Abstract
Antibacterial activity of actinomycetes isolated from Riyadh desert area of Saudi Arabia was studied. A total of 130 actinomycetes were subjected to primary screening by perpendicular streak method against human pathogenic Gram-positive (Bacillus subtilis ATCC 6633 and Staphylococcus aureus ATCC 25923) and Gram-negative (Salmonella suis ATCC 13076, Pseudomonasaeruginosa ATCC 27583, Escherichia coil ATCC 25922 and Shigella sonnei ATCC 11060) bacteria and yeast like human pathogenic fungus Candida albicans ATCC 10231. Preliminary screening test showed that about 100 isolates were active against one or more examined test pathogens. All isolates were subjected to secondary screening by agar well diffusion method. Finally 28 isolates were selected for further study on the basis of (a) broad spectrum activity and (b) larger zone of inhibition (>20 mm) in comparison to others. The result of primary and secondary screening revealed that most of the potent isolates were active against gram positive bacteria (Bacillus subtilis and Staphylococcus, aureus) compared with gram negative bacteria (Salmonella suis ATCC 13076, Pseudomonas aeruginosa ATCC 27583, Escherichia coli ATCC 25922 and Shigella sonnei ATCC 11060). Our results indicated that there is a great probability of finding new compounds in unexplored region like desert area of Riyadh, Saudi Arabia because of its wide and very unique diversity of anbioactive compounds producing genus Streptomyces in the family Streptomycetaceae. Therefore, farther research should be done to explore the new antibiotics from the new species of the producing organism.