Research focuses on the transmission dynamics and within-host population biology of infectious disease. It combines in vivo (murine) experimental studies with statistical and mathematical modeling (population-dynamical) approaches to address questions in these areas. Present research interests include:
Population dynamics of pneumococcal carriage and transmission. I use mathematical models to study the transmission dynamics of multiple serotypes of Streptococcus pneumoniae and the interactions among these serotypes. In the lab, we are doing experiments on the population dynamics of intranasal carriage of pneumococci in mice to measure parameters and test assumptions and predictions of the mathematical models. A central question of interest in this experimental and mathematical work whether widespread use in the human population of conjugate vaccines against a subset of serotypes will result in increased carriage of non-vaccine serotypes ("serotype replacement"), and if so, what the public health consequences will be.
I am also developing statistical models to test for evidence of serotype replacement in clinical trials. Antimicrobial resistance in hospital- and community-acquired pathogens. We use mathematical models and epidemiological data to evaluate the relationships between antimicrobial use and antimicrobial resistance in a number of bacterial and viral pathogens.
We are also interested in the within-host population dynamics of antimicrobial resistance, the development of improved treatment protocols to reduce the selection for resistant bacteria, and the design of studies to measure the selective effect of treatment on antimicrobial resistance. See also article "The Secret Life of Hospital Bugs: Non-resistant Bacteria Shown to Be Hidden Ally in Fight Against Drug-resistant Strains" in Harvard Focus. Population biology of plasmids.
With Carl Bergstrom and Bruce Levin (Emory University), I am working on mathematical models of plasmid persistence in bacterial populations. We are particularly interested in the roles of interspecific plasmid transfer and environmental heterogeneity in preserving plasmids when the plasmids impose a selective disadvantage on their bacterial hosts.