Title

Property of accumulation associated protein (AAP) in Staphylococcus epidermidis and biofilm inhibition by AAP specific monoclonal antibodies

Date of Completion

January 2004

Keywords

Engineering, Chemical

Degree

Ph.D.

Abstract

The goal of this research project is to characterize Staphylococcus epidermidis accumulation associated protein (AAP), and develop monoclonal antibodies against AAP to prevent bacterial colonization of a model biomaterial. The specific adhesion/biofilm accumulation of S. epidermidis appears to be governed in part by AAP, the exact mechanism of which has not been detailed. Prior work suggests that binding antibodies specific to this protein can interrupt biofilm formation. Preliminary data indicates that AAP may be involved in both adhesion and biofilm formation events. In this project, monoclonal antibodies against this protein were developed and proved to inhibit formation of S. epidermidis biofilm. These monoclonal antibodies have enabled a variety of experiments that quantify the mode of operation of the AAP. Bacterial number, extracellular polysaccharide production, surface expression and secretion of AAP were quantified as functions of time in three different bacterial growth systems. A mathematical model was developed to simulate S. epidermidis biofilm formation process as mediated by AAP. ^ Results shows that immunospecific probes (monoclonal antibodies and F(ab)2 fragments) against AAP block the biofilm formation activity of the AAP in S. epidermidis RP62A by 42% and 30%, respectively. Mixtures of Mabs recognizing different epitopes of AAP are more efficient for biofilm inhibition than single Mab. A 200-KDa protein, which shares significant sequence homology with AAP, was discovered in the biofilm negative mutant, S. epidermidis M7. Results from AAP dynamic studies indicate that soluble AAP may play a role in biofilm accumulation process. A mathematical model based on the assumption that AAP serves as a cell:cell signal successfully simulates the dynamics of bacterial accumulation (both suspended and attached), AAP numbers per cell (suspended and attached) and extracellular biofilm polysaccharide in three different reactor systems and also in Mab inhibition studies. Although the good agreement between experimental data and model prediction is not a justification of the model, use of the computer model can help in planning future experiments to further define the role of AAP. ^