الفهرس 
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Abstract
Bacteriological examination of a total number of 200 broiler chickens of ages (3-5weeks) and 100 samples from baby chicks of ages (one day- 14 days) that suffered from loss of body weight, diarrhea, mortalities, omphalitis and respiratory manifestations revealed that 168 cases were harbored bacterial strains with an incidence of 56%.
Bacterial species isolated from the examined cases (300) were predominately, the most prevalent bacterial isolates were E. coli (120 isolates), Salmonella spp. (24 isolates), Pseudomonas aeruginosa (24 isolates) with an incidence of 40%, 8%, 8% respectively.
E. coli was mainly isolated from liver (60), heart (56), and yolk sac (4) with an incidence of 81.08%, 77.78%, and 20% respectively. Salmonella spp was isolated mainly from liver (10), heart (8), and yolk sac (6) with an incidence of 13.51%, 11.11% and 30% respectively. Pseudomonas aeruginosa was mainly isolated from yolk sac (10), heart (8), liver (4), and air sac (2) with an incidence of 50%, 11.11%, 5.4% and 100% respectively.
The serological typing of 91 E. coli isolates, 6 O-serogroups were obtained. The serogroup O78 was the most prevalent represented 25 isolates (27.5%) followed by serogroups O158; 17 (18.7%) and O128; 15 (16.5%). Then, the serogroups O55, O1 and O168 represented as 12 isolates (13.2%), 9isolates (9.9%) and4 isolates (4.4%), respectively. Moreover, there were 9 isolates (9.9%) were untyped with the available antisera.
Moreover, serological typing of 24 Salmonella isolates revealed that, all the isolates were serotyped as 9 S.Kentuky (37.5%), 8 S. Enteritidis (33.3%) and 7 S.Infantis (29.2%)..
In-vitro the sensitivity test of 55 E. coli isolates, 12 Salmonella spp and 10 Pseudomonas aeruginosa isolates were tested against 12 chemotherapeutic agents revealed that the majority of E. coli isolates were highly resistant to Amoxycillin (100%), Lincomycin (100%), Rifampicin (100%) and Sulphamethaxzole+Trimethoprim (83,63%). On contrary, E. coli strains were highly sensitive to Colistin sulphate (90.9%), Amoxicillin+Clavulinic acid (56.3%), 50.9% for each Spectinomycin and Fosfomycin. While Salmonella spp were highly resistant to Lincomycin, Rifampicin, Amoxicillin+Clavulinic acid and Spectinomycin with an incidence of 100%, 100%, 58.33% and 41.67% respectively. On the other hand Salmonella spp strains were highly sensitive to Colistin sulphate (100%), Enrofloxacin (91.67%), 75% for each Sulphamethaxzole+ Trimethoprim and Fosfomycin. The tested isolates of P. aeruginosa were highly resistant to the most used chemotherapeutic agents.
Due to extensive usage of antibiotics and presence of highly resistance strains, 14 E. coli and 8 Salmonella isolates were tested for detection of some resistance and virulence genes.
PCR was applied on 8 isolates of MDR Salmonella isolates to determine 7 genes; 4 resitance genes (blaTEM, dfrA, sul1 and tetA) as well as 3 virulence genes (invA, sopB and avrA).The results of PCR of Salmonella isolates revealed that invA gene was the most prevalent found in all isolates (100%) followed by sul1and tetA genes found in 6 (75%) and 5 isolates (62.5%), respectively. Then, both blaTEM and avrA genes were found in4 isolates (50%) while neither dfrA nor sopBwas found in any isolate.
The results of PCR of E. coli isolates revealed that blaTEM gene was the most prevalent found in all isolates (100%) followed by sul1,iutA and iss genes which were found in 13 (92.9%), 11 (78.6%) and 10 isolates (71.4%), respectively. Meanwhile tetA, tsh and dfrA genes were found in 5(35.7%), 4 (28.6%) and 3 isolates (21.4%), respectively and aacC gene not detected in any isolates
The antimicrobial activity of Cinnamon, Anise and Oreganium oils were tested against MDR 32 E. coli and 18 MDR Salmonella isolates. Cinnamon oil exerted growth inhibitory activity on E. coli and Salmonella isolates at concentration of 3% (100 %). while at 2% concentration 19 E. coli isolates (59.4%) and 6 Salmonellae isolates (33.3%) were inhibited. On contrary, 1% concentration had no effect on all the tested isolates.
While Anise oil not exerted any growth inhibitory effect at any concentration of (1%, 2%, 3%, 4%, 5% and 6%), on the other hand Oreganium oil exerted a strong growth inhibitory effect on E. coli and Salmonella isolates at concentration of 1% (100%). while at 0.5% concentration all E. coli isolates (100%) and 15Salmonella isolates (83.3%) were inhibited.