الفهرس 
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Abstract
Streptococcal mastitis causes tremendous economic losses in bovine milk production. Milk is a good media for growth of enterococci .In present study a total of 400 mastitic milk samples were collected from apparently healthy and mastitic animals in percent 72.5% and 27.5% respectively .This study was carried out at different Egyptian farms. The percent of Streptococcus species were 4.25% ,while Enterococcus species were 17.5%, ,and 4.5% for streptococcus like bacteria ( 3.5% for Lactococcus lactis and 1.5% Aerococcus viridians among isolated mastitic animals .The isolates were confirmed biochemically by API 20 strep and serologically by lancified grouping. Antimicrobial susceptibility test was assayed by the disc diffusion. Streptococcus species showed high resistance to erythromycin (52.94%) and gentamicin ( 47.06%), while Enterococcus species showed high resistance to erythromycin(72.73%). Molecular approaches PCR were optimized for identification of Enterococcus species by using specific primers and for detection of presence of cylA virulence gene in E. faecium and E .faecalis. All isolates tested confirmed as enterococci and nearly all isolates ( 11 out of 12 isolates of E. faecium and E. faecalis) have cylA virulence gene.