The Journey of Cultures Taken During Revision Joint Arthroplasty: Preanalytical Phase

Can pre-analytical procedures improve microbiological culture yield in patients with periprosthetic infections?

BACKGROUND

The detection of causative pathogens plays a crucial role in the diagnosis and targeted treatment of periprosthetic joint infections (PJI). While there have been improvements in analytic methods in the past, pre-analytical procedures have not yet been sufficiently investigated. The objective of this study was to compare the culture yield of four different pre-analytical procedures.

METHODS

Patients with perioperative diagnosis of PJI were included in a single center cross-sectional study (2021-2022). Tissue samples (n = 20) of each patient were randomly and equally distributed to each of the four study arms. Tissue samples were either send to the laboratory without culture medium (group A) or were transported in thioglycolate medium immediately after sampling at three different temperatures (room temperature, 4 °C, 37° for 24 h; group B-D). Culture media were investigated for growth on days 1, 3, 7, 12, 14. All organisms, the number of positive samples and the time to positivity were recorded and compared between the study arms. Single positive cultures were considered as contamination.

RESULTS

In total, 71 patients were included. The proportions of culture negative samples (10-15%) and polymicrobial infections (51-54%) were comparable between the four arms. Seven patients (10%) were culture-negative in group A, but showed growth in thioglycolate media (group B-D). Furthermore, 13% of patients showed growth in all groups, but additional organisms were cultured in thioglycolate. There was growth beyond day 7 of culturing only in thioglycolate, but not in group A. A storage temperature of 4 °C showed a longer time to positivity compared to the other groups (p < 0.001).

CONCLUSIONS

Pre-analytical storage of tissue samples in thioglycolate broth did not improve the culture yield and did not detect additional cases of infection compared to the standard (pre-analytical storage in sterile containers). However, including a thioglycolate medium to the sampling algorithm reduced the rate of culture-negative infections and helped to identify additional organisms.

Multiple deep tissue cultures in primary total hip arthroplasty: prognostic value for periprosthetic infection

BACKGROUND

The risk of infection after total hip replacement (THR) is significant, with negative impact on quality of life and high costs. Bacteria can contaminate the surgical site despite aseptic techniques; however, there is debate regarding the benefit of identifying bacteria during the primary procedure. Although taking multiple samples for culture is a well-established practice in revision arthroplasty, doing so in primary cases remains controversial. We aimed to investigate whether there is a prognostic value in the culture of samples taken during primary THR, seeking a correlation between the positivity of the cultures and subsequent prosthetic joint infection (PJI).

METHODS

Deep samples (capsule, femoral and acetabular bone) were collected from 426 patients undergoing elective primary THR. Follow-up was at least 3 years. Microbiological profiles of cultures were analysed. Patient data were reviewed for the identification of risk factors presumably associated with a higher risk of PJI.

RESULTS

54 surgeries (12.6%) had positive cultures. 16 cases (3.8%) developed infection, of which 5 had a positive culture in the primary surgery. Infection rate was 9.3% in patients with positive culture and 3% in those with negative culture (p < 0.05), with an odds ratio of 3.34 (95% CI, 1.09-10.24). Patients with previous hip surgery had an infection rate of 8.5%, compared to 2.9% in patients with no previous surgery (p < 0.05).

CONCLUSIONS

Routinely harvesting microbiologic samples in primary THR is not justified, as it has no consequence in clinical decision for most patients. It might be recommended in selected cases that are suspected to be at high risk for infection, especially previously operated patients (conversion arthroplasty).

The impact of sonication cultures when the diagnosis of prosthetic joint infection is inconclusive

BACKGROUND

In the absence of a gold standard criterion for diagnosing prosthetic joint infections (PJI), sonication of the removed implant may provide superior microbiological identification to synovial fluid and peri-implant tissue cultures. The aim of this retrospective study was to assess the role of sonication culture compared to tissue cultures for diagnosing PJI, using different consensus and international guidelines for PJI definition.

METHODS

Data of 146 patients undergoing removal of hip or knee arthroplasties between 2010 and 2018 were retrospectively reviewed. The International Consensus Meeting (ICM-2018), Musculoskeletal Infection Society (MSIS), Infectious Diseases Society of America (IDSA), the European Bone and Joint Infection Society (EBJIS), and a modified clinical criterion, were used to compare the performance of microbiological tests. McNemar´s test and proportion comparison were employed to calculate p-value.

RESULTS

Overall, 56% (82/146) were diagnosed with PJI using the clinical criteria. Out of these cases, 57% (47/82) tested positive on tissue culture and 93% (76/82) on sonication culture. Applying this clinical criterion, the sensitivity of sonication fluid and tissue cultures was 92.7% (95% CI: 87.1%- 98.3%) and 57.3% (95% CI: 46.6%-68.0%) (p<0.001), respectively. When both methods were combined for diagnosis (sonication and tissue cultures) sensitivity reached 96.3% (95% CI: 91.5%-100%). Sonication culture and the combination of sonication with tissue cultures, showed higher sensitivity rates than tissue cultures alone for all diagnostic criteria (ICM-18, MSIS, IDSA and EBJIS) applied. Conversely, tissue culture provided greater specificity than sonication culture for all the criteria assessed, except for the EBJIS criteria, in which sonication and tissue cultures specificity was 100% and 95.3% (95% CI: 87.8-100%), respectively (p = 0.024).

CONCLUSIONS

In a context where diagnostic criteria available have shortcomings and tissue cultures remain the gold standard, sonication cultures can aid PJI diagnosis, especially when diagnostic criteria are inconclusive due to some important missing data (joint puncture, histology).