About FDA

Steven Foley, Ph.D.

Picture of Steven Foley, Ph.D.

Division of Microbiology
National Center for Toxicological Research (NCTR)
Jefferson, AR 72079


  • B.S. in Zoology, North Dakota State University, Fargo, ND
  • Ph.D. in Cellular and Molecular Biology/Infectious Diseases, North Dakota State University, Fargo, ND
  • FDA Experience: 12 years

Research Interests:

My research interests are largely in the fields of bacterial pathogenesis, zoonoses, food safety, and molecular methods for pathogen characterization. Specific areas of interest include understanding the distribution of enteric pathogens, and their virulence and antimicrobial resistance factors in food production environments. By understanding the distribution mechanisms of pathogens, we may be able to develop interventions to reduce the spread of pathogenic microorganisms from food sources to humans. I am also interested in the development of methods to better understand the contribution of plasmid encoded genes to enhanced bacterial function. Plasmids are capable of horizontal gene transfer, which could facilitate the spread of antimicrobial resistance and increased virulence among bacteria leading to more difficult to treat infections. Thus a more comprehensive understanding of plasmid genetics and associated physiology should ultimately lead to improved public health.

Proposed Research Project for FDA Fellow:

Our research group has worked to understand the impact of plasmids on antimicrobial resistance and virulence and how exposure to antimicrobials impacts the transfer of plasmids between bacterial strains. In our studies we have seen that exposure to different antimicrobial agents at varying concentrations appears to impact the rate of plasmid transfer to susceptible organisms. The underlying mechanism of this phenomenon is not known, but is important to understand how the antimicrobial exposure contributes to resistance dissemination. In addition, our work has demonstrated the importance of plasmid transferred in these strains and others also contribute to increased virulence in in vitro models. The exact contribution of the plasmids to virulence is also in need of further study. Thus the proposed research project for the Commissioner’s Fellow will be to utilize cutting edge tools to dissect the genetic and physiological bases for these plasmids-related functions that contribute to the dissemination of antimicrobial resistance and virulence in Salmonella enterica. Overall, a better knowledge of plasmid genetics, along with an understanding which drugs are more likely to select for resistance and virulence transfer will help in the judicious selection of antimicrobial agents for poultry and egg production that minimizes the potential for the spread of antimicrobial resistance and virulence.

Applicant Requirements:

Ph.D. in Microbiology, Immunology or similar fields, preferably with research experience utilizing molecular methods to study bacteria.

Selected Recent Publications:

Johnson, T. J., Thorsness, J. L., Anderson, C. P., Lynne, A. M., Foley, S. L., Han, J., Fricke, W. F., McDermott, P. F., White, D. G., Khatri, M., Stell, A. L., Flores, C., and Singer, R. S. 2010. Horizontal gene transfer has resulted in a dominant avian clonal type of Salmonella enterica serovar Kentucky. PLoS One 5:e15524

Han, J., Lynne, A. M., David, D. E., and Foley, S.L. 2012. Sequencing of plasmids from a multi-antimicrobial resistant Salmonella enterica serovar Dublin strain. Food Res. Int. 45:931-934.

Han, J., Lynne, A. M., David, D. E., Tang, H., Xu, J., Nayak, R., Kaldhone, P., Logue, C. M. and Foley, S. L. 2012. DNA sequence analysis of multidrug resistance encoding plasmids from Salmonella enterica serotype Heidelberg isolates. PLoS One 7(12): e51160.

Foley, S. L., Johnson, T. J., Ricke, S. C., Nayak, R., and Danzeisen, J. 2013. Salmonella pathogenicity and host adaptation in chicken-associated serovars. Microbiol. Mol. Biol. Rev. 77: 582-607.

Gokulan, K., Han, J., Khare, S., Rooney, A. W., Lynne, A. M., and Foley, S.L. 2013. Impact of Plasmids, including those encoding VirB4/D4 type IV secretion systems on Salmonella enterica serovar Heidelberg virulence in macrophages and epithelial cells. PLoS One. 8: e77866.

Page Last Updated: 05/26/2015
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