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Open Access Research article

Vaccination with attenuated Salmonella enterica Dublin expressing E coli O157:H7 outer membrane protein Intimin induces transient reduction of fecal shedding of E coli O157:H7 in cattle

Sangeeta Khare15*, Walid Alali2, Shuping Zhang1, Doris Hunter1, Roberta Pugh1, Ferric C Fang4, Stephen J Libby34 and L Garry Adams15*

Author Affiliations

1 Department of Veterinary Pathobiology, College of Veterinary Medicine and Biomedical Sciences, Texas A&M University, College Station, TX 77843 USA

2 Veterinary Integrative Biosciences, College of Veterinary Medicine and Biomedical Sciences, Texas A&M University, College Station, TX 77843 USA

3 Department of Microbiology, North Carolina State University, Raleigh, NC 27695 USA

4 University of Washington School of Medicine, Departments of Laboratory Medicine and Microbiology, Seattle, WA 98195 USA

5 Division of Microbiology, National Center for Toxicological Research, US Food and Drug Administration, Jefferson, AR 72079 USA

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BMC Veterinary Research 2010, 6:35  doi:10.1186/1746-6148-6-35

Published: 7 July 2010

Abstract

Background

Escherichia coli serogroup O157:H7 has emerged as an important zoonotic bacterial pathogen, causing a range of symptoms from self-limiting bloody diarrhea to severe hemorrhagic colitis and hemolytic-uremic syndrome in humans. Beef and dairy cattle are considered the most important animal reservoirs for this pathogen. One of the important virulence characteristics of E. coli O157:H7 is the eaeA gene encoding the 97 kDa surface protein intimin. Intimin is required for attachment and effacement during the interaction of enterohemorrhagic E. coli with human and bovine neonatal enterocytes. The present study was undertaken to test the hypothesis that an adaptive mucosal immune response directed against intimin will reduce or prevent enteric colonization and fecal shedding of E. coli O157:H7 in cattle.

Results

Cattle were orally inoculated with either milk (control), milk with live attenuated Salmonella enterica serovar Dublin (vector), or milk with live attenuated recombinant S. Dublin expressing intimin (vaccinated) on days 0, 14 and 28. On day 98, all calves were challenged orally with E. coli O157:H7 to evaluate whether vaccination with the recombinant S. Dublin expressing intimin would reduce the level of E. coli O157:H7 fecal shedding.

During the first 28 days, vaccinated calves shed both the vector strain and the intimin-expressing S. Dublin strain at a similar level. The vector strain was shed for a significantly longer period as compared to the level of recombinant vaccine strain. Calves that received the intimin-expressed vaccine ceased shedding S. Dublin from day 28 to day 63. All calves were challenged with E. coli O157:H7 on day 98 to determine the effect on fecal shedding of E. coli O157:H7. The amount of E. coli O157:H7 in feces was measured for 30 days post-challenge. We observed a transient clearance of E. coli O157:H7 from the feces in the vaccinated calves. The magnitude of fecal E. coli O157:H7 shedding did not correlate with the presence of intimin-specific fecal IgA.

Conclusion

Oral vaccination with live attenuated recombinant S. Dublin expressing intimin reduced enteric colonization and fecal shedding of E. coli O157:H7. However, the transient clearance of E. coli O157:H7 was not associated with an enhanced IgA-mediated mucosal immune response.