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Publication Date

Fall 2020

Degree Type

Thesis - Campus Access Only

Degree Name

Master of Science (MS)

Department

Biomedical Engineering

Advisor

Anand Ramasubramanian

Subject Areas

Biomedical engineering

Abstract

Many microbes in their natural habitats are found in biofilm ecosystems attached tosurfaces and not as free-floating organisms. Further, it is estimated that nearly 80% of human infections are associated with biofilms. Biofilms are traditionally defined as threedimensional, structured microbial communities that are attached to a surface and encased in a matrix of exopolymeric material. While this view of biofilm largely arises from in vitro studies under static or flow conditions, in vivo observations have indicated that this view of biofilms holds essentially true only for foreign body infections on catheters or implants where biofilms are attached to the biomaterial. In mucosal infections such as chronic wounds or cystic fibrosis, biofilms can be found unattached to a surface, and as three-dimensional aggregates. In this work, we describe a high-throughput model of aggregate biofilms of methicillin-resistant Staphylococcus aureus (MRSA) using a 96- well plate hanging drop technology. We show that MRSA forms biofilms, unattached to a surface, that are distinct from agglutination or pellicles, and that the biofilms are rich in exopolymeric proteins, polysaccharides, and eDNA, and exhibit heightened antibiotic resistance. We also show that the clinical isolates of MRSA obtained from cystic fibrosis infections favors biofilm growth in hanging drops rather than as surface-attached biofilms, while this preference is reversed for isolates obtained from central catheter infection. Overall, these results underscore the choice of a relevant in vitro system to model and more closely mimic the corresponding physiological niche during infection

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