Biofilms in periprosthetic orthopedic infections

Abstract

As the number of total joint arthroplasty and internal fixation procedures continues to rise, the threat of infection following surgery has significant clinical implications. These infections may have highly morbid consequences to patients, who often endure additional surgeries and lengthy exposures to systemic antibiotics, neither of which are guaranteed to resolve the infection. Of particular concern is the threat of bacterial biofilm development, since biofilm-mediated infections are difficult to diagnose and effective treatments are lacking. Developing therapeutic strategies have targeted mechanisms of biofilm formation and the means by which these bacteria communicate with each other to take on specialized roles such as persister cells within the biofilm. In addition, prevention of infection through novel coatings for prostheses and the local delivery of high concentrations of antibiotics by absorbable carriers has shown promise in laboratory and animal studies. Biofilm development, especially in an arthoplasty environment, and future diagnostic and treatment options are discussed.

Keywords: antibiotic resistance; arthroplasty; biofilm; coating; infection; planktonic; prosthesis; treatment.

Figure 1. Diagnosis of infection can be challenging

(A) In this patient with a hot knee, diagnosis was straightforward from clinical signs and symptoms and a positive culture from aspirate. (B) Radiograph from a total knee arthroplasty patient for whom diagnosis was more difficult. The aspirate was culture negative and the radiograph revealed no indications of infection. (C) Intraoperative image from (B) showing purulence and slime in the joint space and an intraoperative positive culture. (D) Radiograph from a patient with only subtle signs of a TKA infection, a culture-negative aspirate, a normal erythrocyte sedimentation rate and slightly elevated C-reactive protein, but over 20,000 white blood cells with more than 90% polymorphonuclear leukocytes. Intraoperative cultures showed coagulase-negative Staphylococcus.

Figure 2. Various configurations of bacteria and biofilms in three different orthopedic patients

(A) Biofilm of live cocci (green) attached to a screw removed from a fixation device in a nonunion. The biofilm demonstrated classic 3D structure. (B) Patch of biofilm attached to periprosthetic tissue from a failed ankle arthroplasty. The upper left panel shows reflected light demonstrating the surface of the tissue (blue). The upper right panel shows a FISH ‘sau’ probe demonstrating Staphylococcus aureus bacteria (red). The lower left panel shows a FISH ‘Eub’ probe demonstrating all stained bacteria (green). The lower right panel shows an overlay demonstrating the S. aureus biofilm cluster attached to the tissue. (C) Periprosthetic tissue from the same patient as (B), showing bacteria that appear to be intracellular. (D) Intraoperative fluid from a patient with a failed elbow showing clumps of live cocci (green). The large red object is a nucleolus from a host cell that appears to have been ‘attacked’ and damaged by the cocci.

Figure 3. How bacteria and biofilms might be distributed in a periprosthetic joint infection using a knee as an example

Biofilms can grow on the prostheses components, the surrounding tissue and the fibrous sheath. Each of these can be considered separate, but communicating niches. The joint fluid might contain planktonic cells or clumps of detached biofilm. The periprosthetic tissue can be invaded by the infecting bacteria. There can be migration of bacteria between each of these locations (prosthesis, surface tissue and matrix, subsurface tissue and fluid), which could contribute to survival. If bacteria in one niche are eradicated by debridement or antibiotic therapy, there is potential for the repopulation of pathogens from the other niches.

Figure 4. Imaging periprosthetic biofilms using quantum dot-labeled antibiofilm antibodies

The antibodies were injected via the intravenous route and allowed to localize in mice with (A) Staphylococcus aureus-infected or (B) sterile pins implanted into the left tibia. Live imaging was performed using an IVIS^® Lumina Series III imager (PerkinElmer, MA, USA). (C) In order to confirm the results of the live imaging, the pins were extracted and probed with with fluorescein isothiocyanate-labeled universal bacterial probe (green) and a rhodamine-labeled universal eukaryotic cell probe (red) that were specific for bacterial and eukaryotic rRNAs, showing well-developed biofilms. (D) No biofilms were evident in the sterile pins. The relative brightness which was proportional to the amount of biofilm is indicated in the ROI. ROI: Region of interest.