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Abstract Escherichia coli (E.coli), a bacterium that is a common inhabitant of the gut of warm blooded animals, including man. Most strains of E.coli are harmless; however, some strains such as E. coli O157:H7 can cause severe food borne disease and are referred to as enterohemorrahgic E .coli (EHEC). This pathogen produces toxins, known as verotoxins or Shiga-like toxins because of their similarity that produced byShigella dysenteriae. (WHO, 1996). E. coli O157:H7 is a gram-negative rod-shaped bacterium. The letter ”O” in the name refers to the somatic antigen number, whereas the ”H” refers to the flagellar antigen (Nataro and Kaper, 1998). E. coli O157:H7 serotype occurred due to the horizontal gene transfer of virulence factors (Whittam et al., 1988). E. coli O157:H7 is one of hundreds of gram negative E. coli. There are more than 170 serogroups of E.coli. Within each serogeroup, there are one or more serotypes. E.coli O157:H7 is the most well known enterohemorrahgic strain (EHEC) (Peacock et al. 2001) E .coli O157:H7 was first recognized as a human pathogen in 1982, when two outbreaks in the United States were associated with eating undercooked hamburgers from a fast-food restaurant chain (Riley et al. 1983). This food borne pathogen has since emerged as a major cause of bloody and non bloody diarrhea, causing up to 20,000 cases and up to 250 deaths per year in the United States (Griffin, 1995). In addition to causing bloody diarrhea, E .coli O157:H7 infection is the most common cause of the hemolytic uremic syndrome (HUS), which cause kidney failure among children in the United States. HUS is associated with significant long-term complications. 3%-5% of patients who develope HUS die, and approximately 12% are left with significant sequelae, including end-stage renal disease, hypertension, and neurologic Injury (Siegler et al., 1994). Consumption of ground beef, lettuce, unpasteurized cider or milk, and untreated water has been associated with outbreaks, and person-to-person transmission is well documented (Griffin, 1995). The VTEC enter the food chain via faecal contamination of milk, contamination of meat with intestinal contents during slaughter or contamination of fruit and vegetables by contact with contaminated manure. VTEC are also transmitted through contact with infected people, animals or animal waste. Moreover, contaminated water which used for irrigating or washing vegetables can also be source of infection for humans or animals (Paton and Paton, 1998). Routine techniques for diagnosis of VTEC focus exclusively on the detection of E. coli O157: H7 in clinical specimens, animal feces, food and environment. There are many problems with the developed techniques for E. coli O157: H7. A major challenge is the isolation of bacterium from different complex sample types. The sample will often contain low numbers of VTEC, very high levels of background flora and natural inhibitors which interfere with isolation of E.coli O157: H7 (Mead and Griffin, 1998; Gross, 1990; Duffy et al. 1999 and WHO, 1998). So techniques to improve the speed of O157 detection have been developed based on immunological or DNA techniques (polymerase chain reaction (PCR)). (Duffy et al. 1999) Aim of the work Thus, keeping in view, the above facts and the magnitude of the problem a more rapid, accurate method to detect E. coli O157:H7 is needed for improved clinical diagnosis, and epidemiological studies. Therefore, the present study was planned and aimed to detect and characterize E. coli O157:H7 from diarrheic and apparently healthy calves, raw milk and from children suffer from diarrhea which can achieve through the following steps:- 1- Isolation of E-coli O157:H7 by using MacConkey agar and sorbitol MacConkey agar with Cefixime Tellurite (CT) supplement (selective media) 2- Identification of E-coli O157:H7 by conventional biochemical reaction and API20E. 3- Serological detection of E.coli O157 by using Latex agglutination kit for O157. 4- Confirmation of the E-coli O157:H7 by polymerase chain reaction (PCR) using specific primers. |