Prevalence and Impact of Bacteriophages on the Presence of Escherichia coli O157:H7 in Feedlot Cattle and Their Environment

Abstract

The relationship between endemic bacteriophages infecting E. coli O157:H7 (referred to as "phage") and levels of shedding of E. coli O157:H7 by cattle was investigated in two commercial feedlots in southern Alberta, Canada. Between May and November 2007, 10 pens of cattle were monitored by collection of pooled fecal pats, water with sediment from troughs, manure slurry from the pen floor, and rectal fecal samples from individual animals (20 per pen) at two separate times. Bacteriophages infecting E. coli O157:H7 were detected more frequently (P < 0.001) after 18 to 20 h enrichment than by initial screening and were recovered in 239 of 855 samples (26.5% of 411 pooled fecal pats, 23.8% of 320 fecal grab samples, 21.8% of 87 water trough samples, and 94.6% of 37 pen floor slurry samples). Overall, prevalence of phage was highest (P < 0.001) in slurry. Recovery of phage from pooled fecal pats was highest (P < 0.05) in May. Overall recovery did not differ (P > 0.10) between fecal grab samples and pooled fecal pats. A higher prevalence of phage in fecal pats or water trough samples was associated (P < 0.01) with reduced prevalence of E. coli O157:H7 in rectal fecal samples. There was a weak but significant negative correlation between isolation of phage and E. coli O157:H7 in fecal grab samples (r ‫؍‬ ؊0.11; P < 0.05). These data demonstrate that the prevalence of phage fluctuates in a manner similar to that described for E. coli O157:H7. Phage were more prevalent in manure slurry than other environmental sources. The likelihood of fecal shedding of E. coli O157:H7 was reduced if cattle in the pen harbored phage.

Naturally resident and exogenously applied T4-like and T5-like bacteriophages can reduceEscherichia coliO157

“…Our data supports previous observations, by both us and others, that O157:H7-infecting phages are naturally present in the intestinal ecosystem of ruminants. 25,29,30,38,39 These results support our previous suggestion that the natural presence of phage needs to be taken into consideration when conducting studies using other antimicrobial agents, since resident phages at levels detectable only by amplification can multiply after inoculation of the pathogenic bacterium (subsequently shown also by Niu et al 2009) and potentially confound the results of an in vivo trial. 25,29,30 This can lead to unacceptable variability or give the false impression that the assayed substance is responsible for the inhibition.…”

“…16,18,44,45 Studies examining the relationship between O157:H7 and O157:H7-infecting phages in cattle feedlots have shown a negative correlation. 25,30 The data we present here in an ovine model further substantiates the hypothesis that O157:H7-infecting phage may play a central role in the transient nature of E. coli O157:H7 in cattle, following classical predatorprey relationship rules. 25,29,30 The presence of a common phage in most members of a single flock is also noteworthy and indicates either horizontal transfer of phage between the flock members or that this phage was acquired by the flock from a common source, such as water or feed.…”

“…25,30 The data we present here in an ovine model further substantiates the hypothesis that O157:H7-infecting phage may play a central role in the transient nature of E. coli O157:H7 in cattle, following classical predatorprey relationship rules. 25,29,30 The presence of a common phage in most members of a single flock is also noteworthy and indicates either horizontal transfer of phage between the flock members or that this phage was acquired by the flock from a common source, such as water or feed. We have no way of determining the original source of CEV2 in the sheep involved in this study due to the nature of their procurement, but the horizontal transfer of phage within a livestock population was previously observed by Smith and collaborators with phage against enteropathogenic E. coli (EPEC).…”

“…This lack of basic knowledge is being addressed as researchers have begun to consider the use of bacteriophages in both pre-and post-harvest pathogen reduction strategies. 29,30 Here we present the detailed characterization of a new O157:H7-infecting phage, CEV2, from a class of phages not previously identified as being of therapeutic use (T5-like), found to naturally occur in the gastrointestinal tract of ruminants and able to greatly reduce O157:H7 levels when the animals experience a large infusion of this pathogen. We also present data demonstrating that the application of exogenous phages can markedly reduce resident E. coli O157:H7 populations throughout the GI-tract of livestock.…”

Activity of Isolated Staphylococcal Bacteriophage in Treatment of Experimentally Induced Chronic Osteomyelitis in Rabbits

“…In studies involving dairy livestock, milk and udders were primary sources for samples from which phages were isolated (Brüssow and Desiere 2001;Garcia et al, 2007Garcia et al, , 2009Shi et al, 2010;Kwiatek et al, 2012). Alternate sources from which phages could be isolated include sewage or wastewater (Yoon et al, 2010), and feces (Oot et al, 2007;Niu et al, 2009;Santos et al, 2011).…”