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Shawn Bearson

Research Microbiologist

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Shawn M.D. Bearson, Ph.D.
Research Microbiologist

Food Safety and Enteric Pathogens Research Unit

National Animal Disease Center

Phone (515) 337-7455
P.O. Box 70
1920 Dayton Ave
Ames, IA


B.S. Judson College, Biology and Chemistry (honors), 1990
Ph.D. University of South Alabama, Microbiology and Immunology, 1997
Postdoc University of California, Los Angeles 1999


Research Interests:

My research program focuses on three factors that influence Salmonella colonization and persistence in food animals: virulence mechanisms of Salmonella, the tactical response from the host, and interactions with the host microbiota residing within the gastrointestinal tract.  My current research efforts are characterizing the effects of antibiotics on MDR Salmonella and identifying antibiotic alternatives to decrease Salmonella on the farm, reduce antibiotic dependence, promote animal health, and provide the public with a safe food supply.

With my collaborators, my research program has:

1.     Developed alternatives to antibiotics, including a live DIVA vaccine that cross-protects against multiple Salmonella serovars in food commodity animals (swine and turkeys)

2.     Characterized the porcine response to Salmonella by 1) classifying genes and pathways that are transcriptionally altered during acute and chronic infections with Salmonella and 2) describing differences in swine-specific responses to host-adapted S. Choleraesuis (systemic disease) and non-host-adapted S. Typhimurium (gastrointestinal disease) that control the outcome of infection

3.     Linked specific genetic polymorphisms in Salmonella-responsive porcine genes to Salmonella shedding and the immune response of pigs

4.     Associated the composition of the porcine gastrointestinal microbiota to Salmonella shedding status in pigs

5.     Identified virulence mechanisms in multi-drug resistant (MDR) Salmonella that are altered during exposure to various antibiotics


Laboratory Personnel:

Margaret Walker, Biological Science Laboratory Technician

Daniel Shippy, Postdoctoral Researcher


Recent Publications:

Complete list of published work:


Bearson S.M., Bearson B.L., Loving C.L., Allen H.K., Lee I., Madson D., Kehrli M.E. Jr. 2016. Prophylacatic administration of vector-encoded porcine granulocyte-colony stimulating factor reduces Salmonella shedding, tonsil colonization, and microbiota alterations of the gastrointestinal tract in Salmonella-challenged swine. Frontiers in Veterinary Science. 3:66.

Bearson B.L., Bearson S.M., Kich J.D. 2016. A DIVA vaccine for cross-protection against Salmonella. Vaccine. 34:1241-1246.


Bao H., Kommadath A., Liang G., Sun X., Arantes A.S., Tuggle C.K., Bearson S.M., Plastow G.S., Stothard P., Guan le L. 2015. Genome-wide whole blood microRNAome and transcriptome analyses reveal miRNA-mRNA regulated host response to foodborne pathogen Salmonella infection in swine. Scientific Reports.5:12620.


Brunelle B.W., B.L. Bearson, S.M. Bearson. 2015. Chloramphenicol and tetracycline decrease motility and increase invasion and attachment gene expression in specific isolates of multidrug-resistant Salmonella enterica serovar Typhimurium. Frontiers in Microbiology. 5:801.


Bearson B.L., S.M. Bearson, J.D. Kich, I.S. Lee. 2014. An rfaH mutant of Salmonella enterica serovar Typhimurium is attenuated in swine and reduces intestinal colonization, fecal shedding, and disease severity due to virulent Salmonella Typhimurium. Frontiers in Veterinary Science. 1:9.


Kommadath A., H. Bao, A.S. Arantes, G.S. Plastow, C.K. Tuggle, S.M. Bearson, Le L. Guan, P. Stothard. 2014. Gene co-expression network analysis identifies porcine genes associated with variation in Salmonella shedding. Biomed Central (BMC) Genomics. 15:452.


Knetter S.M., S.M. Bearson, T.H. Huang, D. Kurkiewicz, M. Schroyen, D. Nettleton, D. Berman, V. Cohen, J.K. Lunney, A.E. Ramer-Tait, M.J. Wannemuehler, C.K. Tuggle. 2014. Salmonella enterica serovar Typhimurium-infected pigs with different shedding levels exhibit distinct clinical, peripheral cytokine and transcriptomic immune response phenotypes. Innate Immununity. 21:227-41.


Kich J.D., J.J. Uthe, M.V. Benavides, M.E. Cantao, R. Zanella, C.K. Tuggle, S.M. Bearson. 2014. TLR4 single nucleotide polymorphisms (SNPs) associated with Salmonella shedding in pigs. Journal of Applied Genetics. 55:267-271.


Bearson S.M., B.L. Bearson, I.S. Lee, J.D. Kich. 2013. Polynucleotide phosphorylase (PNPase) is required for Salmonella enterica serovar Typhimurium colonization in swine. Microbial Pathogenesis. 65:63-66.


Brunelle B.W., S.M. Bearson, B.L. Bearson. 2013. Tetracycline accelerates the temporally-regulated invasion response in specific isolates of multidrug-resistant Salmonella enterica serovar Typhimurium. BioMed Central (BMC) Microbiology. 13:202.


Bearson S.M., H.K. Allen, B.L. Bearson, T. Looft, B.W. Brunelle, J.D. Kich, C.K. Tuggle, D.O. Bayles, D. Alt, U.Y. Levine, T.B. Stanton. 2013. Profiling the gastrointestinal microbiota in response to Salmonella: low versus high Salmonella shedding in the natural porcine host. Infection, Genetics and Evolution. 16:330-340.


Sharma, V.K. and Bearson, S.M., 2013. Evaluation of the impact of quorum sensing transcriptional regulator SdiA on long-term persistence and fecal shedding of E. coli O157:H7 in weaned calves. Microb Pathog. 57:21-26.