Northwestern University Feinberg School of Medicine

Program in Public Health

Blazing New Trails: An Epidemiology of Pneumonia Study in Chicago

LPN 500 by 147

I chose to attend Northwestern for my graduate studies specifically for the combined PhD/MPH program. Having studied in a basic science laboratory as an undergraduate, I knew I enjoyed research. After receiving my bachelor’s degree, I worked at the Centers for Disease Control and Prevention (CDC) as part of the Emerging Infectious Diseases laboratory training fellowship, which is where I officially caught “the public health bug.” I loved science, I loved research, and I loved applying scientific principles to real-world problems. The PhD/MPH program was an obvious next step for me.

The identification of the most prevalent etiologic CAP agents will guide clinical treatment protocols and provide rationale for increased research into the most clinically relevant pathogens.

I became specifically interested in bacterial pathogenesis and thus my PhD thesis focused on Legionella pneumophila, the etiologic agent of Legionnaires’ disease pneumonia. For my MPH culminating experience (CE), I wanted a project that incorporated my laboratory training into a population-based study. Coincidentally, in 2009, the CDC initiated a multi-site prospective study to determine the population-based incidence and etiology of community-acquired pneumonia (CAP). My PhD advisor Dr. Nick Cianciotto and I learned of the CAP epidemiology study through collaborators at the CDC, who were eager to recruit someone with technical knowledge of Legionella to the study. My dual PhD/MPH training positioned me uniquely for this opportunity.

With the national incidence rate of legionellosis on the rise, the CDC wanted to ensure that Legionella, a bacterium that is difficult to culture, was carefully screened for in the study. This assignment required the skills of a PhD with advanced molecular genetics training as well as a thorough understanding of the public health context and implications. Thus the goal of my CE study was to determine the contribution of Legionella to CAP in Chicago.

I started by traveling to the CDC to receive training on how to isolate and identify Legionella from clinical specimens. I took advantage of my brief time there to learn more about public health research and how it differs from academic basic science research. Whereas basic microbiology research traditionally focuses on bacteriology fundamentals, public health research at the CDC focuses on applying these basic science principles towards disease prevention for example by developing diagnostic assays to improve pathogen surveillance in the community.

While I was at CDC, an Epidemic Intelligence Service (EIS) officer had just returned from investigating a Legionella outbreak at the Playboy Mansion and I was able to sit in on a de-briefing meeting of the case. Having researched Legionella for over 4 years at this point, it was fascinating to link a biological understanding of the organism to disease transmission in a real outbreak. I was already learning how to apply basic science to public health and I had just barely started my CE.

We ultimately discovered that the isolate represented a novel species of Legionella which we named Legionella cardiaca, meaning pertaining to the heart

Back in Chicago, I received additional laboratory training from the clinical microbiology laboratory at Northwestern under the direction of Dr. Kurt Reed. Along with principal investigators from the CDC, we performed site visits at the three participating Chicago hospitals. At each site, we spoke with physicians, nurses, and clinical laboratory technicians regarding patient enrollment, specimen collection, and specimen processing. Based on their feedback, we defined the study laboratory operating procedures.  At this point, I was gaining a better understanding of the fundamentals of prospective study design by seeing it firsthand.

Over the course of one year, I screened all sputum and bronchoalveolar washes collected from study participants via culture and molecular-based assays for the presence of Legionella. In total, 698 CAP patients were enrolled in Chicago and L. pneumophila was identified as the etiologic agent in three cases. Chicago was just one site in the study and Legionella was just one of the etiologic agents screened. The study was still in progress when I graduated, but it was already clear then that a study of its magnitude would have an indelible impact on public health. The identification of the most prevalent etiologic CAP agents will guide clinical treatment protocols and provide rationale for increased research into the most clinically relevant pathogens. Analysis of the participant demographics and clinical history will also help assess and re-define CAP risk factors. Lastly, the large specimen and epidemiologic database will serve as an excellent source for retrospective studies, thereby fostering future research initiatives.

As a graduate student in the basic sciences, this study was my first opportunity to participate in population-based research. I was impressed by the scope of this multi-site study and quickly realized the importance of effective communication across interdisciplinary teams. Study organizers frequently met to discuss the study progression and to analyze potential barriers. One challenge was ensuring that everyone was following the same enrollment protocol—a problem that was overcome by improved communication. Coming from a laboratory perspective in which most aspects of study design (right down to mouse model genotype) are controlled, I also gained a profound amount of respect for the difficulties associated with human research. For example, we frequently discussed strategies to increase participant recruitment and minimize loss to follow-up, two issues that don’t normally affect basic scientists working on mouse models. 

My experience with the CDC-initiated multi-state CAP project allowed me to connect with people across multiple disciplines. As a result of my collaboration with Dr. Reed at NMH, I became involved in an additional project independent of my CE. At one of our regular meetings, Dr. Reed mentioned that the clinical microbiology laboratory isolated Legionella from the heart of a patient undergoing aortic valve replacement—a peculiar finding considering Legionella is traditionally a lung pathogen and had not previously been isolated from a native heart. Out of curiosity, I began investigating the genotypic, serologic, and phenotypic characteristics of this rare isolate. We ultimately discovered that the isolate represented a novel species of Legionella which we named Legionella cardiaca, meaning “pertaining to the heart,” and our findings were published in the Journal of Clinical Microbiology and the International Journal of Systematic and Evolutionary Microbiology. This interesting and fruitful side project would not have transpired if not for the connections made through my CE.

The future of innovation and public health progress lies at the intersection of multiple fields.

Overall, this experience allowed me to apply my basic science Legionella expertise toward the surveillance of community-acquired pneumonia and the identification of a novel clinically relevant species, truly melding my PhD and MPH interests. This opportunity and the discoveries made in the process might not have been possible with either path of training alone; together, they serve as a reminder that the future of innovation and public health progress lies at the intersection of multiple fields.

About the Author

Dr. Meghan Pearce received her PhD/MPH from the Driskill Graduate Program at Northwestern University in December 2011. She is currently a post-doctoral associate at Loyola University, Stritch School of Medicine, where she is investigating the prevalence and function of the human urinary microbiome.