الفهرس 
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Abstract
Mastitis represents one of the most important diseases of cattle from economic stand point in Egypt. The disease is characterized by physical, chemical and usually bacteriological changes in the milk and the mammary tissue. The most important changes in the milk are discoloration, presence of clots and blood.
Mastitis caused by streptococci has assumed increased importance in recent years. The prevalence of S. uberis mastitis has increased worldwide. Therefore, this study focused on isolation and identification of Streptococci species from clinical mastitic dairy cattle, in the area of Sharkia, Giza, Suez and Alexandria in Egypt, and detection of the most putative virulence associated genes in the environmental S. uberis isolates by conventional PCR. Furthermore, genotypic diversity among the virulent S. uberis isolates was investigated using RFLP-PCR.
In this study, two hundred milk specimens were collected from dairy cows with clinical mastitis from different private farms in different Governorates in Egypt (Sharkia (n=35), Suez (n=15), Alexandria (n=46) and Giza (n=10) and sporadic samples (n=94) from Belbies, Borden, Awlad-sief, Diarbnegm and Abohammad regions in Sharkia Governorate. The milk samples were collected from different private farms raised in an open housing system without any hygienic measures and with no previous history of treatment.
Conventional methods for streptococcus identification depended mainly on direct milk staining by methylene blue, cultivation on Edward’s, blood agar and bile esculin agar media, Gram staining for detection of streptococcal chains, biochemical identification tests as catalase and sodium hippurate tests, CAMP test, bacitracin susceptibility test and finally serological identification of the unidentified streptococcal isolates. Serotyping of 31 unidentified streptococci isolates revealed 25 Lancefield group C (S. dysgalactiae) isolates and 6 group D non-enterococcus Streptococci with percentages of 17.12% and 4.11%, respectively.