Detection of Shiga toxin-producing Escherichia coli O157 in shellfish (Crassostrea gigas)

One hundred and fifty oysters were tested for faecal coliform bacteria, Sal monella, E. coli and E. coli O157. All samples satisfied French regulations for the quality of live shellfish. However, one strain of E. coli O157 was recovered from one sample that contained 276 cfu of faecal coliform bacter ia per 100 g of tissue, no Salmonella and no other E. coli. This strain tes ted positive for three pathogenicity genes: eae, EHEC-hlyA, and stx. Accord ing to the results of stx genes subtyping, we can conclude to the presence of stx(1) and stx(2c). At the time of this study (1996), this sample could legally have been distributed for human consumption.