Four hindered seventy six clinical samples were collected from patients since June 2003 to May 2004 the number of Staphylococcus aureus isolated from the samples were 163 isolates as follows : urine 52 isolates , wound swab 38 isolates , ear swab 21 isolates , tonsillar swab 17 isolates. Boil swab 11 isolates and Nasal swab 24 isolates Alpha hemolysin of Staphylococcus aureus isolates was designated by hemolysin assay it was found that 42% ( 70 ) of isolates were alpha- hemolysin producers. The extraction of alpha- hemolysin from liquid media from producing isolates was done by cooling centrifugation and purified by ammonium sulphate precipitation and gel - filtration chromatography. Activities of purified alpha-hemolysin were detected, it had 2560 HU/ml the optimum temperature of alpha - hemolysin activity was 20 - 40 C and the optimum incubation period was 14hr. The optimum pH of alpha-hemolysin activity was 7. Cytotoxic activity of alpha - hemolysin against human leukocytes were determined and found the survival ratio of human leukocytes was decreased (38%) after treatment with 15 mg/ml for 30 min. while it lost after treatment with 30 mg/ml for 30 min. too.
