A total of 100 samples from ten random broiler chicken carcasses (about 2kg in weight) were collected after complete preparation involving (washing in achiller, slaughtering, scalding, defeathering and evisceration), at an automatic poultry slaughtering plant in Ismailia city, Egypt. The samples were kept separately in plastic bags, and transported immediately to the laboratory in an insulated ice box under aseptic conditions.

For confirmation of isolated strains and for detection of shiga toxin1 and shiga toxin2 13,14.

DNA extraction from samples was performed using the QIAamp DNA Mini kit (Qiagen, Germany, GmbH) according to manufacturer’s recommendations with modifications. Briefly, 200 µl of the sample suspension was incubated with 10 µl of proteinase K and 200 µl of lysis buffer at 56^OC for 10 min. After incubation, 200 µl of 100% ethanol was added to the lysate. The sample was then washed and centrifuged following the manufacturer’s recommendations. Nucleic acid was eluted with 100 µl of elution buffer.

Primers used were supplied from Metabion (Germany) (Table 1)

Primers were utilized in a 25µl reaction containing 12.5 µl of EmeraldAmp Max PCR Master Mix (Takara, Japan), 1 µl of each primer of 20 pmol concentration, 4.5 µl of water, and 6 µl of DNA template. The reaction was performed in an Applied biosystem 2720 thermal cycler.

The products of PCR were separated by electrophoresis on 1.5% agarose gel (Applichem, Germany, GmbH) in 1x TBE buffer at room temperature using gradients of 5V/cm. For gel analysis, 20 µl of the products was loaded in each gel slot. Generuler 100 bp ladder (Fermentas, Germany) was used to determine fragment sizes. The gel was photographed by a gel documentation system (Alpha Innotech, Biometra) and the data was analyzed through computer software.

All the obtained results were evaluated statistically using Analysis of variance (״Anova test) statistic “16.

Enterobacteriaeace count is more frequently used to assess enteric contamination. Nearly similar results were reported bywhich Enterobacteriaeace counts were 5.26×10⁴ in examined chicken breast muscle samples 23. In a similar study it was reported that Enterobacteriaeace counts were 9.5×10⁴±0.9×10⁴cfu/g in examined chicken breast samples20. In addition, higher counts of Enterobacteriacaecounts were reported (3.9 ×10⁵ and 3×10⁵ cfu/g, respectively)24 in chicken thighs and breast samples tested microbiologically25.Another investigator reported thatEnterobacteriaeace counts in examined chicken carcasses samples were 1.57-2.17×10⁶cfu/g25. On the other hand, a lower count was reported by26 in which the mean counts of Enterobacteriacae in chicken breast samples was 1.5×10³±2.3×10² cfu/g.

The presence of E.coli in food of animal origin is considered as an indicator of faults during preparation, handling, storage or service27. Nearly similar results were reported E.coliwas isolatedfrom 13.33% thigh samples28. Moreover higher percentages of Escherichia coli were reported by29who founded that the prevalence and load of E.coli in chicken meat sold in retail market in Uttar Pradesh was 68% of the examined samples,30 who reported that 45% of the chicken samples collected from retail outlets were positive for E.coli. On the other hand21 failed to detect E. coli O157:H6 targeted samples, whereas only 2% positive samples were reported out of 50 tested31.

Using serology O₁₅₇:H₇ (EHEC),1(16.6%) which was belonged to O114:H21(EPEC), O127:H6 (ETEC) and O26 (EHEC) were identified from breast sampls,. while, O₁₅₇:H₇ (EHEC), O114:H21(EPEC) ,O127:H6 (ETEC) and O126 (ETEC) were identified from thigh samples.

Enterotoxigenic E.coli (ETEC) strains are considered the common cause of traveller`s diarrhea and / or children diarrhea. ETEC may contaminate ready to eat food through a symptomatic carrier, a person who recovers from an ETEC infection and continue to excrete the organism for several months.

On the other hand, Enteroheamorrhagic E.coli (EHEC) can cause sever illnesses characterized by sudden onset of severe crampy abdominal pain followed by watery diarrhea, which later on becomes bloody. There may be little or no fever and the duration of illness is 2 to 9 days. Death rate in some reported outbreaks may reach 36%. Since 1982, more than 10650 outbreaks of EHEC were reported in USA32.

All 100% of Ecoli o_157, isolates identifiedserologically from chicken meat samples were positive by PCR. Thus there was complete agreement between the results of serological methods and PCR technique for identification of Ecoli o_157. Accordingly, the application of one of these trials is sufficient and accurate for identification of such organism.

This agrees with the report33 who observed similar findings between multiplex PCR and microbiological/biochemical methods Microbiological method is still the method of choice of isolation and identification of food pathogens owing to its availability and ease of application.