الفهرس 
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Abstract
The current study was carried out on a total of 232 raw milk samples. The recovery rate of E. coli from the collected raw milk samples was 14.65% (34/232) after cultivation on of MacConkey’s agar (Oxoid) plates and incubated aerobically at 37°C for 24 hours, followed by purification suggestive colonies of pink colored on MaCconkey’s agar plates on the surface of Eosin Methylene Blue (EMB) (Oxoid) agar plates. Among the recovered E. coli strains, 12 different E. coli serotypes were identified namely, O26:H11(n꞊6), O111:H2 (n꞊5), O128:H2 (n꞊5), O91:H21(n꞊4), O124 (n꞊3), O127:H6 (n꞊3), O103:H21(n꞊2), O153(n꞊1), O113:H4 (n꞊2), O6 (n꞊1), O121:H7 (n꞊1), O146 (n=1). E. coli isolates were analyzed for the existence of hemolysin gene (hly) and enterotoxin genes (Sta, Lt) using PCR, 7 strains carried hly gene (20.59%) and 31 (91.19%) strains carried Sta, while, Lt gene couldn’t be identified in all tested E. coli strains. Also, 34 E. coli isolates were analyzed for β-haemolysis on sheep blood agar plates 5% and the presence of hemolysin gene (hly) on 5% washed sheep RBCS. Out of 34 E. coli isolates 15 E. coli isolates showed no haemolysis on sheep blood agar 5% .and so had no haemolysis titre .while 19 E. coli isolates showed β-haemolysis on sheep blood agar plates 5%. When 19 E. coli isolates titrated for haemolysin gene (hly) on 5% washed sheep RBCS, 3 E. coli isolates had titeration (½ ), 4 E. coli isolates had titeration (¼) whereas 4 E. coli isolates had titeration (1/8),1 E. coli isolates had titeration (1/16), While 2 E. coli isolates had titeration (1/32), followed by 2 E. coli isolates had titeration (1/64), and 3 E. coli isolates had the highest titeration of haemolysin gene (hly) (1/128).