الفهرس 
Introduction1
FluoroquinolonesOnly 14 pages are availabe for public view
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Abstract
The pathogenic bacteria were collected from the various clinical samples. Isolates were identified using routine standard tests according to Bergey’s Manual of Determinative Bacteriology, including morphological, cultural and biochemical characteristics; while identification to the species level was done using the MicroScan WalkAway Diagnostic Microbiology System. Antimicrobial susceptibility of the isolated strains were determined. Fourty one various isolates of actinomycetes obtained from different localities of farming soils were screened to evaluate their antagonistic capacity against 23 pathogenic bacteria included 18 Gram-positive and 5 Gram-negative under laboratory conditions. These microorganisms were most resistance to the widely used antibiotics. Results indicated that 44% of all actinomycetes isolates were active against, at least, one of the test organisms. According to antibacterial activity and spectrum broadness, ten of the isolates were selected and characterized by conventional methods. Ten isolates exhibited strong activities against only Gram-positive bacteria. The ten antagonistic actinomycetes were identified by studying their chemical composition and through studying their morphological, cultural physiological, biochemical properties and enzymatic activities. The spore morphology and cell wall chemotype suggest that the ten isolates were belonging to the genus Streptomyces. According to the colour of the sporulated aerial mycelium, the experimental isolates were differentiated into two colour series: grey series and yellow series. In this study, PCR-based random amplified polymorphic DNA (RAPD) was also used to amplify random DNA fragments from the genome of five isolates to elucidate the taxonomic position and relationships among closely related Streptomyces species.