Background

The reduction of E. coli O157:H7 in both pre- and post-harvest areas continues to be a major goal of the beef industry. It has been demonstrated that cattle hides are the major source of E. coli O157:H7 contamination in processing plants. The reduction of E. coli O157:H7 on cattle hides will go a long way in ensuring the safety of the beef supply. The survival time of E. coli O157:H7 on cattle hides is not well understood. A greater understanding of survival time will help to improve the design of new interventions to further reduce or eliminate the presence of E. coli O157:H7 on cattle hides and in the meat processing system.

The objective of this study was to assess the survival time of E. coli O157:H7 on cattle hides. Researchers theorized that larger numbers of cattle in the same pen would contribute to cross- contamination of hides between cattle. Therefore, in order to measure survival of E. coli O157:H7 on cattle hides it would be necessary to segregate cattle one per pen and measure the presence of E. coli over time. The percentage of E. coli positive cattle that were penned separately should decrease more over time versus the cattle that were penned together.

Methodology

Researchers selected 78 cattle that tested positive for E. coli O157:H7 on their hide and/or in their feces. Half of these cattle (39) were penned together where hide contamination could readily reoccur between animals. The other half of the cattle were kept six to a pen where hide contamination between cattle would not be as likely. After two weeks these cattle would be penned separately (one to a pen) and the prevalence of E. coli O157:H7 would be measured at specific time periods.

Findings

When first penned, all (100%) of the cattle who were put into small pens (≈ 6 head/pen) tested positive for E. coli on their hides. However, after two weeks this percentage had decreased substantially, so that just over half (53%) of these cattle were E. coli hide-positive. On the other hand the percentage of hide-positive cattle that were penned together (39 in one pen) was unchanged (87% of cattle were hide-positive) at the beginning and after two weeks of commingling. It should be noted that the presence of E. coli O157:H7 was not detected in any pen or stall prior to the housing of the cattle.

The cattle that were penned together remained that way, while the cattle in small pens were each transferred to individual stalls. The percentage of cattle in each group that tested positive for E. coli O157:H7 either on their hide and/or in their feces decreased over time. However, the cattle that were penned separately showed a much greater decrease in E. coli O157:H7 both on their hides and in their feces compared to the commingled cattle (See Table 1). At day 9 of the testing there was no E. coli found on the cattle that were penned separately indicating that the survival time of E. coli O157:H7 on cattle hides is less than 9 days.

Implications

Holding cattle in individual stalls prevents recontamination of hides due to cross-contamination by other animals. Information about E. coli O157:H7 survival time on cattle hides is expected to help improve the design of new technologies to further reduce or eliminate this pathogen from the beef supply.