H
authors.lastname: Mohd Sidek
authors.affiliation: School of Diagnostic and Biomedical Sciences, Faculty of Medicine and Health Sciences, University Sultan Zainal Abidin, Kuala Terengganu, Terengganu, Malaysia.
authors.forename: Dayang Fredalina
authors.initials: DF
authors.lastname: Basri
authors.affiliation: School of Diagnostic and Applied Health Sciences, Faculty of Health Sciences, University Kebangsaan Malaysia, Kuala Lumpur, Malaysia.
authors.forename: Noraziah Mohamad
authors.initials: NM
authors.lastname: Zin
keywords: Culture; MRSA; Streptomyces sp.