(622aj) Impacts of Varying Hydrodynamics Conditions and Mass Transfer on Staphylococcus Aureus Biofilms and Their Resistance to Antimicrobial Agents

Impacts of Varying Hydrodynamics Conditions and Mass Transfer on Staphylococcus aureus Biofilms and Their Resistance to Antimicrobial Agents

Abiye Mekonnen and Patrick Ymele-Leki

Chemical Engineering Department, Howard University

Abstract

Biofilms occur when microorganisms attach to a surface and form a biolayer, which acts as a single organism. Staphylococcus aureus is one of the most common causes of bacterial biofilm infections. Growth of these biofilms and their ability to resist antimicrobial agents are the main cause of numerous tenacious and chronic bacterial infections. Bacteria within biofilms tend to be up to 1,000 times more resistant to antibiotics than free-floating bacteria. Biofilm development can be affected by several factors such as media 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 media concentration and shear rate on the application of antibacterial drugs. We hypothesized that the combined effect of media concentration and shear rate applied to the bacterial biofilm has statistically significant influence on the ability of antimicrobial drugs to degrade bacterial biofilms. To test this hypothesis, biofilms were grown under different media 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. The data found during this study suggest that: 1) Media concentration has significant impact on the growth of bacteria in a static system. Increasing nutrient strength, from 0.5X to 2X, corroborated with a significant increase in bacteria growth. 2) The growth of a biofilm at a constant shear rate was not dependent on media concentration under the conditions tested in a flow system. 3) At lower shear rates, biofilm growth curves overlap in the early stages of growth, regardless of media concentration. 4) The data also reveal that biofilms exposed to low media concentration continue to grow for much longer periods of time (> 2 hours) than biofilm grown with higher media concentration. 5) The previously mentioned differences in biofilm characteristics had significant impact on the action of a given antimicrobial agent and their dosage.  This research can have different implications on combating the infections/contaminations caused by biofilms in both biological and industrial settings.