A nationwide surveillance study on E.coli 0157:H7 and enterobacteriaceae in Irish minced beef products

Abstract

A surveillance study on prevalence and numbers of E . coli O157: H7 in minced beef (unpackaged or packaged) and beefburgers (frozen, fresh and unpackaged or packaged) was carried out over a period of 12 months in the Republic of Ireland. A total of 1533 products were tested with approximately 15 products collected from each of the 26 counties every 3 months. Mince and beefburgers were collected from both supermarkets and butcher shop outlets. A standard analysis was conducted by sample enrichment, IMS extraction and plating onto SMAC agar with confirmation by PCR. The results showed that 43 retail beef products (2.8 %) contained E .coli O157:H7. The number of E .coli O157: H7 in 21 of these samples ranged from log100.51 - 4.03 cfu g-1 ( i.e. 3 to 10,700 bacteria per gram) while in the remaining 22 the pathogen was detectable by enrichment only. There was a seasonal effect observed with 33 of 43 positive samples detected in January (n = 8), April /May(n=20) and August (n=5) and the remaining 10 positive samples detected over the other 8 months. Of the beef products testing positive, 32 were purchased from supermarkets and 11 from butcher shops. E .coli O157:H7 was recovered from 2.8% (13 / 457) of fresh packaged mince and from 1.88 % (3 / 160) of fresh unpackaged burgers purchased from butcher shops. Of the 43 isolates recovered, 41 contained the virulence genes v t1, v t2, E aeA and H lyA while the remaining 2 isolates contained only one of the vtproducing genes (v t1or v t2).