Microbiological pathogen analysis in native versus periprosthetic joint infections: a retrospective study.

Background: The presence or absence of an implant has a major impact on the type of joint infection therapy. Thus, the aim of this study was the examination of potential differences in the spectrum of pathogens in patients with periprosthetic joint infections (PJI) as compared to patients with native joint infections (NJI).

Methods: In this retrospective study, we evaluated culture-positive synovial fluid samples of 192 consecutive patients obtained from January 2018 to January 2020 in a tertiary care university hospital. For metrically distributed parameters, Mann-Whitney U was used for comparison between groups. In case of nominal data, crosstabs and Chi-squared tests were implemented.

Results: Overall, 132 patients suffered from periprosthetic joint infections and 60 patients had infections of native joints. The most commonly isolated bacteria were coagulase-negative Staphylococci (CNS, 28%), followed by Staphylococcus aureus (S. aureus, 26.7%), and other bacteria, such as Streptococci (26.3%). We observed a significant dependence between the types of bacteria and the presence of a joint replacement (p < 0.05). Accordingly, detections of CNS occurred 2.5-fold more frequently in prosthetic as compared to native joint infections (33.9% vs. 13.4% p < 0.05). In contrast, S. aureus was observed 3.2-fold more often in NJIs as compared to PJIs (52.2% vs. 16.4%, p < 0.05).

Conclusion: The pathogen spectra of periprosthetic and native joint infections differ considerably. However, CNS and S. aureus are the predominant microorganisms in both, PJIs and NJIs, which may guide antimicrobial therapy until microbiologic specification of the causative pathogen.