Abstract
Introduction
A timely isolation of the causative bacterial species is of paramount importance in the treatment of periprosthetic joint infection (PJI). Sonication of the explanted endoprosthesis and the microbiological culture of sonicate fluid (SFC) has been proven to increase the rate of bacterial isolations in comparison to the conventional microbiological methods. The cultivation of aspired synovial fluid in blood culture bottles (BCB) has been shown to yield a higher rate of bacterial isolations and produce a lower rate of contaminants than cultivation on conventional agar plates. The primary aim of this study was to investigate whether the inoculation of BCB with sonicate fluid leads to a higher rate of bacterial isolations than the culture on agar plates. Secondly, we wanted to investigate whether the utilization of BCB leads to an earlier identification of the causative bacterial species. To our knowledge this is the first study to investigate the effects of BCB use on SFC.
Methods
We performed a retrospective analysis comparing the results of the two different culture methods. To detect slow growing species all microbiological cultures, regardless of the culture method, were incubated for 14 days.
Results
Of the 206 patients included in our study 112 showed a positive bacterial isolation. 50 patients showed a positive bacterial growth in the intraoperative tissue cultures, 45 patients showed a positive bacterial isolation in the synovial aspiration and 104 patients showed a positive bacterial growth in the SFC. From these 45 positive isolations in synovial cultures 24 were achieved through agar plate culture and 37 were achieved through incubation in BCB. From the 104 patients with a positive bacterial isolation through SFC 51 were possible through agar plate cultures and 101 were achieved through incubation in BCB.
The utilization of BCB also reduced the culture time for both the culture of synovial fluid as well as for SFC. On average the BCB produced a positive bacterial growth one day before the conventional agar plate cultures for synovial fluid and over one day earlier for sonicate fluid.
Discussion and conclusion
When sonicate fluid is cultured in blood culture bottles it leads to both an increase in positive bacterial isolations and quicker bacterial growth than the culture on conventional agar plates.
