Susceptibility pattern of methicillin resistance Staphylococcus aureus (MRSA) by flow cytometry analysis and characterization of novel lead drug molecule from Streptomyces species.

Background: Actinomycetes particularly, Streptomyces species are producing wide variety of natural products with potential bioactivities. The microbial-derived metabolites hold a strong position to combat emerging and re-emerging antimicrobial drug-resistant pathogens.

Objectives: A diverse group of actinomycetes strains were isolated from unexplored regions of mangrove sediment. Further, a polyphasic approach based on 16S rRNA gene sequence analysis and to evaluate their antibacterial potential against a panel of bacterial pathogens and methicillin resistance Staphylococcus aureus (MRSA).

Methods: The mangrove sediment samples were serially diluted with sterile water and plated on inorganic starch agar medium. A total of 20 isolates were pure cultured and 16S rRNA gene sequences were deposited in the public nucleotide databases (GenBank, NCBI). All the isolates were screened for the antibacterial activity by agar overlay method. Further, the susceptibility pattern of MRSA by flow cytometry and fluorescence microscopy was analysed.

Results: These twenty different isolates were grouped under nine major clad and they shared 95-99% sequence identity to the 16S rRNA gene sequences of the genus Streptomyces in the public nucleotide databases. Among these strains, the isolates namely JRG-02, JRG-03, JRG-04, JRG-10 and JRG-12 exhibited a broad-spectrum antibacterial activity against Methicillin-resistant Staphylococcus aureus(MRSA) and Gram negative bacteria Klebsiella pneumoniae MTCC109. Furthermore, we have characterized the antibacterial compound production and its properties from the isolate JRG-02, a potential drug candidate. The culture conditions and various nutrient components of strain Streptomyces sp. JRG-02 were optimized for enhanced antibiotics production of the isolate. The FT-IR and LCMS spectrum analysis envisaged the chemical nature of the substance. The effect of antibacterial compound on the viability of MRSA was alone examined by flow cytometry (FACS) and fluorescence microscopy analysis.

Conclusions: The present study clearly shows that the survival of diverse inhabitants of Streptomyces in the mangrove sediments. Hence, the mangrove sediment inhabiting strain Streptomyces sp. JRG-02 has potential pharmaceutical activity and genetic diversity.