Improved detection of infection in hip replacements

Intraoperative Direct Sonication Versus Conventional Sonication in the Diagnosis of Periprosthetic Joint Infection: Comparison of Diagnostic Accuracy and Time to Positivity of Fluid Culture

BACKGROUND

Conventional sonication is a recommended method in the diagnosis of periprosthetic joint infection (PJI), but the accuracy of diagnosis is still not ideal. We have applied the use of a handheld ultrasonic device and the intraoperative direct sonication of prostheses and soft tissues retrieved during surgery to improve the efficacy of the microbiological diagnosis of PJI and the incubation time of pathogens.

METHODS

This was a retrospective study of patients diagnosed with PJI or aseptic loosening who underwent revision, DAIR (debridement, antibiotics, and implant retention), or resection, and for whom either sonication method was used between July 2017 and June 2023. Starting in August 2021, the removed implants and adjacent soft tissue were directly sonicated in a small metal container, and then the sonication fluid was incubated in blood culture bottles in the operating room under laminar air flow. Conventional sonication was continued through July 2021, and included vortex mixing for 30 seconds, sonication for 5 minutes, and additional vortex mixing for 30 seconds, as described by Trampuz et al. in 2007. The sensitivity, specificity, and time to positivity (TTP) of pathogen cultures were compared between intraoperative direct sonication and conventional sonication.

RESULTS

Of the 415 included patients, 266 had PJI and 149 had aseptic loosening. Fluid from intraoperative direct sonication and conventional sonication showed sensitivities of 88% and 69% (p < 0.001) and specificities of 84% and 93% (p = 0.105), respectively. Higher sensitivity was obtained by intraoperative direct sonication of only soft tissue than by direct sonication of only the prosthesis (80% versus 75%). Culture results from intraoperative direct sonication of soft tissue and the prosthesis were inconsistent in 55 cases (soft tissue plus prosthesis: 28 cases, soft tissue only: 17 cases, and prosthesis only: 10 cases). Gram-positive organisms grew significantly faster following direct sonication (median TTP for soft-tissue, 2.12 days [interquartile range (IQR), 1.40 to 3.16 days], and median TTP for the prosthesis, 2.02 days [IQR, 1.08 to 3.04 days]) compared with conventional sonication (median TTP, 2.92 days [IQR, 1.83 to 3.96 days]) (p = 0.003 and p < 0.001, respectively).

CONCLUSIONS

Intraoperative direct sonication was more sensitive than conventional sonication for the microbiological diagnosis of PJI and slightly shortened the TTP of microorganisms.

LEVEL OF EVIDENCE

Diagnostic Level III. See Instructions for Authors for a complete description of levels of evidence.

Exploring the Role of Sonication Fluid Culture in Periprosthetic Joint Infection: A Comparative Study with Conventional Methods

OBJECTIVE

The aim of this study is to evaluate and compare the diagnostic effectiveness of sonication fluid culture (SFC) compared to conventional methods in identifying the causative microorganisms in periprosthetic joint infections.

METHODS

In this study, three cultures were evaluated for diagnosing periprosthetic joint infection intraoperative periprosthetic tissue culture, implant culture, and SFC. The sensitivity, specificity, and predictive values were calculated for each method, using the 2018 definition of periprosthetic hip and knee infection and clinical evaluation as references. Of the 92 patients who had implants removed, 49 were for mechanical reasons and 43 for infection.

RESULTS

Positive cultures were obtained in 13 out of 49 patients with mechanical issues and 31 out of 43 with infections. The sensitivity of periprosthetic tissue cultures (53.5%) is slightly higher than SFC (48.8%), suggesting better detection of positive cases. However, SFC's specificity (83.7%) is higher, indicating more accurate identification of negative cases compared to periprosthetic cultures (73.5%). However, SFC identified additional pathogens in patients with negative periprosthetic tissue and implant cultures. Examination of the infected knee and hip prostheses showed that SFC enhanced pathogen detection, particularly in patients with negative implant cultures. Despite this, SFC was not statistically superior to other methods.

CONCLUSION

This study supports the combined use of periprosthetic tissue culture and SFC for identifying causative microorganisms in implant infections. Despite not being statistically superior, SFC provides additional pathogen detection, especially when other methods fail, thereby enhancing overall diagnostic accuracy.

Antimicrobial Efficacy of Five Wound Irrigation Solutions in the Periprosthetic Joint Infection Microenvironment In Vitro and Ex Vivo

Background/Objectives: Periprosthetic joint infections (PJI) are difficult to treat due to biofilm formation on implant surfaces and the surrounding tissue, often requiring removal or exchange of prostheses along with long-lasting antibiotic treatment. Antiseptic irrigation during revision surgery might decrease bacterial biofilm load and thereby improve treatment success. This in vitro study investigated and compared the effect of five advanced wound irrigation solutions to reduce bacterial burden in the PJI microenvironment. Methods: We treated in vitro biofilms grown on titanium alloy implant discs with clinical bacterial strains isolated from patients with PJIs, as well as abscess communities in a plasma-supplemented collagen matrix. The biofilms were exposed for 1 min to the following wound irrigation solutions: Preventia®, Prontosan®, Granudacyn®, ActiMaris® forte ('Actimaris'), and Octenilin®. We measured the bacterial reduction of these irrigation solutions compared to Ringer-Lactate and to the strong bactericidal but not approved Betaseptic solution. Additionally, ex vivo free-floating bacteria isolated directly from clinical sonication fluids were treated in the same way, and regrowth or lack of regrowth was recorded as the outcome. Results: Irrigation solutions demonstrated variable efficacy. The mean CFU log10 reduction was as follows: Octenilin, 3.07, Preventia, 1.17, Actimaris, 1.11, Prontosan, 1.03, and Granudacyn, 0.61. For SACs, the reduction was: Actimaris, 8.27, Octenilin, 0.58, Prontosan, 0.56, Preventia, 0.35, and Granudacyn, 0.24. Conclusions: All solutions achieved complete bacterial eradication in all tested ex vivo sonication fluids, except Granudacyn, which was ineffective in 33% of the samples (2 out of 6). Advanced wound irrigation solutions have the potential to reduce bacterial burden in the PJI microenvironment during revision surgery. However, their efficacy varies depending on bacterial species, growth state, and the composition of the irrigation solution. This underscores the importance of considering these factors when developing future PJI-specific irrigation solutions.

Intraoperative Direct Sonication of Implants and Soft Tissue for the Diagnosis of Periprosthetic Joint Infection

BACKGROUND

Sonication is very efficacious for the microbiological diagnosis of periprosthetic joint infection (PJI), but it involves many steps and multiple workplaces and personnel and therefore carries a potential contamination risk. We present an innovative version of the sonication culture method that involves direct sonication of the retrieved implant and soft tissue, without a sonication tube, intraoperatively and incubation using a BACT/ALERT 3D blood culture system to enhance the efficacy of microbiological diagnosis of PJI.

METHODS

We performed a prospective study of consecutive patients requiring implant removal and classified them as having PJI or aseptic failure according to standard criteria. The removed prosthetic components and adjacent soft tissue were directly sonicated in a small metal container, without a sonication tube, during the operation. The sonication fluid was immediately incubated in blood culture bottles in the operating room and cultured in the BACT/ALERT 3D blood culture system. The synovial fluid was also cultured in the BACT/ALERT 3D system to serve as a comparison.

RESULTS

Of the 64 included patients, 36 had PJI and 28 had aseptic failure. Fluid from direct sonication and conventional synovial fluid showed sensitivities of 91.7% and 55.6% (p < 0.001) and specificities of 82.1% and 92.9%, respectively. Fourteen cases of PJI were detected by culture of fluid from direct sonication but not by culture of synovial fluid. Higher sensitivity was obtained by direct sonication of only tissue than by direct sonication of only the implant (88.9% versus 75.0%). No significant difference in detection time was found between Staphylococcus aureus and coagulase-negative Staphylococcus.

CONCLUSIONS

When combined with incubation in BACT/ALERT bottles, direct intraoperative sonication of implants and soft tissues without a sonication tube was more sensitive than conventional synovial fluid culture and could reliably and rapidly detect the bacteria commonly found in PJI.

LEVEL OF EVIDENCE

Diagnostic Level II . See Instructions for Authors for a complete description of levels of evidence.

The role of sonication in the diagnosis of periprosthetic joint infection in total shoulder arthroplasty

An increased sensitivity of sonication compared to periprosthetic tissue cultures in the diagnosis of periprosthetic joint infection (PJI) of hip and knee arthroplasty has been reported. The goal of this study was to determine if there is also an added value of implant sonication in the diagnosis of PJI in total shoulder arthroplasty (TSA). A retrospective analysis of patients who underwent removal of their TSA combined with sonication of the implant for suspicion of PJI between April 2009 and August 2017 was performed. The diagnosis of PJI was based on the major criteria described by Parvizi. We calculated sensitivity, specificity, predictive values, likelihood ratios and diagnostic accuracy for sonication cultures in comparison with periprosthetic tissue cultures. Data from 41 patients were analysed. Standard synovial fluid cultures combined with intraoperative periprosthetic tissue cultures had a sensitivity of 95%, specificity of 95% and total accuracy of 95%. Sonication cultures had a sensitivity of 91%, specificity of 68% and total accuracy of 80%. Six patients had negative standard cultures but positive sonication cultures. In patients with only one positive standard culture, the pathogen of the sonication culture corresponded to the pathogen of the positive soft tissue culture. We found a possible added value of sonication of TSA in the diagnosis of PJI in conjunction with standard intraoperative cultures. In some patients with suspicion of low-grade TSA infection, sonication could identify a possible causal microorganism despite negative standard cultures.

Unexpected intraoperative positive culture (UIPC) in presumed aseptic revision spine surgery: a systematic review and meta-analysis

BACKGROUND CONTEXT

Unexpected intraoperative positive culture (UIPC) has recently become increasingly common in revision spine surgery, being implicated as an etiological factor in revision spine surgery indications such as implant failure or pseudoarthrosis.

PURPOSE

Utilizing the available literature, this study aimed to investigate the prevalence of UIPC, and its clinical importance in patients following presumed aseptic revision spine surgery.

STUDY DESIGN

Meta-analysis and systematic review.

METHODS

Multiple databases and reference articles were searched until May 2022. The primary outcome was the pooled rate of UIPC, and the secondary outcomes were the microbiological profile of UIPC, the risk factors of UIPC, and the clinical fate of UIPC.

RESULTS

Twelve studies were eligible for meta-analysis, with a total of 1,108 patients. The pooled rate of UIPC was 24.3% (95% CI=15.8%-35.5%) in adult patients, and 43.2% (95% CI=32.9%-54.2%) in pediatric patients. The UIPC rate was higher when both conventional wound culture and sonication were used together compared to sonication alone or conventional wound culture alone. The rates were 28.9%, 23.6%, and 15.5 %, respectively. In adult and pediatric patients, the most commonly cultured organism was Cutibacterium acnes (42.5% vs 57.7%), followed by coagulase-negative Staphylococcus (39.9% vs 30.5%). Male patients had a higher rate of UIPC (OR= 2.6, 95% CI=1.84-3.72, p<.001), as did patients with a longer fusion construct (MD=0.76, 95% CI=0.27-1.25, p<.001).

CONCLUSIONS

The pooled rate of UIPC in aseptic spine revision surgery was 24.3% and 43.2% in adult and pediatric patients respectively. The most common organisms were C. acnes and coagulase-negative Staphylococcus. The impact of UIPC on patients` clinical outcomes is not fully understood. We are not able to recommend routine culture in revision spine surgery, however, adding sonication may aid in the diagnosis of UIPC. There is not enough evidence to recommend specific treatment strategies at this time, and further studies are warranted.

Diagnostic accuracy of sonication fluid cultures from prosthetic components in periprosthetic joint infection: an updated diagnostic meta-analysis

BACKGROUND

Periprosthetic joint infection (PJI) is the most serious complication following total joint arthroplasty (TJA) and has a significant impact on patients and the national healthcare system. To date, the diagnosis of PJI is still confronted with dilemmas. The present study investigated the validity of sonication fluid culture (SFC) for removing implants in the diagnosis of PJI after joint replacement.

METHODS

From database establishment to December 2020, relevant literature was retrieved from the PubMed, Web of Science, Embase and Cochrane Library databases. Two reviewers independently performed quality assessment and data extraction to calculate the pooled sensitivity, specificity, positive likelihood ratio (PLR), negative likelihood ratio (NLR), area under the curve (AUC) and diagnostic odds ratio (DOR) to evaluate the diagnostic value of overall SFC for PJI.

RESULTS

A total of 38 eligible studies including 6302 patients were selected in this study. The pooled sensitivity, specificity, PLR, NLR, and DOR of SFC for PJI diagnosis were 0.77 (95% confidence interval [CI], 0.76-0.79), 0.96 (95% CI, 0.95-0.96), 18.68 (95% CI, 11.92-29.28), 0.24 (95% CI, 0.21-0.29), and 85.65 (95% CI, 56.46-129.94), respectively, while the AUC was 0.92.

CONCLUSION

This meta-analysis showed that SFC was of great value in PJI diagnosis, and the evidence of SFC on PJI was more favorable but not yet strong. Therefore, improvement of the diagnostic accuracy of SFC is still necessary, and the diagnosis of PJI continues to warrant a multiplex approach before and during a revision procedure.

Profiling the Immune Response to Periprosthetic Joint Infection and Non-Infectious Arthroplasty Failure

Arthroplasty failure is a major complication of joint replacement surgery. It can be caused by periprosthetic joint infection (PJI) or non-infectious etiologies, and often requires surgical intervention and (in select scenarios) resection and reimplantation of implanted devices. Fast and accurate diagnosis of PJI and non-infectious arthroplasty failure (NIAF) is critical to direct medical and surgical treatment; differentiation of PJI from NIAF may, however, be unclear in some cases. Traditional culture, nucleic acid amplification tests, metagenomic, and metatranscriptomic techniques for microbial detection have had success in differentiating the two entities, although microbiologically negative apparent PJI remains a challenge. Single host biomarkers or, alternatively, more advanced immune response profiling-based approaches may be applied to differentiate PJI from NIAF, overcoming limitations of microbial-based detection methods and possibly, especially with newer approaches, augmenting them. In this review, current approaches to arthroplasty failure diagnosis are briefly overviewed, followed by a review of host-based approaches for differentiation of PJI from NIAF, including exciting futuristic combinational multi-omics methodologies that may both detect pathogens and assess biological responses, illuminating causes of arthroplasty failure.

Preoperative contrast-enhanced ultrasound (CEUS) of long bone nonunions reliably predicts microbiology of tissue culture samples but not of implant-sonication

INTRODUCTION

Bacterial infection in the context of fracture repair remains a severe complication in trauma surgery and may result in long bone nonunion. Since treatment options for aseptic and infected nonunions vary greatly, diagnostic methods should ideally differentiate between these two entities as accurately as possible. Recently, contrast-enhanced ultrasound (CEUS) has been introduced as a preoperative imaging technique to evaluate hypervascularity at the fracture site as sign of bacterial infection.

HYPOTHESIS

Preoperative CEUS predicts results of microbiological evaluation obtained either by culture of tissue samples or by analyzing the sonication fluid following removal and sonication of the implant.

PATIENTS AND METHODS

Over the course of 6 months, 26 patients with long bone nonunions were included in this study. Patients' clinical data were evaluated. Tissue samples were collected intraoperatively and examined by standard microbiological techniques. The sonication method was applied to removed implants. Additionally, 1-3 days before surgery, CEUS was performed to determine hypervascularity at the nonunion site as a possible parameter for infection.

RESULTS

Culture of tissue samples indicated infection in 50% of cases and implant sonication in 57.7% of cases. However, there was merely a fair agreement (κ=0.231) between these two diagnostic methods. CEUS predicted results of tissue culture reliably (sensitivity 92.3% and specificity 100%), whereas implant sonication showed no significant correlations with results from CEUS. Hypertrophic and atrophic nonunions were evaluated separately to determine possible differences in vascularity. We found that contrast peak enhancement of CEUS was similar in atrophic and hypertrophic nonunions with positive culture of tissue samples. Both differed significantly from culture negative cases (p=0.0016 and 0.0062). Results of implant-sonication positive or negative cases in atrophic and hypertrophic nonunions, however, were less clear and could be misleading.

DISCUSSION

We were able to confirm CEUS as a valuable preoperative diagnostic tool that reliably predicts microbiology of tissue culture samples, but not of implant sonication.

LEVEL OF EVIDENCE

I; diagnostic study.

What is the best technic to dislodge Staphylococcus epidermidis biofilm on medical implants?

Background

Bacterial biofilm can occur on all medical implanted devices and lead to infection and/or dysfunction of the device.

In this study, artificial biofilm was formed on four different medical implants (silicone, piccline, peripheral venous catheter and endotracheal tube) of interest for our daily clinical and/or research practice. We investigated the best conventional technic to dislodge the biofilm on the implants and quantified the number of bacteria. Staphylococcus epidermidis previously isolated from a breast implant capsular contracture on a patient in the university hospital of Dijon was selected for its ability to produce biofilm on the implants. Different technics (sonication, Digest-EUR®, mechanized bead mill, combination of sonication plus Digest-EUR®) were tested and compared to detach the biofilm before quantifying viable bacteria by colony counting.

Results

For all treatments, the optical and scanning electron microscope images showed substantial less biofilm biomass remaining on the silicone implant compared to non-treated implant.

This study demonstrated that the US procedure was statistically superior to the other physical treatment: beads, Digest-EUR® alone and Digest-EUR® + US (p < 0.001) for the flexible materials (picc-line, PIV, and silicone). The number of bacteria released by the US is significantly higher with a difference of 1 log on each material. The result for a rigid endotracheal tube were different with superiority for the chemical treatment dithiothreitol: Digest-EUR®. Surprisingly the combination of the US plus Digest-EUR® treatment was consistently inferior for the four materials.

Conclusions

Depending on the materials used, the biofilm dislodging technique must be adapted. The US procedure was the best technic to dislodge S. epidermidis biofilm on silicone, piccline, peripheral venous catheter but not endotracheal tube. This suggested that scientists should compare themselves different methods before designing a protocol of biofilm study on a given material.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12866-022-02606-x.

Diagnosing Periprosthetic Joint Infection: a Scoping Review

PURPOSE OF REVIEW

The goal of this review is to provide an up to date understanding of the utility and limitations of the current tests utilized in the diagnosis of periprosthetic joint infection (PJI) in total knee and hip arthroplasty.

RECENT FINDINGS

Despite the growth in literature surrounding PJI diagnosis, there remains challenges in establishing a diagnosis of PJI. A combination of clinical, serum, and synovial tests and microbiologic and histologic examinations can yield a diagnosis in the majority of cases. Novel molecular and imaging studies may be beneficial for indeterminant cases. A number of emerging diagnostic tests have been proposed and may be incorporated into diagnostic algorithms in the future. Recently proposed stepwise diagnostic algorithms have shown high sensitivity and specificity. The diagnosis of PJI remains challenging due to a lack of tests that can definitively rule out infection. Diagnosis and investigations should occur in a stepwise fashion. There has been a plethora of new diagnostic tests introduced in attempts to improve the accuracy of diagnostic algorithms. The definition and algorithms for the diagnoses of PJI will continue to evolve as new techniques and tests are introduced.

[Research progress of antibacterial modification of orthopaedic implants surface]

OBJECTIVE

To summarize the related research progress of antibacterial modification of orthopaedic implants surface in recent years.

METHODS

The domestic and foreign related literature in recent years was extensively consulted, the research progress on antibacterial modification of orthopaedic implants surface was discussed from two aspects of characteristics of infection in orthopedic implants and surface anti-infection modification.

RESULTS

The orthopaedic implants infections are mainly related to aspects of bacterial adhesion, decreased host immunity, and surface biofilm formation. At present, the main antimicrobial coating methods of orthopaedic implants are antibacterial adhesion coating, antibiotic coating, inorganic antimicrobial coating, composite antimicrobial coating, nitric oxide coating, immunomodulation, three-dimensional printing, polymer antimicrobial coating, and "smart" coating.

CONCLUSION

The above-mentioned antibacterial coating methods of orthopedic implants can not only inhibit bacterial adhesion, but also solve the problems of low immunity and biofilm formation. However, its mechanism of action and modification are still controversial and require further research.

Diagnostic value of fluoroscopy-guided hip aspiration for periprosthetic joint infection

PURPOSE

To assess the value of preoperative joint aspiration in detecting periprosthetic joint infection (PJI) in patients undergoing revision hip arthroplasty and to compare these with the clinical findings, serum markers, and intraoperative findings.

MATERIALS AND METHODS

Fluoroscopically guided hip aspirations in patients with pain after hip arthroplasty were retrospectively reviewed from January 2014 to December 2018. All hips underwent subsequent revision hip arthroplasty. Antibiotics were discontinued at least 2 weeks before the aspiration. The 2018 Musculoskeletal Infection Society (MSIS) criteria served as a standard of reference for PJI. Clinical, serum, synovial, and intraoperative parameters were recorded in all patients. Correlations between all parameters with PJI diagnosis were analyzed using linear and logistic regression models with ROC analysis.

RESULTS

In 202 hips that included 91 septic hips, hip aspiration (AUC = 0.78) and intraoperative (0.80) parameters performed better than serum-based tests (0.64) and clinical parameters (0.68) in detecting PJI. Using MSIS criteria as a standard of reference, hip aspiration had a sensitivity of 64.0% and an accuracy of 78.5% for cultures and a sensitivity of 74.2% and an accuracy of 82.1% for synovial polymorphonuclear neutrophils% (PMN%). Results substantially improved sensitivity after excluding patients that were treated with antibiotics, particularly culture results.

CONCLUSIONS

Preoperative hip aspiration showed good diagnostic performance in diagnosing PJI compared with MSIS criteria as a standard of reference. But a negative result from aspirate could not rule out PJI. Based on our findings, hip aspiration is an essential test for treatment planning in patients with pain after hip arthroplasty.

Diagnosis of orthopaedic-implant-associated infections caused by slow-growing Gram-positive anaerobic bacteria - a clinical perspective

Slow-growing Gram-positive anaerobic bacteria (SGAB) such as Cutibacterium acnes are increasingly recognized as causative agents of implant-associated infections (IAIs) in orthopaedic surgeries. SGAB IAIs are difficult to diagnose because of their non-specific clinical and laboratory findings as well as the fastidious growth conditions required by these bacteria. A high degree of clinical suspicion and awareness of the various available diagnostic methods is therefore important. This review gives an overview of the current knowledge regarding SGAB IAI, providing details about clinical features and available diagnostic methodologies. In recent years, new methods for the diagnosis of IAI were developed, but there is limited knowledge about their usefulness in SGAB IAI. Further studies are required to determine the ideal diagnostic methodology to identify these infections so that they are not overlooked and mistakenly classified as aseptic failure.

Deciphering the low abundance microbiota of presumed aseptic hip and knee implants

16S rRNA gene sequencing of DNA extracted from clinically uninfected hip and knee implant samples has revealed polymicrobial populations. However, previous studies assessed 16S rRNA gene sequencing as a technique for the diagnosis of periprosthetic joint infections, leaving the microbiota of presumed aseptic hip and knee implants largely unstudied. These communities of microorganisms might play important roles in aspects of host health, such as aseptic loosening. Therefore, this study sought to characterize the bacterial composition of presumed aseptic joint implant microbiota using next generation 16S rRNA gene sequencing, and it evaluated this method for future investigations. 248 samples were collected from implants of 41 patients undergoing total hip or knee arthroplasty revision for presumed aseptic failure. DNA was extracted using two methodologies-one optimized for high throughput and the other for human samples-and amplicons of the V4 region of the 16S rRNA gene were sequenced. Sequencing data were analyzed and compared with ancillary specific PCR and microbiological culture. Computational tools (SourceTracker and decontam) were used to detect and compensate for environmental and processing contaminants. Microbial diversity of patient samples was higher than that of open-air controls and differentially abundant taxa were detected between these conditions, possibly reflecting a true microbiota that is present in clinically uninfected joint implants. However, positive control-associated artifacts and DNA extraction methodology significantly affected sequencing results. As well, sequencing failed to identify Cutibacterium acnes in most culture- and PCR-positive samples. These challenges limited characterization of bacteria in presumed aseptic implants, but genera were identified for further investigation. In all, we provide further support for the hypothesis that there is likely a microbiota present in clinically uninfected joint implants, and we show that methods other than 16S rRNA gene sequencing may be ideal for its characterization. This work has illuminated the importance of further study of microbiota of clinically uninfected joint implants with novel molecular and computational tools to further eliminate contaminants and artifacts that arise in low bacterial abundance samples.

Is implant sonication useful when screening for infection in conversion of prior hip fracture fixation to total hip arthroplasty?

Objective

To examine sonication results in presumed aseptic conversion total hip arthroplasty (THA) after hip fracture fixation and to evaluate its implications on the treatment outcome.

Methods

This retrospective cohort study reviewed the data from presumed aseptic patients that underwent conversion of prior internal fixation of proximal femoral fractures to THA between 2012 and 2018. Microbiological analysis was performed using sonication of osteosynthesis material and tissue samples. Treatment outcome including the occurrence of periprosthetic joint infection (PJI) was recorded.

Results

A total of 32 patients were included in the study. Of these, five patients (15.6%) had positive intraoperative cultures. The mean follow-up following conversion THA was 43.0 months (range, 19.0–91.5 months). Sonication was positive in three patients (9.4%), all of whom were deemed contaminated and did not develop PJI. Tissue cultures were positive in two patients (6.3%). One patient with Enterococcus faecalis received antibiotic treatment and did not develop PJI. Another patient with growth of Cutibacterium acnes that was initially classified as a contaminant later developed acute PJI caused by the same pathogen. Overall, PJI occurred in two patients (6.3%) after conversion THA.

Conclusion

Sonication of internal fixation devices did not add diagnostic value in clinically aseptic conversion THA. Further studies are needed to better understand the relevance of unexpected positive cultures, and to develop diagnostic criteria for the management of these patients.

Cutibacterium acnes in shoulder surgery: a scoping review of strategies for prevention, diagnosis, and treatment

BACKGROUND

Cutibacterium acnes is a commensal, gram-positive, facultatively anaerobic bacillus that resides in the dermis. Historically thought to be a contaminant when identified on cultured specimens, recent advances in diagnostic technology have now implicated it as the most common organism responsible for postoperative shoulder infections. Despite a recognition of the role of this organism and a significant research interest in recent years, there is clear lack of consensus guideline on strategies to prevent, diagnose, and treat postoperative shoulder infection.

METHOD

The electronic databases PubMed, MEDLINE, CINAHL, Scopus, and Web of Science were searched in March 2020. All experimental and nonexperimental studies that investigate C acnes in shoulder surgery were included. Inclusion was limited to articles published after 2000 and written in English; reviews, gray literature, or abstracts were excluded. A total of 70 studies were included in this review. This scoping review was performed in accordance with the Extended Preferred Reporting Items of Systematic Reviews and Meta-Analyses Statement for Scoping Reviews (PRISMA-ScR).

RESULTS

Standard surgical prophylactic regimens such as intravenous antibiotics and topical chlorhexidine are ineffective at removing C acnes from the deep layer of the dermis, and there is a shift toward using topical benzoyl peroxide with significantly improved efficacy. An improved understanding of the bacteria has demonstrated that a prolonged culture time of up to 14 days is needed, especially in cases of established infection. Advances in diagnostics such as sonication and molecular-based testing are promising. Although usually thought to be susceptible to a broad range of antibiotics, resistance is emerging to clindamycin. An improved understanding of its ability to form a biofilm highlights the difficulty in treating an established infection.

CONCLUSION

The role of C acnes causing postoperative infection following shoulder surgery is being increasingly recognized. Strategies for prevention, diagnosis, and treatment have been outlined from both an antimicrobial and surgical perspective. A number of these strategies are emerging and require further research to demonstrate efficacy before implementation into clinical guidelines.

Prevalence of Occult Infections in Posterior Instrumented Spinal Fusion

STUDY DESIGN

This is a prospective observational study.

OBJECTIVE

The aim of this study is to determine the rate of occult infection after instrumented spine surgery in presumed aseptic patients.

SUMMARY OF BACKGROUND DATA

The reported incidence rate of delayed/occult infection determined by positive culture swabs after instrumented spine surgery in prospective studies is 0.2%-6.9%. However, this rate may be higher as delayed infections are challenging to diagnose. Fever can be absent and inflammatory markers are often normal. If indolent organisms exist in low concentrations surrounding the instrumentation, these organisms can possibly avoid detection and disrupt bone formation leading to instrumentation loosening, pain generation, and/or failure of a solid fusion.

MATERIALS AND METHODS

This study included 50 consecutive presumed aseptic patients undergoing a posterior revision requiring removal of instrumentation at least 6 months following their index procedure. Common markers of infection were examined preoperatively. Multiple culture swabs were taken directly from the removed instrumentation and cultured for 14 days.

RESULTS

Of the 50 patients, 19 (38%) were culture-positive (CP) for bacteria upon removal of their instrumentation, with 14 patients (28%) having ≥2 positive specimens of the same organism. The average length of time between the index procedure and the revision surgery was 4.55 years (range: 0.53-21 y). Polymicrobial infections were found in 26% (5/19) of CP patients. The most prevalent microorganism found was Propionibacterium acnes, in 63% (12/19) of CP patients. There was no significant difference between CP and culture-negative patients regarding preoperative markers for infection, age, or length between index and revision procedures.

CONCLUSIONS

The results of this study indicate a positive culture rate of 38% in presumed aseptic patients who had previously undergone instrumented spine surgery. These results are consistent with other retrospective studies and are >6 times greater than any previous prospective study utilizing culture swabs.

LEVEL OF EVIDENCE

Level-III.

Highly variable effect of sonication to dislodge biofilm-embedded Staphylococcus epidermidis directly quantified by epifluorescence microscopy: an in vitro model study

BACKGROUND

In 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.

METHODS

We 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.

RESULTS

Epifluorescence 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.

CONCLUSION

There is an unexpected high variation seen in the ability of sonication to dislodge biofilm-embedded S. epidermidis in this in vitro model.

Ultrasound frequency of sonication applied in microbiological diagnostics has a major impact on viability of bacteria causing PJI

OBJECTIVES

Sonication of explanted prosthesis constitutes an element of microbiological diagnostics. The aim of performing this procedure is to remove biofilm and to increase sensitivity of diagnostics. Ultrasound used in medical purposes are low-frequency and low-intensity. With this wide range of frequency which can be used in sonication process it is necessary to find the golden mean between biofilm dislodging and planktonic bacteria sparing.

MATERIALS AND METHODS

The aim of this study was to determine the least harming low-intensity ultrasound frequency (35 kHz, 40 kHz or 53 kHz) used during sonication process with other parameters constant. Four bacteria species were examined: S. aureus, E. faecalis, E. coli, K. pneumoniae. Number of microbiological studies (n) for each group (g) counted 40 specimens (based on scheme 1 bacteria type - 4 groups, 40 studies each).

RESULTS

A detailed analysis of gathered data was conducted. Based on study findings following conclusions were drawn. Sonication has a significant and negative impact on survival of sonicated planktonic bacteria. Part of bacteria in planktonic state are damaged/killed by ultrasound, which is demonstrated by lower CFU count in sonicated samples versus control group.

CONCLUSIONS

Optimal ultrasound frequencies for sonication of S. aureus, P. aeruginosa and E. coli are 35 kHz and 40 kHz. Ultrasound frequencies used in sonication process (35 kHz, 40 kHz, 53 kHz) of E. coli showed same impact on bacteria survival. It is crucial to perform further assessment of ultrasound parameters on clinical effects of sonication used in PJI diagnostics.

Time to positivity of acute and chronic periprosthetic joint infection cultures

INTRODUCTION

A prolonged incubation time is generally recommended for diagnosing periprosthetic joint infections (PJI). However, in literature, no distinction is made between acute and chronic infections.

METHODS

All patients with a PJI that underwent surgical debridement between November 2015 and February 2019 with or without revision of the prosthesis were retrospectively evaluated. Synovial fluid, 5 intraoperative periprosthetic tissue samples, and the sonicated prosthesis were cultured.

RESULTS

Fifty-nine patients were analyzed, including 21 acute PJIs (33 isolates) and 38 chronic PJIs (46 isolates). In acute PJIs, all isolates grew within 5 days, while this took 11 days for chronic PJIs. Sonication fluid showed the shortest time to positivity (78% at day 2) for chronic PJIs, but no difference was observed for acute PJIs compared to tissue cultures.

CONCLUSION

In contrast to cultures from chronic PJIs, acute PJIs do not need a prolonged incubation time and no clear benefit is observed for sonication.

A nanocarrier system that potentiates the effect of miconazole within different interkingdom biofilms

Background

Novel and new therapeutic strategies capable of enhancing the efficacy of existing antimicrobials is an attractive proposition to meet the needs of society.

Objective

This study aimed to evaluate the potentiating effect of a miconazole (MCZ) nanocarrier system, incorporated with iron oxide nanoparticles (IONPs) and chitosan (CS) (IONPs-CS-MCZ). This was tested on three representative complex interkingdom oral biofilm models (caries, denture and gingivitis).

Materials and methods

The planktonic and sessile minimum inhibitory concentrations (MICs) of IONPs-CS-MCZ against different Candida albicans strains were determined, as well as against all represented bacterial species that formed within the three biofilm models. Biofilms were treated for 24 hours with the IONPs-CS nanocarrier system containing MCZ at 64 mg/L, and characterized using a range of bioassays for quantitative and qualitative assessment.

Results

MIC results generally showed that IONPs-CS-MCZ was more effective than MCZ alone. IONPs-CS-MCZ also promoted reductions in the number of CFUs, biomass and metabolic activity of the representative biofilms, as well as altering biofilm ultrastructure when compared to untreated biofilms. IONPs-CS-MCZ affected the composition and reduced the CFEs for most of the microorganisms present in the three evaluated biofilms. In particular, the proportion of streptococci in the biofilm composition were reduced in all three models, whilst Fusobacterium spp. percentage reduced in the gingivitis and caries models, respectively.

Conclusion

In conclusion, the IONPs-CS-MCZ nanocarrier was efficient against three in vitro models of pathogenic oral biofilms, showing potential to possibly interfere in the synergistic interactions among fungal and bacterial cells within polymicrobial consortia.

Implant Sonication versus Tissue Culture for the Diagnosis of Spinal Implant Infection

MINI: We compared the sensitivity and specificity of peri-implant tissue culture to the vortexing-sonication technique for the diagnosis of spinal implant infection (SII). Lower thresholds of sonicate fluid culture positivity showed increased sensitivity with maintained specificity. We recommend a threshold of 20 CFU/10 mL for sonicate culture positivity for the diagnosis of SII.

STUDY DESIGN

This is a retrospective study comparing the diagnosis of spinal implant infection (SII) by peri-implant tissue culture to vortexing-sonication of retrieved spinal implants.

OBJECTIVE

We hypothesized that vortexing-sonication would be more sensitive than peri-implant tissue culture.

SUMMARY OF BACKGROUND DATA

We previously showed implant vortexing-sonication followed by culture to be more sensitive than standard peri-implant tissue culture for diagnosing of SII. In this follow-up study, we analyzed the largest sample size available in the literature to compare these two culture methods and evaluated thresholds for positivity for sonicate fluid for SII diagnosis.

METHODS

We compared peri-implant tissue culture to the vortexing-sonication technique which samples bacterial biofilm on the surface of retrieved spinal implants. We evaluated different thresholds for sonicate fluid positivity and assessed the sensitivity and specificity of the two culture methods for the diagnosis of SII.

RESULTS

A total of 152 patients were studied. With more than 100 colony forming units (CFU)/10 mL as a threshold for sonicate fluid culture positivity, there were 46 patients with SII. The sensitivities of peri-implant tissue and sonicate fluid culture were 65.2% and 79.6%; the specificities were 88.7% and 93.4%, respectively. With more than 50 CFU/10 mL as a threshold, there were 50 patients with SII. The sensitivities of peri-implant tissue and sonicate fluid culture were 68.0% and 76.0%; the specificities were 92.2% for both methods. Finally, with more than or equal to 20 CFU/10 mL as a threshold, there were 52 patients with SII. The sensitivities of peri-implant tissue and sonicate fluid culture were 69.2% and 82.7%; the specificities were 94.0% and 92.0%, respectively.

CONCLUSION

Implant sonication followed by culture is a sensitive and specific method for the diagnosis of SII. Lower thresholds for defining sonicate fluid culture positivity allow for increased sensitivity with a minimal decrease in specificity, enhancing the clinical utility of implant sonication.

LEVEL OF EVIDENCE

4.

Multidisciplinary Diagnostic Algorithm for Evaluation of Patients Presenting with a Prosthetic Problem in the Hip or Knee: A Prospective Study

The predominant indications for revision surgery after total hip (THA) or knee arthroplasty (TKA) are an aseptic failure (AF) and prosthetic joint infection (PJI). Accurate diagnosis is crucial. Therefore, we evaluated prospectively a multidisciplinary diagnostic algorithm including multi-modal radionucleid imaging (RNI) and extended microbiological diagnostics. If the surgeon suspected PJI or AF, revision surgery was performed with multiple samples obtained in parallel for special culture procedures and later molecular analyses. Alternatively, if the underlying cause was not evident, RNI was scheduled comprising 99Tc - HDP SPECT/CT, 111In-labeled white blood cells combined with 99Tc-nanocoll bone marrow SPECT/CT, and 18F-FDG PET/CT. A multidisciplinary clinical team made a recommendation on the indication for a diagnostic procedure guided by RNI images or revision surgery. A total of 156 patients with 163 arthroplasties were included. Fifty-five patients underwent RNI. In all, 118 revision surgeries were performed in 112 patients: 71 on the indication of AF and 41 revision of PJI. Thirty-four patients were concluded with chronic pain, and revision surgery refrained. The effective median follow-up period was 13 months. A structured approach offered by the algorithm was useful for the clinician in the evaluation of patients with a failing TKA or THA. Surgical revision was possibly obviated in approximately 20% of patients where an explanation or cause of failure was not found. The algorithm served as an effective tool.

Cutibacterium acnes Infection in Orthopedics: Microbiology, Clinical Findings, Diagnostic Strategies, and Management

Cutibacterium (formerly called Propionibacterium) acnes is a human skin flora often implicated in orthopedic infections. The unique characteristics of this microorganism make the diagnosis of infection difficult. The diagnosis often is made based on clinical evidence, radiographic signs, and laboratory and/or surgical findings combined. Treatment often involves both pharmacologic and surgical methods. In addition, formation of biofilms and increased resistance to drugs exhibited by the microorganism can require combined antimicrobial therapy. Prophylactic measures are particularly important, but no single method has been shown to fully eliminate the risk of C acnes infections. Previous reports have focused on C acnes infections involving surgical implants or after certain orthopedic procedures, particularly in the shoulder and spine. This article reviews current clinical, diagnostic, and treatment principles for C acnes in orthopedics in general. [Orthopedics. 2020; 43(1):52-61.].

72 revision surgeries for aseptic failure after hip or knee arthroplasty: a prospective study with an extended diagnostic algorithm

BACKGROUND

Unrecognized periprosthetic joint infections are a concern in revision surgery for aseptic failure (AF) after total hip (THA) or knee (TKA) arthroplasties. A gold diagnostic standard does not exist. The aim of the current study was to determine the prevalence of unrecognized periprosthetic joint infection (PJI) in a cohort of revision for AF, using an experimental diagnostic algorithm.

METHODS

The surgeons' suspicion of AF was based primarily on patient history and clinical evaluation. X-ray imaging was used to reveal mechanical problems. To rule out an infectious aetiology standard blood biochemical tests were ordered in most patients. Evaluation followed the existing practice in the institute. Cases were included if revision surgery was planned for suspected AF. Intraoperatively, five synovial tissue biopsies were obtained routinely. PJI was defined as ≥3 positive cultures with the same microorganism(s). Patients were followed for 1 year postoperatively. Protocol samples included joint fluid, additional synovial tissue biopsies, bone biopsy, swabs from the implant surface, and sonication of retrieved components. Routine and protocol samples were cultured with extended incubation (14 days) and preserved for batchwise 16S rRNA gene amplification. Patients were stratified based on culture results and a clinical status was obtained at study end.

RESULTS

A total of 72 revisions were performed on 71 patients (35 THA and 37 TKA). We found five of 72 cases of unrecognized PJI. Extended culture and protocol samples accounted for two of these. One patient diagnosed with AF was treated for a PJI during follow-up. The remaining patients did not change status from AF during follow-up.

CONCLUSIONS

We found a low prevalence of unrecognized periprosthetic joint infections in patients with an AF diagnosis. The algorithm strengthens the surgeons' preoperative diagnosis of a non-infective condition. Evaluation for a failing TKA or THA is complex. Distinguishing between AF and PJI pre-operatively was a clinical decision. Our data did not support additional testing in routine revision surgery for AF.

Biofilm-stimulated epithelium modulates the inflammatory responses in co-cultured immune cells

The gingival epithelium is a physical and immunological barrier to the microbiota of the oral cavity, which interact through soluble mediators with the immune cells that patrol the tissue at the gingival epithelium. We sought to develop a three-dimensional gingivae-biofilm interface model using a commercially available gingival epithelium to study the tissue inflammatory response to oral biofilms associated with “health”, “gingivitis” and “periodontitis”. These biofilms were developed by sequential addition of microorganisms to mimic the formation of supra- and sub-gingival plaque in vivo. Secondly, to mimic the interactions between gingival epithelium and immune cells in vivo, we integrated peripheral blood mononuclear cells and CD14⁺ monocytes into our three-dimensional model and were able to assess the inflammatory response in the immune cells cultured with and without gingival epithelium. We describe a differential inflammatory response in immune cells cultured with epithelial tissue, and more so following incubation with epithelium stimulated by “gingivitis-associated” biofilm. These results suggest that gingival epithelium-derived soluble mediators may control the inflammatory status of immune cells in vitro, and therefore targeting of the epithelial response may offer novel therapies. This multi-cellular interface model, both of microbial and host origin, offers a robust in vitro platform to investigate host-pathogens at the epithelial surface.

Are Sonication Cultures of Antibiotic Cement Spacers Useful During Second-stage Reimplantation Surgery for Prosthetic Joint Infection?

BACKGROUND

Organisms may persist on polymethylmethacrylate (PMMA) spacer surfaces, and subclinical infection is postulated to be a source of infection recurrence. Several small patient series have shown a high proportion of positive sonication cultures on PMMA spacers at the second stage of a two-stage revision. However, the association between a positive sonication culture and the risk for recurrence of infection after two-stage exchange is not fully elucidated.

QUESTIONS/PURPOSES

Are cultures derived from sonication of antibiotic spacers associated with infection control or recurrence after two-stage revision for prosthetic joint infection (PJI)?

METHODS

Between September 2013 and April 2016, we treated 67 patients with PJI with two-stage revisions. At the second stage, all cement spacers were explanted and sonicated. A total of`10 (15%) patients were lost to followup or failed to reach 1-year followup during the study period, and another 16 (24%) were excluded for prespecified reasons, leaving 41 patients for analysis in this study. Of the 41 patients included in this study, there were 25 TKAs, 15 THAs, and one distal femoral replacement. All patients met the Musculoskeletal Infection Society criteria for PJI at Stage 1 of the two-stage revision. The most common infecting organisms prompting two-stage revision were methicillin-sensitive Staphylococcus aureus and coagulase-negative staphylococci. PMMA spacers were most frequently loaded with gentamicin or gentamicin/vancomycin. Standard 6-week intravenous antibiotic courses were used for index infections and postreimplantation suppression was used for 3 months in all patients as determined by cultures and sensitivities. Patients were assessed for recurrence of infection at postoperative clinic visits completed at standard intervals. The average length of followup was 1.9 years with a range of 1 to 3.3 years.

RESULTS

Sonication cultures that reached a threshold of 5 colony-forming units for positive culture had poor screening utility for subclinical persistent infection (sensitivity: 0%; confidence interval [CI], 0%-60%), but reasonable use for ruling in successful two-stage revision (specificity: 95%; 95% CI, 82%-99%). Positive sonication culture results in the two of 41 (4.9%) explanted spacers yielded coagulase-negative staphylococci, different from primary prosthesis cultures in both patients (Corynebacterium and Proteus mirabilis), and did not alter antibiotic choice. Neither of the patients has developed a reinfection at followup of 1.2 and 1.9 years. Of the 39 two-stage revisions with negative spacer sonication cultures, four developed reinfections.

CONCLUSIONS

Positive sonication fluid culture of PMMA spacers during reimplantation surgery was not associated with persistent or recurrent infection at minimum followup of 1 year. We do not recommend routine sonication of explanted PMMA spacers in the absence of clinical evidence suggesting persistent infection. Multicenter, prospective studies with long-term followup are needed to determine if sonication of PMMA spacers can predict persistent or recurrent infection.

LEVEL OF EVIDENCE

Level III, diagnostic study.

Comparison of Diagnostic Accuracy of Periprosthetic Tissue Culture in Blood Culture Bottles to That of Prosthesis Sonication Fluid Culture for Diagnosis of Prosthetic Joint Infection (PJI) by Use of Bayesian Latent Class Modeling and IDSA PJI Criteria for Classification

We have previously demonstrated that culturing periprosthetic tissue in blood culture bottles (BCBs) improves sensitivity compared to conventional agar and broth culture methods for diagnosis of prosthetic joint infection (PJI). We have also shown that prosthesis sonication culture improves sensitivity compared to periprosthetic tissue culture using conventional agar and broth methods. The purpose of this study was to compare the diagnostic accuracy of tissue culture in BCBs (subsequently referred to as tissue culture) to prosthesis sonication culture (subsequently referred to as sonicate fluid culture). We studied 229 subjects who underwent arthroplasty revision or resection surgery between March 2016 and October 2017 at Mayo Clinic in Rochester, Minnesota. Using the Infectious Diseases Society of America (IDSA) PJI diagnostic criteria (omitting culture criteria) as the gold standard, the sensitivity of tissue culture was similar to that of the sonicate fluid culture (66.4% versus 73.1%, P = 0.07) but was significantly lower than that of the two tests combined (66.4% versus 76.9%, P < 0.001). Using Bayesian latent class modeling, which assumes no gold standard for PJI diagnosis, the sensitivity of tissue culture was slightly lower than that of sonicate fluid culture (86.3% versus 88.7%) and much lower than that of the two tests combined (86.3% versus 99.1%). In conclusion, tissue culture in BCBs reached sensitivity similar to that of prosthesis sonicate fluid culture for diagnosis of PJI, but the two tests combined had the highest sensitivity without compromising specificity. The combination of tissue culture in BCBs and sonicate fluid culture is recommended to achieve the highest level of microbiological diagnosis of PJI.

Bacterial Biofilms in Jones Tubes

PURPOSE

To investigate the presence and microbiology of bacterial biofilms on Jones tubes (JTs) by direct visualization with scanning electron microscopy and polymerase chain reaction (PCR) of representative JTs, and to correlate these findings with inflammation and/or infection related to the JT.

METHODS

In this study, prospective case series were performed. JTs were recovered from consecutive patients presenting to clinic for routine cleaning or recurrent irritation/infection. Four tubes were processed for scanning electron microscopy alone to visualize evidence of biofilms. Two tubes underwent PCR alone for bacterial quantification. One tube was divided in half and sent for scanning electron microscopy and PCR. Symptoms related to the JTs were recorded at the time of recovery.

RESULTS

Seven tubes were obtained. Five underwent SEM, and 3 out of 5 showed evidence of biofilms (60%). Two of the 3 biofilms demonstrated cocci and the third revealed rods. Three tubes underwent PCR. The predominant bacteria identified were Pseudomonadales (39%), Pseudomonas (16%), and Staphylococcus (14%). Three of the 7 patients (43%) reported irritation and discharge at presentation. Two symptomatic patients, whose tubes were imaged only, revealed biofilms. The third symptomatic patient's tube underwent PCR only, showing predominantly Staphylococcus (56%) and Haemophilus (36%) species. Two of the 4 asymptomatic patients also showed biofilms. All symptomatic patients improved rapidly after tube exchange and steroid antibiotic drops.

CONCLUSIONS

Bacterial biofilms were variably present on JTs, and did not always correlate with patients' symptoms. Nevertheless, routine JT cleaning is recommended to treat and possibly prevent inflammation caused by biofilms.

A novel enzyme with antioxidant capacity produced by the ubiquitous skin colonizer Propionibacterium acnes

The role of the skin microbiota in human health is poorly understood. Here, we identified and characterized a novel antioxidant enzyme produced by the skin microbiota, designated RoxP for radical oxygenase of Propionibacterium acnes. RoxP is uniquely produced by the predominant skin bacterium P. acnes, with no homologs in other bacteria; it is highly expressed and strongly secreted into culture supernatants. We show that RoxP binds heme, reduces free radicals, and can protect molecules from oxidation. Strikingly, RoxP is crucial for the survival of P. acnes in oxic conditions and for skin colonization of P. acnes ex vivo. Taken together, our study strongly suggests that RoxP facilitates P. acnes’ survival on human skin, and is an important beneficial factor for the host-commensal interaction. Thus, RoxP is the first described skin microbiota-derived mutualistic factor that potentially can be exploited for human skin protection.

Culture-Negative Infection After Operative Fixation of Fractures

OBJECTIVES

(1) Compare the outcomes of patients with orthopaedic trauma with culture-negative infection with those with pathogens identified; (2) identify the incidence of culture-negative infection and describe the common characteristics.

DESIGN

Retrospective study.

SETTING

Two level 1 trauma centers.

PATIENTS

A total of 391 patients 16 years of age or older who underwent irrigation and debridement for surgical site infection after having undergone fracture fixation were included.

INTERVENTION

Patients underwent irrigation and debridement with cultures, and antibiotic therapy was initiated.

MAIN OUTCOME MEASUREMENT

Treatment failure due to unsuccessful eradication of infection and time to union.

RESULTS

We found 9% incidence of culture-negative infection. Approximately one-third of patients in both groups went on to have treatment failure (25% of pathogen-specific infections, 38% of culture-negative infections, P = 0.15), and there was no difference between the 2 groups with regard to time to union (22 vs. 24 weeks, P = 0.55). More than one-third of patients required subsequent reconstructive procedure and 5% of patients in each group required amputation to control their infection. There was no difference between the groups with respect to the use of antibiotics before intervention and culture.

CONCLUSION

This study confirms the devastating effect that postoperative infections can have and suggests that, with clinical sign of infection, negative cultures do not portend a better prognosis. These entities should be treated in a similar manner to infections with positive cultures. Furthermore, we believe that future studies should not strictly rely on the presence of positive intraoperative cultures. Consensus as to what constitutes a clinical infection, in the absence of positive cultures, is needed.

LEVEL OF EVIDENCE

Prognostic Level III. See Instructions for Authors for a complete description of levels of evidence.

DISC (Degenerate-disc Infection Study With Contaminant Control): Pilot Study of Australian Cohort of Patients Without the Contaminant Control

STUDY DESIGN

Prospective cohort study.

OBJECTIVE

To evaluate if degenerative disc-related back or neck pain and/or radicular symptoms are caused by infection with low virulent bacterial organisms.

SUMMARY OF BACKGROUND DATA

The potential relationship between disc infection and disc degeneration-related symptoms remains controversial, with contradictory evidence available in the literature. Several studies have demonstrated the presence of infected extruded nucleus tissue from first-time disc herniation, implicating the role of disc microbial infection in disc degeneration. The current study is a pilot study evaluating if high infection rates are prevalent in the Australian degenerate disc cohort.

METHODS

Institutional ethics approval was obtained (HREC 13/218). The pilot project was a single spine center prospective cohort of patients undergoing spine surgery for degenerate disc disease. In each case, disc material was obtained and prolonged aerobic and anaerobic cultures performed as per methods used by Stirling et al.

RESULTS

To date, a total of 168 patients have been enrolled, with male: female = 1:1. Surgical caseload includes 17.9% anterior cervical fusion, 35.0% anterior lumbar fusion, 40.7% lumbar discectomy, and 5.7% posterior lumbar fusions; 34.1% patients presented with neck pain, 31.6% with arm pain, 59.3% with leg pain, and 64.2% with back pain, and 20.2% of the patients received transforaminal or epidural or facet joint injections prior to surgery. In this pilot study, 19.6% were culture positive, with P. acnes predominant in 50%. Disc-only cultures were positive in 27.8% of lumbar cases and 18.5% of cervical cases, with predominant organisms being P. acnes.

CONCLUSION

Similar to the infection rates from previous studies, this Australian cohort had 19.6% infection rates when disc-only cultures are performed. P. acnes is the predominant organism followed by Streptococcus sp. It is imperative to perform contaminant controls as such high infection with skin bugs is a significant finding.

LEVEL OF EVIDENCE

4.

Role of Sonication for Detection of Infection in Explanted Orthopaedic Trauma Implants

OBJECTIVES

Sonication is a new technology that uses high-frequency sound waves to mechanically dislodge bacteria adherent in biofilms. Unlike arthroplasty, its role in orthopaedic trauma has not been described. The goal of this study was to explore the utility of sonication in orthopaedic trauma.

DESIGN

Retrospective review.

SETTING

Level I trauma center.

PATIENTS

One hundred forty-six sonicated metallic orthopaedic devices from September 2010 to May 2013 were included. Patients were divided into 3 groups: clinically infected, elective implant removals, and nonunion.

INTERVENTION

Sonication culture results were retrospectively reviewed for all patients undergoing implant removal.

OUTCOMES

Sonication results were the primary study outcome and were considered positive for culture growth if equal to or greater than 20 colony-forming units per plate.

RESULTS

In 32 patients with clinical infection, tissue cultures were positive in 30 (94%) and negative in 2 (6%). In contrast, sonication cultures were positive in 19 patients (59%) and did not identify additional organisms. Of the 72 patients who underwent elective implant removal, 52 had pain. Sonication cultures were positive in 5 of these 52 patients (10%) and in 0 of 20 patients with no pain. Sonication culture results were negative in all 42 patients who underwent nonunion surgery.

CONCLUSIONS

Sonication of orthopaedic trauma implants in patients with clinically apparent infection or "aseptic" nonunion offered negligible additional information. Sonication demonstrated a positive microbiologic yield in a subset of patients with painful implants; further research is required to better establish the frequency of subclinical infection and to determine the diagnostic role of traditional cultures and sonication.

LEVEL OF EVIDENCE

Diagnostic Level III. See Instructions for Authors for a complete description of levels of evidence.

Propionibacterium acnes Infection in the Native Hip: A Case Report

CASE

A sixty-five-year-old immunocompetent man with bilateral osteonecrosis of the hip and no prior surgical procedures or trauma was found to have a subacute Propionibacterium acnes infection of the femoral head. To our knowledge, this is the first reported case of Propionibacterium acnes infection in a native hip in the orthopaedic literature.

CONCLUSION

Diagnosing a subacute P. acnes infection can be challenging because of nonspecific clinical findings, normal laboratory values, and delayed growth of this organism on culture. Clinicians should maintain a high degree of suspicion as these infections are frequently missed.

26Postoperative diagnosis and outcome in patients with revision arthroplasty for aseptic loosening

BACKGROUND

The most common cause of implant failure is aseptic loosening (AL), followed by prosthetic joint infection (PJI). This study evaluates the incidence of PJI among patients operated with suspected AL and whether the diagnosis of PJI was predictive of subsequent implant failure including re-infection, at 2 years of follow up.

METHODS

Patients undergoing revision hip or knee arthroplasty due to presumed AL from February 2009 to September 2011 were prospectively evaluated. A sonication fluid of prosthesis and tissue samples for microbiology and histopathology at the time of the surgery were collected. Implant failure include recurrent or persistent infection, reoperation for any reason or need for chronic antibiotic suppression.

RESULTS

Of 198 patients with pre-and intraoperative diagnosis of AL, 24 (12.1 %) had postoperative diagnosis of PJI. After a follow up of 31 months (IQR: 21 to 38 months), 9 (37.5 %) of 24 patients in the PJI group had implant failure compared to only 1 (1.1 %) in the 198 of AL group (p < 0.0001). Sensitivity of sonicate fluid culture (>20 CFU) and peri-prosthetic tissue culture were 87.5 % vs 66.7 %, respectively. Specificities were 100 % for both techniques (95 % CI, 97.9-100 %). A greater number of patients with PJI (79.1 %) had previous partial arthroplasty revisions than those patients in the AL group (56.9 %) (p = 0.04). In addition, 5 (55.5 %) patients with PJI and implant failure had more revision arthroplasties during the first year after the last implant placement than those patients with PJI without implant failure (1 patient; 6.7 %) (RR 3.8; 95 % CI 1.4-10.1; p = 0.015). On the other hand, 6 (25 %) patients finally diagnosed of PJI were initially diagnosed of AL in the first year after primary arthroplasty, whereas it was only 16 (9.2 %) patients in the group of true AL (RR 2.7; 95 % CI 1.2-6.1; p = 0.03).

CONCLUSIONS

More than one tenth of patients with suspected AL are misdiagnosed PJI. Positive histology and positive peri-implant tissue and sonicate fluid cultures are highly predictive of implant failure in patients with PJI. Patients with greater number of partial hip revisions for a presumed AL had more risk of PJI. Early loosening is more often caused by hidden PJI than late loosening.

Antimicrobial delivery systems for local infection prophylaxis in orthopedic- and trauma surgery

Infectious complications occur in a minor but significant portion of the patients undergoing joint replacement surgery or fracture fixation, particularly those with severe open fractures, those undergoing revision arthroplasty or those at elevated risk because of poor health status. Once established, infections are difficult to eradicate, especially in the case of bacterial biofilm formation on implanted hardware. Local antibiotic carriers offer the prospect of controlled delivery of antibiotics directly in target tissues and implant, without inducing toxicity in non-target organs. Polymeric carriers have been developed to optimize the release and targeting of antibiotics. Passive polymeric carriers release antibiotics by diffusion and/or upon degradation, while active polymeric carriers release their antibiotics upon stimuli provided by bacterial pathogens. Additionally, some polymeric carriers gelate in-situ in response to physiological stimuli to form a depot for antibiotic release. As antibiotic resistance has become a major issue, also other anti-infectives such as silver and antimicrobial peptides have been incorporated in research. Currently, several antibiotic loaded biomaterials for local infection prophylaxis are available for use in the clinic. Here we review their advantages and limitations and provide an overview of new materials emerging that may overcome these limitations.

Propionibacterium acnes: from commensal to opportunistic biofilm-associated implant pathogen

Propionibacterium acnes is known primarily as a skin commensal. However, it can present as an opportunistic pathogen via bacterial seeding to cause invasive infections such as implant-associated infections. These infections have gained more attention due to improved diagnostic procedures, such as sonication of explanted foreign materials and prolonged cultivation time of up to 14 days for periprosthetic biopsy specimens, and improved molecular methods, such as broad-range 16S rRNA gene PCR. Implant-associated infections caused by P. acnes are most often described for shoulder prosthetic joint infections as well as cerebrovascular shunt infections, fibrosis of breast implants, and infections of cardiovascular devices. P. acnes causes disease through a number of virulence factors, such as biofilm formation. P. acnes is highly susceptible to a wide range of antibiotics, including beta-lactams, quinolones, clindamycin, and rifampin, although resistance to clindamycin is increasing. Treatment requires a combination of surgery and a prolonged antibiotic treatment regimen to successfully eliminate the remaining bacteria. Most authors suggest a course of 3 to 6 months of antibiotic treatment, including 2 to 6 weeks of intravenous treatment with a beta-lactam. While recently reported data showed a good efficacy of rifampin against P. acnes biofilms, prospective, randomized, controlled studies are needed to confirm evidence for combination treatment with rifampin, as has been performed for staphylococcal implant-associated infections.

Use of broth cultures peri-operatively to optimise the microbiological diagnosis of musculoskeletal implant infections

We compared the use of broth culture medium for samples taken in theatre with the standard practice of placing tissue samples in universal containers. A total of 67 consecutive patients had standard multiple samples of deep tissue harvested at surgery and distributed equally in theatre either to standard universal containers or to broth culture medium. These samples were cultured by direct and enrichment methods. The addition of broth in theatre to standard practice led to an increase in sensitivity from 83% to 95% and an increase in negative predictive value from 77% to 91%. Placing tissue samples directly into broth in the operating theatre is a simple, inexpensive way to increase the sensitivity of cultures from infected patients, and does not appear to compromise the specificity of these cultures.

Prosthetic joint infection

Prosthetic joint infection (PJI) is a tremendous burden for individual patients as well as the global health care industry. While a small minority of joint arthroplasties will become infected, appropriate recognition and management are critical to preserve or restore adequate function and prevent excess morbidity. In this review, we describe the reported risk factors for and clinical manifestations of PJI. We discuss the pathogenesis of PJI and the numerous microorganisms that can cause this devastating infection. The recently proposed consensus definitions of PJI and approaches to accurate diagnosis are reviewed in detail. An overview of the treatment and prevention of this challenging condition is provided.

Improvement in the detection rate of PJI in total hip arthroplasty through multiple sonicate fluid cultures

The microbiological culture of sonicate fluid (SFC) of explanted endoprosthetic components has increased the rate of bacterial isolation in comparison to conventional microbiological methods. However, this creates the problem of interpreting cases of singular bacterial isolation through SFC, while all other microbiological samples remain negative. The aim of this study was to reference these singular positive SFC against, the histological classification of the periprosthetic membrane (PM), and the utilization of multiple SFC (separate sonication of individual endoprosthetic components). In this prospective study we compared the effect of multiple SFC for detection of periprosthetic joint infection (PJI) in patients with total hip revision surgery. All microbiological results were referenced against PM. Of the 102 cases there were 37 cases of PJI. Single SFC achieved the highest sensitivity of all individual parameters with 89% and a specificity of 72%. When multiple SFC were employed the sensitivity and specificity increased to 100%. There was a concordance of 86% between the PM and SFC. SFC achieved the highest sensitivity and it was possible to further improve the sensitivity and specificity when using multiple cultures. Multiple SFC and PM are beneficial to help reference singular bacterial isolations and achieve the diagnosis of PJI.

Toll-like receptor 2 in serum: a potential diagnostic marker of prosthetic joint infection?

Prosthetic joint infection (PJI) is a severe complication of arthroplasty and is still lacking diagnostic gold standards. PJI patients display high Toll-like receptor 2 (TLR2) serum levels, correlating with canonical inflammatory markers (C-reactive protein [CRP], interleukin 6 [IL-6], tumor necrosis factor alpha [TNF-α], and IL-1). Therefore, TLR2 serum levels could be considered a new potential diagnostic tool in the early detection of PJI.

Use of real-time polymerase chain reaction for the diagnosis of infection and differentiation between gram-positive and gram-negative septic arthritis in children

BACKGROUND

Diagnosis and identification of the etiological agent of septic arthritis (SA) in children is an important issue, as early treatment based on accurate diagnosis of joint infections can prevent potentially disabling complications. The purpose of this study was to evaluate the efficacy of real-time polymerase chain reaction (PCR) for the diagnosis of SA in children.

PATIENTS AND METHODS

Twenty children with suspected SA who had joint pain and underwent surgical treatment were enrolled in this study. Their preoperative clinical and laboratory findings were investigated. Tissues obtained during operation were subjected to microbiological culture and real-time PCR, including methicillin-resistant Staphylococcus (MRS)-specific PCR and broad range universal PCR. Infection was confirmed if the result of microbiological culture was positive. Furthermore, abnormal clinical and laboratory findings and improvement in the symptoms and posttreatment data were also defined as the final diagnosis of infection.

RESULTS

Out of the 20 patients, 19 were diagnosed with the infection. The remaining patient was postoperatively diagnosed with juvenile idiopathic arthritis. Abnormal preoperative body temperatures, white blood cell counts, C-reactive protein levels, and erythrocyte sedimentation rates were observed in 6, 9, 15, and 12 cases, respectively. The results of microbiological culture, MRS-PCR, and universal PCR were positive in 9, 2, and 15 cases, respectively. Analysis of the melting peak in universal PCR revealed that of the 15 cases, 10 had gram-positive and 5 had gram-negative infections. The sensitivity and specificity for the diagnosis of SA were, respectively, 0.47 and 1.00 in microbiological culture and 0.79 and 1.00 in real-time PCR.

CONCLUSIONS

Successful diagnosis of infection and differentiation between gram-positive and gram-negative bacteria were achieved using MRS-PCR and universal PCR. Hence, real-time PCR is useful and has greater sensitivity than microbial culture for diagnosing SA in children.

LEVEL OF EVIDENCE

Level II diagnostic study investigating a diagnostic test.

Diagnosis and management of prosthetic joint infection: clinical practice guidelines by the Infectious Diseases Society of America

These guidelines are intended for use by infectious disease specialists, orthopedists, and other healthcare professionals who care for patients with prosthetic joint infection (PJI). They include evidence-based and opinion-based recommendations for the diagnosis and management of patients with PJI treated with debridement and retention of the prosthesis, resection arthroplasty with or without subsequent staged reimplantation, 1-stage reimplantation, and amputation.

Bacteria on catheters in patients undergoing peritoneal dialysis

BACKGROUND

Peritonitis is the leading cause of morbidity for peritoneal dialysis (PD) patients, and microbial biofilms have previously been identified on catheters from infected patients. However, few studies of catheters from patients without clinical signs of infection have been undertaken. The aim of the present study was to investigate the extent to which bacteria are present on catheters from PD patients with no symptoms of infection.

METHODS

Microbiologic culturing under aerobic and anaerobic conditions and confocal laser scanning microscopy were used to determine the distribution of bacteria on PD catheters from 15 patients without clinical signs of infection and on catheters from 2 infected patients. The 16S rRNA gene sequencing technique was used to identify cultured bacteria.

RESULTS

Bacteria were detected on 12 of the 15 catheters from patients without signs of infection and on the 2 catheters from infected patients. Single-species and mixed-microbial communities containing up to 5 species were present on both the inside and the outside along the whole length of the colonized catheters. The bacterial species most commonly found were the skin commensals Staphylococcus epidermidis and Propionibacterium acnes, followed by S. warneri and S. lugdunensis. The strains of these micro-organisms, particularly those of S. epidermidis, varied in phenotype with respect to their tolerance of the major classes of antibiotics.

CONCLUSIONS

Bacteria were common on catheters from patients without symptoms of infection. Up to 4 different bacterial species were found in close association and may represent a risk factor for the future development of peritonitis in patients hosting such micro-organisms.

Management of periprosthetic joint infection: the current knowledge: AAOS exhibit selection

Periprosthetic joint infection continues to frustrate the medical community. Although the demand for total joint arthroplasty is increasing, the burden of such infections is increasing even more rapidly, and they pose a unique challenge because their accurate diagnosis and eradication can prove elusive. This review describes the current knowledge regarding diagnosis and treatment of periprosthetic joint infection. A number of tools are available to aid in establishing a diagnosis of periprosthetic joint infection. These include the erythrocyte sedimentation rate, serum C-reactive protein concentration, synovial white blood-cell count and differential, imaging studies, tissue specimen culturing, and histological analysis. Multiple definitions of periprosthetic joint infection have been proposed but there is no consensus. Tools under investigation to diagnose such infections include the C-reactive protein concentration in the joint fluid, point-of-care strip tests for the leukocyte esterase concentration in the joint fluid, and other molecular markers of periprosthetic joint infection. Treatment options include irrigation and debridement with prosthesis retention, one-stage prosthesis exchange, two-stage prosthesis exchange with intervening placement of an antibiotic-loaded spacer, and salvage treatments such as joint arthrodesis and amputation. Treatment selection is dependent on multiple factors including the timing of the symptom onset, patient health, the infecting organism, and a history of infection in the joint. Although prosthesis retention has the theoretical advantages of decreased morbidity and improved return to function, two-stage exchange provides a lower rate of recurrent infection. As the burden of periprosthetic joint infection increases, the orthopaedic and medical community should become more familiar with the disease. It is hoped that the tools currently under investigation will aid clinicians in diagnosing periprosthetic joint infection in an accurate and timely fashion to allow appropriate treatment. Given the current knowledge and planned future research, the medical community should be prepared to effectively manage this increasingly prevalent disease.

Use of F-18 fluoride PET to differentiate septic from aseptic loosening in total hip arthroplasty patients

PURPOSE

The preoperative differentiation of aseptic and septic loosening following a total hip arthroplasty (THA) remains a challenging issue for clinicians to which several molecular imaging techniques have been applied. In our current study, we used F-18 fluoride positron emission tomography (PET) to evaluate THA cases with stable, septic or septic loosened implants to assess the possibility of differentiating these clinical settings using a novel uptake-type classification approach.

MATERIALS AND METHODS

A total of 65 joints were enrolled in this prospective study comprising 27 asymptomatic stable hips (control group), 11 painful hips conservatively treated after THA due to a suspicion of loosening, and 27 painful hips surgically treated after THA. PET imaging was classified into 3 types according to the uptake pattern. The maximum standardized uptake value (SUVmax) was then measured for each joint. A final diagnosis was made via tissue examinations of surgically treated cases, and by serological and radiographic findings in conservatively treated cases.

RESULTS

There were significant differences found between the SUVmax values for the aseptic and septic loosening THA cases. In the diagnosis of infection with type 3 pattern, the sensitivity and specificity were measured at 0.95 and 0.98 for all cases, and 0.95 and 0.88 for surgically treated cases, respectively.

CONCLUSIONS

The results of our current study demonstrate that F-18 fluoride PET has considerable potential as a method for differentiating septic from aseptic loosening following a THA. The type classification of the uptake pattern can be performed relatively simply, and quantifications using the SUVmax values can then provide an objective evaluation.