الفهرس 
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Abstract
Bacteriological examination of a total number of 150 broiler chickens that suffering from pericarditis, mortalities and respiratory manifestations revealed that 139 cases were positive for G-ve bacilli (92.7%).
The following bacterial species were recovered, E. coli (84 isolates), P. aeruginosa (29 isolates), P. putida (3 isolates), P. multocida (14 isolates), B. trehalosi (6 isolates) and P. avium (3 isolates) with an incidence of 60.4%, 20.9%, 2.2%, 10.1%, 4.3%, 2.2% respectively.
Using disk diffusion method against 10 different antimicrobials, twenty randomly selected isolates of E. coli were tested. All isolates were completely resistant to amoxicillin, gentamicin, florfenicol, lincomycin. Sensitivity to amoxicillin+clavulanic acid and cefotaxime was 40% and 20 % respectively. Sensitivity to doxycycline, kanamycin, ciprofloxacin, trimethoprim- sulfamethoxazole was recorded in 2 out of 20 tested isolates (10%). For all 29 isolates of P. aeruginosa: all isolates were highly resistant to amoxicillin, kanamycin, lincomycin, while sensitivity to amoxicillin+clavulanic acid, doxycycline, trimethoprim- sulfamethoxazole and florfenicol was 93.1%. sensitivity to gentamicin, cefotaxime and ciprofloxacin was 86.2%. With regard to all 14 of P. multocida isolates: all isolates were highly resistant to amoxicillin, doxycycline, gentamicin, florofenicol and lincomycin. Four isolates were sensitive to cefotaxime 28.6%. Two isolates were sensitive to amoxicillin+clavulanic acid, kanamycin and ciprofloxacin 14.3%. one isolate was sensitive to trimethoprim- sulfamethoxazole 7.1%.
Fifteen MDR isolates randomly selected for detection of biofilm formation by using Congo Red assay 7 isolates show positive result 46.7%.
The antimicrobial activity of black pepper, peppermint, capsaicin, and ginger oils were tested against 15 MDR isolates. All isolates grow when exposure to black pepper, peppermint, capsaicin, and ginger oils in both concentrations 0.1% and 0.01%. On other hand oregano, cinnamon, and clove oils inhibit growth of all isolates in concentration 0.1%, while in concentration 0.01% all isolates grow.
RT-PCR was applied before and after exposure to non-inhibitory concentration of cinnamon and clove oils (0.01%) to determine CT values and fold changes of 3 biofilm genes (pslA, tadG and sfa) as well as 3 qurom sensing genes (lasI, luxS and luxS) for two P. aeruginosa, one P. multocida, and one E. coli isolates respectively. CT values of most isolates were below 29 indicate very strong positive reactions. After treatment with non-inhibitory dose of cinnamon and clove oils, CT values and fold changes of the same genes were down regulated in a range from 0.0390 to 0.5035.