Examination of verotoxin producing Escherichia coli in some Egyptian dairyproducts with special reference to serotype O157 : H7

Damietta and Kareish are the most popular cheeses consumed in Egypt. Both a re produced from raw milk and consumed either fresh (Kareish) or after ripe ning for 2 months in brine containing about 7 to 10% NaCl (Damietta). Becau se contamination of cheese, particularly with coliform bacteria including E . coli, from the raw material and during the manufacturing process is a com mon occurrence and the coliforms can survive this process, the incidence of toxigenic strains, i.e. serotype O157:H7, should be examined. A total of 114 samples, consisting of soft Damietta cheese (40), soft Karei sh cheese (24), hard Ras cheese (30) and raw milk (20), were examined for c oliforms and E. coli. Coliforms failed to be detected in 26.3% of the sampl es while 73.7% showed most probable number counts ranging from 0.3x10(1) to 10(6)/g or ml. E. coli was not detected in 74% of the samples examined whi le 26% had E. coli counts between 0.3x10(1) and 10(5)/g or ml. None of the isolated E. coli strains belonged to serogroup O157 and the gen e sequences for verotoxins (VT1 and VT2) were not detected in any of the is olates by colony blot hybridization.