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., and Stanford, K.I.M. (2014). "Differing populations of endemic bacteriophages in cattle shedding high and low numbers of escherichia coli O157:H7 bacteria in feces.", Applied and Environmental Microbiology, 80(13), pp. 3819-3825. doi : 10.1128/AEM.00708-14  Access to full text

Abstract

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 • g1 of E. coli O157:H7 in feces at a single time point were identified as supershedders (SS; n = 6), and cattle excreting <104 CFU • g1 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.

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