GSBS Dissertations and Theses



Publication Date


Document Type

Doctoral Dissertation

Academic Program

Millennium PhD


Emergency Medicine, Microbiology and Physiological Systems

First Thesis Advisor

Beth McCormick


Elderly, Microbiome, Clostridium difficile, colonization, infection, medications


The widespread use of antibiotics has led to dramatic increases in the incidence and severity of Clostridium difficile infection (CDI). No group of patients suffers more from CDI than the elderly. Nursing homes (NH) represent the perfect storm of a vulnerable group of frail elders living in confined communities. Nursing home residents suffer from increased morbidity and mortality from CDI and corresponding high rates of C. difficile colonization. Upwards of 40 to 50% of CDI current cases originate from NHs and the prevalence of colonization rates remain high within these facilities, with as many as half of the residents being colonized with C. difficile at any given time. One factor that has become of increasing interest and a target of preventive strategies is the human intestinal microbiome. A healthy, diverse microbiome interacts with the host immune system and contributes to pathogen resistance. In this investigation, we first examine elder specific variables to determine if the associated risks of CDI differ by home living environment (nursing home versus community-dwelling). We then go on explore the relationships of NH environment, frailty, nutritional status, and residents’ age with microbiome composition and potential metabolic function. Finally, we describe the C. difficile colonization patterns among elderly NH residents and the associated risk of colonization based on clinical variables and microbiome determinants. A better understanding of the microbiome’s contribution to C. difficile colonization will provide the basis for informing rational interventions and public health policies to better combat CDI in the nursing home.



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