Abstract
BackgroundIn cases of prosthetic joint infections, culture of sonication fluid can supplement culture of harvested tissue samples for correct microbial diagnosis. However, discrepant results regarding the increased sensitivity of sonication have been reported in several studies. To what degree bacteria embedded in biofilm are dislodged during the sonication process has to our knowledge not been fully elucidated. In the present in vitro study, we have evaluated the effect of sonication as a method to dislodge biofilm by quantitative microscopy.MethodsWe used a standard biofilm method to cover small steel plates with biofilm forming Staphylococcus epidermidis ATCC 35984 and carried out the sonication procedure according to clinical practice. By comparing area covered with biofilm before and after sonication with epifluorescence microscopy, the effect of sonication on biofilm removal was quantified. Two series of experiments were made, one with 24-h biofilm formation and another with 72-h biofilm formation.Confocal laser scanning microscopy (CLSM) and scanning electron microscopy (SEM) were used to confirm whether bacteria were present after sonication. In addition, quantitative bacteriology of sonication fluid was performed.ResultsEpifluorescence microscopy enabled visualization of biofilm before and after sonication. CLSM and SEM confirmed coccoid cells on the surface after sonication. Biofilm was dislodged in a highly variable manner.ConclusionThere is an unexpected high variation seen in the ability of sonication to dislodge biofilm-embedded S. epidermidis in this in vitro model.
Highlights
In cases of prosthetic joint infections, culture of sonication fluid can supplement culture of harvested tissue samples for correct microbial diagnosis
It has been claimed that sonication of explanted prostheses with subsequent culture of sonication fluid can increase the sensitivity of the test compared to culture of tissue samples [16, 18, 25, 27]
Confocal laser scanning microscopy (CLSM) and scanning electron microscopy (SEM) were used to confirm whether bacteria were present after sonication
Summary
In cases of prosthetic joint infections, culture of sonication fluid can supplement culture of harvested tissue samples for correct microbial diagnosis. Discrepant results regarding the increased sensitivity of sonication have been reported in several studies. A major challenge is the evolving bacterial resistance to antibiotics and bacteria forming biofilm which makes it difficult to treat PJI. Culture of harvested tissue biopsies during prosthetic revision is commonly used when diagnosing a PJI. The sensitivity of bacterial culture of tissue samples is not optimal. It has been claimed that sonication of explanted prostheses with subsequent culture of sonication fluid can increase the sensitivity of the test compared to culture of tissue samples [16, 18, 25, 27]
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