(228am) Efficacy of Antibacterial Agents on Staphylococcus Aureus biofilms Based on the Hydrodynamic Conditions and Nutrient Concentrations of the Growth Environment

Biofilms arise when microorganisms attach to a surface of their host and form a bio-layer. Growth of these biofilms and their ability to resist antimicrobial agents are the main cause of numerous tenacious and chronic bacterial infections. Staphylococcus aureus is one of the most common causes of bacterial infections and has the ability develop biofilms easily. Bacteria within biofilms tend to be hundreds of folds more resistant to antibiotics than planktonic bacteria. Biofilm development can be affected by several factors such as nutrient concentrations, hydrodynamics conditions (fluid shear stress and shear rate), types of bacteria, and cell-cell communication (quorum sensing). This project aims to determine the isolated and combined effects of nutrient concentration and shear rate on the application of antibacterial drugs. We hypothesized that the combined effect of nutrient concentration and shear rate applied to the bacterial biofilm would have statistically significant influence on the ability of antimicrobial drugs to degrade bacterial biofilms. To test this hypothesis, biofilms were grown under different nutrient concentrations (2X, 1X, 0.5X, 0.1X) of TSB and fluid shear rates (ranging from 10 s^-1 to and 300 s^-1) conditions in the presence or absence of known antibacterial agents. Biofilm cultures of S. aureus were grown under continuous flow of TSB nutrient to determine the impact of hydrodynamic conditions on the growth of bacteria. The cultures were grown at 37°C and exposed to various fluid flow rates under the control of a BioFlux 1000z flow system (Fluxion Biosciences Inc., South San Francisco, CA). The acquired images from the experiment were then analyzed to determine the area coverage. From this study we can conclude that the application of antibiotics is greatly affected by the shear force where the biofilm was developed under. The study suggests that the efficacy of antibiotics is greatly affected by the shear forces present within the growth environment and, to a lesser extent, by nutrient strength. These results may be used to predict the efficiency of antimicrobial dosage regimens against pathogens prone to biofilm formation under hydrodynamic milieus.