What's New in Musculoskeletal Infection: Update on Biofilms.

Abstract

Infections involving orthopaedic surgical implants present unique challenges when compared with infections that do not involve implants. Microorganisms have a high affinity for adhering to foreign materials commonly used in orthopaedics, including cobalt-chromium, titanium, polyethylene, and polymethylmethacrylate (PMMA) cement. When bacteria adhere to these surfaces, they can form a complex structure surrounded by a self-generated extracellular polymeric substance (EPS) matrix formed by multiplex agents of biopolymers consisting of proteins, polysaccharides, lipids, nucleic acids, and humic substances1-3. The term “biofilm” is commonly used to describe this network of microorganisms, a term popularized by Dr. J. William Costerton et al. in 19784. Biofilms are formed by a confluence of bacteria commonly encountered in orthopaedic infections. Up to 65% of bacterial infections are caused by biofilm-producing organisms5. Staphylococci, specifically Staphylococcus aureus ( S. aureus ) and Staphylococcus epidermidis ( S. epidermidis ), are the most common biofilm-forming bacteria found in orthopaedics, and, when combined with Pseudomonas aeruginosa ( P. aeruginosa ), they represent nearly 75% of biofilm infections observed in medical devices6. Propionibacterium acnes ( P. acnes ), an organism commonly found in shoulder infections, has also been shown to form biofilm. Biofilms can be composed of a single organism or can be polymicrobial; polymicrobial biofilms are more difficult to eradicate7. Once bacteria adhere to the surface of implants, they may replicate and may form a complex network of microorganisms that communicate with one another via cell-to-cell signaling that facilitates the participation of bacteria in quorum sensing7. Quorum sensing serves as an elementary endocrine system whereby bacteria sense the local cell population density and regulate gene expression by releasing extracellular molecules to facilitate synchronized changes in the bacteria within the biofilm. These transcriptional changes can occur with the exchange of plasmids between bacteria, which can confer genes …