الفهرس 
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Abstract
Bacteriological examination of a total number of 105 samples of broiler chickens .The results of E. coli isolation showed that 78 out of 105 samples (74.28%) resulted in E. coli isolation and all 78 E. coli isolates (100%) showed congo red binding activity and were considered as congo red positive (CR+). Of the isolates, 21 were mannose resistant haemaglutinating with an incidence of 26.92%. and 57 (73%) were positive biofilm on a YESCA CR agar. Response of E. coli isolates recovered from broiler chickens to various chemotherapeutic agents in-vitro: showed that, the majority of E. coli isolates were awfully resistant to amoxycillin (100%), lincomycin (100%), rifampicin (100%), clindamycin (100%), doxycycline (100%), spiramycin (100%), amoxicillin + clavulanic acid (100%), sulphamethaxzole + trimethoprim (73%), ceftriaxone (53, 84%) and fosfofmycin (50%). On the contrary, E. coli isolates were extremely sensitive to colistin sulphate (100%), gentamycin (84.46%), [and moderately sensitive for ciprofloxacin (42.23%) and apramycin (34.61%).
Multidrug resistant and virulent E. coli isolates (n=30) were selected for serogrouping to the O somatic antigen. Seven seroroups were distinguished amongst the isolates into O119, O78, O25, O55, O111, O1 and O26 with an incidence of 30%, 20%, 20%, 10%, 10%, 3.33% and 3.33%, respectively .
The results of PCR of E coli isolates revealed that adrA, tetA, blaTEM and sul1 genes were the most dominant genes as they were found in all isolates (100%) shadowed by fimH (80%), papC (40%) and hly (20%).
In this study the immune status of broiler chickens infected with E. coli after administration of lectin and probiotic and oregano essential oil.
The results showed that the clinical symptoms, mortality rates and reisolating rates revealed that All of the administered groups had significantly reduced clinical symptoms, post mortem lesions, and rates than the challenge control group
The assessment of performance reviews the average body mass of the birds across all groups was remarkably consistent. before challenge while, after the challenge, significant differences in both bodyweights and FCR were noticed.
Avian cytokines gene expression analysis using qrt- pcr: lectins administrated group: There was an increase of IL-4 in lectins group fold change than other groups before challenge to 8.3397, and to 0.8362after challenge in comparison with positive control group (0.1914). While,IL-6 and INFG fold change were linearly inhibited inIL-6 from10.0561 to 0.2045 before challenge, to 3.1602after challenge, INFG fold change from 7.3871 to 0.3214 before challenge, and to 2.0878 .
Probiotic administrated group: There was an increase ofIL-4 in probiotic group fold change before challenge to4.8065, and to 0.6811 after challenge in comparison to positive control group (0.1914). While, IL-6, and INFG
fold changes were linearly inhibited in IL-6 from10.0561in positive control group to 0.3998 before challenge, to6.6900 after challenge, INFG fold change from 7.3871 to 0.5586 before challenge, and to 4.0954 after challenge.
Oregano essential oil administrated group there was an increase of IL-4 in essential oil group fold change before challenge to 4.8065, and to 0.6811 after challenge in comparison with positive control group (0.1914). While IL-6 and INFG fold change were linearly inhibited in IL-6, from 10.0561 in positive control group to 0.3998 before challenge, to 6.6900 after challenge, INFG fold change from 7.3871 to 0.5586 before challenge and to 4.0954 after challenge.