Carriage of four bacterial pathogens by beef cattle in Northern Ireland at time of slaughter

Aims: To determine the prevalence of four bacterial zoonotic pathogens in beef cattle at time of slaughter in Northern Ireland (NI), in order to assess their potential for reducing beef safety. Methods and Results: Faeces were collected postmortem from beef cattle (n =220) at seven EU registered abattoirs. Standard enrichment culturing methods were employed, plus immunomagnetic enrichment in the case of Escherichia coli O157:H7. Campylobacter spp. were found in 52 samples (24·8%), Listeria monocytogenes in 10 (4·8%), E. coli O157:H7 in 2 (0·9%) whilst Salmonella spp. were isolated from six out of 200 samples (3·0%). Five salmonellas were Salmonella Chandans and one was Salmonella Liverpool. Conclusions: Campylobacter spp. were the most frequently isolated pathogen, despite being relatively rare in beef. Genotyping showed the campylobacters to be very diverse, indicating cattle encounter campylobacters from many sources. The remaining three pathogens, which are associated with meats, occurred at relatively low frequencies, especially E. coli O157:H7. The Salmonella serovars found rarely infect humans. Significance and Impact of the Study: The low prevalence of E. coli O157:H7 in NI beef cattle was confirmed and the reasons for this merit further study. The four pathogens should have little impact on beef quality.