Standardized quantification of biofilm in a novel rabbit model of periprosthetic joint infection

Abstract

Abstract. Periprosthetic joint infection (PJI) is one of the most devastating complications of total joint arthroplasty. The underlying pathogenesis involves the formation of bacterial biofilm that protects the pathogen from the host immune response and antibiotics, making eradication difficult. The aim of this study was to develop a rabbit model of knee PJI that would allow reliable biofilm quantification and permit the study of treatments for PJI. In this work, New Zealand white rabbits (n=19) underwent knee joint arthrotomy, titanium tibial implant insertion, and inoculation with Xen36 (bioluminescent Staphylococcus aureus) or a saline control after capsule closure. Biofilm was quantified via scanning electron microscopy (SEM) of the tibial explant 14 d after inoculation (n=3 noninfected, n=2 infected). Rabbits underwent debridement, antibiotics, and implant retention (DAIR) (n=6) or sham surgery (n=2 noninfected, n=6 infected) 14 d after inoculation, and they were sacrificed 14 d post-treatment. Tibial explant and periprosthetic tissues were examined for infection. Laboratory assays supported bacterial infection in infected animals. No differences in weight or C-reactive protein (CRP) were detected after DAIR compared to sham treatment. Biofilm coverage was significantly decreased with DAIR treatment when compared with sham treatment (61.4 % vs. 90.1 %, p<0.0011) and was absent in noninfected control explants. In summary, we have developed an experimental rabbit hemiarthroplasty knee PJI model with bacterial infection that reliably produces quantifiable biofilm and provides an opportunity to introduce treatments at 14 d. This model may be used to better understand the pathogenesis of this condition and to measure treatment strategies for PJI.

Combination d-Amino Acid and Photothermal Hydrogel for the Treatment of Prosthetic Joint Infections

“…Twenty SEM images were collected from each of the implants in a statistically guided area distribution (Figure A). The obtained images were analyzed using a machine-learned algorithm to calculate percent coverage, which we have previously developed to investigate infection in our in vivo rabbit model for PJI . Three implants for each treatment type were analyzed: no treatment (NT), DAIR, and PhotothermAA 1000 gel.…”

“…For high-resolution images, an FEI Quanta 450 FEG environmental scanning electron microscope (FEI Company, Hillsboro, OR) was used, and measurements were conducted at 5 kV. In order to aid in the quantitative mapping of total biofilm coverage, a script written in DigitalMicrograph software (Gatan, Inc., Pleasanton, CA) was utilized to automate the SEM stage and image capture process . Twenty images were collected at 1500× magnification and 5 kV from the top of each of the implants, each image was set ∼2 mm apart and were selected based on a statistically designed area distribution.…”

“…The obtained images were analyzed using a machine-learned algorithm to calculate percent coverage, which we have previously developed to investigate infection in our in vivo rabbit model for PJI. 30 Three implants for each treatment type were analyzed: no treatment (NT), DAIR, and PhotothermAA 1000 gel. Figure 6B−D shows representative SEM images obtained from each treatment, with the remaining biofilms falsely colored purple and the implant surface colored green for ease of interpretation.…”

“…Therefore, our method has great potential for translation to in vivo studies. We have recently developed an animal model for PJI, 30 and we are currently exploring our PhotothermAA gel treatment toward our rabbit animal model.…”

“…Biofilm dispersal activities were evaluated by removing the culture media from the biofilms and applying the different treatments; saline solution (0.9%) was used as the control treatment. To mimic the debridement, antibiotics, and implant retention (DAIR) treatment, 30 the implants were irrigated 3× using 3 mL of saline delivered through a 25G needle (BD Plastipak 3 mL syringe, Fisher Scientific, Pittsburgh, PA) and then scrubbed with an interdental brush (Up&Up, Minneapolis, MN) for 1 min. Following scrubbing, an additional three rinses of 3 mL of saline was used to irrigate the implant, and 3 mL of Cefazolin (20 mg/kg in sterile water) was used to treat the implant before analysis.…”