Melinda Pettigrew, PhD

My research focuses on Streptococcus pneumoniae and non-typeable Haemophilus influenzae. The bacteria that I study asymptomatically colonize the respiratory tract of 10-50% of healthy individuals. While asymptomatic colonization is far more common than disease, S. pneumoniae and H. influenzae are important causes of bacterial infections in children and adults (e.g., otitis media, pneumonia, and exacerbations of chronic obstructive pulmonary disease (COPD)). Moreover, these infections are frequently, and controversially, treated with antibiotics. We use state-of-the-art methods that integrate clinical epidemiologic, and laboratory studies to elucidate factors that tip the balance between asymptomatic bacterial colonization and disease.

Additional projects focus on how disruptions of homeostasis in the respiratory and gastrointestinal microbiota influence colonization resistance, development of antibiotic resistance, and risk of hospital-acquired infections. We use data and specimens from clinical epidemiologic studies and next-generation sequencing methods to address several key questions including: 1) How does the duration of antibiotic use impact the prevalence of antibiotic resistance genes in the respiratory and gastrointestinal microbiota? 2) How do antibiotic induced changes in the composition and diversity of the gastrointestinal microbiota contribute to antibiotic-associated diarrhea? and 3) How does the diversity and composition of the microbiota relate to risk of colonization, expansion, and infection due to antibiotic-resistant pathogens? Over the long-term, our research will help identify new methods to exploit protective mechanisms provided by an intact microbiota and lead to new interventions to prevent development of antibiotic resistance and hospital-acquired infections.