New York Medical College

Debra Bessen, Ph.D.
Professor of Microbiology and Immunology

Debra Bessen, PhD




Dept. of Microbiology & Immunology
Basic Sciences Building
New York Medical College
Valhalla, NY 10595


Personal Profile:

1990 - 1992, Assistant Professor, Bacterial Pathogenesis & Immunology, Rockefeller University, NY, NY

1992 - 1996, Assistant Professor, Epidemiology & Public Health, Yale University, New Haven, CT

1997 - 2001, Associate Professor, Epidemiology & Public Health, Yale University, New Haven, CT

2002 - 2003, Research Scientist, Ecology & Evolutionary Biology, Yale University, New Haven, CT

2003 - 2004, Associate Professor, Microbiology & Immunology, New York Medical College

2004 - present, Professor, Microbiology & Immunology, New York Medical College

Professional Interests:

Our research is primarily focused on group A beta-hemolytic streptococci (Streptococcus pyogenes), which are among the most prevalent of bacterial pathogens; humans are its sole biological host. A hallmark feature of S. pyogenes is its molecular and biological diversity among strains. Although S. pyogenes infection can produce serious illness, such as autoimmune and severe invasive disease, most often it causes only a mild disease at superficial tissue sites - the oropharynx (strep throat) or epidermis (impetigo). The throat and skin are the primary tissue reservoirs for S. pyogenes, whereby the organism is most successful in reproductive growth and transmission to new hosts.

It is widely recognized that many strains of S. pyogenes differ in their tissue site preference, giving rise to the concept of distinct throat and skin strains. One of our long-term goals is to determine the molecular basis for throat- and skin-specific infections caused by S. pyogenes. Because throat and skin strains are often separated in time and space, they provide a model for mapping candidate genes that confer tissue tropisms. Gene products under investigation include transcriptional regulators and surface proteins. In addition, the consequences of ecological separation on lateral gene exchange between strains are explored.

Additional studies in our lab investigate antibiotic resistance in S. pyogenes, the unique properties of strains that trigger rheumatic fever, and the role of group A streptococcal infections in triggering acute episodes of common neuropsychiatric disorders in children (Tourette's syndrome and chronic tic disorders, obsessive-compulsive disorder), via an autoimmune mechanism.

Tools used in our lab include genomics, population genetics and animal models for disease.

Bessen Lab website is at

Projects on streptococci include:

1. Multi-locus sequence typing (MLST). Go to for data and tools.

2. Characterizing the role of streptococcal genes in tissue tropisms, by testing genetic mutants of S. pyogenes in a humanized mouse model for skin infection. The streptococcal products under study include a secreted cysteine proteinase (SpeB), a plasminogen activator (streptokinase), a plasminogen-binding surface protein (PAM), extracellular matrix-binding surface proteins, and global regulators of transcription.

3. The development and testing of predictive models that can aid in the design of effective vaccines, by assessing the impact of selection by the host immune response, through examination of its imprint on the bacterial population genetic structure.

4. Understanding the molecular evolutionary processes underlying niche adaptation, with a special focus on recombinational replacements by orthologous genes.

5. Deciphering the molecular evolution of antibiotic resistance.

6. Assessing immunological changes in pediatric patients with tics or OCD, in correspondence with changes in the clinical severity of neuropsychiatric symptoms.

Education Profile:

Post Graduate Studies   The Rockefeller University

Graduate Degree:   Ph.D.

Graduate Degree Institution:   The Rockefeller University

Undergraduate Institution:   Hampshire College

Selected Bibliography:

Bessen, D.E., N. Kumar, G.S. Hall, D.R. Riley, F. Luo, S. Lizano, C.N. Ford, W.M. McShan, S.V. Nyugen, J.C. Dunning Hotopp and H. Tettelin, 2011. Whole genome association study on tissue tropism phenotypes in group A Streptococcus. J. Bacteriol. 193: 6651-63

Willems, R.J.L., W.P. Hanage, D.E. Bessen, and E.J. Feil, 2011. Population biology of Gram-positive bacteria: high-risk clones for dissemination of antibiotic resistance. FEMS Microbiology Reviews, 35: 872-900

Bessen, D.E., 2010. Population genetics of Streptococcus. In: Bacterial Population Genetics in Infectious Disease. John Wiley & Sons, Inc., p. 345-377.

Bessen, D.E. and S. Lizano, 2010. Tissue tropisms in group A streptococcal infection. Future Microbiology 5:623-638.

Lizano, S., F. Luo, F.K. Tengra and D.E. Bessen, 2008. Impact of orthologous gene replacement on the circuitry governing pilus gene transcription in streptococci. PLoS ONE, 3(10): e3450

Wertz, J.E., K.F. McGregor and D.E. Bessen, 2007. Detecting key structural features within highly recombined genes. PLoS Comp. Biol. 3: 137-150

Lizano, S., F. Luo and D.E. Bessen, 2007. Role of streptococcal T-antigens in superficial skin infection. J. Bacteriol. 189: 1426-1434

Luo, F., J.F. Leckman, L. Katsovich, D. Findley, H. Grantz, D.M. Tucker, P.J. Lombroso, R.A. King and D.E. Bessen, 2004. A prospective longitudinal study of children with tic disorders and/or obsessive-compulsive disorder: Relationship of symptom exacerbations to newly acquired streptococcal infections. Pediatrics 113: 578-585

Search PubMed for all available publications of Debra Bessen, Ph.D.


Page updated: March 13, 2013








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