Production of Antibiotics from Soil-Isolated Actinomycetes and Evaluation of their Antimicrobial Activities.

Abstract

The scourge of bacterial infections and diseases has continued to haunt humanity worldwide despite the significant efforts made to understand and treat them. Antibiotics are the usual treatment for such serious bacterial infections. Bacteria are very adaptable, and the overuse of antibiotics has led to the emergence of MDR strains that can no longer be controlled with the usual antibiotics. This has led to the search of novel antibiotics from different sources. The secondary metabolites, especially those isolated from soil inhabitant Actinomycetes have shown an astonishing success for the production of novel effective antibiotics that are harmless to the host tissues. Combination of antibiotics is an effective approach for the elevation of antibiotics’ efficiency and demotion of their side effects. In the course of screening for antibiotic producing microorganisms, fourteen isolates showing antimicrobial activity were isolated from a total of thirty three soil samples collected from various habitats in 6th of October city. Several biochemical tests were performed in order to identify the isolated Actinomycetes which were based on Bergey’s manual of Determinative Bacteriology. Furthermore, the antimicrobial activity was evaluated by Agar Plug Diffusion, and Broth Dilution methods. The MIC of the soil isolated Actinomycetes was calculated with a value of 0.27 as means of optical density. Finally, the soil isolated Actinomycetes were combined with semi-synthetic Penicillin and Erythromycin to evaluate their synergistic effect against some pathogenic bacterial strains which were B. subtilis, E. coli, and Staph. aureus. Antibiotics combinations showed higher inhibitory effects than when each of them was used alone which proves that combinations of antibiotics is a promising strategy for treating severe bacterial infections and can be the solution for the MDR bacterial strains.