Screening for Escherichia coli 0157:H7 in Irish ground beef using two commercial detection systems

Escherichia coli 0157:H7 poses a significant threat to public health, as has been illustrated by a number of recent outbreaks in the USA and Britain. The organism produces a potent verotoxin, and is primarily associated with undercooked ground beef. Two commercially available tests were used to screen for 0157:H7 in ground beef purchased in the Munster region. The two test systems, an enzyme-linked immunosorbent assay (EHEC-TEK™) and immunomagnetic seperation (Dynabeads®), were assayed for their sensitivity to deliberately spiked ground beef samples before testing was initiated. The EHEC-TEK™ assay consistently detected 0157:H7 at an initial level of four organisms/g ground beef, while the Dynabeads® assay was reliable at an initial level of 40 organisms/g ground beef. These detection limits were deemed to be sufficiently sensitive for the purposes of the screening study. Almost 600 samples of ground beef were screened in total (296 using EHEC-TEK™ and 586 using Dynabeads®). The same single positive sample was detected with both test systems. The positive isolate was confirmed serologially and was shown by polymerase chain reaction (PCR) to possess a verotoxin gene. The amplified fragment was sequenced and shown to share 96% identity with published sequences. This is the first report of the presence of 0157:H7 in Irish meat.