Isolation and Screening of Streptomyces Species Producing Anti-Microbial Compounds Active against Multi-Drug Resistant Pathogens causing Respiratory Tract Infections

Author(s): Arjuman Surti* and Vinita D’souza

Abstract: Background: The members of the family Actinomycetaceae, are the largest known group of microbes that act as reservoirs of biologically active compounds i.e. antibiotics. Aim: The current study was carried out with an aim to isolate Actinomycetes from soil samples and screen for antibiotic producers effective against Multi-Drug Resistant (MDR) pathogens causing Respiratory Tract Infections (RTIs). Methods: Twenty-one isolates were obtained from various soil samples in our study, and were subjected to primary screening for antibiotic production by agar strip method, Wilkins overlay method, agar diffusion and disc diffusion assays. Identification of Actinomycetes was carried out on the basis of morphological, cultural, biochemical tests and cell wall characteristics. Results: Among the Actinomycetes isolated in our study, 12 isolates showed considerable antibacterial activity against test pathogens. Four isolates showed inhibition of pathogenic S. aureus but were ineffective against gram-negative and fungal pathogens. Three isolates inhibited gram-positive and fungal pathogens but were ineffective against gram-negative test pathogens. However, 5 isolates showed promising anti-microbial activity against gram positive and gram negative bacteria as well as fungal pathogens. Four of these 5 isolates were identified as Streptomyces noboritoensis, Streptomyces nigrifaciens, Streptomyces griseorubiginosus and Streptomyces rubiginosohelvolus. The remaining one isolate showed characteristics of a fungus. Conclusion: The antibiotic-producing strains isolated in our study can be a good candidate for broad-spectrum antibiotic production which is not only effective against MDR bacteria but also fungal pathogens causing RTIs.

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