D-lactate is a promising biomarker for the diagnosis of periprosthetic joint infection.

Introduction: Reliable biomarkers for the diagnosis of periprosthetic joint infection (PJI) are of paramount clinical value. To date, synovial fluid leukocyte count is the standard surrogate parameter indicating PJI. As D-lactate is almost solely produced by bacteria, it represents a promising molecule in the diagnostic workflow of PJI evaluation. Therefore, the purpose of this study was to assess the performance of synovial fluid D-lactate for diagnosing PJI of the hip and knee. Materials and Methods: These are preliminary results of a prospective multicenter study from one academic center. Seventy-two consecutive patients after total hip arthroplasty (THA) or total knee arthroplasty (TKA) were prospectively included. All patients received a joint aspiration in order to rule out or confirm PJI, which was diagnosed according to previously published institutional criteria. Synovial fluid D-lactate was determined spectrophotometrically at 450 nm. Receiver operating characteristic (ROC) analysis was performed to assess the diagnostic performance. Results: Eighteen patients (25%) were diagnosed with PJI and 54 patients (75%) were classified as aseptic. Synovial fluid D-lactate showed a sensitivity of 90.7% (95% CI: 79.7%-96.9%) and specificity of 83.3% (95% CI: 58.6%-96.4%) at a cut-off of 0.04 mmol/L. The median concentration of D-lactate was significantly higher in patients with PJI than in those with aseptic conditions (0.048 mmol/L, range, 0.026-0.076 mmol/L vs. 0.024 mmol/L, range, 0.003-0.058 mmol/L, p < 0.0001). The predominat microogranisms were staphylococci, followed by streptococci and gram-negative bacteria. Conclusion: D-lactate bears a strong potential to act as a valuable biomarker for diagnosing PJI of the hip and knee. In our study, a cutoff of 0.04 mmol/L showed a comparable sensitivity to synovial fluid leukocyte count. However, its specificity was higher compared to conventional diagnostic tools. The additional advantages of D-lactate testing are requirement of low synovial fluid volume, short turnaround time and low cost.

Influence of retrieved hip- and knee-prosthesis biomaterials on microbial detection by sonication.

Microorganisms' ability to adhere and form a biofilm differs among biomaterials; however, clinical data are conflicting. Microbial adherence and biofilm formation on different biomaterials of explanted joint prosthesis components were investigated. Consecutive patients with explanted joint prosthesis were prospectively included. The bacterial load dislodged from retrieved prosthetic components was evaluated qualitatively and quantitatively in sonication-fluid cultures. For comparison between groups, one-way ANOVA and Wilcoxon signed-rank test were used. A total of 112 components originating from 58 knee and 54 hip prostheses were retrieved from 40 patients. Components were made of titanium alloy in 42 cases, cobalt-chromium alloy in 38 and polyethylene in 32. Bacteria in sonication-fluid cultures grew in all polyethylene components (100 %), followed by titanium alloy (79 %) and cobalt-chromium components (71 %). Larger bacterial counts were found on polyethylene than on titanium (p < 0.013) or cobalt-chromium alloy (p = 0.028). Coagulase-negative Staphylococcus aureus and Streptococcus species were most commonly isolated. In conclusion, polyethylene showed larger biofilm burden than metal alloys, indicating their higher microbial adhesion affinity in vivo. Sonication of polyethylene liners, rather than the whole prosthesis, was sufficient for diagnosis of prosthetic joint infection. Moreover, bacterial counts were larger after sonication of polyethylene liners than of metal alloys, suggesting intrinsic differences in the ability for biofilm formation on various biomaterials. Polyethylene liners allowed the diagnosis of prosthetic joint infections (PJIs) in all investigated cases, suggesting that sonication of polyethylene liners rather than of the complete prosthesis was sufficient for pathogen detection in PJIs.

[Ecological tolerance of Salmonellae isolated from the water of surface reservoirs]. / K voprosu ob ékologicheskoi tolerantnosti sal'monell, vydelennykh iz vody poverkhnostnykh vodoemov.

On the basis of the study of different physico-chemical and sanitary parameters in the open water basins of the Volga delta and the comparison of these parameters with the changes in the size of Salmonella populations the confines of the ecological tolerance of this species have been shown.