Abstract
Bacterial pathogens play an important role in causing respiratory disease in domestic poultry species, so the present study was carried out for isolation of bacteria from broiler chickens suffering from respiratory manifestations with special reference to molecular characterization of E. coli, Detection of virulence genes of E. coli associated with respiratory system infection was carried out in addition to antibiogram activities and plasmid profile of Pseudomonas aeruginosa from nasal swabs, tracheal swabs and lung samples which were collected from twenty seven broiler flocks at private farm in El-Bohira governorate. A total of 41 samples were subjected to bacterial isolation and identification by using cultural, biochemical, PCR, antibiogram and plasmid profile. Out of 41 samples, 63 isolates were recovered which categorized as 21 (33.3%) E. coli, 17 (26.9%) Pseudomonas aeruginosa, 4 (6.3%) Salmonella Enteritidis, 1 (1.6%) Pasteurella multocida, 10 (15.9%) Corynebacterium species, 3 (4.8%) Staphylococcus aureus and 7 (11.1%) coagulase negative Staphylococcus isolates. The results of amplification of phoA gene (specific for genus of E. coli ) revealed that out of 21 tested isolates, 10 (47.6%) isolates were positive. The results of amplification of virulence genes (tsH, fimH and papC) of E. coli revealed that out of ten isolates of E. coli; of them 3 (30%) isolates were positive for tsH gene, 7 (70 %) isolates were positive for fimH gene and 1 (10 %) isolate was positive for papC gene. The antibiotic resistance pattern showed that Pseudomonas aeruginosa showed high resistance (94.6%) to levofloxacin, streptomycin, ciprofloxacin, ofloxacin, erythromycin, chloramphenicol and neomycin , 76.5% were resistant to norfloxacin but 5.9% of pseudomonas aeruginosa isolates were intermediate susceptible to erythromycin, chloramphenicol and neomycin, (17.7 %) to norfloxacin and (5.9%) were susceptible to levofloxacin, streptomycin, ciprofloxacin, ofloxacin and norfloxacin. Out of 17 Pseudomonas aeruginosa isolates, 15(88, 2%) isolates showed plasmid DNA profile (specific band at 25kbp).

Key words: E. coli, Pseudomonas aeruginosa, virulence genes, antibiogram, plasmid profile