A total of 194 milk samples from clinically mastitis cattle cows were collected from Giza, Monofia, Fayoum, Ismailia,
and Beni-Suef Governorates. All samples were collected during the period from December 2016 till June 2017.
Bacteriological study gave a total of 29 positive strains of Escherichia coli (E.coli) in the rate of (14.9%) from all collected
samples. Twelve E.coli isolates were identified from cultured samples in a single manner (6.2%) and was isolated with
Staphylococcus aureus (S.aureus) by 8/194(4.1%), with Streptococcus species (Strept. spp) by 3/194(1.57%), meanwhile
it was isolated with S.aureus and Strept. spp. by 6/194(3.1%). On the other hand 18 clinical mastitic milk samples were
showed no growth of any pathogenic microorganisms on ordinary and specific used media of bacteriology from all
investigated milk samples by (9.3%). It was observed that several serotypes were recovered from clinical cases of milk
sample with different E.coli infection as O27, O146, O125, O126, O111, O20, and O157. Concerning the sensitivity test
to choice the suitable antibacterial drug(s) for treatment clinical mastitis in cattle cows the data revealed that ,Cefiquinom,
Gentamycin and Amoxicillin +Clavulinic acid were the antibacterial drugs of first choice that could be used to overcome
a great number of single isolated E.coli causing clinical mastitis. Vice versa, the resistant antibiotics for single E.coli
infection causing clinical mastitis were Amoxicillin, Ampicillin, and Neomycin. Studied strains were gave a positive
results for virulence E.coli genes: phoA ,ompA and fimH in 5 examined strains (100 %),classified as follow :(two strains
of O27/28.6%) ,( one strain of O125/14.3%) ,( one strain of O126/14.3%) , and (one strain of O146/14.3% ). while Stx1
and Stx2 virulence genes were detected in only 2 studied strains of E.coli in a total percentage of 28.6 %, divided into,
O111(14.3%) and O157(14.3%).