Microbiological diagnosis of prosthetic joint infections: a prospective evaluation of four bacterial culture media in the routine laboratory

Future directions for early detection of fracture related infections

Introduction

Fracture related infection (FRI) refers to pathogens infecting a fracture site and hence impeding fracture healing. It is a significant complication that carries substantial disease burden and socio-economic costs, but has had limited scientific development. Hence, this paper will review the existing strategies for early detection of FRI, in the form of serum markers, molecular diagnostics and imaging modalities, and further discuss potential future directions for improved detection of FRI.

Existing Strategies for Diagnosis of FRI

The Anti-infection Global Expert Committee (AIGEC) developed a consensus definition for FRI in 2017, which includes confirmatory and suggestive criteria for diagnosis of FRI. Existing strategies for diagnosis include clinical, laboratory, histopathological, microbiological and radiological investigations.

Future Directions for Early Detection of FRI

With increasing recognition of FRI, early detection is crucial for early treatment to be enforced. We have identified potential areas for future development in diagnostics for early detection of FRI, which are discussed in this manuscript. They include inflammatory cytokines, serum calcium levels, platelet count, improved management of histopathological and microbiological specimens, metagenomics, wound biomarkers, gut microbiota analysis, and novel imaging technologies.

Improved cure rate of periprosthetic joint infection through targeted antibiotic therapy based on integrated pathogen diagnosis strategy

Objectives

This study aimed to determine whether combined of pathogen detection strategies, including specimen acquisition, culture conditions, and molecular diagnostics, can improve treatment outcomes in patients with periprosthetic joint infections (PJI).

Methods

This retrospective study included suspected PJI cases from three sequential stages at our institution: Stage A (July 2012 to June 2015), Stage B (July 2015 to June 2018), and Stage C (July 2018 to June 2021). Cases were categorized into PJI and aseptic failure (AF) groups based on European Bone and Joint Infection Society (EBJIS) criteria. Utilization of pathogen diagnostic strategies, pathogen detection rates, targeted antibiotic prescription rates, and treatment outcomes were analyzed and compared across the three stages.

Results

A total of 165 PJI cases and 38 AF cases were included in this study. With the progressive implementation of the three optimization approaches across stages A, B and C, pathogen detection rates exhibited a gradual increase (χ2 = 8.282, P=0.016). Similarly, utilization of targeted antibiotic therapy increased stepwise from 57.1% in Stage A, to 82.3% in Stage B, and to 84% in Stage C (χ2 = 9.515, P=0.009). The 2-year infection control rate exceeded 90% in both stages B and C, surpassing stage A (71.4%) (χ2 = 8.317, P=0.011). Combined application of all three optimized protocols yielded the highest sensitivity of 91.21% for pathogen detection, while retaining higher specificity of 92.11%.

Conclusion

The utilization of combined pathogen diagnostic strategies in PJI can increase pathogen detection rates, improve targeted antibiotic prescription, reduce the occurrence of antibiotic complications, and achieve better treatment outcomes.

Optimized decision algorithm for the microbiological diagnosis of osteoarticular infections in adults using synovial fluid samples: a prospective study in two French hospitals including 423 samples of synovial fluid

No consensus exists about the techniques to use for microbiological diagnosis of bone and joint infections (BJIs). The objective herein was to define an algorithm to optimize BJI diagnosis in adults using various bacteriological methods on synovial fluid samples. This prospective multi-center study included 423 synovial fluids collected from adult patients with suspected BJIs. Culture (using five solid media, an enrichment broth, and blood culture bottles), universal 16S rRNA PCR followed by Sanger sequencing, and seven specific bacterial PCRs were systematically performed. Combinations of methods were compared to arrive at the optimized algorithm. Among 423 synovial fluids, 242 infections were diagnosed (57.2 %): 213 mono- and 29 poly-microbial for a total of 284 bacteria (staphylococci at 54.6 %, streptococci-enterococci at 16.5 %, Gram-negative bacilli at 15.5 %, anaerobic species at 8.8 %). Comparing culture techniques, blood culture bottles had the highest sensitivity (67.6 % for pediatric and 63.9 % for anaerobic bottles) but are not sufficient alone and require being combined with solid media. The 16S rDNA PCR detected only 52.3 % of the bacteria, whereas specific PCRs had a higher sensitivity (Staphylococcus spp. at 66.2 %, S. aureus at 85.2 %, Streptococcus spp. at 91.2 %). Based on these results, an algorithm was proposed associating three solid media; inoculation into blood culture bottles; and 16S, Staphylococcus spp., and Streptococcus spp. PCRs, which would have detected 90.5 % of bacteria in the present cohort versus 79.2 % using all culture techniques on synovial fluid. This prospective study shows that a combination of culture and molecular methods on synovial fluids allows the optimization of bacterial detection.

Periprosthetic hip infections caused by Brucella: a rare case report and literature review

Periprosthetic hip infection caused by Brucella abortus is rare and only a few cases have been reported. This current case report presents a case of a man in his early 50s who developed periprosthetic hip infection 2 years after right hip arthroplasty. There was no fever or pain, the usual cardinal signs of infection, except for a sinus tract at the previous surgical incision. Laboratory and arthrocentesis culture examinations (done twice) confirmed infection with B. abortus. Accordingly, a two-stage revision surgery was performed accompanied by antibiotic treatment with doxycycline and rifampicin after each stage. There was no recurrence at the 2-year follow-up, with good functional recovery of the hip joint. Clinically, this case serves to highlight the fact that periprosthetic hip infections caused by B. abortus might not present with the typical symptoms such as fever or hip pain. Furthermore, this current case involved a chronic sinus tract, so the diagnostic and therapeutic course of this case offers useful insights for managing similar cases in the future. In addition, a review of the literature on the diagnosis and treatment of Brucella-caused periprosthetic hip infection is presented.

The role of biopsy in diagnosing infection after hip and knee arthroplasty: a meta-analysis

INTRODUCTION

Early diagnosis of periprosthetic hip and knee infection still represents a major challenge, as no single test can achieve ideal results. Currently, multiple preoperative indicators were performed to diagnose periprosthetic joint infection (PJI) to confirm or exclude infection in the early stage. However, the diagnostic value of biopsy-related tests in diagnosing periprosthetic hip and knee infection remains unclear.

MATERIALS AND METHODS

Publications in PubMed, Embase, and the Web of Science databases were searched systematically until October 2020. Inclusion and exclusion criteria were used for screening biopsy-related studies of the diagnosis of periprosthetic hip and knee infection.

RESULTS

Three biopsy-related tests were identified in 14 articles and further analyzed in the present meta-analysis. The combined method had the highest value for the area under the curve (0.9805), followed by histology (0.9425) and microbiological tests (0.9292). In the subgroup, statistical differences were identified in sensitivity and specificity for PJI diagnosis between the synovial fluid culture and biopsy culture group, as well as in the biopsy-related combined method and serum C-reactive protein.

CONCLUSIONS

Biopsy culture does not appear to be advantageous compared to synovial fluid culture in the preoperative diagnosis of periprosthetic hip and knee infection. In contrast, combined biopsy microbial culture with histology analysis shows great potential in improving the preoperative diagnosis of PJI. The standard procedure of biopsy needs to be further explored. Further research is required to verify our results.

The role of metagenomic next-generation sequencing in the pathogen detection of invasive osteoarticular infection

OBJECTIVE

This study aimed to analyzed the pathogenic bacteria spectrum in invasive and primary osteoarticular infection (IOI and POI), and compared the pathogen detection rate of metagenomic next-generation sequencing (mNGS) and microbial culture in IOI and POI.

METHODS

The suspected POI and IOI cases from 2008 to 2021 were included. The diagnosis of POI or IOI were made by at least two orthopaedic surgeons, two infectious diseases specialist and one senior microbiologist. Demographic characteristics, microbial culture results and so on were recorded. The pathogenic bacteria spectrum in IOI and POI were analyzed and the ability of mNGS and microbial culture in pathogen detection in IOI and POI were compared.

RESULTS

There were 63 POI cases and 92 cases, the common pathogen in POI and IOI were both Staphylococcus aureus. There are more cases with negative microbial culture results and multiple infections in IOI, and many cases were caused by rare and fastidious bacteria. The introduction of the mNGS could significantly increase the pathogen detection rate to 92.39% in IOI, which was 8.69% higher than that of microbial culture (P=0.007), while the improvement in POI was limited to about 2%.

CONCLUSIONS

mNGS was an ideal tool for IOI pathogen detection.

Causative Pathogens Do Not Differ between Early, Delayed or Late Fracture-Related Infections

Fracture-related infections (FRIs) are classically considered to be early (0−2 weeks), delayed (3−10 weeks) or late (>10 weeks) based on hypothesized differences in causative pathogens and biofilm formation. Treatment strategies often reflect this classification, with debridement, antimicrobial therapy and implant retention (DAIR) preferentially reserved for early FRI. This study examined pathogens isolated from FRI to confirm or refute these hypothesized differences in causative pathogens over time. Cases of FRI managed surgically at three centres between 2015−2019 and followed up for at least one year were included. Data were analysed regarding patient demographics, time from injury and pathogens isolated. Patients who underwent DAIR were also analysed separately. In total, 433 FRIs were studied, including 51 early cases (median time from injury of 2 weeks, interquartile range (IQR) of 1−2 weeks), 82 delayed cases (median time from injury of 5 weeks, IQR of 4−8 weeks) and 300 late cases (median time from injury of 112 weeks, IQR of 40−737 weeks). The type of infection was associated with time since injury; early or delayed FRI are most likely to be polymicrobial, whereas late FRIs are more likely to be culture-negative, or monomicrobial. Staphylococcus aureus was the most commonly isolated pathogen at all time points; however, we found no evidence that the type of pathogens isolated in early, delayed or late infections were different (p = 0.2). More specifically, we found no evidence for more virulent pathogens (S. aureus, Gram-negative aerobic bacilli) in early infections and less virulent pathogens (such as coagulase negative staphylococci) in late infections. In summary, decisions on FRI treatment should not assume microbiological differences related to time since injury. From a microbiological perspective, the relevance of classifying FRI by time since injury remains unclear.

Microbiological Diagnosis of Osteoarticular Infections: Comparison between BacT/Alert Bottles and Schaedler Broth

Microbiological diagnosis of osteoarticular infections (OAIs) is based on culture on several media. Experts recommend the use of liquid media, such as Schaedler broth, but many laboratories use blood culture media with automated detection instead for convenience. We aimed to evaluate the performance of culturing in BacT/Alert (bioMérieux) bottles for the microbiological diagnosis of OAI versus culturing in Schaedler broth. This prospective study was conducted on all osteoarticular specimens sent to the microbiology laboratories of the Versailles and Diaconesses Croix Saint-Simon hospitals between October 2016 and February 2017. Each sample was inoculated onto solid agar, into BacT/Alert bottles incubated for 14 days, and into a Schaedler broth incubated for 14 days with daily reading. The gold standard was defined as follow: OAI was diagnosed for a patient if at least two samples were positive for a nonskin microorganism and at least three for a cutaneous species. The times to detection were compared. A total of 1,616 specimens from 349 patients were collected. BacT/Alert bottles were significantly more sensitive than the Schaedler process for OAI diagnosis (114/135 OAI detected by BacT/Alert bottles; 91/135 OAI detected by Schaedler broth; +17.0% [95% confidence interval {CI}, 6.8%, 27.3%]; P = 0.0004). The time to detection was significantly shorter using BacT/Alert bottles (2.0 ± 2.2 days) than using Schaedler broth (4.6 ± 3.6 days, P < 0.0001). The culture of osteoarticular specimens in BacT/Alert bottles allows bacterial enrichment with an automated detection of positivity. Their use decreased detection time and increased sensitivity, making it a useful tool for the diagnosis of OAI that should be included among the recommended media. IMPORTANCE Microbiological diagnosis of OAI is based on culture on several media. French experts recommend the use of liquid media such as Schaedler broth, but many laboratories use blood culture media with automated detection in substitution because it is more convenient. We report here a prospective multicentric study evaluating the performance of culture in BacT/Alert (bioMérieux) bottles for microbiological diagnosis of OAI in comparison with culture in Schaedler broth. A total of 1,616 osteoarticular specimens from 349 patients were collected and inoculated onto agar, into BacT/Alert aerobic and anaerobic bottles, and into a Schaedler broth. BacT/Alert bottles were significantly more sensitive than the Schaedler process for OAI diagnosis (+17.0% [95% CI, 6.8%, 27.3%], P = 0.0004). The time to detection was significantly shorter for the BacT/Alert bottles (2.0 ± 2.2 days) than for Schaedler broth (4.6 ± 3.6 days, P < 0.0001). This study suggests that the use of BacT/Alert bottles should be recommended in microbiological diagnosis of OAI.

Cutibacterium acnes clonal complexes display various growth rates in blood culture vials used for diagnosing orthopedic device-related infections

OBJECTIVES

Blood culture bottles (BCBs) are commonly used for the diagnosis of infections associated with orthopedic devices. Although Cutibacterium acnes is an important pathogen in orthopedics, relatively little is known about its growth characteristics in BCBs. This prompted us to analyze the influence of bacterial genotype and clinical significance on time-to-detection (TTD) in BCBs.

METHODS

We reviewed 59 cases of orthopedic device-related infections in which at least one intraoperative specimen yielded a pure C. acnes culture from anaerobic BCBs (BD Bactec Lytic/10 Anaerobic/F; Lytic-Ana) and/or solid media. A strain was considered infectant if the same genotype was present in two or more intraoperative samples. From these cases, we isolated a total of 72 unique C. acnes strains belonging to four multilocus sequence type clonal complexes (CCs): CC18, CC28, CC36 and CC53. Growth rate and TTD in Lytic-Ana BCB were studied under experimental conditions (inoculation of standard inoculum) and in clinical samples (inoculation of periprosthetic tissue samples).

RESULTS

Median TTD values were shorter for CC53 compared to other CCs under experimental conditions (69 vs. 103 h; p < 0.001) and from clinical specimens (70 vs. 200 h; p = 0.02). Infectant strains had a shorter median TTD compared to contaminant strains in a clinical situation, while the difference was not observed under experimental conditions.

CONCLUSIONS

The detection dynamics of C. acnes in Lytic-Ana BCBs were associated with genotype. Thus, TTD not only reflects the bacterial load in clinical samples, but may also reflect the intrinsic properties of the clonal complex of C. acnes.

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).

Low Diagnostic Value of Synovial Aspiration Culture Prior to Reimplantation in Periprosthetic Joint Infection

BACKGROUND/AIM

We aimed to determine the diagnostic value of the synovial aspiration culture prior to reimplantation in two- (or more) stage exchange of periprosthetic joint infection.

PATIENTS AND METHODS

This was a retrospective study, spanning over ten years including all synovial cultures of patients with two- (or more) stage exchange due to periprosthetic joint infection.

RESULTS

A total of 183 patients were included, mean age was 66.6 years (range=12.8-93.4 years). Overall sensitivity of synovial aspiration cultures before reimplantation was 56.6%, specificity 84.6%, negative predictive value (NPV) 63.8%, positive predictive value (PPV) 80.2%, area under the curve (AUC) 70.6%. Sensitivity of the knee in comparison to the hip culture was significantly higher, as well as the NPV and the AUC (p=0.038). In case of complete removal of prosthesis, the sensitivity and AUC were significantly reduced, whereas the specificity was comparable with prosthesis in situ, partial removal or complete removal.

CONCLUSION

Due to the low sensitivity, obtaining several synovial cultures in the prosthesis-free interval to exclude persistence of infection, does not seem reasonable.

Optimal microbiological sampling for the diagnosis of osteoarticular infection

Infection is a dire complication afflicting every field of orthopaedics and traumatology. If specific clinical, laboratory and imaging parameters are present, infection is often assumed even in the absence of microbiological confirmation. However, apart from confirming infection, knowing the exact infecting pathogen(s) and their antimicrobial susceptibility patterns is paramount to help guide treatment. Every effort should therefore be undertaken with that goal in mind.Not all microbiological findings carry the same relevance, and knowing exactly how and where a sample was collected is key. Several different sampling techniques are available, and one must be aware of both advantages and limitations. Microbiological sampling alternatives in some of the most common clinical scenarios such as native and prosthetic joint infections, osteomyelitis and fracture-related infections, spinal and diabetic foot infections will be discussed.Orthopaedic surgeons should also be aware of basic laboratory sample processing techniques as they have a direct impact on the way specimens should be dealt with and transported to the laboratory. Only by knowing these basic principles will surgeons be able to participate in the multidisciplinary discussion and decision making around how to interpret microbiological findings in each specific patient. Cite this article: EFORT Open Rev 2021;6:390-398. DOI: 10.1302/2058-5241.6.210011.

Effects of different tissue specimen pretreatment methods on microbial culture results in the diagnosis of periprosthetic joint infection

Aims

Microbiological culture is a key element in the diagnosis of periprosthetic joint infection (PJI). However, cultures of periprosthetic tissue do not have optimal sensitivity. One of the main reasons for this is that microorganisms are not released from the tissues, either due to biofilm formation or intracellular persistence. This study aimed to optimize tissue pretreatment methods in order to improve detection of microorganisms.

Methods

From December 2017 to September 2019, patients undergoing revision arthroplasty in a single centre due to PJI and aseptic failure (AF) were included, with demographic data and laboratory test results recorded prospectively. Periprosthetic tissue samples were collected intraoperatively and assigned to tissue-mechanical homogenization (T-MH), tissue-manual milling (T-MM), tissue-dithiothreitol (T-DTT) treatment, tissue-sonication (T-S), and tissue-direct culture (T-D). The yield of the microbial cultures was then analyzed.

Results

A total of 46 patients were enrolled, including 28 patients in the PJI group and 18 patients in the AF group. In the PJI group, 23 cases had positive culture results via T-MH, 22 cases via T-DTT, 20 cases via T-S, 15 cases via T-MM, and 13 cases via T-D. Three cases under ongoing antibiotic treatment remained culture-negative. Five tissue samples provided the optimal yield. Any ongoing antibiotic treatment had a relevant influence on culture sensitivity, except for T-DTT.

Conclusion

T-MH had the highest sensitivity. Combining T-MH with T-DTT, which requires no special equipment, may effectively improve bacterial detection in PJI. A total of five periprosthetic tissue biopsies should be sampled in revision arthroplasty for optimal detection of PJI.

Cite this article: Bone Joint Res 2021;10(2):96–104.

Optimizing culture methods according to preoperative mNGS results can improve joint infection diagnosis

AIMS

Metagenomic next-generation sequencing (mNGS) is useful in the diagnosis of infectious disease. However, while it is highly sensitive at identifying bacteria, it does not provide information on the sensitivity of the organisms to antibiotics. The purpose of this study was to determine whether the results of mNGS can be used to guide optimization of culture methods to improve the sensitivity of culture from intraoperative samples.

METHODS

Between July 2014 and October 2019, patients with suspected joint infection (JI) from whom synovial fluid (SF) was obtained preoperatively were enrolled. Preoperative aspirated SF was analyzed by conventional microbial culture and mNGS. In addition to samples taken for conventional microbial culture, some samples were taken for intraoperative culture to optimize the culture method according to the preoperative mNGS results. The demographic characteristics, medical history, laboratory examination, mNGS, and culture results of the patients were recorded, and the possibility of the optimized culture methods improving diagnostic efficiency was evaluated.

RESULTS

A total of 56 cases were included in this study. There were 35 cases of JI and 21 cases of non-joint infection (NJI). The sensitivity, specificity, and accuracy of intraoperative microbial culture after optimization of the culture method were 94.29%, 76.19%, and 87.5%, respectively, while those of the conventional microbial culture method were 60%, 80.95%, and 67.86%, respectively.

CONCLUSION

Preoperative aspirated SF detected via mNGS can provide more aetiological information than preoperative culture, which can guide the optimization and improve the sensitivity of intraoperative culture. Cite this article: Bone Joint J 2021;103-B(1):39-45.

Isolation of clinically significant microorganisms from prosthetic joint tissue using BacT/ALERT paediatric blood culture bottles compared with solid culture media and enrichment broth

The diagnosis of prosthetic joint infections and isolation of causative microorganisms has been found to be challenging in microbiology laboratories due to low sensitivity of microbiological culture. The aim of this study was to compare the use of conventional culture methods with the use of both enrichment broth and BacT/ALERT paediatric blood culture bottles, for the diagnosis of prosthetic joint infections. A total of 121 specimens from 44 patients were processed using three methods of microbiological culture: solid media, enrichment broth and paediatric bottles. The paediatric bottle method had a significantly lower (p<0.0001) time to detection than the standard solid media method, and was significantly more sensitive than solid media when used independently (93.33%, CI 83.27-98.09, vs 60.00%, CI 45.43-73.33). The combination use of solid media with paediatric bottles was found to be superior to the conventional solid media method and combination use with enrichment broth.

Effective and Rapid Microbial Identification in Pediatric Osteoarticular Infections Using Blood Culture Bottles

BACKGROUND

The detection and identification of pathogenic microorganisms are essential for the treatment of osteoarticular infection. However, obtaining a sufficient amount of specimen from pediatric patients is often difficult. Herein, we aimed to demonstrate the effectiveness of the blood culture bottle (BCB) system in pediatric osteoarticular infections. We hypothesized that our BCB culture method is superior to the conventional swab and tissue culture methods in terms of required specimen size, incubation time, and microbial identification rate.

METHODS

We analyzed the prospectively collected data of pediatric patients who underwent surgical treatment for osteoarticular infections between August 2016 and October 2019. Four needles were dipped in the infected fluid or tissue during the surgical procedure as soon as the infected area was exposed and were used to inoculate 2 aerobic pediatric BCBs and 2 anaerobic general BCBs. We also collected 2 conventional swab samples and 2 tissue samples from the identical area. The microbial identification rate and the time required for identification were compared between BCB, swab, and tissue cultures.

RESULTS

Forty patients constituted the study group; 13 patients had osteomyelitis, 17 patients had septic arthritis, and 10 patients had both. Of these 40 patients, the microbial identification rate was higher with BCB cultures (27 [68%]) than with swab cultures (18 [45%]; p = 0.004) or tissue cultures (15 [38%]; p < 0.001). Nine samples (9 patients [23%]) were only positive in the BCB culture. Positive microbial growth was not detected with conventional culture methods when microorganisms did not grow on the BCB culture. Compared with swab culture (4.3 ± 1.1 days; p < 0.001) or tissue culture (4.4 ± 1.1 days; p < 0.001), the BCB culture reduced the time required for microbial identification (3.5 ± 0.9 days).

CONCLUSIONS

In pediatric osteoarticular infections, the BCB culture system improved the microbial identification rate, reduced the time to identification, and permitted a smaller-volume specimen, compared with traditional culture systems.

LEVEL OF EVIDENCE

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

Is There an Optimal Cutoff for Aspiration Fluid Volume in the Diagnosis of Periprosthetic Joint Infection?

BACKGROUND

The diagnosis of periprosthetic joint infection is often challenging in the setting of low aspiration volumes, or in the presence of infection with a slow-growing organism. We sought to determine if an optimal threshold of aspiration fluid volume exists when cultures from the preoperative aspiration are compared to intraoperative cultures.

METHODS

All revision total hip and knee arthroplasty procedures over 5 years at our institution were reviewed. Cases were excluded if they underwent joint lavage during aspiration, had an antibiotic spacer in place, were suspected of adverse local tissue reaction to metal debris, did not have an accurate aspiration volume recorded, or if there were no aspiration or operative cultures available. Receiver operating characteristic curves were used to evaluate aspiration volume for identifying cases with identical aspiration and culture results.

RESULTS

A total of 857 revision cases were reviewed, among which 294 met inclusion criteria. There were 45 cases (15.3%) with discordant aspiration and operative cultures. The mean aspiration volume for identical cases was significantly higher than for discordant cases (19.1 vs 10.2 mL, P = .02). The proportion of slow-growing organisms was significantly greater among discordant compared to identical operative cultures (52.4% for discordant cases vs 8.2% for identical cases, P < .001). The optimal cutoff value for predicting identical cultures was 3.5 mL for typical organisms and 12.5 mL for slow-growing organisms.

CONCLUSION

Aspiration cultures are more likely to correlate with intraoperative cultures with higher aspiration volumes, and the optimal aspiration volume is higher for slow-growing organisms.

Detecting the presence of bacterial RNA by polymerase chain reaction in low volumes of preoperatively aspirated synovial fluid from prosthetic joint infections

Aims

Preoperative diagnosis is important for revision surgery after prosthetic joint infection (PJI). The purpose of our study was to determine whether reverse transcription-quantitative polymerase chain reaction (RT-qPCR), which is used to detect bacterial ribosomal RNA (rRNA) preoperatively, can reveal PJI in low volumes of aspirated fluid.

Methods

We acquired joint fluid samples (JFSs) by preoperative aspiration from patients who were suspected of having a PJI and failed arthroplasty; patients with preoperative JFS volumes less than 5 ml were enrolled. RNA-based polymerase chain reaction (PCR) and bacterial culture were performed, and diagnostic efficiency was compared between the two methods.According to established Musculoskeletal Infection Society (MSIS) criteria, 21 of the 33 included patients were diagnosed with PJI.

Results

RNA-based PCR exhibited 57.1% sensitivity, 91.7% specificity, 69.7% accuracy, 92.3% positive predictive value, and 55.0% negative predictive value. The corresponding values for culture were 28.6%, 83.3%, 48.5%, 75.0%, and 40.0%, respectively. A significantly higher sensitivity was thus obtained with the PCR method versus the culture method.

Conclusion

In situations in which only a small JFS volume can be acquired, RNA-based PCR analysis increases the utility of preoperative puncture for patients who require revision surgery due to suspected PJI.

Cite this article:Bone Joint Res. 2020;9(5):219–224.

Culturing Periprosthetic Tissues in BacT/Alert® Virtuo Blood Culture Bottles for a Short Duration of Post-operative Empirical Antibiotic Therapy

Introduction: A post-operative empirical antibiotic therapy (PEAT) is required in periprosthetic joint infections. It commonly uses broad-spectrum antibiotics to cover most Gram-positive cocci and Gram-negative bacilli. It is currently continued until first microbiological results are available, no less than five days later. Methods: We performed a retrospective study in order to evaluate duration of incubation required for surgical samples using the BacT/Alert® Virtuo blood culture bottles system. Results: Among 216 surgical interventions and 199 clinical strains (53.8% staphylococci, 22,1% streptococci and enterococci, 14,6% Gram-negative bacilli, 5,5% anaerobes), 90.5% of the strains were detected between day 0 and day 2; 15 infective strains are cultured from day 3 including 8 Cutibacterium sp., 4 staphylococci, 2 streptococci and 1 Enterococcus. Conclusions: We suggest that the duration of PEAT in patients operated for a periprosthetic joint infection may be shortened to three days as Gram-negative rods are unlikely to grow after three days of culture by using BacT/Alert® Virtuo blood culture bottles. This is likely to shorten the overall length of hospital stay, to diminish the occurrence of adverse side effects, and the emergence of antimicrobial resistance. However, coverage of Gram-positive cocci should be maintained for 14 days until the definite culture results are available.

Diagnosis of Shoulder Arthroplasty Infection: New Tests on the Horizon

Periprosthetic shoulder infection (PSI), although less common than prosthetic hip and knee infections, continues to be a devastating complication of shoulder arthroplasty. Unlike its counterparts in the hip and knee, infection with nonsuppurative bacteria is more common than infection with more virulent bacteria in periprosthetic shoulder infection. The diagnosis of PSI can be challenging because the traditional clinical and laboratory findings are not always present. The authors present a narrative review of the current methods used in the diagnosis of PSI, as well as recently developed tests that may hold promise for the diagnosis of PSI. [Orthopedics. 2020; 43(2):76-82.].

Diagnosing Fracture-Related Infection: Current Concepts and Recommendations

Fracture-related infection (FRI) is a severe complication after bone injury and can pose a serious diagnostic challenge. Overall, there is a limited amount of scientific evidence regarding diagnostic criteria for FRI. For this reason, the AO Foundation and the European Bone and Joint Infection Society proposed a consensus definition for FRI to standardize the diagnostic criteria and improve the quality of patient care and applicability of future studies regarding this condition. The aim of this article was to summarize the available evidence and provide recommendations for the diagnosis of FRI. For this purpose, the FRI consensus definition will be discussed together with a proposal for an update based on the available evidence relating to the diagnostic value of clinical parameters, serum inflammatory markers, imaging modalities, tissue and sonication fluid sampling, molecular biology techniques, and histopathological examination. Second, recommendations on microbiology specimen sampling and laboratory operating procedures relevant to FRI will be provided. LEVEL OF EVIDENCE:: Diagnostic Level V. See Instructions for Authors for a complete description of levels of evidence.

Differences in Diagnostic Properties Between Standard and Enrichment Culture Techniques Used in Periprosthetic Joint Infections

BACKGROUND

Culture-negative infections can complicate the diagnosis and management of orthopedic infections, particularly periprosthetic joint infections (PJIs). This study aimed to identify differences in rate of detection of infection and organisms between cultured using standard and enriched methods.

METHODS

This retrospective, cross-sectional study evaluated PJI samples obtained between January 2013 and December 2017 at Yokohama City University Hospital. Samples were assessed using standard and enrichment culture techniques. White blood cell counts, C-reactive protein levels, type of microorganism (coagulase-positive or coagulase-negative), and methicillin-resistant Staphylococcus were investigated.

RESULTS

A total of 151 PJI samples were included in the analysis; of these, 68 (45.0%) were positive after standard culture while 83 (55.0%) were positive only after enrichment culture. The mean white blood cell counts and C-reactive protein levels were significantly lower in the enrichment culture group than in the standard culture group (P < .01). The rate of methicillin-resistant Staphylococcus and coagulase-negative Staphylococci was significantly higher in the enrichment culture group than in the standard culture group (P < .01).

CONCLUSION

The enrichment culture method has a higher rate of detection of infection than standard culture techniques and should, therefore, be considered when diagnosing orthopedic infections, particularly PJI.

Growth detection of Cutibacterium acnes from orthopaedic implant-associated infections in anaerobic bottles from BACTEC and BacT/ALERT blood culture systems and comparison with conventional culture media

Cutibacterium acnes is a major etiologic agent of orthopaedic implant-associated infections (IAIs) and requires up to 14 days of incubation in an anaerobic atmosphere for growth detection. As blood culture (BC) systems are increasingly being used to monitor the growth of IAI specimens, we compared different BC media for growth detection of C. acnes. Non-duplicate C. acnes isolates (n = 99) obtained from sonicate-fluid cultures of orthopaedic IAIs from Slovenia (n = 54), conventional tissue samples of monomicrobial orthopaedic IAIs from France (n = 43) and two reference strains were inoculated to anaerobic BC bottles of two major BC systems and 3 conventional culture media types (thioglycolate broth, Schaedler and chocolate agar). Growth and time-to-detection (TTD) were recorded. Only Lytic (BACTEC) and SN (BacT/ALERT) bottles consistently detected growth of C. acnes within 14 days with 94% (n = 93) and 92% (n = 91) detection rates, respectively (p = 0.79). Lytic was superior to Plus BACTEC medium (p < 0.001), while SN was superior to all other BacT/ALERT media (p < 0.001). Mean TTD was 128 ± 43 h (61-336 h) for Lytic and 158 ± 65 h (77-336 h) for SN medium. Among the conventional media, 99% (n = 98) of the isolates grew on Schaedler agar, 96% (n = 95) in thioglycolate broth and 74% (n = 73) on chocolate agar. Inconsistent growth of C. acnes in different BC media can critically influence the detection of this major IAI pathogen. Only Lytic (BACTEC) and SN (BacT/ALERT) BC media types were consistently able to detect C. acnes within 14 days of incubation. However, visible growth was observed faster in thioglycolate broth and Schaedler agar media.

Pathogenesis and management of fracture-related infection

BACKGROUND

Both fracture-related infections (FRIs) and periprosthetic joint infections (PJIs) include orthopaedic implant-associated infections. However, key aspects of management differ due to the bone and soft tissue damage in FRIs and the option of removing the implant after fracture healing. In contrast to PJIs, research and guidelines for diagnosis and treatment in FRIs are scarce.

OBJECTIVES

This narrative review aims to update clinical microbiologists, infectious disease specialists and surgeons on the management of FRIs.

SOURCES

A computerized search of PubMed was performed to identify relevant studies. Search terms included 'Fracture' and 'Infection'. The reference lists of all retrieved articles were checked for additional relevant references. In addition, when scientific evidence was lacking, recommendations are based on expert opinion.

CONTENT

Pathogenesis, prevention, diagnosis and treatment of FRIs are presented. Whenever available, specific data of patients with FRI are discussed.

IMPLICATIONS

Management of patients with FRI should take into account FRI-specific features. Treatment pathways should implement a multidisciplinary approach to achieve a good outcome. Recently, international consensus guidelines were developed to improve the quality of care for patients suffering from this severe complication, which are highlighted in this review.

Culturing periprosthetic tissue in BacT/Alert® Virtuo blood culture system leads to improved and faster detection of prosthetic joint infections

Background

Blood culture bottles (BCBs) provide a semiautomated method for culturing periprosthetic tissue specimens. A study evaluating BCBs for culturing clinical samples other than body fluids is needed before implementation into clinical practice. Our objective was to evaluate use of the BacT/Alert® Virtuo blood culture system for culturing periprosthetic tissue specimens.

Methods

The study was performed through the analysis of spiked (n = 36) and clinical (n = 158) periprosthetic tissue samples. Clinical samples were analyzed by the BCB method and the results were compared to the conventional microbiological culture-based method for time to detection and microorganisms identified.

Results

The BacT/Alert® Virtuo blood culture system detected relevant bacteria for prosthetic joint infection in both spiked and clinical samples. The BCB method was found to be as sensitive (79%) as the conventional method (76%) (p = 0.844) during the analyses of clinical samples. The BCB method yielded positive results much faster than the conventional method: 89% against 27% detection within 24 h, respectively. The median detection time was 11.1 h for the BCB method (12 h and 11 h for the aerobic and the anaerobic BCBs, correspondingly).

Conclusion

We recommend using the BacT/Alert® Virtuo blood culture system for analyzing prosthetic joint tissue, since this detect efficiently and more rapidly a wider range of bacteria than the conventional microbiological method.

Electronic supplementary material

The online version of this article (10.1186/s12879-019-4206-x) contains supplementary material, which is available to authorized users.

Culture of periprosthetic tissue in blood culture bottles for diagnosing periprosthetic joint infection

BACKGROUND

The purpose of this meta-analysis was to evaluate the diagnostic accuracy of periprosthetic tissue culture in blood culture bottles (BCB) for periprosthetic joint infection (PJI).

METHODS

PubMed, Web of Science, and Embase were systematically searched for eligible studies evaluating the diagnostic performance of periprosthetic tissue culture in BCB for the diagnosis of PJI. The pooled data were analysed by Meta-Disc software.

RESULTS

Four studies with a total of 1071 patients were included in this meta-analysis. The summarized estimates showed that periprosthetic tissue culture in BCB may be of great value in PJI diagnosis with a pooled sensitivity of 0.70 (95% confidence interval [CI]; 0.66-0.75), specificity of 0.97 (95% CI: 0.95-0.98); positive likelihood ratio (PLR) of 20.98 (95% CI: 11.52-38.2); negative likelihood ratio (NLR) of 0.28 (95% CI: 0.20-0.40); and diagnostic odds ratio (DOR) of 92.26 (95% CI: 43.93-193.78).

CONCLUSIONS

The present meta-analysis showed that periprosthetic tissue in BCB improves the results of microorganism cultures, with a sensitivity of 70% and a specificity of 97%. However, more large-scale, well-performed studies are needed to verify our findings.

Proceedings from the 2018 International Consensus Meeting on Orthopedic Infections: evaluation of periprosthetic shoulder infection

The Second International Consensus Meeting on Orthopedic Infections was held in Philadelphia, Pennsylvania, in July 2018. More than 800 experts from all 9 subspecialties of orthopedic surgery and allied fields of infectious disease, microbiology, and epidemiology were assembled to form the International Consensus Group. The shoulder workgroup reached consensus on 27 questions related to culture techniques, inflammatory markers, and diagnostic criteria used to evaluate patients for periprosthetic shoulder infection. This document contains the group's recommendations and rationale for each question related to evaluating periprosthetic shoulder infection.

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

Background: Microbiological culture has been considered the standard for pathogen identification for decades. However, culture is a laborious, time consuming, imperfect and outdated process. This study aims to inform the orthopedic community of the steps and timing of routine culture processing. Methods: We prospectively tracked 103 cultures from 33 revision hip and knee arthroplasty patients between September 2017-February 2018. Times were recorded at intraoperative collection; time of pick up from OR, transportation time; arrival at the laboratory; culture processing and plating time; and time to final result reporting. Results: Of the 103 cultures, 45.6% were processed and incubated in less than two hours, and 54.4% greater than or equal to two hours. The mean time spent in the OR, during transport, and within the laboratory prior to incubation was 0:53, 0:06 and 1:12. The range of time that samples remained at each stage varied considerably in the OR (0:03-3:33), in transit(0:04-0:16), and in the lab prior to incubation(0:26-3:01). The proportion of the total time to incubation attributed to idle time samples spent in the OR after initial sampling was 40.0%. In contrast, transport to the laboratory represented 5.1% of the total time. Idle time in the laboratory represented the greatest share at 54.9%. Conclusion: There is significant variability in the time to transport, process and incubate culture samples. Almost half of the specimens were processed outside the 2-hour recommended window. Surgeons should be aware of idle time during processing and seek to optimize their institutional pathways to maximize culture yield.

Studying Biofilm and Clinical Issues in Orthopedics

The association between biofilm-forming microorganisms and prosthetic joint infection influences all aspect of management including approaches to diagnosis, management and prevention. This article will provide an overview of new anti-biofilm strategies for management of prosthetic joint infection.

Sonication Improves the Diagnosis of Megaprosthetic Infections

Limited data are available for the diagnosis of patients with tumors with infected endoprosthetic reconstructions. The purpose of this study was to evaluate whether sonication is effective for the diagnosis of infection and to compare it with tissue cultures. The files of 58 patients who underwent revision surgery for suspected infected endoprosthetic reconstructions were reviewed. Cultures were performed on 5 tissue samples obtained from each patient and on fluid obtained by sonication of the megaprosthesis. The sensitivity, specificity, and negative and positive predictive values of tissue and sonication fluid cultures were evaluated. Overall, tissue and sonication fluid cultures confirmed an infection in 42 of the 58 patients. In 36 of the 42 infected endoprosthetic reconstructions, tissue and sonication fluid cultures identified the same bacterial isolate. In 5 cases, a bacterial isolate was identified only in sonication fluid cultures, and in 1 case, a bacterial isolate was identified only in tissue cultures. The sensitivity and negative predictive value of sonication fluid cultures were statistically significantly better than those of tissue cultures, while the specificity and positive predictive value were not different between the 2 culture types. Compared with tissue cultures for the diagnosis of infected megaprostheses in patients with tumors, sonication fluid cultures are associated with a better sensitivity and negative predictive value and a similar specificity and positive predictive value. Therefore, sonication should be considered a useful adjunct for the optimal diagnosis and management of these patients. [Orthopedics. 2019; 42(1):28-32.].

Sonication versus Tissue Sampling for Diagnosis of Prosthetic Joint and Other Orthopedic Device-Related Infections

Current guidelines recommend collection of multiple tissue samples for diagnosis of prosthetic joint infections (PJI). Sonication of explanted devices has been proposed as a potentially simpler alternative; however, reported microbiological yield varies. We evaluated sonication for diagnosis of PJI and other orthopedic device-related infections (DRI) at the Oxford Bone Infection Unit between October 2012 and August 2016. We compared the performance of paired tissue and sonication cultures against a "gold standard" of published clinical and composite clinical and microbiological definitions of infection. We analyzed explanted devices and a median of five tissue specimens from 505 procedures. Among clinically infected cases the sensitivity of tissue and sonication culture was 69% (95% confidence interval, 63 to 75) and 57% (50 to 63), respectively (P < 0.0001). Tissue culture was more sensitive than sonication for both PJI and other DRI, irrespective of the infection definition used. Tissue culture yield was higher for all subgroups except less virulent infections, among which tissue and sonication culture yield were similar. The combined sensitivity of tissue and sonication culture was 76% (70 to 81) and increased with the number of tissue specimens obtained. Tissue culture specificity was 97% (94 to 99), compared with 94% (90 to 97) for sonication (P = 0.052) and 93% (89 to 96) for the two methods combined. Tissue culture is more sensitive and may be more specific than sonication for diagnosis of orthopedic DRI in our setting. Variable methodology and case mix may explain reported differences between centers in the relative yield of tissue and sonication culture. Culture yield was highest for both methods combined.

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.

Periprosthetic joint infection caused by anaerobes. Retrospective analysis reveals no need for prolonged cultivation time if sensitive supplemented growth media are used

BACKGROUND

In microbiological diagnosis of periprosthetic joint infection (PJI) culture media and incubation time are controversially discussed, especially if anaerobic bacteria are the causative agent. This study was conducted to demonstrate the influence of sensitive supplemented growth media on the duration of culturing anaerobes.

METHODS

Twenty-five consecutive cases were included in this retrospective study. For definition of PJI, the criteria of the Musculoskeletal Infection Society (MSIS) were considered. Histopathological analysis was interpreted according to the classification by Krenn et al. The quantity and time to positivity of detected anaerobes were monitored. Furthermore, antimicrobial activity within the tissue and sonicate fluid was phenotypically tested.

RESULTS

In all cases, even if the patients had received antibiotics before recovery, culture of anaerobes (Propionibacterium species, Finegoldia magna, Parvimonas micra and Robinsoniella peoriensis), both from tissue samples and prosthetic components, first became detectable in supplemented liver thioglycollate broth within six days (median: four days).

CONCLUSION

Recommendations for prolonged cultivation for up to 14 days mostly aim at detection of anaerobes. Here we present a laboratory procedure that can shorten cultivation time considerably.

Diagnostic Methods for Prosthetic Joint Infection in Korea

Prosthetic joint infection (PJI) poses a burden on patients and health care resources. PJI diagnosis can be challenging, owing to imperfect definition, alongside inadequate diagnostic techniques. In this review, we describe consensus definitions of PJI, approaches to diagnosis using methods available in Korea, and novel diagnostic methods.

Laboratory Workflow Analysis of Culture of Periprosthetic Tissues in Blood Culture Bottles

Culture of periprosthetic tissue specimens in blood culture bottles is more sensitive than conventional techniques, but the impact on laboratory workflow has yet to be addressed. Herein, we examined the impact of culture of periprosthetic tissues in blood culture bottles on laboratory workflow and cost. The workflow was process mapped, decision tree models were constructed using probabilities of positive and negative cultures drawn from our published study (T. N. Peel, B. L. Dylla, J. G. Hughes, D. T. Lynch, K. E. Greenwood-Quaintance, A. C. Cheng, J. N. Mandrekar, and R. Patel, mBio 7:e01776-15, 2016, https://doi.org/10.1128/mBio.01776-15), and the processing times and resource costs from the laboratory staff time viewpoint were used to compare periprosthetic tissues culture processes using conventional techniques with culture in blood culture bottles. Sensitivity analysis was performed using various rates of positive cultures. Annualized labor savings were estimated based on salary costs from the U.S. Labor Bureau for Laboratory staff. The model demonstrated a 60.1% reduction in mean total staff time with the adoption of tissue inoculation into blood culture bottles compared to conventional techniques (mean ± standard deviation, 30.7 ± 27.6 versus 77.0 ± 35.3 h per month, respectively; P < 0.001). The estimated annualized labor cost savings of culture using blood culture bottles was $10,876.83 (±$337.16). Sensitivity analysis was performed using various rates of culture positivity (5 to 50%). Culture in blood culture bottles was cost-effective, based on the estimated labor cost savings of $2,132.71 for each percent increase in test accuracy. In conclusion, culture of periprosthetic tissue in blood culture bottles is not only more accurate than but is also cost-saving compared to conventional culture methods.

Procalcitonin and α-Defensin for Diagnosis of Periprosthetic Joint Infections

BACKGROUND

Current methods to diagnose periprosthetic joint infection (PJI) before revision surgery have limited diagnostic accuracy. This meta-analysis was performed to estimate the accuracy of procalcitonin (PCT) and α-defensin for the diagnosis of PJI.

METHODS

Articles on the diagnostic value of PCT or α-defensin for PJI diagnosis were searched in the PubMed database. Sensitivity, specificity, diagnostic odds ratio, the area under the curve of summary receiver operating characteristic curves (AUC), the positive likelihood ratio, and the negative likelihood ratio were calculated to evaluate the diagnostic ability of PCT and the α-defensin test for the diagnosis of PJI.

RESULTS

The pooled sensitivities for detecting PJI using PCT and α-defensin were 0.53 (95% confidence interval [CI], 0.24-0.80) and 0.96 (95% CI, 0.85-0.99), respectively. The pooled specificities for detecting PJI using PCT and α-defensin were 0.92 (95% CI, 0.45-0.99) and 0.95 (95% CI, 0.89-0.98), respectively. The pooled diagnostic odds ratios for detecting PJI using PCT and α-defensin were 13 (95% CI, 3-70) and 496 (95% CI, 71-3456), respectively. The pooled AUCs for PCT and α-defensin were 0.76 (95% CI, 0.72-0.80) and 0.99 (95% CI, 0.97-0.99), respectively. The positive likelihood ratio and the negative likelihood ratio of PCT were 6.8 (95% CI, 1.0-48.1) and 0.51 (95% CI, 0.31-0.84), respectively, whereas those of α-defensin were 19.6 (95% CI, 8.2-46.8) and 0.04 (95% CI, 0.01-0.17), respectively.

CONCLUSION

Synovial fluid α-defensin has a great potential to diagnose PJI.

Management of the Infected Total Hip Arthroplasty

In the United Kingdom approximately 80,000 total hip arthroplasties are undertaken on an average each year. The popularity and demand for this operation are continually increasing. Our understanding of arthroplasty surgery and its complications has evolved greatly, and as a result infection rates are undeniably at an all-time low. The increasing volume of operations being performed does, however, mean that we still continue to see an increased number of cases of infection. There is no doubt that periprosthetic joint infection (PJI) poses a complex clinical and diagnostic predicament to clinicians. Delay in the diagnosis and treatment of PJI can not only be detrimental in terms of patient morbidity, but it also poses a significant financial burden to health care institutions. It is therefore in the best interest of the patient, surgeon, and institution to optimize the diagnosis and treatment of this devastating complication. There remains considerable variability in terms of approach to diagnosis and treatment of PJI among orthopedic surgeons. In this review, we will, therefore, examine in detail the current body of evidence available on PJI. We will discuss the most robust and up-to-date methods of diagnosis and offer a comparison of management strategies.

Optimal Periprosthetic Tissue Specimen Number for Diagnosis of Prosthetic Joint Infection

We recently demonstrated improved sensitivity of prosthetic joint infection (PJI) diagnosis using an automated blood culture bottle system for periprosthetic tissue culture [T. N. Peel et al., mBio 7(1):e01776-15, 2016, https://doi.org/10.1128/mBio.01776-15]. This study builds on the prior research by examining the optimal number of periprosthetic tissue specimens required for accurate PJI diagnosis. Current guidelines recommend five to six, which is impractical. We applied Bayesian latent class modeling techniques for estimating diagnostic test properties of conventional culture techniques (aerobic and anaerobic agars and thioglycolate broth) compared to inoculation into blood culture bottles. Conventional, frequentist receiver operating characteristic curve analysis was conducted as a sensitivity analysis. The study was conducted at Mayo Clinic, Rochester, MN, from August 2013 through April 2014 and included 499 consecutive patients undergoing revision arthroplasty from whom 1,437 periprosthetic tissue samples were collected and processed. For conventional periprosthetic tissue culture techniques, the greatest accuracy was observed when four specimens were obtained (91%; 95% credible interval, 77 to 100%), whereas when using inoculation of periprosthetic tissues into blood culture bottles, the greatest accuracy of diagnosis was observed when three specimens were cultured (92%; 95% credible intervals, 79 to 100%). Results of this study show that the greatest accuracy of PJI diagnosis is obtained when three periprosthetic tissue specimens are obtained and inoculated into blood culture bottles or four periprosthetic tissue specimens are obtained and cultured using standard plate and broth cultures. Increasing the number of specimens to five or more, per current recommendations, does not improve accuracy of PJI diagnosis.

Treatment With Dithiothreitol Improves Bacterial Recovery From Tissue Samples in Osteoarticular and Joint Infections

BACKGROUND

Prosthetic implants, periprosthetic and osteoarticular tissues are specimens of choice for diagnosis of bone and joint infections. Homogenization is considered the best procedure for treatment of tissues samples, but, it is not always performed in all laboratories. Dithiothreitol (DTT) has been proposed as an alternative treatment to sonication for microbiological diagnosis of prosthetic joint infections. In this study, the applicability of DTT treatment for processing of periprosthetic and osteoarticular tissues for diagnosis of bone and joint infections was evaluated and compared with normal saline solution treatment.

METHODS

Periprosthetic tissue samples were collected from 70 consecutive patients (25 infected and 45 not infected). For each patient, samples from the same site were randomly allocated to DTT or saline treatment. Treated samples were centrifuged at 3000 rpm for 10 minutes. Aliquots from the concentrated samples were plated on agar plates and inoculated in broths. Sensitivity and specificity were calculated for each treatment.

RESULTS

Microbial growth was observed in samples from 14 and 11 infected patients after DTT and saline treatments, respectively. Concordance between the 2 methods was observed in the 85.7% of cases. Sensitivity was 88.0% for DTT and 72.0% for saline. Specificity was 97.8% and 91.1% for DTT and saline, respectively. Treatment with DTT showed higher sensitivity and specificity with respect to the method routinely used in our laboratory.

CONCLUSION

DTT treatment may be considered a practicable strategy for microbiological analysis of tissues for diagnosis of bone and joint infections.

Advancements in Diagnosing Periprosthetic Joint Infections after Total Hip and Knee Arthroplasty

Periprosthetic joint infection (PJI) is a complication of total joint arthroplasty that is challenging to diagnose. Currently, there is no "gold standard" for definite diagnosis of PJI. A multi-criteria definition has been described for PJI based on microbiology cultures, serum markers, such as erythrocyte sedimentation rate and C-reactive protein (CRP), synovial fluid biomarkers, such as leukocyte esterase and histopathology assessment of the periprosthetic tissue. The conventional serum markers are generally nonspecific and can be elevated in inflammatory conditions. Therefore, they cannot be relied on for definite diagnosis of PJI. Hence, with the use of proteomics, synovial fluid biomarkers such as α-defensin, IL-6, and CRP have been proposed as more accurate biomarkers for PJI. Current methods to culture micro-organisms have several limitations, and can be false-negative and false-positive in a considerable number of cases. In an attempt to improve culture sensitivity, diagnostic methods to target biofilms have recently been studied. The understanding of the concept of biofilms has also allowed for the development of novel techniques for PJI diagnosis, such as visualizing biofilms with fluorescent in-situ hybridization and detection of bacteria via DNA microarray. Lastly, the use of amplification-based molecular techniques has provided methods to identify specific species of bacteria that cause culture-negative PJI. While diagnosing PJI is difficult, these advances could be valuable tools for clinicians.

Prosthetic Device Infections

The immunocompromised host is a particularly vulnerable population in whom routine and unusual infections can easily and frequently occur. Prosthetic devices are commonly used in these patients and the infections associated with those devices present a number of challenges for both the microbiologist and the clinician. Biofilms play a major role in device-related infections, which may contribute to failed attempts to recover organisms from routine culture methods. Moreover, device-related microorganisms can be difficult to eradicate by antibiotic therapy alone. Changes in clinical practice and advances in laboratory diagnostics have provided significant improvements in the detection and accurate diagnosis of device-related infections. Disruption of the bacterial biofilm plays an essential role in recovering the causative agent in culture. Various culture and nucleic acid amplification techniques are more accurate to guide directed treatment regimens. This chapter reviews the performance characteristics of currently available diagnostic assays and summarizes published guidelines, where available, for addressing suspected infected prosthetic devices.

Will Regulatory and Financial Considerations Dampen Innovation in the Clinical Microbiology Laboratory?

Over a million prosthetic joints are placed in patients in the United States annually. Of those that fail, 25% will be due to infection, with an estimated cost approaching 1 billion dollars. Despite the clinical and economic importance of these infections, the techniques for their detection are relatively insensitive. An innovative method for detecting these infections by using blood culture bottles (BCB) to culture specimens of periprosthetic tissue (PPT) was described in a recent article [T. N. Peel, et al., mBio 7(1):e01776-15, 2016, doi:10.1128/mBio.01776-15]. There are two potential stumbling blocks to the widespread implementation of this innovation. First, the FDA judges such an application of BCB as an "off-label use" and as such, a laboratory-developed test (LDT). LDTs are coming under greater scrutiny by the FDA and may require extensive, costly validation studies in laboratories that adopt this methodology. Second, the Center for Medicare and Medicaid Services has established a Hospital Acquired Condition Reduction Act under which institutions performing in the lowest quartile forfeit 1% of their Medicare reimbursement. Hospital-acquired infections are an important component of this quality metric. Although prosthetic joint infection (PJI) rates are not currently a hospital quality metric, given their cost and increasing frequency, it is reasonable to expect that they may become one. Will those with financial oversight allow an innovative technique that will require an expensive validation and may put the institution at risk for loss of CMS reimbursement?

How Many Samples and How Many Culture Media To Diagnose a Prosthetic Joint Infection: a Clinical and Microbiological Prospective Multicenter Study

Although numerous perioperative samples and culture media are required to diagnose prosthetic joint infection (PJI), their exact number and types have not yet been definitely determined with a high level of proof. We conducted a prospective multicenter study to determine the minimal number of samples and culture media required for accurate diagnosis of PJI. Over a 2-year period, consecutive patients with clinical signs suggesting PJI were included, with five perioperative samples per patient. The bacteriological and PJI diagnosis criteria were assessed using a random selection of two, three, or four samples and compared with those obtained using the recommended five samples (references guidelines). The results obtained with two or three culture media were then compared with those obtained with five culture media for both criteria. The times-to-positivity of the different culture media were calculated. PJI was confirmed in 215/264 suspected cases, with a bacteriological criterion in 192 (89%). The PJI was monomicrobial (85%) or polymicrobial (15%). Percentages of agreement of 98.1% and 99.7%, respectively, for the bacteriological criterion and confirmed PJI diagnosis were obtained when four perioperative samples were considered. The highest percentages of agreement were obtained with the association of three culture media, a blood culture bottle, a chocolate agar plate, and Schaedler broth, incubated for 5, 7, and 14 days, respectively. This new procedure leads to significant cost saving. Our prospective multicenter study showed that four samples seeded on three culture media are sufficient for diagnosing PJI.

Improved Diagnosis of Prosthetic Joint Infection by Culturing Periprosthetic Tissue Specimens in Blood Culture Bottles

Despite known low sensitivity, culture of periprosthetic tissue specimens on agars and in broths is routine. Culture of periprosthetic tissue samples in blood culture bottles (BCBs) is potentially more convenient, but it has been evaluated in a limited way and has not been widely adopted. The aim of this study was to compare the sensitivity and specificity of inoculation of periprosthetic tissue specimens into blood culture bottles with standard agar and thioglycolate broth culture, applying Bayesian latent class modeling (LCM) in addition to applying the Infectious Diseases Society of America (IDSA) criteria for prosthetic joint infection. This prospective cohort study was conducted over a 9-month period (August 2013 to April 2014) at the Mayo Clinic, Rochester, MN, and included all consecutive patients undergoing revision arthroplasty. Overall, 369 subjects were studied; 117 (32%) met IDSA criteria for prosthetic joint infection, and 82% had late chronic infection. Applying LCM, inoculation of tissues into BCBs was associated with a 47% improvement in sensitivity compared to the sensitivity of conventional agar and broth cultures (92.1 versus 62.6%, respectively); this magnitude of change was similar when IDSA criteria were applied (60.7 versus 44.4%, respectively; P = 0.003). The time to microorganism detection was shorter with BCBs than with standard media (P < 0.0001), with aerobic and anaerobic BCBs yielding positive results within a median of 21 and 23 h, respectively. Results of our study demonstrate that the semiautomated method of periprosthetic tissue culture in blood culture bottles is more sensitive than and as specific as agar and thioglycolate broth cultures and yields results faster.

Prosthetic joint infections are a devastating complication of arthroplasty surgery. Despite this, current microbiological techniques to detect and diagnose infections are imperfect. This study examined a new approach to diagnosing infections, through the inoculation of tissue samples from around the prosthetic joint into blood culture bottles. This study demonstrated that, compared to current laboratory practices, this new technique increased the detection of infection. These findings are important for patient care to allow timely and accurate diagnosis of infection.

Deep infection after hip arthroplasty

Periprosthetic joint infection (PJI) complicates between 0.5% and 1.2% primary total hip arthroplasties (THAs) and may have devastating consequences. The traditional assessment of patients suffering from PJI has involved the serological study of inflammatory markers and microbiological analysis of samples obtained from the joint space. Treatment has involved debridement and revision arthroplasty performed in either one or two stages.

We present an update on the burden of PJI, strategies for its diagnosis and treatment, the challenge of resistant organisms and the need for definitive evidence to guide the treatment of PJI after THA.

Cite this article: Bone Joint J 2016;98-B(1 Suppl A):27–30.

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.

Sonication of explanted prosthesis combined with incubation in BD bactec bottles for pathogen-based diagnosis of prosthetic joint infection

Prosthetic joint infection (PJI) is a rare but refractory complication of arthroplasty. Accurate identification of pathogens is a key step for successful treatment of PJI, which remains a challenge for clinicians and laboratory workers. We designed a combined culture method with sonication of implants and incubation in a BD Bactec system to improve the effectiveness of pathogen diagnosis in PJI. The aims of this study were to investigate the diagnostic accuracy of sonicate fluid cultures in the BD Bactec system and to compare the results with those of synovial fluid cultures in the BD Bactec system. The prosthetic components removed were sonicated in Ringer's solution, and then sonicate fluid was incubated in Bactec bottles for 5 days. Synovial fluid was incubated in Bactec bottles for 5 days as a control. Synovial fluid cultures with Bactec bottles and sonicate fluid cultures with Bactec bottles showed sensitivities of 64% and 88%, respectively (P = 0.009), with specificities of 98% and 87% (P = 0.032), respectively. Sonicate fluid cultures with Bactec bottles were more sensitive than synovial fluid cultures with Bactec bottles regardless of whether antimicrobial agents were used within 14 days before surgery (81% versus 52%; P = 0.031) or not (93% versus 72%; P = 0.031). Sonication of explanted prostheses followed by incubation of the resulting sonicate fluid in Bactec bottles detected many more pathogens than did synovial fluid cultures with Bactec bottles. This method is also effective in cases with antibiotic treatment before surgery.