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.
