Use Of Bacteriophage To Control Esherichia Coli O157:H7 In Cattle And Their Environment

The food-borne pathogen Escherichia coli O157:H7(E.coli O157:H7) is a significant public health concern.Cattle are recognized as primary reservoirs of E.coli O157:H7 and contaminated foods of bovine origin or vegetable products contaminated with bovine feces are important vehicles of human infection;therefore,effective interventions targeted at reducing shedding of E.coli O157:H7 by live cattle(preharvest) and presence of their environment are desirable.Currently there is no one preferred on-farm method that has given satisfactory and consistent results in reducing E.coli O157:H7 populations in cattle and their environment.The objectives of this research were to assess the use of bacteriophage (phages) as an on-farm strategy in mitigating occurrence of E.coli O157:H7 in feedlot cattle and their environment and thereby construct an effective,green,safe and pollution-free biological control stage to ensure food safety from origin and environment safety.To evaluate oral administration of four bacteriophages(rV5,wV7,wV8,wV11) in mitigating the fecal shedding of E.coli O157:H7 by steers under production conditions,and compare fecal grab(FEC) and rectoanal mueosal swab(RAMS) techniques as sampling methods for surveillance of E.coli O157:H7 in conjunction with administration of a mitigation therapy.Overall,Oral treated steers presented fewer(P＜0.05) E.coli O157:H7 culture positive samples compared to control treatment.E.coli O157:H7 was detected more frequently(P＜0.01) by FEC than by RAMS.Kappa values(0.36 to 0.45) indicated only fair to moderate agreement between FEC and RAMS.Oral administration of bacteriophage could be an efficacious large-scale method for mitigating E.coli O157:H7 in cattle. Asessment of FEC samples by DP plus enrichment/IMS was more effective than RAMS/IMS for investigating E.coli O157:H7 mitigation strategies in E.coli O157:H7-challenged feedlot cattle.To evaluate host range and lyric capability of four bacteriophages(rV5,wV7,wV8, wV11) against E.coli O157:H7(n=422) obtained from cattle and humans in Alberta, CANADA.Multiplicity of infection(MOI) of the four phages were estimated via mircoplate virulence assay.All bovine E.coli O157:H7 isolates were subject to pulsed field gel electrophoresis(PFGE) and phage typing(PT).Phage wV7 lyzed all human and bovine isolates irrespective of PFGE genotype or PT phenotype and exhibited the lowest MOI(0.004 to 0.006,P＜0.0001) of all phages.Phages rV5 and wV11 exhibited a lower MOI(0.002 to 0.04,P＜0.0001) than phage wV8(25 to 29) and a narrower host range than phages wV7 or wV8.Phages rV5,wV11 and wV8 lyzed 342(81.0%),321(76.1%) and 407(96.4%), respectively,of the 422 isolates.Excluding phage wV7,susceptibility of bovine E.coli O157:H7 isolates to phages rV5,w11 and wV8 was influenced by both by the PFGE genotype and/or PT phenotype of the targeted host.Each of the four phages studied in the present experiment exhibited activity against the majority of bovine and human E.coli O157:H7 isolates.Susceptibility of bovine E.coli O157:H7 to phage may differ among farms.Both lytic capability based on MOI and host range should be considered in the selection of therapeutic phage.The present work indicates that a four-phage cocktail should be equally effective at mitigating E.coli O157:H7 isolates of both cattle and human origin.Distribution,fluctuation of endemic bacteriophages infecting E.coli O157:H7(PHAGE) and the relationship between PHAGE and shedding levels of E.coli O157:H7 by cattle were investigated in two commercial feedlots in southern Alberta.Between May and November 2007,10 pens of cattle were monitored by collection of pooled fecal pats(PAT),water with sediment from troughs(WAT),manure slurry from pen floor(when present,SLU) and rectal fecal samples from individual animals(FEC),collected at implantation and prior to slaughter. Bacteriophages infecting E.coli O157:H7 were recovered(by initial screening and/or enrichment) in 239 of 855 samples(109 PAT,76 FEC,19 WAT and 35 SLU).Overall, prevalence of PHAGE was highest(P＜0.001) in SLU.Recovery of PHAGE from PAT was highest(P＜0.05) in May.Overall,recovery did not differ(P＞0.10) between FEC and PAT.A higher prevalence of PHAGE in PAT or WAT was associated(P＜0.01) with reduced prevalence of E.coli O157:H7-positive FEC.There was a weak but significant negative correlation between isolation of PHAGE and E.coli O157:H7 in FEC(r＝-0.11; P＜0.05).These data demonstrate that the prevalence of PHAGE fluctuates periodically similar to that described for E.coli O157:H7.Endemic 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.In conclusion,this study demonstrated that phages.as biological control agents have great potential to effectively control E.coli O157:H7 on farm and thus pioneered a green,safe, pollution-free strategy to ensure food safety from origin and environment safety.