الفهرس 
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Abstract
The poultry industry occupies an important position in the provision of animal protein to man as well as manure for crops and generally plays a vital role in the national economy as an income provider and provides employment.
The object of this work was to isolate and identify Streptococcus and Enterococcus spp. existing in broiler chikens and to demonstrate their antibiotic sensitivity and detection presence of some resistance and virulence genes in these isolates.
In this study a total of 272 samples were collected aseptically from the affected organs including pericardium, lung, liver and kidney of slaughtered diseased and freshly dead broiler chickens.
Bacteriological examination of the collected samples revealed the recovery of 49 positive isolates with an overall prevalence of 18.1% including 24(49%) Streptococcus spp. , 20 ( 40.8% ) Enterococcus spp. and 5 (10.2%) unidentified isolates . All isolates were identified by Vitek2 compact system for identification using Vitek2 ID-GP kits. The results were represented as follow: Streptococccus isolates were identified as S.gallinaceous , S. dysgalactae and S. durans . on the other hand all Enterococcus isolates were identified as E. faecalis only .
The in- vitro antimicrobial susceptibility test using disc diffusion method against 12 antimicrobial agents of 6 different antimicrobial classes of both veterinary and human significance revealed that Streptococcus and Enterococcus isolates showed high sensitivity to Amoxicillin (77.6%),Sulfamethoxazole- trimethoprim (73.5%) and Amoxicillin- clavulanic acid (65.3 %) . Meanwhile, high resistances were recorded against other antimicrobials including Cephalexin ,Cefotaxime sodium, Cefipime, cefotriaxone , Tetracyclin, Kanamycin and Apramycin (100% for each) followed by Gentamicin (87.8%) and Enrofloxacin (63.2%) .Moreover , multidrug resistance was dected in 100% of the inspected isolates .
Using the polymerase chain reaction ( PCR ) for detection of resistance-associated genes including tetO , aac(6’)aph(2’’), blaZ and Pbp1A , among selected MDR isolates revealed exsistance of all tested genes in 100% of isolates . As well as PCR was used to assess virulence associated genes including cylE , brpA , hyl , cylA , asa1and gelE in randomly selected MDR isolates of both Streptococcus and Enterococcus . The results showed that all the tested isolates (100%) harbored cylE , brpA , cylA asa1 genes . On the other hand hyl gene was not detected in any Stereptococci isolates as well as gelE gene not detected in Enterococci isolates .