ANTIMICROBIAL RESISTANCE AND BIOFILM FORMATION PATTERNS OF Escherichia coli ISOLATED FROM MARKET RAW MILK AT ZAGAZIG CITY

Abstract

In the present study, one hundred samples of raw cow milk were collected randomlyfrom different dairy shops and markets in Zagazig city for isolation and identification of Escherichiacoli which is considered a reliable indicator for fecal contamination and an important cause of foodpoisoning. Identification was done microscopically, biochemically by different biochemical tests(IMVIC) and serologically. The incidence of E. coli in raw milk samples was 47%. Also, theserological identification of E. coli isolates revealed that O26 is the most predominant serogroup bypercentage of 21.3%. E. coli pose the greatest threat to human health because of its growing resistanceto antibiotics. Antimicrobial susceptibility testing (AST) was done by disc diffusion method against 10antimicrobials 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% and100.0%, respectively. However, they were highly sensitive to chloramphenicol, ciprofloxacin andtetracycline with percentage of 100.0%, 100.0% and 93.6% respectively. In addition, 89.4% of E. coliisolates showed multi drug resistance (MDR). The ability of bacteria for adherence to food surfacesand biofilm formation is a source of food contamination that affect food safety and industry. Microtiter plate assay used for testing biofilm formation and represented that 78.7% of E. coli isolates werenon-biofilm producers, 6.4% were weak biofilm producers, 14.9% were moderate biofilm producersand none of isolates was strong biofilm producers