Thurs., 10/13/11 Basic Science, Paper #34, 4:24 pm OTA-2011
Δ Can We Trust Intraoperative Culture Results in Nonunions?
Daniel T. Altman, MD; Gregory T. Altman, MD; Jeffrey J. Sewecke, DO;
Trenton M. Gause, II, BA; William J. Costerton, PhD;
Allegheny General Hospital, Pittsburgh, Pennsylvania, USA
Purpose: Orthopaedic infections can become chronic when bacteria adopt a biofilm mode of growth, which is resistant to both host defense mechanisms and antibiotics. Direct microscopy has shown that biofilms can inhabit the surface of internal fixation devices. As they grow poorly on agar media, the bacteria in biofilms are difficult to identify using standard culture techniques. The purpose of this study was to determine the validity of routine intraoperative cultures in detecting the true presence of biofilm bacteria in delayed osseous healing.
Methods: 34 patients with nonunions were scheduled for surgery and enrolled in this ongoing, double-blinded, prospective study funded by the OTA. Intraoperative samples of tissue and membrane were collected from removed biomaterials. The nonunion sites and hardware were tested for bacterial contamination and biofilms utilizing standard cultures, DNA-based technology (Ibis, Abbott), and RNA-based fluorescent in situ hybridization (FISH). Samples were visualized using confocal microscopy to visualize FISH probes specific to bacteria found during culture and Ibis analysis.
Results: The mean age of the patients was 48.41 years (range, 17-71 years). The anatomic sites of nonunions were: 7 femoral shafts, 2 distal femur, 2 proximal femur, 1 femoral neck, 1 femoral neck and shaft, 2 supracondylar humerus, 1 humeral shaft, 14 tibial shaft, 3 tibial pilon, and 1 tibial plateau. 13 patients had open fractures. Of the 34 patients with nonunions, 23 (67%) had negative cultures and positive Ibis results for bacterial presence. Six of the 23-culture negative, Ibis-positive patients required additional surgery to achieve union. Cultures taken from the 6 patients during subsequent surgeries were positive in 50% of the cases (3 of 6). Of the 34 nonunions, 9 (27%) had positive cultures, all of which yielded positive Ibis results. Three of the culture-positive, Ibis-positive patients required additional procedures for infections or continued nonunions. Cultures taken from the culture-positive, Ibis-positive patients at subsequent surgeries were positive in 67% of the patients (2 of 3). Two patients (6%) had negative culture and Ibis results, none of which required surgical revision, and both healed with the index procedure to repair nonunion. FISH analysis confirmed the culture and Ibis data.
Conclusions: Our preliminary data indicate that culture results taken at the site of nonunion should be read with a degree of skepticism since negative cultures often do not detect bacteria in biofilms. The failure to identify the bacterial presence may result in continued nonunion and need for additional surgery.
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• The FDA has not cleared this drug and/or medical device for the use described in this presentation (i.e., the drug or medical device is being discussed for an “off label” use). ◆FDA information not available at time of printing. Δ OTA Grant.