Down Regulation of Biofilm and Quorum Sensing Genes in E. coli Isolated from Broiler Chickens Pericarditis Lesions by the Action of Some Essential Oils

E. coli is one of the most important pathogenic bacteria in poultry industry. It causes high economic losses, high morbidity and mortality rates due to collibacillosis. Moreover, it is multidrug resistant bacteria. In the last few years, scientists directed their efforts to the use of essential oils which have antimicrobial actions by inhibition of some virulence properties such as biofilm formation and quorum sensing. In this study, out of 150 examined samples, 139 were found to be bacteriologically positive for G-ve bacilli (92.7%) and 84 E. coli isolates (60.4%) were recovered from broilers suffering from pericarditis. Twenty random recovered isolates were selected for antimicrobial susceptibility test. All isolates were completely resistant to amoxicillin, gentamicin, lincomycin and florfenicol and 90% resistant to trimethoprim- sulfamethoxazole, kanamycin, ciprofloxacin and doxycycline while sensitivity to amoxicillin+clavulanic acid and cefotaxime was 40% and 20% respectively. We screened 15 randomly selected MDR isolates by CR assay for detection of biofilm formation at which CR positive isolates represent 80%. Cinnamon and clove oils showed antimicrobial effect and cause down regulation in both biofilm gene (sfa) and quorum sensing gene (luxS).