In the present study, one hundred samples of raw cow milk were collected randomly
from different dairy shops and markets in Zagazig city for isolation and identification of Escherichia
coli which is considered a reliable indicator for fecal contamination and an important cause of food
poisoning. Identification was done microscopically, biochemically by different biochemical tests
(IMVIC) and serologically. The incidence of E. coli in raw milk samples was 47%. Also, the
serological identification of E. coli isolates revealed that O26 is the most predominant serogroup by
percentage of 21.3%. E. coli pose the greatest threat to human health because of its growing resistance
to antibiotics. Antimicrobial susceptibility testing (AST) was done by disc diffusion method against 10
antimicrobials and the results revealed that E. coli isolates were highly resistant to amoxicillinclavulanate,
ampicillin, cefotaxime and ceftazidime with percentages of 89.4%, 89.4%, 100.0% and
100.0%, respectively. However, they were highly sensitive to chloramphenicol, ciprofloxacin and
tetracycline with percentage of 100.0%, 100.0% and 93.6% respectively. In addition, 89.4% of E. coli
isolates showed multi drug resistance (MDR). The ability of bacteria for adherence to food surfaces
and biofilm formation is a source of food contamination that affect food safety and industry. Micro
titer plate assay used for testing biofilm formation and represented that 78.7% of E. coli isolates were
non-biofilm producers, 6.4% were weak biofilm producers, 14.9% were moderate biofilm producers
and none of isolates was strong biofilm producers