Abstract
Aim
To provide proof of concept in an in vivo animal model for the prevention of prosthetic joint infection prevention using electric fields along with conventional antibiotic prophylaxis.
Corresponding Author: Marti Bernaus
Method
First, we standardized the animal model to simulate implant contamination during the surgical procedure. We then implanted cobalt-chrome prostheses adapted to both knees of two New Zealand White rabbits, under standard aseptic measures and antibiotic prophylaxis with cefazolin. Prior to implantation, we immersed the prostheses in a 0.3 McFarland inoculum of S. aureus (ATCC 25923) for 30 seconds. In the first animal (control), the joint was directly closed after washing with saline. In the second animal (case), both prostheses were treated with electric current pulses for 30 seconds, washed with saline, and the joint was closed. After 72 hours, both animals were reoperated for the collection of periprosthetic tissue and bone samples, and prosthesis removal. In all samples, we performed quantitative cultures prior to vortexing and sonication, as well as prolonged cultures of the sonication broth. We confirmed the absence of contamination by identification with MALDI-TOF (VITEK-MS) and automated antibiotic susceptibility testing of the isolated colonies (VITEK-2).
Results
In the “control” animal, we isolated S. aureus in all studied samples. The bacterial count expressed as log10 (cfu/cm2) in the prostheses of the right and left legs was 9.38 and 8.86, respectively. The bacterial count expressed as log10 (cfu/mL) in bone and periprosthetic tissue biopsies was 2.70 and 2.72 in the right leg and 3.24 and 3.87 in the left leg, respectively. In the “case” animal, where an electric field was applied to the implant after placement in addition to cefazolin prophylaxis, all samples (prosthesis, bone, and periprosthetic tissue) were negative, and no isolation of the inoculated strain of S. aureus was obtained after incubation of the sonication broth for 14 days.
Conclusions
This in vivo model suggests the potential effectiveness of applying an electric field to a prosthetic implant in combination with cefazolin for the prevention of PJI development, after exposure of the implant to an inoculum of S. aureus (ATCC 25923). Our findings need to be confirmed using a larger sample size.
