Improving the microbiological diagnosis of fracture-related infection and prosthetic joint infection through culturing sonication fluid in Bactec blood culture bottles.

Background: Sonication of surgically removed implants appears to optimize the microbiological diagnosis in orthopedic implant-associated infections (OIAI). However, reports of infection with negative cultures can still reach high rates. A study evaluating the inoculation of sonication fluid into blood culture bottles (SFBCB) in patients with fracture-related infection (FRI) and prosthetic joint infection (PJI) is necessary. This study compared the accuracy SFBCB over the conventional sonication fluid cultures (CSFC) and tissue culture (TC).

Methods: Consecutive patients who underwent implant removal surgeries due to any reason had their implants sonicated according to standardized method. Definitions of PJI and FRI were based upon criteria by European Bone and Joint Infection Society (EBJIS) and Metsemakers, respectively. Between three to five intraoperative tissue samples were processed. The implant`s sonication fluid was seeded onto sheep blood agar, chocolate agar, thioglycolate broth and on tryptic soy broth for CSFC, while was also inoculated into blood culture bottles and incubated in the automated system during 5 days for SFBCB.

Results: Overall, 74 patients were analyzed, of which 57 with OIAI (48 FRI and 09 PJI) and 17 aseptic failures (03 arthroplasties and 14 osteosynthesis). Interestingly, SFBCB demonstrated significantly higher sensitivity compared to CSFC (96.5% [95% CI, 88-100] vs. 78.9% [95% CI, 66-89], p = 0.004), and to TC (96.5% [95% CI, 88-100], vs. 57.9% [95% CI, 44-71], p < 0.001), whereas there were no significant differences in specificity between the three methods.

Conclusion: In comparison to CSFC and TC, SFBCB improved sensitivity for diagnosing OIAI without compromising specificity.