Poster P13 - An Integrative Approach to Bacterial Adhesion Studies under Hydrodynamic Conditions Using BioFlux Microfluidics and COMSOL Multiphysics Simulations

Introduction: This study explores the dynamics of Staphylococcus aureus adhesion to abiotic surfaces under varying shear stress conditions using the BioFlux 200 microfluidic system and COMSOL Multiphysics simulations. Focusing on the impact of fluid dynamics on bacterial behavior, we conducted real-time adhesion assays to assess how shear stress influences the spatial distribution and adhesion kinetics of S. aureus. The findings reveal that while the overall spatial distribution of bacteria remains consistent across different shear stress levels, the proximity of neighboring cells decreases over time, suggesting increased compactness under higher stresses. Additionally, the adhesion rate shows a non-linear relationship with shear stress, with notable variations at intermediate levels, pointing to complex interactions beyond mere mechanical forces. These insights enhance our understanding of bacterial adhesion mechanisms and could inform the development of new therapeutic strategies for preventing medical device-related infections.

Materials and

Methods: In this investigation of Staphylococcus aureus adhesion dynamics, we utilized the BioFlux 200 microfluidic system to conduct real-time adhesion assays under varied hydrodynamic conditions. The bacterial strain used, known for its robust biofilm-forming capabilities, was cultured in Tryptic Soy Broth and diluted in a phosphate-buffered saline solution to stabilize cell concentration for the experiments. Adhesion assays were performed at controlled wall shear stresses ranging from 1 to 5 dyn/cm², with the BioFlux system facilitating precise flow and shear conditions. Cell adhesion was monitored using a Zeiss AXIO Observer microscope, capturing images over 60 minutes at 5 minute intervals to quantify bacterial surface concentrations and spatial distributions using the OpenCFU software. Data were analyzed using MATLAB to assess spatial patterns and adhesion kinetics. COMSOL Multiphysics® was employed to simulate the adhesion processes under the same shear conditions, using two-dimensional models to replicate the microfluidic environment and analyze the influence of fluid dynamics on bacterial behavior. These methodologies allowed for a comprehensive analysis of the factors influencing S. aureus adhesion, contributing to a deeper understanding of the interplay between bacterial adhesion and shear stress in hydrodynamic environments.

Results, Conclusions, and Discussions: Our investigation into Staphylococcus aureus adhesion under varied shear stresses revealed key insights into the mechanisms governing bacterial adhesion and biofilm initiation. Experimental results using the BioFlux microfluidic system demonstrated a significant decrease in bacterial surface concentration and adhesion rates with increasing shear stress. Specifically, at the highest shear stress of 5 dyn/cm², there was a 64% reduction in surface concentration and a 49% decrease in maximum adhesion rate compared to the lowest stress condition of 1 dyn/cm². Despite these variations, the average spatial distance between cells remained stable at approximately 25 µm. However, under higher shear conditions, the proximity between adjacent cells notably decreased over time, indicating tighter clustering. Contrasting these experimental findings with results from COMSOL Multiphysics simulations underscored the current limitations of computational models to fully capture these complex biological interactions. The simulations failed to replicate the precise experimental trends, particularly the non-linear response of bacterial adhesion to varying shear stresses. This discrepancy highlights the need for advanced simulation tools that integrate artificial intelligence to improve predictive accuracy and better mimic real-world biological dynamics. This study advances our understanding of S. aureus adhesion mechanisms under shear stress, which is critical for the development of effective anti-biofouling strategies and novel therapeutic approaches against biofilm-associated infections. Moreover, it emphasizes the necessity for enhancing computational models to better reflect the nuanced interplay of physical forces and biological responses in microbial adhesion processes.

Acknowledgements (Optional): This study was supported by an NSF CMMI Award # 200030 to Dr Patrick Ymele-Leki.