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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

USDA, ARS, 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

USDA Microbiologist, 1999-present


Research Interests:

Dr. Bearson's 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. Current research efforts are investigating genetic features of emerging Salmonella outbreak isolates associated with food animals, examining antimicrobial resistance mechanisms in multidrug-resistant (MDR) Salmonella serovars, and identifying antibiotic alternatives to decrease Salmonella on the farm.

With her exceptional collaborators, her 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

6.   Transcriptionally profiled the turkey response to the MDR Salmonella Heidelberg 2011 ground turkey outbreak stain; the limited host response to the 10 billion S. Heidelberg-challenge supports the hypothesis that S. Heidelberg (and other Salmonella serovars) can establish a commensal-like state in turkeys.

7.   Described the presence of multiple metal tolerance genes in Salmonella serovar I 4,[5], 12:i:- associated with the 2015 pork outbreak; enhanced metal tolerance appears to have provided this serovar with a competitive advantage in a production environment whereby metals are commonly used as an antimicrobial agent, thereby offering an explanation for the increase in prevalence of this Salmonella serovar in swine.





Complete list of published work: