Differing populations of endemic bacteriophages in cattle shedding high and low numbers of escherichia coli O157:H7 bacteria in feces
Hallewell, J., Niu, Y.D., Munns, K., McAllister, T.A., Johnson, R.P., Ackermann, H.W., Thomas, J.E., Stanford, K. (2014). Differing populations of endemic bacteriophages in cattle shedding high and low numbers of escherichia coli O157:H7 bacteria in feces, 80(13), 3819-3825. http://dx.doi.org/10.1128/AEM.00708-14
The objectives of this study were to identify endemic bacteriophages (phages) in the feedlot environment and determine relationships of these phages to Escherichia coli O157:H7 from cattle shedding high and low numbers of naturally occurring E. coli O157:H7. Angus crossbred steers were purchased from a southern Alberta (Canada) feedlot where cattle excreting ≥104 CFU · g-1 of E. coli O157:H7 in feces at a single time point were identified as supershedders (SS; n=6), and cattle excreting <104 CFU · g-1 of feces were identified as low shedders (LS; n=5). Fecal pats or fecal grabs were collected daily from individual cattle for 5 weeks. E. coli O157:H7 in feces was detected by immunomagnetic separation and enumerated by direct plating, and phages were isolated using short- and overnight-enrichment methods. The total prevalence of E. coli O157:H7 isolated from feces was 14.4% and did not differ between LS and SS (P=0.972). The total prevalence of phages was higher in the LS group (20.9%) than in the SS group (8.3%; P=0.01). Based on genome size estimated by pulsed-field gel electrophoresis and morphology determined by transmission electron microscopy, T4-and O1-like phages of Myoviridae and T1-like phage of Siphoviridae were isolated. Compared to T1-and O1-like phages, T4-like phages exhibited a broad host range and strong lytic capability when targeting E. coli O157:H7. Moreover, the T4-like phages were more frequently isolated from feces of LS than SS, suggesting that endemic phages may impact the shedding dynamics of E. coli O157:H7 in cattle. © 2014, American Society for Microbiology.
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