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Debra E. Bessen, Ph.D.
Professor
Department of Microbiology and Immunology
New York Medical College
Valhalla, New York
Debra Bessen received her Ph.D. in 1987 from The Rockefeller University in the field of Microbiology. She continued her post-doctoral studies at Rockefeller whereupon she developed a keen interest in the natural history of streptococci, largely through reading a rich treasure trove of original notes and correspondence from Dr. Rebecca Lancefield, an early 20th century pioneer in the classification and epidemiology of bacterial pathogens. Dr. Bessen joined the faculty of Yale University in 1992, where she held appointments in the Departments of Epidemiology and Public Health, and Ecology and Evolutionary Biology. In 2003, she moved to New York Medical College, where she is currently a Professor of Microbiology and Immunology.
Dr. Bessen maintains an active research program that seeks to understand the mechanisms by which group A streptococcus causes disease, as well as the molecular evolution of this bacterial species. Using an epidemiological approach combined with evolutionary genetics, many well-supported hypotheses concerning the role of specific virulence factors can be generated and subsequently tested in animal models for disease. Her group is also investigating the link between strep throat infections and common neuropsychiatric disorders, such as Tourette syndrome and obsessive-compulsive disorder. Her streptococcal research program has received funding support for > 15 years, and has yielded ~ 70 primary publications, review articles, and book chapters.
In the classroom, Dr. Bessen has taught students of numerous degree programs in biology, biomedical science, medicine, and public health. She was a co-organizer for the ASM-sponsored Streptococcal Genetics meeting (2006), and has also served as an appointed member of scientific grant review panels for the National Institutes of Health (2005-09) and American Heart Association (2000-03).
About the lecture
"Group A Streptococci: Global Population Biology and Antibiotic Resistance"
Group A streptococci (GAS) are highly prevalent bacterial pathogens that infect humans throughout the world, primarily at the throat or skin. Genes encoding surface fibrils provide genotypic markers for strains exhibiting preferential infection for the throat (pharyngitis) versus skin (impetigo).
Using multilocus sequence typing of house-keeping genes, the global population of GAS is found to be highly diverse and highly recombin-ogenic. Furthermore, strains preferentially infect-ing the throat versus skin do not compromise distinct evolutionary lineages, although genetic diversification by mutation (versus recombination) is higher among the throat strains.
Many of the genes conferring antibiotic resistance among GAS are acquired by horizontal transfer. The number of independent acquisitions of resistance to macrolides and tetracyclines is surprisingly high. Tetracycline-resistance clones outnumber macrolide-resistant clones by >15-fold; tetracycline resistance may drive the spread of macrolide resistance. Clonal groups having an inter-continental distribution account for >75% of the macrolide-resistant isolates examined. Macrolide-resistant clones display a shift in their primary mechanism for genetic diversification, raising the possibility that the acquisition of drug resistance may alter the population genetic structure of this species.
Quoted from the 2009-2010 Loyd E. Harris Lecture Series Announcement Brochure