DETECTION OF THE AETIOLOGICAL AGENT IN PRE-SURGICAL JOINT ASPIRATION FLUID USING A COMMERCIAL MULTIPLEX PCR SYSTEM* DESIGNED FOR DIAGNOSIS OF IMPLANT AND TISSUE INFECTION

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Aim Periprosthetic joint infection (PJI) is nowadays the most important problem leading to failure in primary and revision total knee (TKA) and total hip arthroplasty (THA), therefore accurate diagnosis of PJI is necessary. We evaluated a commercial multiplex PCR system1 for diagnosis of PJI in joint aspiration fluids prior to surgery. Method A total of 32 patients were included in the study. Twenty-four patients had TKA and eight had THA. Joint aspiration fluids were examined by standard bacteriological procedures. Excess material of joint aspirates was frozen at −20°C until testing by multiplex PCR1. Inclusion criteria were a minimum leucocyte count of 2.000 per ml and at least 60% of polymorphonucleaur neutrophils (PNN) in the joint aspiration fluid. Results For 21 patients with TKA, both standard bacteriological culture and PCR1 were negative. In these patients the mean leucocyte count in the joint fluid was 15.385/ml with 80% PNN. For three patients culture was negative, but PCR1 was positive. In one patient PCR1 detected Corynebacterium sp. which was considered as contamination as this patient had crystal arthropathy; for the second patient Propionibacterium acnes was detected by PCR1, this patient was treated as having an infection of unknown origin in another hospital. For the third patient PCR1 detected Pseudomonas aeruginosa. This patient was known as having chronic P. aeruginosa infection of his TKA and joint aspiration was done shortly after arrest of antibiotic therapy by ciprofloxacin. The mean leucocyte count in the patients with positive PCR was 61.800/ml with 89% PNN. In three of the eight patients with THA, standard bacterial culture and PCR1 were both negative. The mean leucocyte count in joint aspirates of these patients was 10.087/ml with 77% PNN. In five patients with THA, both culture and PCR1 were positive and concordant. In one case culture and PCR1 detected Staphylococcus aureus, and in the other culture and PCR1 detected P. acnes. In two cases culture grew S. epidermidis and PCR1 detected coagulase negative Staphylococcus. In the fifth patient culture grew C. jeikeium and PCR1 detected Corynebacterium spp. Conclusions We found concordant results for culture and PCR1 in all eight patients with THA and in 22/24 patients (92%) with TKA. Multiplex PCR1 results are available in 4 hours whereas culture results may demand several days. The commercial multiplex PCR system1 designed for diagnosis of implant and tissue infection can be helpful for the diagnosis of PJI. *Unyvero i60©, Curetis Strasbourg, France

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