MALDI-TOF Analysis of K-wire Biofilms: A Pilot Study

Category: Basic Sciences/Biologics Introduction/Purpose: In orthopedic foot and ankle surgery, temporary fixation utilizing percutaneous Kirschner wires (K- wires) is required for a variety of procedures. Reported infection rates at the pin site are highly variable, and may be as high as 20%. Currently, there is a paucity of literature regarding the microbiology of K-wires used in foot and ankle surgery, as most wires are typically disposed of once removed. The purpose of this pilot study was to determine the specific pathogens which take advantage of K-wires, in order to further elucidate the etiology of pin tract infection, as well as inform antibiotic prophylaxis decisions with wire fixation. Methods: In this study K-wires were removed from patients in a sterile environment, and divided into external and internal segments. Each segment was cultured separately, and the dominant pathogen was isolated in a subculture. Matrix Assisted Laser Desorption/Ionization-Time of Flight (MALDI-TOF) was employed for analysis, allowing for speciation of the dominant pathogen growing on the wire. Results from internal and external samples were then compared. Results: At this time a total of 10 samples have been analyzed: internal and external segments from 5 individual wires. Biofilm growth was exhibited on 60% of both the external (3/5) and internal samples (3/5). In one sample, growth occurred in the internal segment only, while the external segment was found to be sterile. Of the 5 wires tested, only one was found to be sterile (20%). All cultures were identified as Staph. Epidermidis by MALDI-TOF analysis. Conclusion: More attention should be given to microbial growth on these wires, especially in patients predisposed to infection. It is concerning that S. Epidermidis, with its propensity to form biofilms, was the dominant pathogen on our samples, especially internally. We are currently collecting further samples in order to determine which other pathogens may be taking advantage of K-wires, such that more informed decisions about antibiotic prophylaxis can be made, and to elucidate further the etiology of pin tract infections, etiology of pin tract infections.