الملخص

Abstract The research included extraction of siderophores from three pathogenic bacterial isolates: Escherichia coli ,Pseudomonas aeruginosa, Staphylococcus aureus isolated from urinary tract, burn, upper respiratory tract infections respectively which were identified according to cultural, physiological, and biochemical characteristics. The extracted siderophores from the three isolates were detected by the chemical and bioassay methods, The results showed the ability of the three isolates to produce siderophores. The In vivo virulence assay for the isolates were performed to determine the LD-50 on mice by injecting them Intraperitanially with serial different concentrations of each bacterial isolate. The three isolates subjected to 12.5µm `of 5_o_ (N_salicyal)_ subfamily adenosine) (SAL_AMS) In order to inhibit their abilities to produce siderophores, the siderophores were extracted from the treated isolates then their detection were performed, the results showed inability of treated isolates to produce siderophores.` The in vivo virulence assay performed for the treated and untreated isolates were compared, the results showed Increases in the lethal dose values of 50% in mice injected with the treated isolates. The extracted siderophores from the isolates before treatment injected at 2mg/ml with different serial concentration of the treated isolates then the lethal dose values for 50% of mice calculated and compared with the LD50% for mice injected with the treated isolates and saline as a control, the results showed reduction in LD50% for mice injected with treated isolates and extracted siderophores and this result means increase of the virulence and pathogenicity of treated isolates after injection of extracted siderophores in vivo.