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Improved Diagnosis of Prosthetic-Joint Infections?
Sonicate-fluid cultures of explanted prostheses may improve diagnostic yield in patients with recent antibiotic exposure.
Periprosthetic-tissue cultures lack sensitivity for the microbiologic diagnosis of prosthetic-joint infection, perhaps because the organisms are present in biofilm on the prosthesis surface. In a prospective trial involving 331 Mayo Clinic patients who were undergoing joint removal for aseptic failure (n=252) or suspected infection (n=79), investigators evaluated a method for culturing samples obtained from explanted hip and knee prostheses. The researchers obtained standard preoperative joint-fluid cultures and intraoperative periprosthetic-tissue cultures; they also placed the explanted prosthetic components in Ringer’s solution, vortexed them, sonicated them for 5 minutes, and cultured the sonicate fluid. Of note, four of the investigators have a patent pending for a sonication device and culture method.
The overall sensitivity of sonicate-fluid culture was superior to that of tissue culture (79% vs. 61%; P<0.001); specificity was equal (99%). Fourteen cases of prosthetic-joint infection were detected by sonicate-fluid culture but not by tissue culture; however, in 6 such cases, the same organism was grown in synovial-fluid culture, and in an additional 7 cases, the same organism had been identified in a culture previously obtained at another institution. The increased sensitivity of sonicate-fluid cultures was seen only among patients exposed to antibiotic therapy within 14 days before explantation (75%, vs. 45% for tissue culture; P<0.001). Among patients with no antibiotic exposure within the 14 days before surgery, sonicate-fluid and tissue cultures showed equivalent sensitivity (82% vs. 77%).
Comment: Sonication of removed prostheses might increase culture sensitivity among patients with recent antibiotic exposure. However, all but one infection detected in sonicate-fluid but not tissue culture was also detected in joint-fluid or earlier tissue culture, so the clinical importance of these findings is unclear. In addition, sonicate-fluid culture might be prone to contamination when performed outside of a carefully controlled environment.
Published in Journal Watch Infectious Diseases August 15, 2007
Citation(s):
Trampuz A et al. Sonication of removed hip and knee prostheses for diagnosis of infection. N Engl J Med 2007 Aug 16; 357:654-63.
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