Abstract
A total of 700 different samples were collected from dairy cows and their surrounding environment from different dairy farms located in Kafr El-Sheikh including; milk (150 samples from clinically suspected cases and another 150 samples from apparently healthy cows) and swabs from teats, milking machines and hands of workers as well as bedding materials (100 samples/each) for isolation and identification of Streptococcus species. It was found that 82 samples were positive for California Mastitis Test (CMT) indicative for subclinical mastitis. Also, it was found that the frequency of isolation of Streptococcus species from clinical mastitis milk samples was 44 % (66 isolate) and 37.8% (31 isolate) in milk subclinical mastitis milk samples while the frequency of isolation of Streptococcus spp. from environmental samples revealed that the highest frequency was recorded in the examined samples of bedding materials (57%) followed by milking machine swabs (43%) and teat swabs (42%) then lastly hand swabs (23%). Moreover, the biochemical identification of the obtained Streptococci clarified the presence of Str. agalactiae, Str. dysgalactiae, Str. bovis and Str. uberis with various rates. Antibiogram pattern of S. agalactiae demonstrated high level of resistance against Chloramphenicol (90%) followed by Co-Trimoxazole (78%) while the highest sensitive antibiotic was Spiramycin (72%) followed by Gentamicin (70%) while that of S. uberis demonstrated high level of resistance against Amoxicillin (78%) followed by Amoxyclav (72%) while the highest sensitive antibiotic was Spiramycin (78%) followed by Cefotaxime (64%) and Gentamicin (60%). Finally, four commercial types of disinfectant commonly used in dairy farms including Iodine, Phenol, Virkon S® and TH4; beside Rosemary (Rosmarinus officinalis) which was a herbal agent rich in phenolic compounds with high antimicrobial activity were tested against the obtained isolates of Streptococci.

Key words: Mastitis, Streptococci, antibiogram pattern, disinfectant sensitivity