Bas.J.Vet.Res.Vol.11,No.2,2012 47 PREVALENCE AND ANTIMICRIBIAL SUSCEPTIBILITY OF ESCHERICHIA COLI O157:H7 ISOLATED FROM HUMAN AND ANIMAL SOURCES IN BASRAH PROVINCE Bassam Y. Khudaier, Basil A. Abbas, Khulood A. Khleel Department of Microbiology, College of Veterinary Medicine, University of Basrah, Basrah, Iraq. (Received 9 May2012 , Accepted 21June 2012 ) Keywords; Escherichia coli O157,Sorbitol, Milk. ABSTRACT The present study assessed the prevalence of Escherichia coli O157 in diarrhea patients ,beef, and raw milk. A total of 675 samples were inoculated in trypticase soy broth to enhance the growth of E. coli O157:H7. Out of total samples 73.5% isolated as E. coli then cultured on Sorbitol MacConkey agar ,31.8% non fermenting sorbitol (NSF) E. coli colonies were isolated and confirmed by specific biochemical tests . From NSFEC 13.7% were diagnosed as E.coli O157:H7 by serological test ,the result revealed no significant differences in the level of contamination with E. coli O157:H7 between beef ,stool and milk .The isolated bacteria were tested for antibiotic susceptibility test which showed resistance 100% to cephalothin ,cefoxitin , cefixime, trimethoprim , amoxicillin, azithromycin, and amoxicillin/clavulanic acid and sensitive 100% to ciprofloxacin ,imepenim ,nitrofurantion gentamycin and amikacin . No major differences in antibiotic susceptibility patterns among the isolates were observed. INTRODUCTION Escherichia coli is commonly found in human and animal intestinal tracts and , result of fecal contamination or contamination during food animal slaughter, is often found in soil, water, and foods [1].DiarrheagenicE. coli are an important cause of endemic and epidemic diarrhea worldwide .These organisms are currently classified in six categories as follows: enteropathogenicE. coli (EPEC), enterotoxogenicE. coli (ETEC), enteroinvasiveE. coli (EIEC),diffusely adhering E.coli(DAEC),enteroaggregativeE. coli (EAEC),and enterohemorrhagicE. coli (EHEC) [2].One of the most significant food –borne pathogen that has gained increased attention in recent years is E. coli O157:H7 [3] .E. coli O157:H7 cause diarrhea , sever abdominal pain , hemorrhagic colitis, hemolytic –uremic syndrome, and thrombotic thrombocytopenic purpura .The pathogenic factors of enterohemorrhagicE.