الفهرس 
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Abstract
Streptococcus agalactiae is a major contagious pathogen causing bovine clinical and subclinical mastitis. Although this bacterium has a short life span in the environment, it can survive indefinitely within the mammary gland as an obligate pathogen of the udder. Programs to reduce the impact of S. agalactiae infection have been enforced in many countries over years as eradication from a herd may not be achieved if S. agalactiae becomes resistant to the antibiotic used, either by genetic mutation or by production of a coating to known as biofilm shield cells from the antibiotic.
This work was designed for isolation, identification and antimicrobial susceptibility testing of Streptococci species recovered from clinical mastitic dairy cattle, followed by qualitative and quantitative detection of biofilm formation by S. agalactiae. Furthermore, evaluation of the alternative agents as cinnamon oil and silver nanoparticles in comparable to amoxicillin clavulanic acid for better understanding their effect on the genes responsible for biofilm formation and their regulator using semi quantitative real-time PCR and scanning electron microscope in order to reduce the drawbacks of antibiotic resistance.
The bacteriological analysis revealed that Streptococci species were detected in 146 out of 200 mastitis milk samples with a percentage of 73%. According to the presumptive conventional identification, the 146 streptococci isolates were identified as S. agalactiae (n=7), S. uberis (n=23), Enterococcus species (n=40), S. pyogenes (n=45), group C streptococci (n=25) and group D non-enterococcus streptococci (n=6).