Prosthetic joint infection: challenges of diagnosis and treatment

The role of human extracellular matrix proteins in defining Staphylococcus aureus biofilm infections

Twenty to forty one percent of the world's population is either transiently or permanently colonized by the Gram-positive bacterium, Staphylococcus aureus. In 2017, the CDC designated methicillin-resistant S. aureus (MRSA) as a serious threat, reporting ∼300 000 cases of MRSA-associated hospitalizations annually, resulting in over 19 000 deaths, surpassing that of HIV in the USA. S. aureus is a proficient biofilm-forming organism that rapidly acquires resistance to antibiotics, most commonly methicillin (MRSA). This review focuses on a large group of (>30) S. aureus adhesins, either surface-associated or secreted that are designed to specifically bind to 15 or more of the proteins that form key components of the human extracellular matrix (hECM). Importantly, this includes hECM proteins that are pivotal to the homeostasis of almost every tissue environment [collagen (skin), proteoglycans (lung), hemoglobin (blood), elastin, laminin, fibrinogen, fibronectin, and fibrin (multiple organs)]. These adhesins offer S. aureus the potential to establish an infection in every sterile tissue niche. These infections often endure repeated immune onslaught, developing into chronic, biofilm-associated conditions that are tolerant to ∼1000 times the clinically prescribed dose of antibiotics. Depending on the infection and the immune response, this allows S. aureus to seamlessly transition from colonizer to pathogen by subtly manipulating the host against itself while providing the time and stealth that it requires to establish and persist as a biofilm. This is a comprehensive discussion of the interaction between S. aureus biofilms and the hECM. We provide particular focus on the role of these interactions in pathogenesis and, consequently, the clinical implications for the prevention and treatment of S. aureus biofilm infections.

Failed 2-Stage Revision Knee Arthroplasty for Periprosthetic Joint Infection-Patient Characteristics and Outcomes

BACKGROUND

Chronic prosthetic joint infection (PJI) is most frequently treated with 2-stage revision in conjunction with antibiotic treatment. The aims of this study were 1) to investigate the characteristics of patients who have recurrent infection following 2-stage revision for PJI and 2) to identify risk factors associated with treatment failure.

METHODS

A multicenter retrospective review of 90 total knee arthroplasty (TKA) patients who underwent 2-stage revision for treatment of PJI from March 1, 2003 to July 31, 2019, and had recurrent PJI was conducted. The minimum follow-up was 12 months (median follow up of 2.4 years). Microorganisms, subsequent revision, PJI control status, and final joint status were collected. The infection-free survival after initial 2-stage revision was plotted utilizing the Kaplan-Meier method.

RESULTS

Mean survival time to reinfection was 21.3 months (range, 0.3 to 160.5). There were 14 recurrent infections that were acute PJIs treated with debridement, antibiotics, and implant retention (DAIR), while 76 were chronic and treated with repeat 2-stage revision. The most common pathogen identified for both index and recurrent PJI was coagulase-negative Staphylococci. Pathogen persistence was observed in 14 (22.2%) of recurrent PJIs. In total, 61 (67.8%) patients possessed a prosthetic reimplantation at their most recent follow-up, and 29 (35.6%) patients required intervention following repeat 2-stage.

CONCLUSION

Overall, 31.1% of the patients obtained infection control after treatment of a failed 2-stage revision due to PJI. The high rate of pathogen persistence and the relatively low survival time to recurrence suggests a need to more closely monitor PJIs cases within 2 years.

Utility of Blood Cell Ratio Combinations for Diagnosis of Periprosthetic Joint Infection

Background

Periprosthetic joint infection (PJI) is a serious complication following joint replacement surgery, and its diagnosis can be challenging due to the similarity of symptoms to other conditions and the lack of confirmatory imaging tests. Platelet/mean platelet volume ratio (PVR), platelet/lymphocyte ratio, monocyte/lymphocyte ratio, and neutrophil/lymphocyte ratio have been proposed as potential markers to aid in the diagnosis of PJI. This study aimed to further assess the utility of these blood cell ratio combinations for the diagnosis of PJI.

Methods

A retrospective chart review was conducted on patients who presented to a university hospital for evaluation for PJI or underwent aseptic revision surgery. All patients were reviewed for inclusion in the study. Data were collected on several markers, including complete blood counts, synovial fluid white blood cell count, and polymorphonuclear percentage. Receiver operator characteristic curve analysis was used to evaluate the diagnostic capabilities of the markers and marker combinations.

Results

The combination of erythrocyte sedimentation rate, C-reactive protein, synovial white blood cell count, and synovial polymorphonuclear percentage, with PVR, had the highest area under the curve of 0.97, with a sensitivity of 94.3% and a specificity of 88.9%, and a positive predictive value of 97.1% and a negative predictive value of 80.0%.

Conclusions

This study further supports the use of PVR calculated from complete blood count commonly ordered laboratory values obtained during routine complete blood counts when combined with established serum and synovial markers to increase the diagnostic accuracy for diagnosing PJI.

Molecular Imaging of Periprosthetic Joint Infections

Infection is an infrequent complication of lower extremity prosthetic joint surgery. Approximately one third develop within 3 months (early), another third within 1 year (delayed), and the remainder more than 1 year (late) after surgery. The diagnosis of periprosthetic joint infection is not always straightforward. Pain, the most common symptom, is present in 90%-100% of patients. The presence of fever is more variable, ranging from less than 5% to more than 40% of patients with infection. Erythema and joint swelling are often present in acute infections, but are less common in chronic infections. Erythrocyte sedimentation rate, C-reactive protein and interleukin-6 levels are useful "rule out" tests, while peripheral blood leukocyte count and serum tumor necrosis factor α are not helpful. The diagnosis of periprosthetic joint infection often requires a combination of blood, synovial fluid, and tissue sample tests, as well as imaging. Plain radiographs lack sensitivity and specificity. Molecular imaging is useful for evaluating painful joint replacements. Bone scintigraphy is most useful as a screening test. If it is negative then infection and aseptic loosening are unlikely. Combined labeled leukocyte/bone marrow imaging is a very specific test for diagnosing lower extremity joint arthroplasty infection; sensitivity is more variable. Despite more than two decades of investigation, there still is no consensus on the value of ¹⁸F-FDG for diagnosing periprosthetic joint infection. Differing test probabilities, an inability to discriminate between infection and inflammation secondary to physiologic reactions, and lack of standardized interpretative criteria are obstacles to incorporating ¹⁸F-FDG into the routine diagnostic imaging workup of periprosthetic joint infection. Preliminary results for gallium-68 citrate, fluorine-18, and technetium-99m labeled antimicrobial fragments are encouraging but no large scale trials with these agents have been conducted. Limited data suggest that labeled leukocyte/bone marrow SPECT/CT and ¹⁸F-FDG-PET/CT are specific but not sensitive for diagnosing periprosthetic infection of shoulder arthroplasties. There are minimal data on molecular imaging for monitoring treatment response in periprosthetic infections.

Induction of Viable but Non-Culturable State in Clinically Relevant Staphylococci and Their Detection with Bacteriophage K

Prosthetic joint infections are frequently associated with biofilm formation and the presence of viable but non-culturable (VBNC) bacteria. Conventional sample culturing remains the gold standard for microbiological diagnosis. However, VBNC bacteria lack the ability to grow on routine culture medium, leading to culture-negative results. Bacteriophages are viruses that specifically recognize and infect bacteria. In this study, we wanted to determine if bacteriophages could be used to detect VBNC bacteria. Four staphylococcal strains were cultured for biofilm formation and transferred to low-nutrient media with different gentamycin concentrations for VBNC state induction. VBNC bacteria were confirmed with the BacLight^TM viability kit staining. Suspensions of live, dead, and VBNC bacteria were incubated with bacteriophage K and assessed in a qPCR for their detection. The VBNC state was successfully induced 8 to 19 days after incubation under stressful conditions. In total, 6.1 to 23.9% of bacteria were confirmed alive while not growing on conventional culturing media. During the qPCR assay, live bacterial suspensions showed a substantial increase in phage DNA. No detection was observed in dead bacteria or phage non-susceptible E. coli suspensions. However, a reduction in phage DNA in VBNC bacterial suspensions was observed, which confirmed the detection was successful based on the adsorption of phages.

Trabecular Titanium for Orthopedic Applications: Balancing Antimicrobial with Osteoconductive Properties by Varying Silver Contents

Periprosthetic joint infection (PJI) and implant loosening are the most common complications after joint replacement surgery. Due to their increased surface area, additively manufactured porous metallic implants provide optimal osseointegration but they are also highly susceptible to bacterial colonization. Antibacterial surface coatings of porous metals that do not inhibit osseointegration are therefore highly desirable. The potential of silver coatings on arthroplasty implants to inhibit PJI has been demonstrated, but the optimal silver content and release kinetics have not yet been defined. A tight control over the silver deposition coatings can help overcome bacterial infections while reducing cytotoxicity to human cells. In this regard, porous titanium sputtered with silver and titanium nitride with increasing silver contents enabled controlling the antibacterial effect against common PJI pathogens while maintaining the metabolic activity of human primary cells. Electron beam melting additively manufactured titanium alloys, coated with increasing silver contents, were physico-chemically characterized and investigated for effects against common PJI pathogens. Silver contents from 7 at % to 18 at % of silver were effective in reducing bacterial growth and biofilm formation. Staphylococcus epidermidis was more susceptible to silver ions than Staphylococcus aureus. Importantly, all silver-coated titanium scaffolds supported primary human osteoblasts proliferation, differentiation, and mineralization up to 28 days. A slight reduction of cell metabolic activity was observed at earlier time points, but no detrimental effects were found at the end of the culture period. Silver release from the silver-coated scaffolds also had no measurable effects on primary osteoblast gene expression since similar expression of genes related to osteogenesis was observed regardless the presence of silver. The investigated silver-coated porous titanium scaffolds may thus enhance osseointegration while reducing the risk of biofilm formation by the most common clinically encountered pathogens.

Fast and specific detection of staphylococcal PJI with bacteriophage-based methods within 104 sonicate fluid samples

The number of prosthetic joint infection (PJI) cases is increasing along with total joint arthroplasties. There is currently no diagnostic test available with 100% sensitivity to identify PJI. The aim of the study was to assess and compare two different bacteriophage K-based methods with standard microbiological culturing methods to detect staphylococci. Samples were retrieved from 104 patients undergoing revision surgery due to suspected PJI. Implants were subjected to sonication and sonicate fluid (SF) was assessed with the methods of qPCR detection of bacteriophage K DNA and adenosine triphosphate (ATP) detection after bacteriophage K lysis. The results were compared with the results of standard microbiological culturing methods. PJI was confirmed in 33 cases according to the PJI definition. Using the methods of ATP and bacteriophage K DNA detection 100% specificity and predictive value were achieved. The sensitivity of qPCR detection was higher (81.25%) than the sensitivity of ATP detection (62.50%) when analyzing SF directly. The sensitivity of the methods significantly improved (to 94.12%) with SF pre-cultivation. Importantly, both methods provided results in 3-4 h when analyzing SF directly, while results from pre-cultivated SF were obtained 19-20 h after sample collection. Our results suggest that bacteriophage-based methods are specific and sensitive and importantly, faster than standard culturing methods. The addition of new bacteriophages to expand the bacterial detection spectrum could lead to the development of a faster, more sensitive, specific, and also economical, and handy method for PJI diagnosis.

Shotgun-metagenomics based prediction of antibiotic resistance and virulence determinants in Staphylococcus aureus from periprosthetic tissue on blood culture bottles

Shotgun-metagenomics may give valuable clinical information beyond the detection of potential pathogen(s). Identification of antimicrobial resistance (AMR), virulence genes and typing directly from clinical samples has been limited due to challenges arising from incomplete genome coverage. We assessed the performance of shotgun-metagenomics on positive blood culture bottles (n = 19) with periprosthetic tissue for typing and prediction of AMR and virulence profiles in Staphylococcus aureus. We used different approaches to determine if sequence data from reads provides more information than from assembled contigs. Only 0.18% of total reads was derived from human DNA. Shotgun-metagenomics results and conventional method results were consistent in detecting S. aureus in all samples. AMR and known periprosthetic joint infection virulence genes were predicted from S. aureus. Mean coverage depth, when predicting AMR genes was 209 ×. Resistance phenotypes could be explained by genes predicted in the sample in most of the cases. The choice of bioinformatic data analysis approach clearly influenced the results, i.e. read-based analysis was more accurate for pathogen identification, while contigs seemed better for AMR profiling. Our study demonstrates high genome coverage and potential for typing and prediction of AMR and virulence profiles in S. aureus from shotgun-metagenomics data.

A trilogy antimicrobial strategy for multiple infections of orthopedic implants throughout their life cycle

Bacteria-associated infection represents one of the major threats for orthopedic implants failure during their life cycles. However, ordinary antimicrobial treatments usually failed to combat multiple waves of infections during arthroplasty and prosthesis revisions etc. As these incidents could easily introduce new microbial pathogens in/onto the implants. Herein, we demonstrate that an antimicrobial trilogy strategy incorporating a sophisticated multilayered coating system leveraging multiple ion exchange mechanisms and fine nanotopography tuning, could effectively eradicate bacterial infection at various stages of implantation. Early stage bacteriostatic effect was realized via nano-topological structure of top mineral coating. Antibacterial effect at intermediate stage was mediated by sustained release of zinc ions from doped CaP coating. Strong antibacterial potency was validated at 4 weeks post implantation via an implanted model in vivo. Finally, the underlying zinc titanate fiber network enabled a long-term contact and release effect of residual zinc, which maintained a strong antibacterial ability against both Staphylococcus aureus and Escherichia coli even after the removal of top layer coating. Moreover, sustained release of Sr2+ and Zn2+ during CaP coating degradation substantially promoted implant osseointegration even under an infectious environment by showing more peri-implant new bone formation and substantially improved bone-implant bonding strength.

Prevalence of idiopathically elevated ESR and CRP in patients undergoing primary total knee arthroplasty as a function of body mass index

BACKGROUND

Erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) are commonly used inflammatory markers utilized to aid in the diagnosis of periprosthetic infection (PJI). Patients with obesity, however, are known to have elevated baseline levels of these inflammatory markers. Therefore, this retrospective study aimed to determine the relationship between elevated ESR and CRP and body mass index (BMI) in patients undergoing total knee arthroplasty (TKA). In doing so, physicians can better determine whether BMI should be taken into account when evaluating the prognostic value of elevated preoperative ESR and CRP levels for risk of PJI in primary TKA patients.

METHODS

This is a retrospective case series of 181 patients who had undergone primary TKA at a single institution. Patients undergoing primary unilateral TKA were eligible unless they had undergone previous TKA, contralateral knee symptoms, or elevated white blood cell (WBC) count. A linear regression model was utilized to demonstrate the relationship between proportions of patients with elevated biomarker values and categories of BMI. Analysis of variance and independent two-sample t-tests were utilized to assess differences in mean ESR, CRP, and WBC levels between the "healthy patients" and "patients with comorbidities" subgroups within each BMI category.

RESULTS

Eligible patients (n = 181) were stratified by BMI category. Elevated ESR was associated significantly with BMI (ESR: r2 = 0.89, P < 0.001) unlike elevated CRP (r2 = 0.82, P = 0.133) and WBC count (r2 = .01; P = .626). No statistically significant differences in ESR values and WBC count between the "healthy patients" versus "patients with comorbidities" were demonstrated within any BMI category. In patients of normal weight (BMI 20-25 kg/m2), "healthy patients" had a statistically significantly higher mean CRP level than "patients with comorbidities" (1.73 mg/L vs. 0.70 mg/L, P < 0.001). There were no other statistically significant differences in mean CRP levels by health status.

CONCLUSION

Caution is advised when utilizing ESR and CRP to diagnose periprosthetic joint infection without considering BMI given that increasing preoperative levels of ESR and CRP are correlated with higher BMI.

Advantages of 16S rRNA PCR for the diagnosis of prosthetic joint infection

16S ribosomal RNA (rRNA) PCR has been reported to be an effective diagnostic means in patients with prosthetic joint infection (PJI). The aim of the present meta-analysis is to establish the overall diagnostic accuracy of the measurement of 16S rRNA PCR for diagnosing PJI. PubMed, Web of Science, Cochrane Library, EMBASE and Wiley Online Library were searched for studies on 16S rRNA PCR in the diagnosis of PJI. The search incorporated all literature published up until December 2018 and the QUADAS-2 checklist were used for quality assessment. The sensitivity, specificity and other measures of accuracy of 16S rRNA PCR in the diagnosis of PJI were pooled. Statistical analysis was performed by employing Meta-Disc 1.4 and Stata 12.0 software. A total of 15 studies met the inclusion criteria. The summary estimates for 16S rRNA PCR in the diagnosis of PJI in these studies were pooled: Sensitivity, 0.70 (95% CI, 0.67-0.73); specificity, 0.93 (95% CI, 0.91-0.94); positive likelihood ratio, 10.93 (95% CI, 5.55-21.51); negative likelihood ratio, 0.33 (95% CI, 0.28-0.40); diagnostic odds ratio, 41.77 (95% CI, 19.90-87.68); and the area under the curve, 0.89. Subgroup analysis showed that the use of sonicate fluid and periprosthetic tissue has higher sensitivity (0.76; 95% CI, 0.69-0.82; and 0.73; 95% CI, 0.68-0.78, respectively), specificity (0.93, 95% CI, 0.90-0.96; and 0.95; 95% CI, 0.90-0.98, respectively) and area under the curve (0.93 and 0.98, respectively). 16S rRNA PCR assay plays an important role in the diagnosis of PJI. The results of 16S rRNA PCR assays should be interpreted in parallel with clinical findings, the results of microbiological, and other laboratory tests.

Linezolid in the treatment of periprosthetic joint infection caused by coagulase-negative staphylococci

Background: Periprosthetic joint infection (PJI) caused by coagulase-negative staphylococci (CoNS) is increasingly common and is sometimes treated with off-label use of linezolid. Methods: We conducted a retrospective study of patients with PJI caused by CoNS treated with surgical intervention and orally administrated linezolid during the period 1995-2014 (n = 28). Clinical outcomes and adverse events related to linezolid administration were evaluated. Mean time to follow-up was 4.3 years (range: 0.2-12). Results: Twenty-two of 28 patients were infection-free at follow-up. No CoNS strain was resistant to vancomycin, but 16 of 28 were resistant to rifampicin, 23 of 28 to clindamycin and 20 of 27 to quinolones. The mean duration of linezolid treatment was 4.2 weeks (range: 1-12). Eleven of 28 patients had an adverse event related to the antimicrobial treatment, and four had to discontinue linezolid, but all adverse events were reversible within 2 months after discontinuation. Conclusions: Oral linezolid administration combined with adequate surgical treatment may be useful for the treatment of PJIs caused by CoNS.

Surgical Technique to Manage Periprosthetic Fractures of the Knee in Patients with Infected Leg Ulcers: A Report of Two Cases

CASES

We describe 2 cases of nonagenarians with periprosthetic knee fractures that were not amenable to either standard internal fixation nor prosthesis revision because of infected leg ulcers in the same limb. The fractures were internally fixed by percutaneous insertion of medial and lateral plates that spanned the knee. Both patients returned to their baseline level of activity without developing surgical site infections.

CONCLUSIONS

Percutaneous bridging plates that span the knee are a useful option for treating these difficult cases.

Bilateral native knee septic arthritis due to Propionibacterium acnes; a case report and review of literature

Propionibacterium acnes should be considered in any case of indolent septic arthritis. Cultures should be followed for 2 weeks as our cultures were negative for 7 days before growing P. acnes. Irrigation and debridement followed by antibiotics is the standard of care.

Indolent Propionibacterium acnes infection associated with orthopedic hardware in the ankle: A case report and literature review

Propionibacterium acnes (P. acnes) infections of the foot and ankle are very rare and require a unique approach to prevention, diagnosis, and treatment. Clinicians should consider P. acnes as a cause for all late and indolent orthopedic infections, as appropriate surgical and medical management can result in a good outcome.

Prospective Analysis of a Sterile, Semi-automated Tissue Biopsy Homogenization Method in the Diagnosis of Prosthetic Joint Infections

BACKGROUND/AIM

Prosthetic joint infection (PJI) remains a serious complication of total joint arthroplasty. To effectively treat PJI, it is essential to identify the microorganism causing it and be able to combine correct surgical and anti-infective treatments. This cannot always be achieved with the currently employed diagnostic methods. The aim of this study was to evaluate a semi-automated tissue biopsy bead milling method (Ultra-TurrAX, Axonlab AG; Reichenbach, Germany) based on the hypothesis that the results are more sensitive for microbe detection and less prone to contamination.

MATERIALS AND METHODS

We included 35 consecutive patients undergoing 38 hip or knee arthroplasty revisions in this study. In addition to manually processed biopsies, we processed tissue specimens harvested intraoperatively using a semi-automated method. The sensitivity and specificity of both methods were calculated using MSIS criteria and sonication results as gold standards.

RESULTS

For total hip arthroplasty samples were evaluated separately based on MSIS criteria as the reference standard, Ultra-TurrAX processing yielded 81% (62-100%) sensitivity and 100% specificity. Using sonication as the gold standard, a sensitivity of 80% (60-100%) and specificity of 80% (45-100%) were calculated. In total knee arthroplasty, Ultra-TurrAX processing yielded 27% (1-54%) sensitivity and 57% (20-94%) specificity when using MSIS criteria as the gold standard. Using sonication as the gold standard, a sensitivity of 60% (17-100%) and specificity of 77% (54-100%) were calculated.

CONCLUSION

This is the first study to analyze bead mill processing in total hip and knee arthroplasty revisions in a consecutive patient series. The method's sensitivity was comparable to and its specificity superior to regular sample processing results reported in the literature with respect to hip arthroplasties and to both hip and knee arthroplasties collectively. With respect to total knee arthroplasties, the method fared worse in our collective, most likely due to the small number of patients in the sample. Integrating the method into the clinical workflow allowed for speedier and more efficient sample handling and processing. The theoretical advantage of a lower risk of contamination because of fewer manual processing steps is, in our opinion, valid.

Multidrug-Resistant Organisms in the Setting of Periprosthetic Joint Infection-Diagnosis, Prevention, and Treatment

BACKGROUND

Periprosthetic joint infection (PJI) is a rare yet challenging problem in total hip and knee arthroplasties. The management of PJI remains difficult primarily due to the evolution of resistance by the infecting organisms.

METHODS

This review profiles acquired mechanisms of bacterial resistance and summarizes established and emerging techniques in PJI diagnosis, prevention, and treatment.

RESULTS

New techniques in PJI diagnosis and prevention continue to be explored. Antibiotics combined with 1 or 2-stage revision are associated with the higher success rates and remain the mainstay of treatment.

CONCLUSION

With higher prevalence of antibiotic-resistant organisms, novel antibiotic implant and wound care materials, improved methods for organism identification, and well-defined organism-specific treatment algorithms are needed to optimize outcomes of PJI.

Non-compliance with IDSA guidelines for patients presenting with methicillin-susceptible Staphylococcus aureus prosthetic joint infection is a risk factor for treatment failure

OBJECTIVE

The long-term impact of treatment strategies proposed by the IDSA guidelines for patients presenting with methicillin-susceptible S. aureus (MSSA) prosthetic joint infection (PJI) is not well-known.

PATIENTS AND METHODS

Retrospective (2000-2010) cohort study including patients presenting with MSSA hip or knee PJI. A univariate Cox analysis was performed to determine if the non-compliance with IDSA surgical guidelines was a risk factor for treatment failure.

RESULTS

Eighty-nine patients with a mean follow-up of 2.8 years were included. Non-compliance with IDSA surgical guidelines was associated with treatment failure (hazard ratio 2.157; 95% CI [1.022-4.7]). The American Society of Anesthesiologists score, inadequate antimicrobial therapy, and a rifampicin-based regimen did not significantly influence patient outcome.

CONCLUSION

Based on the IDSA guidelines, if a patient presenting with MSSA PJI is not eligible for implant retention, complete implant removal is needed to limit treatment failure.

Complete Eradication of Biofilm From Orthopedic Materials

BACKGROUND

Interest exists in finding alternatives to current management strategies in periprosthetic joint infections, which typically include a 2-stage revision with placement of an antibiotic spacer and delayed placement of a new implant. We studied the efficacy of autoclaving, ultrasonication, and mechanical scrubbing for sterilization and biofilm eradication on infected cobalt-chrome discs.

METHODS

Strains of Staphylococcus aureus MRSA252 or Staphylococcus epidermidis RP62A were grown on the discs. For each strain, discs were divided into 5 groups (5 discs each) and exposed to several sterilization and biofilm eradication treatments: (1) autoclave, (2) autoclave + sonication, (3) autoclave + saline scrub, (4) autoclave + 4% chlorhexidine (CHC) scrub, and (5) autoclave + sonication + CHC scrub. Sterilization and biofilm eradication were quantified with crystal violet assays and scanning electron microscopy.

RESULTS

Relative to nontreated controls, autoclaving alone reduced biofilm load by 33.9% and 54.7% for MRSA252 and RP62A strains, respectively. Biofilm removal was maximized with the combined treatment of autoclaving and CHC scrub for MRSA252 (100%) and RP62A (99.5%). The addition of sonication between autoclaving and CHC scrubbing resulted in no statistically significant improvement in biofilm removal. High-resolution scanning electron microscopy revealed no cells or biofilm for this combined treatment.

CONCLUSION

Using 2 commonly encountered bacterial strains in periprosthetic joint infection, infected cobalt-chrome discs were sterilized and eradicated of residual biofilm with a combination of autoclaving and CHC scrubbing.

Role of Nuclear Medicine for Diagnosing Infection of Recently Implanted Lower Extremity Arthroplasties

Infection is an infrequent complication of lower extremity prosthetic joint surgery. Approximately one-third develop within 3 months (early), another third within 1 year (delayed), and the remainder more than 1 year (late) after surgery. Diagnosing prosthetic joint infection, especially in the early postoperative period during the first year, is challenging. Pain is almost always present. The presence of fever is variable, ranging from less than 5% to more than 40% of patients. Leukocytosis is a poor predictor of infection. After primary uncomplicated arthroplasty, the C-reactive protein remains elevated for up to 3 weeks. The erythrocyte sedimentation rate can remain elevated for up to 1 year. Although joint aspiration with culture, the definitive preoperative diagnostic procedure, is specific, its sensitivity is variable. Plain radiographs lack sensitivity and specificity. Radionuclide studies are useful for evaluating painful joint replacements, but data on their utility during the early postoperative period are limited. During the first year after arthroplasty insertion, the bone scan can exclude infection. It is a good "rule-out" test, but it is not reliable for "ruling in" infection. Gallium-67 accumulates in normally healing surgical incisions and in aseptic inflammation. With an accuracy of 60%-80% for diagnosing prosthetic joint infection, there is little role for this radiopharmaceutical for evaluating prosthetic joints, regardless of age. Although data about diagnosing prosthetic joint infection with ¹⁸F-FDG in the early postoperative period are lacking, uptake of this radiopharmaceutical in a variety of postoperative settings for variable time periods is well known. Furthermore, its utility for diagnosing prosthetic joint infection in general, after nearly 2 decades of investigation, remains to be established. Indium-111-labeled leukocytes do not accumulate in normally healing surgical wounds, and in combination with marrow imaging, the test is about 90% accurate for diagnosing prosthetic joint infection. Preliminary data indicate a comparable accuracy in the early postoperative period.

Staphylococcus capitis isolated from prosthetic joint infections

Further knowledge about the clinical and microbiological characteristics of prosthetic joint infections (PJIs) caused by different coagulase-negative staphylococci (CoNS) may facilitate interpretation of microbiological findings and improve treatment algorithms. Staphylococcus capitis is a CoNS with documented potential for both human disease and nosocomial spread. As data on orthopaedic infections are scarce, our aim was to describe the clinical and microbiological characteristics of PJIs caused by S. capitis. This retrospective cohort study included three centres and 21 patients with significant growth of S. capitis during revision surgery for PJI between 2005 and 2014. Clinical data were extracted and further microbiological characterisation of the S. capitis isolates was performed. Multidrug-resistant (≥3 antibiotic groups) S. capitis was detected in 28.6 % of isolates, methicillin resistance in 38.1 % and fluoroquinolone resistance in 14.3 %; no isolates were rifampin-resistant. Heterogeneous glycopeptide-intermediate resistance was detected in 38.1 %. Biofilm-forming ability was common. All episodes were either early post-interventional or chronic, and there were no haematogenous infections. Ten patients experienced monomicrobial infections. Among patients available for evaluation, 86 % of chronic infections and 70 % of early post-interventional infections achieved clinical cure; 90 % of monomicrobial infections remained infection-free. Genetic fingerprinting with repetitive sequence-based polymerase chain reaction (rep-PCR; DiversiLab®) displayed clustering of isolates, suggesting that nosocomial spread might be present. Staphylococcus capitis has the potential to cause PJIs, with infection most likely being contracted during surgery or in the early postoperative period. As S. capitis might be an emerging nosocomial pathogen, surveillance of the prevalence of PJIs caused by S. capitis could be recommended.

Does Preoperative Antimicrobial Prophylaxis Influence the Diagnostic Potential of Periprosthetic Tissues in Hip or Knee Infections?

BACKGROUND

Undiagnosed low-grade prosthetic joint infections (PJI) are recognized as an important reason for early failure of presumably aseptic revisions. Preoperatively administered antimicrobial prophylaxis reduces the incidence of PJI but it may reduce the sensitivity of microbiologic periprosthetic tissue cultures and consequently increase the incidence of undiagnosed septic prosthetic joint failures, which can lead to catastrophic serial revisions.

QUESTIONS/PURPOSES

We wished to determine whether administration of preoperative antibiotics decreases the likelihood of diagnosing PJI in patients undergoing revision hip or knee arthroplasty in whom infection is suspected.

METHODS

We prospectively enrolled and evaluated 40 patients (29 with THAs and 11 with TKAs) who met the following inclusion criteria: older than 18 years, with suspected PJI of unknown cause, undergoing surgical revision. After arthrotomy, three tissue samples were obtained for microbiologic analysis and diagnosis, and antimicrobial prophylaxis (cefazolin 2 g intravenously) then was administered. Later during the procedure, but before débridement and irrigation, the second set of three tissue samples was obtained from the same surgical area and was cultured. Tissue concentration of prophylactic antibiotic was verified with the second set of samples. A positive culture result was defined as one or more positive cultures (growth on agar at or before 14 days). We then compared the yield on the microbiologic cultures obtained before administration of antibiotics with the yield on the cultures obtained after antibiotics were administered. An a priori analysis was performed; with the numbers available, we had 98% power to detect a difference in diagnostic sensitivity of 33%.

RESULTS

With the numbers available, we found no difference in the likelihood that an infection would be diagnosed between the samples obtained before and after administration of antimicrobial prophylaxis (odds ratio [OR] for positive microbial culture = 0.99; 95% CI, 0.40-2.48; p = 0.99). All measured tissue concentrations of cefazolin were greater than the minimum inhibitory concentration, therefore we found that antibiotic prophylaxis was adequate at the time of second-set tissue specimen recovery.

CONCLUSIONS

Results from this small, prospective series suggest that preoperative antimicrobial prophylaxis may be administered safely even in patients undergoing revision hip or knee arthroplasty in which microbiologic sampling is planned without compromising the diagnostic sensitivity of tissue sample cultures. However, before applying our results more generally, our findings need to be confirmed in larger, multicenter studies that would allow evaluation by sex, procedure, bacteriology, and other potentially important factors.

LEVEL OF EVIDENCE

Level I, diagnostic study.

Prevention and treatment of Staphylococcus aureus biofilms

S. aureus colonizes both artificial and tissue surfaces in humans causing chronic persistent infections that are difficult to cure. It is a notorious pathogen due to its antibiotic recalcitrance and phenotypic adaptability, both of which are facilitated by its ability to develop biofilms. S. aureus biofilms challenge conventional anti-infective approaches, most notably antibiotic therapy. Therefore there is an unmet need to develop and include parallel approaches that target S. aureus biofilm infections. This review discusses two broad anti-infective strategies: (1) preventative approaches (anti-biofilm surface coatings, the inclusion of biofilm-specific vaccine antigens); and (2) approaches aimed at eradicating established S. aureus biofilms, particularly those associated with implant infections. Advances in understanding the distinct nature of S. aureus biofilm development and pathogenesis have led to growing optimism in S. aureus biofilm targeted anti-infective strategies. Further research is needed however, to see the successful administration and validation of these approaches to the diverse types of infections caused by S. aureus biofilms from multiple clinical strains.

Antibiotic prophylaxis for preventing infectious complications in orthognathic surgery

BACKGROUND

Orthognathic surgery (OS) is a term that refers to many elective surgical techniques to correct facial deformity; the associated malocclusion and functional disorders related to the stomatognathic system. Whilst such surgery is classed as "clean-contaminated", the usefulness of and the most appropriate regimen for antibiotic prophylaxis in these patients are still debated.

OBJECTIVES

To assess the effects of antibiotic prophylaxis for preventing surgical site infection (SSI) in people undergoing orthognathic surgery.

SEARCH METHODS

In June 2014, we searched the Cochrane Wounds Group Specialised Register; the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library); Ovid MEDLINE; Ovid MEDLINE (In-Process & Other Non-Indexed Citations); Ovid EMBASE; and EBSCO CINAHL. We also searched Google Scholar and performed manual searches in journals relevant to the topic, conference proceedings and lists of references of potentially included articles. We did not restrict the search and study selection with respect to language, date of publication or study setting.

SELECTION CRITERIA

We included randomised controlled trials (RCTs) involving people undergoing orthognathic surgery comparing one regimen of antibiotic prophylaxis with any other regimen or placebo. The primary outcome was SSI, and secondary outcomes were systemic infections, adverse events, duration of hospital stay and health-related quality of life. Two review authors screened articles independently.

DATA COLLECTION AND ANALYSIS

Data were abstracted independently by two review authors, and agreement was checked. Risk of bias was assessed using the Cochrane risk of bias tool. Antibiotic regimens were classified as preoperative (one dose before surgery), short-term (before or during surgery and/or during the same day of surgery) and long-term (before or during surgery and longer than one day after surgery) antibiotic prophylaxis. Random-effects meta-analyses using inverse variance methods were undertaken when possible. We report risk ratios (RRs) and their corresponding 95% confidence intervals (CIs).

MAIN RESULTS

A total of 11 trials were included in this review. Most of the studies had an unclear risk of bias prompting us to downgrade the quality of evidence for our outcomes. Seven of these trials provided evidence for the main comparison and the primary outcome and these were pooled. Overall, long-term antibiotic prophylaxis probably reduces the risk of SSI (plausible effects range between a 76% to a 0.26% relative reduction in SSI with long-term antibiotic prophylaxis) (472 participants; RR 0.42, 95% CI 0.24 to 0.74; moderate-quality evidence). There is uncertainty surrounding the relative effects of short-term antibiotics compared with a single dose (220 participants; RR 0.34, 95% CI 0.09 to 1.22; low-quality evidence). No reports described adverse effects associated with the drugs in those trials that reported in this outcome. None of these trials assessed or reported data regarding other outcomes, and information was insufficient to show whether a specific antibiotic is better than another.

AUTHORS' CONCLUSIONS

For people undergoing orthognathic surgery, long term antibiotic prophylaxis decreases the risk of SSI compared with short-term antibiotic prophylaxis and the is uncertainty of whether short-term antibiotic prophylaxis decreases SSi risk relative to a single pre-operative dose of prophylactic antibiotics.

Pulse lavage is inadequate at removal of biofilm from the surface of total knee arthroplasty materials

In acute periprosthetic infection, irrigation and debridement with component retention has a high failure rate in some studies. We hypothesize that pulse lavage irrigation is ineffective at removing biofilm from total knee arthroplasty (TKA) components. Staphylococcus aureus biofilm mass and location was directly visualized on arthroplasty materials with a photon collection camera and laser scanning confocal microscopy. There was a substantial reduction in biofilm signal intensity, but the reduction was less than a ten-fold decrease. This suggests that irrigation needs to be further improved for the removal of biofilm mass below the necessary bioburden level to prevent recurrence of acute infection in total knee arthroplasty.

Role and antimicrobial resistance of staphylococci involved in prosthetic joint infections

PURPOSE

Staphylococci are responsible for approximately half of all prosthetic joint infections (PJIs) and they are often multi-drug resistant. The main purpose of this study was to evaluate the incidence of PJIs caused by staphylococci in our hospital from March 2010 to February 2012, with particular reference to antibiotic resistance in relation to their classification as contaminant or infecting isolates.

METHODS

We analyzed samples recovered from 124 patients: most of them were male (55.8%) and the mean age was 66 ± 14 years. Prostheses derived from hip (54.8%) or knee (45.2%) replacement and they were processed by sonication. Isolates were identified using conventional biochemical methodologies. Antimicrobial susceptibility testing was carried out using the disk diffusion method as described by the European Committee on Antimicrobial Susceptibility Testing.

RESULTS

A total of 135 staphylococci were isolated: the prevalent species was Staphylococcus aureus, but, on the whole, coagulase-negative staphylococci represented 57% of cases. Fifty-one isolates were recovered from a single sample and were therefore defined as contaminant. Linezolid and glycopeptides showed excellent activity versus all the tested isolates, while penicillin, levofloxacin, and erythromycin offered reduced activity against staphylococci. Interestingly, high resistance rates were observed for coagulase-negative staphylococci other than S. epidermidis classified as contaminant strains.

CONCLUSIONS

We observed a remarkable spread of coagulase-negative staphylococci as causative agents of PJIs; but most of them were classified as contaminants. However, because of their low susceptibility to the antibiotics tested, further studies are necessary to evaluate their role as pathogens or as true contaminants.

Clinical characteristics, microbiology, and outcomes of prosthetic joint infection in Taiwan

BACKGROUND

Prosthetic joint infection (PJI) after total knee or hip replacement is a devastating complication associated with substantial morbidity and economic cost. The incidence of prosthetic joint infection is increasing as the use of mechanical joint replacement increases. The treatment approach to prosthetic joint infection is based on different clinical situations such as a patient's comorbidities, epidemic microbiology data, and surgical procedures. The aim of our study was to understand clinical characteristics of prosthetic joint infection, the microbiology of the prosthetic joint infection, and the outcomes of different treatment strategies during 2006-2011.

METHODS

We retrospectively collected cases of prosthetic joint infection in the National Taiwan University Hospital between January 1, 2006 and December 31, 2011. The patients' characteristics, microbiology, outcomes, and factors associated with treatment success were recorded.

RESULTS

One hundred and forty-four patients were identified as having PJI. Of these, 92 patients were entered into per-protocol analysis. Staphylococcus aureus was the most common causative organism (29.9%), followed by coagulase-negative Staphylococci (16.7%), and Enterococci (9.7%). The overall treatment success rate was 50%. Patients who received a two-stage revision had a better outcome, compared to patients who underwent other types of surgeries (70% vs. 32.7%, respectively; p < 0.001). In multivariate analysis, the two-stage revision was significantly associated with treatment success (odds ratio = 3.923, 95% confidence interval = 1.53-10.04).

CONCLUSION

Our study demonstrates that Staphylococcus aureus was the most common causative organisms in PJI. Performing two-stage revisions was significantly associated with a better outcome.

Revision in cemented and cementless infected hip arthroplasty

Infection is a frequent cause of failure after joint replacement surgery. The infection rate after total hip arthroplasty (THA) has been reduced to 1-2% in the last years. However, it still represents a challenging problem for the orthopedic surgeon. Difficulty of therapeutic approach, and poor functional outcomes together with length of treatment and overall cost are the main burden of this issue. Even the diagnosis of an infected hip could be challenging although it is the first step of an accurate treatment. At the end, many cases require removing the implants. Afterwards, the treatment strategy varies according to authors with three different procedures: no re-implantation, immediate placement of new implants or a two-stage surgery re-implantation. Based on the most recently systematic review there is no suggestion that one- or two-stage revision methods have different re-infection outcomes. The two-stage implant-exchange protocol remains the gold standard. It is considered as the most efficacious clinical approach for the treatment of periprosthetic infection, especially in patients with sinus tracts, swelling, extended abscess formation in depth and infection of Methicillin Resistant Staphylococcus Aureus (MRSA), and other multidrug-resistant bacteria as reported in recent consensus documents.

High incidence of postoperative hypothermia in total knee and total hip arthroplasty: a prospective observational study

Hypothermia, a body temperature of <36°C, has been shown to increase cardiac mortality, the incidence of postoperative infections, and the length of hospitalization following general surgery. However, studies assessing the incidence of hypothermia during primary total hip and total knee arthroplasty (THA and TKA) have not previously been demonstrated. In this prospective observational study, incidence of hypothermia was measured among 672 patients (415 underwent THA and 257 TKA). The incidence of hypothermia for THA and TKA was 26.3 and 28.0%, respectively. In conclusion, over a quarter of patients in this study are exposed to hypothermia. This study highlights the requirement for interventions to prevent peri-operative hypothermia.

Outpatient parenteral antibiotic therapy in primary hip and knee arthroplasty infection managed with debridement and retention of prosthesis: a retrospective cohort study

BACKGROUND

Attempted joint salvage of infected primary arthroplasty traditionally has utilized joint washouts in combination with costly long-term inpatient parenteral antibiotic regimens. Outpatient and home parenteral antibiotic therapy (OHPAT) represents a potential alternative. However, there is a lack of published data on its value for primary deep arthroplasty infection. This paper describes the surgical and microbiologic outcomes of a cohort of patients with deep arthroplasty infections treated with OHPAT after surgical washout and debridement.

METHODS

Local OHPAT records identified all patients who underwent attempted joint salvage of a primary hip or knee replacement complicated by a deep post-operative infection between February 2006 and February 2009. Minimum follow-up for all patients was 24 mos. For each patient, hospital records were reviewed to ascertain the effectiveness of treatment.

RESULTS

In total, 14 patients (10 total knee replacements; four total hip replacements) were identified from the records. Eleven joints (79%) were salvaged. There was a trend toward a higher salvage rate with early infection (<6 mos after primary surgery), with eight of nine joints (89%) being salvaged, versus 60% (three of five) for later presentation. Methicillin-sensitive Staphylococcus aureus was the most common organism identified (43% of cases), and 57% of infections were polymicrobial. The average duration of OHPAT was 58 days. Two patients were readmitted because of clinical deterioration, both of whom later required revision. All patients, regardless of their outcomes, stated they were satisfied with the OHPAT service and believed it was more convenient than inpatient treatment. We estimate OHPAT saved approximately £13,000 per patient episode.

CONCLUSIONS

Use of OHPAT for deep infection after primary arthroplasty has a high success rate. It is effective at identifying patients failing treatment, is cost-effective, and has a high level of patient satisfaction.

Clinical indicators in surgery: a critical review of the Australian experience

BACKGROUND

A set of clinical measures (indicators), developed by an Australian Council on Healthcare Standards (ACHS) and Royal Australasian College of Surgeons (RACS) working party, was introduced into the accreditation programme in 1997. Although early qualitative and quantitative reporting by health-care organizations (HCOs) reflected their value in stimulating change, the number of HCOs reporting data on this set of clinical indicators (CIs) has declined, despite an increase in the number of HCOs reporting data on the CIs programme overall. Possible reasons for this decline were sought.

METHODS

A retrospective review of prospectively collected surgical CI data was performed, a national survey of stakeholders in the ACHS programme was conducted and a comparison was made with published international data.

RESULTS

From a maximum of 247 HCOs reporting data in 2002, the number fell to 168 by 2011. While favourable trends were evident with some CIs, for example, a decline in the rate of negative histology in childhood appendicectomy and in the rate of in-hospital infection in total hip joint replacement, there was minimal change with many of the CIs, suggesting limited responsiveness as measures of care. In the national survey, stakeholder's response was positive overall, but there was a requirement for regular review of CIs. Although some colleges viewed the CIs as simplistic and not reliable, comparisons with similar measures available in the international literature were favourable.

CONCLUSIONS

Possible reasons for the declining number of HCOs reporting surgical CI data are a lack of a recent revision of the CIs and a lack of engagement of clinicians from the RACS. Revision of the surgical CI set is required.

Clostridium perfringens infection complicating periprosthetic fracture fixation about the hip: successful treatment with early aggressive debridement

Periprosthetic fracture and infection are both challenges following hip arthroplasty. We report the case of an 87 year old female who underwent open reduction and internal fixation of a periprosthetic femoral fracture. Her post-operative course was complicated by infection with Clostridium perfringens. Early aggressive antibiotic treatment and surgical debridement were successful, and allowed retention of the original components.

Eight years experience in treatment of prosthetic joint infections at a teaching hospital in Central Taiwan

BACKGROUND/PURPOSE

Prosthetic joint infection (PJI) has become an important issue in the management of patients who receive prostheses. We compared the clinical outcomes of PJIs caused by Gram-negative bacteria (GN PJIs) and Gram-positive bacteria (GP PJIs).

METHODS

Patients with culture-proven PJIs admitted to China Medical University Hospital between March 2001 and March 2009 were included in this retrospective study.

RESULTS

Fifty-nine patients were diagnosed with PJI during the study period. Nineteen patients had GN PJIs (mean age: 68 years) and 40 had GP PJIs (mean age: 61 years). The most common comorbid condition was diabetes mellitus (23.7%) and the most common presentation was joint pain (79.7%). Staphylococcus aureus was the most common pathogen, whereas Klebsiella pneumoniae was the most common Gram-negative pathogen. The GN PJI group included more cases of hematogenous infection (36.8% vs. 20%; p < 0.001), showed a shorter interval between onset of infection symptoms and surgical intervention (median: 8 days vs. 21 days; p = 0.04), and required longer medical treatment (median: 259 days vs. 161 days; p = 0.04). In comparison with patients whose prostheses were eventually removed, patients whose prostheses were not removed had a shorter interval between onset of infection symptoms and surgical intervention (median: 6 days vs. 90 days; p = 0.004 and median: 6 days vs. 44 days; p = 0.04) in the GP PJI and GN PJI groups, respectively.

CONCLUSION

GN PJI was less common than GP PJI, but GN PJI was more complicated and required longer treatment. Prospective randomized clinical studies are needed to investigate whether prosthesis implantation should be reserved if the patient undergoes early surgical intervention for PJI.