Hydrodynamic Evaluation of Microtiter Plate Assay Using Computational Fluid Dynamics for Biofilm Formation

Abstract

Biofilms are complex surface associated communities where bacterial cells are enclosed by self-produced extra cellular polymeric substances (EPS), mainly consisting of exopolysaccharides, proteins and extracellular DNA. Treatment of biofilm associated persistent infections is an emerging issue for clinicians as bacterial cells adhere with human epithelial cells or indwelling medical devices such as implants and catheters, used in urinary tract and respiratory infections. Several methods are in practice to assess the biofilm formation of bacterial strains. Most of these are phenotypic methods which include Congo red assay (CRA), Air liquid interface (ALI), tissue culture plate method and Microtiter plate assay (MTPA). MTPA is considered as a standard screening method for comparing adherence pattern and is the most widely used quantitative method for detection of biofilm formation. Generally, the assay is performed under standard static conditions and little is known about the hydrodynamics in the microtiter plates. A few studies have applied computational fluid dynamics (CFD) simulations to describe flow pattern in microtiter plates during biofilm production and optimized the suitable conditions to detect the biofilm formation which have proven to be efficient. In this work the dependencies of biofilm formation on the hydrodynamics in microtiter plate assays were evaluated using OpenFOAM® an open-source toolbox for numerical simulation. It was found that higher flow rates increase the nutrient availability, promote cell growth, and attachment pattern with increased production of exopolymer, while the increase in flow velocity increases the shear rate causing erosion and disassembly of biofilm production because of detachment from the surface.