Abstract
This study was planned to throw the light on the most important Streptococcus bacteria that isolated from the milk and pus and the most important laboratory tests that used in differentiation between the streptococcal bacterial species.
This study was carried-out on atotal number of 100 random samples of milk were collected from different markets at Behera Governorate. The samples were placed separately in clean sterileplastic bags and transferred in an ice box tolaboratory under complete a septic conditions without any delay. Also, on 100 samples from closed abscesses have been obtained with sterilesyringe which transferred directly and rotated in enriched selective media.
Our results concluded that, the streptococcus agalactiae and streptococcus pyogenes are the most important bacterial isolates that causes severe losses to milk industry , also the streptococcus pyogenes of zoonotic importance as it transmitted to human. The catalase test, oxidatse test and hemolytic test are the main tests used for diagnosis and differentiation between streptococcus agalactiae and streptococcus pyogenes. The bacitracin sensitivity test is main test for differentiation between streptococcus agalactiae and streptococcus pyogenes The results also indicated that the level of streptococcus agalactiae in milk higher than that of streptococcus pyogenes and reached to 7 % and 3 % for streptococcus agalctiae and pyogenes, while, in pus its levels reached to 0 and 40 % for streptococcus agalactiae and pyogenes in pus. Also the results cleared that the PCR method for detection of mastitis considered as the best method

Key words: Streptococcus species, Laboratory differentiation, Bacteria