Submitted to: Letters in Applied Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/1/2007
Publication Date: 10/18/2007
Citation: Oot, R.A., Raya, R.R., Callaway, T.R., Edrington, T.S., Kutter, E.M., Brabban, A.D. 2007. Prevalence of Escherichia coli O157 and O157:H7-infecting bacteriophages in feedlot cattle feces. Letters in Applied Microbiology. 45:445-453. Interpretive Summary: E. coli O157:H7 is a dangerous pathogenic bacteria found in feedlot cattle. Bacteriophage are viruses that feed specifically on bacteria, and have been suggested as a method to kill pathogens such as E. coli O157:H7. However, before phage can be used as a tool to reduce foodborne illness, we must understand how common they are in the animal. We demonstrated that phage that infected E. coli were found in 58 of 60 samples, additionally phage that infected E. coli O157:H7 were found in 39 of 60 samples, albeit at very low levels. These results suggest that phages that infect E. coli (including O157:H7) may play a significant role in the ecology and colonization of cattle by E. coli O157:H7.
Technical Abstract: To determine the prevalence of both Escherichia coli O157 and O157:H7-infecting bacteriophages within a 50,000 head commercial beef feedlot. E. coli O157 was detected in 25% of the individual samples distributed across 7 of the 10 pens screened. In a simple primary screen to detect O157:H7-infecting phages, none were detected in any feedlot pen or individual sample. In contrast after a series of enrichment procedures O157:H7-infecting phages were detected in every feedlot pen and usually in the vast majority of the samples from that pen; virulent bacteriophages active against E. coli O157:H7 were detected post-enrichment from 39/60 of the feedlot samples and 58/60 contained phage that infected E. coli B or O157:H7. The data we present here indicates that we may be grossly underestimating the prevalence of O157:H7-infecting phages in livestock by simple screening and that enrichment screening is required to truly determine the presence of phages in these ecosystems. Our data suggests that O157:H7-infecting phages may play a role in the ecology and transient colonisation of cattle by E. coli O157:H7. Further, this and previous data suggest that before in vivo pathogen eradication studies using phage or any other regime are begun an enrichment screen should be carried out on these test animals to ensure that researchers avoid erroneous results.