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1 Development of a Two-Stage Computational Modeling Method For Development of a Two-Stage Computational Modeling Method for Drinking Water Microbial Ecology Effects on Legionella pneumophila Growth Thesis Presented in Partial Fulfillment of the Requirements for the Degree Master of Science in the Graduate School of The Ohio State University By David Augustus Hibler Graduate Program in Public Health The Ohio State University 2020 Thesis Committee Dr. Mark Weir, Advisor Dr. Michael Bisesi Dr. Kerry Hamilton Dr. Natalie Hull 1 Copyrighted by David A. Hibler 2020 2 Abstract Legionella pneumophila (L. pneumophila) has become a significant public health issue due to its growth in water distribution systems.1,2 In natural water systems L. pneumophila is often found in relatively low concentrations.1,3–12 However, in distribution systems it is able to thrive through the use of biofilms and invasion of larger host organisms such as protozoa.1–3,10,12–35 Additionally, the altered microbial ecology of water distribution systems seems to play a role in facilitating its ability to proliferate and persist.1,20,22,28,34,36–41 L. pneumophila can cause respiratory infections when contaminated water is aerosolized as it exits from distribution or premise plumbing systems and is then inhaled.2,42–45 Research has shown that some tap water organisms can exhibit inhibitory or commensal effects on L. pneumophila.11,13,28,34,37,40,46 Understanding more about these relationships will allow us to better estimate L. pneumophila concentrations in premise plumbing. A systematic literature review was conducted to gather relevant information regarding the interactions of L. pneumophila with tap water biofilm microbial ecology. From the resulting information a stochastic model has been produced to simulate (1) these interactions within a tap water biofilm and (2) the inhibitory or commensal effects on L. pneumophila concentrations. The model simulates the interactions of L. ii pneumophila within a tap water biofilm. These interactions are used to calculate the resulting L. pneumophila concentrations in the biofilm and bulk tap water. Theses concentrations are then used in a quantitative microbial risk analysis (QMRA) of a 15- minute showering event and used to determine the exposure hazard to humans and associated risk of L. pneumophila infection based off this novel ecological modeling method. The models that my method develops are a means of improving the precision of estimates for exposure of bacteria after its growth in premise plumbing. From this, we can better understand how communities of microorganisms in biofilms affect the associated health risks, and thus use that to target intervention options. iii Dedication To my incredibly loving family, who have always supported me, encouraged me to learn and think for myself, and who always show interest in my ideas and projects, even if they don’t understand what or why I am doing the things I am doing. Also, thanks and appreciation to those members of the Ohio Army National Guard, and including specifically the soldiers of the 285th Area Support Medical Company for their brotherhood, and encouragement to continue in my education. It was during our 2006- 2008 medical deployment to Baghdad, Iraq that the seeds of these ideas first started to take root. And to my myriad of close, patient friends who have allowed me to think out loud in their presence, bounce ideas off them, and willingness to spur on and enrich my thought process by offering their perspectives and feedback. iv Acknowledgments I would like to thank my advisor, Dr. Mark Weir for giving me the opportunity to work under him. The tremendous amount of guidance, support, and especially motivation that he has supplied during the course of this program, goes well beyond this degree and impacts the totality of my life. Dr. Weir offered me the ability to explore research concepts that energized me, while helping me to encapsulate them within the framework of attainable and useful research projects, an invaluable skill. His advice and support always extended beyond the lab. I cannot over state how fortunate I am to have a mentor whose true concern was not just my performance in his lab, but my success with my own career and life goals. His perspective, knowledge, and dedication are uncommon in today’s world, and even more uncommonly valuable. I expected to learn a lot from him during this time, and I was not disappointed. I am extremely grateful for the mentorship that he provided. I would like to thank Dr. Michael Bisesi, who served as a member of my committee, but took me under his wing far before that. His perspective and dedication is also an uncommon and treasured commodity in today’s world. His experience and knowledge in public health is staggering and may only be seconded by his dedication to his students. He has gone far out of his way to give me the best opportunities to succeed, and I am extremely grateful for his efforts and his mentorship. v I would also like to specifically thank other members of my committee, Dr. Natalie Hull and Dr. Kerry Hamilton, who have been willing to listen to my struggles, offer me advise, review my writing, provide me with insightful and knowledgeable feedback, and who have offered up their support. Their support is something that without which, this project could not have been accomplished. The challenges presented by the global situation during the last few months of this project would have crippled me if it were not for their help. I cannot express how grateful I am to have them as part of my committee. I would also like to thank my friends, family and loved ones, who have encouraged me and offered me support and stress relief when needed. Specifically, I would like to that Anthony Cannizzaro, Ben Wheat, David Sabo, John Cannizzaro, Derrick Whan, Chaz Perin, and Travis Grizzle, who have been the iron to my iron, sharpening my thoughts and providing structure and support for my pursuit of learning. I also owe a great deal of gratitude to the Ohio State University College of Public Health and the Office of Military and Veteran Services, for not only giving me the opportunity to study topics that I am passionate about, but also allowing me to pursue my passion of helping veterans while I obtain my degrees. And finally, I would like to thank my most persistent studying and writing partners, my four-legged companions, Orion and Atlas. These long stressful days and even harder nights would not have been bearable without the support (and too often distraction) of these dogs in my life. They ensure that I keep on schedule and get at least a short break out of the office every day. These distractions are invaluable, they help me vi to take a moment away from the papers and computer screens and give me an opportunity to re-center and remember the bigger picture. I do not know where I would be without these loveable creatures. vii Vita Education B.S. Biology, Ohio State University………………………………………………...3/2012 B.S. Psychology, Ohio State University…………………………………………….3/2012 Publications Smith, Laureen, Alai Tan, Janna D. Stephens, David Hibler, and Sonia A. Duffy. "Overcoming Challenges in Multisite Trials." Nursing research 68, no. 3 (2019): 227- 236. Fields of Study Major Field: Public Health Specialization: Environmental Health Sciences, Demography viii Table of Contents Abstract ............................................................................................................................... ii Dedication .......................................................................................................................... iv Acknowledgments............................................................................................................... v Vita ................................................................................................................................... viii List of Tables .................................................................................................................... xii List of Figures .................................................................................................................. xiii Chapter 1. Introduction ....................................................................................................... 1 Background on Legionella .............................................................................................. 1 History and Health ...................................................................................................... 1 Pontiac Fever and Legionnaires’ Disease ................................................................... 2 Public Health Impact................................................................................................... 3 L. pneumophila in Water Distribution Systems .............................................................. 6 Host Cells .................................................................................................................... 8 Biofilms....................................................................................................................... 9 Problem Statement .................................................................................................... 10 Chapter 2. Inhibitory Microorganisms ............................................................................. 14 Microorganisms ............................................................................................................ 14 Protozoa ...................................................................................................................
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