Fluid dynamic factors as a cause and effect of biofilm formation of Staphylococcus aureus biofilms

Sherman, Erica, "Fluid dynamic factors as a cause and effect of biofilm formation of Staphylococcus aureus biofilms" (2016). Staphylococcus aureus bacteria are able to form biofilms and distinctive tower structures that facilitate their ability to tolerate treatment and to spread within the human body. The formation of towers, which break off, get carried downstream and serve to initiate biofilms in other parts of the body are of particular interest here. It is known that flow conditions play a role in the development, dispersion and propagation of biofilms in general. The influence of flow on tower formation and ultimately what factors lead to tower formation, however, is not at all understood. This work is focused on the effect of applied shear stress on tower development. The hypothesis being examined is that tower structures form within a specific range of shear stresses and that there is an as yet ill-defined fluid dynamic phenomenon that occurs hours before a tower forms. In this study, a range of shear stresses is examined that brackets 0.6 dynes/cm 2 , the nominal shear stress where towers seem most likely to form. The biofilm structure is known to be a temporally and spatially heterogeneous structure, which must be taken into account when considering the tower formation frequency and the local flow environment. How this structure differs as a function of applied shear, the experimental stage of biofilm development, and the likelihood of tower formation is analyzed. This work includes µPTV measurements and cell density data indicating variations in flow and biofilm evolution as a function of the applied shear. Causal relations between flow and biofilm development will be discussed as well as the presentation of specific biofilm development terms as predictive measures of tower formation. iii DEDICATION This work is dedicated to my grandfather, Enzio Macor. His passion for learning was evident in everything he did and shone through no matter what life sent his way. His example leaves me humbled and sparks a fire in my heart. iv ACKNOWLEDGEMENTS My work is a cumulative result of the support, inspiration, and effort of those around me who have helped me to become who I am today. Each person has played a role, no matter how big or small, which has fostered my growth and for that I am thankful. First and foremost, my parents have provided tremendous support and encouragement to try and keep trying no matter …