الفهرس 
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Abstract
6.In this study 60 farms from El minia governorate (40 treated with different antibiotics or antimycoplasmal drugs from 2-3 days before sampling and 15un treated)broilers chicken flocks were positive for E. coli isolation while 5 treated farms were negative.
Geographical distribution of positively flocks treated and un treated were : Magaga (3 treated -1un treated) , Benimazar (11 treated -2un treated) , Mattai (3 treated -1un treated), Samalout (6 treated -3un treated) , El Minya (8 treated -5un treated) ,Abokorkas (3 treated -2un treated) and Malawi(6 treated -1un treated).
Seventy two (72) different bacterialisolates of suspected E coli were isolated from Magaga (six isolates from treated flocks and one isolate from un treated flocks ) , Benimazar (eight isolates from treated flocks and three isolates from un treated flocks) , Mattai ( three isolates from treated flocks and two isolates from un treated flocks ), Samalout (ten isolates from treated flocks and four isolates from un treated flocks ) , El Minya (ten isolates from treated and six isolates from un treated flocks) , Abokorkas ( four isolates from treated flocks and four isolates from un treated flocks ) and Malawi (nine isolates from treated flocks and two isolates from un treated flocks ) .
The biochemical identification of such isolates revealed that 56 of them were E. coli with an incidence of 77.8%, 14 isolates belonged to Klyuvera spp .with an incidence of 19% and 1 isolate belonged to each shigella and Enterobacter cloacae spp with an incidence of 1.4% . The isolated E. coli strains were examined for the following virulence factors: Congo red binding assay and hemolytic activity.
All of E. coli isolates showed Congo red binding activity. Only one isolate gave beta hemolysis on blood agar. 25 E. coli from the most redness isolates on congo red agar were serotyped and examined for O-serogroup determination test showed that the isolates belonged to eleven different O serogroups including: O115, O6, O125, O20, O55, O158, O27, O8, O129 and O142serogroups , the most prevalent serogroups were O125 andO158with percent 16 and 12 respectively. The majority of E. coli isolates were sensitive to Colistin sulphate (38%) and Norofloxacin (38%) followed by Ciprofloxacin (19%), Cefotaxim (19%) and Ofloxacin (19%). On the other hand, E. coli were resistant (100%)to Amoxicillin, Clindamycin, Erythromycin and Streptomycin. PCR analysis of 12 serogroups of E. colifor presence or absence of antibiotic resistance genes of Streptomycin, Cefotaxim and Doxycycline.
The experimental infections of isolated E. coli O125 in 14th days old chicks either orally or subcutaneously were carried out as well as evaluating the role of guardizen-m probiotic which act by competitive exclusion product in drinking water for 7 successive days before the first day of infection show increase of weekly feed consumption, weekly body weight gain, main weekly body weights and FCR and also compared antibiotic using. The symptoms described by pathological and histopathological effects of liver and intestinal samples from infected chickens.
from results of our study we can conclude that:
1. The most prevalent bacterial isolated from diseased broiler was E. coli serotypes.
2.The obtained isolates showed different patterns of sensitivity to the tested antibiotics.
3. from our study O125 was the most common Enterobacteriacae distributed in broiler flocks and caused economic loses.
4. Probiotics played an important role in preventing the infection and improvement of the performance parameters of chicks. Therefore we recommended the routine use of probiotics especially in drinking water.
5.Using of Ciprofloxacin have a great effect against Enterobacteriaceae infection.