Analysis of postoperative and hematogenous prosthetic joint-infection microbiological patterns in a large cohort

Moving Beyond Systemic Inflammatory Response Syndrome and Bacteremia: Are Modern Critical Care Calculators Useful in Predicting Debridement, Antibiotics, and Implant Retention Treatment Outcomes in Periprosthetic Joint Infection?

BACKGROUND

In critically ill periprosthetic joint infection (PJI) patients, surgeons need to balance the need for aggressive, definitive treatment against the health state of a potentially unstable patient. A clear understanding of the association between treatment outcomes and assessment scores for sepsis would benefit clinical decision-making in these urgent cases. The current study evaluates the effect of critical illness on debridement, antibiotics, and implant retention (DAIR) outcomes, as defined by systemic inflammatory response syndrome (SIRS) and, for the first time, by contemporary markers quick sequential organ failure assessment (qSOFA) and Modified Early Warning Score (MEWS).

METHODS

We retrospectively identified 253 patients who underwent DAIR for PJI at a single institution between 2017 and 2021. The SIRS, qSOFA, and MEWS scores were calculated based on variables on admission. A DAIR treatment failure, defined as reoperation or mortality, was measured at 90 days and two years. Univariate analysis was used to determine the association between elevated critical care scores and DAIR failure.

RESULTS

The DAIR treatment success was 59% at two years, with hip procedures and Charlson comorbidity index ≥ one independently associated with higher odds of DAIR failure. There were 43 patients (16%) who presented with SIRS; however, only four (2%) had positive qSOFA scores. Neither SIRS nor qSOFA was predictive of DAIR failure. Only for knees, elevated MEWS scores were predictive of 90-day DAIR failure (P = 0.019).

CONCLUSIONS

Over one in six patients undergoing DAIR for PJI presented with SIRS, while only one in 50 had a positive qSOFA. The SIRS and qSOFA scores were not predictive of DAIR failure. Elevated MEWS scores were associated with DAIR failure at 90 days postoperatively in knee PJIs only and should be confirmed in a larger cohort. Our results suggest that SIRS is not predictive of DAIR outcomes, possibly because it overestimates the proportion of critically ill patients.

Application value of baicalein in the management of periprosthetic joint infection: a preliminary in vitro study

BACKGROUND

This study aims to evaluate the efficacy of baicalein, a flavonoid derived from Scutellaria baicalensis, against Staphylococcus aureus (S. aureus), focusing on its inhibitory and eradicative effects on biofilms, as well as its cellular cytotoxicity. The goal is to provide preliminary evidence for its potential application in the management of periprosthetic joint infection (PJI).

METHODS

The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of baicalein against the standard strain of S. aureus ATCC 29213, a clinical strain of methicillin-sensitive S. aureus 115 (MSSA 115), and a clinical strain of methicillin-resistant S. aureus 49 (MRSA 49) were determined using broth microdilution and colony counting methods. Bactericidal kinetics over a 24-h period were evaluated using a time-kill assay. Biofilm inhibition and eradication were assessed on 96-well and titanium alloy plates, while the cellular cytotoxicity of baicalein was examined using the cell counting kit-8 (CCK-8) assay on human primary synovial fibroblasts and chondrocytes.

RESULTS

The MIC of baicalein was 32 μg/mL for the ATCC 29213, and 64 μg/mL for both MSSA115 and MRSA49. Meanwhile, the MBC for all three strains was 128 μg/mL. Baicalein exhibited a time-dependent bactericidal activity, with maximum efficacy at 24 h. Biofilm inhibition was evident at concentrations equal to or exceeding the MIC, as confirmed by biofilm biomass and metabolic activity assays, along with scanning electron and confocal laser microscope. However, baicalein was unable to completely eradicate preformed biofilms. Baicalein demonstrated significant cytotoxic effects on both synovial fibroblasts and chondrocytes after exposure for 16 and 24 h.

CONCLUSIONS

Baicalein shows significant bactericidal effects and effectively inhibits S. aureus biofilm formation. These findings suggest its potential as a promising local antibacterial agent for postoperative continuous intra-articular lavage in the treatment of S. aureus-related early postoperative or acute hematogenous PJIs.

Simultaneous Periprosthetic Joint Infection and Infective Endocarditis: Prevalence, Risk Factors, and Clinical Presentation

BACKGROUND

Infective endocarditis (IE) and periprosthetic joint infections (PJI) occur due to hematogenous bacterial spread, theoretically increasing the risk for concurrent infections. There is a scarcity of literature investigating this specific association. We aimed to assess the prevalence, comorbidities, and clinical presentation of patients who have simultaneous PJI and IE.

METHODS

We retrospectively identified 655 patients (321 men, 334 women; 382 total hip arthroplasty, 273 total knee arthroplasty) who developed a PJI from July 1, 2015, to December 31, 2020, at one institution. There were two groups created: patients diagnosed with PJI with IE (PJI + IE) and PJI patients who did not have IE (PJI). We analyzed clinical outcomes and comorbidities.

RESULTS

There were nine patients who had PJI with IE (1.4% of PJI patients). The C-reactive protein (170.9 versus 78, P = 0.026), Elixhauser comorbidity score (P = 0.002), length of hospital stay (10.9 versus 5.7 days, P = 0.043), and the 2-year postdischarge mortality rate (55.6 versus 9.0%, P = 0.0007) were significantly greater in the PJI + IE group. Comorbidities such as iron deficiency anemia (P = 0.03), coagulopathy (P = 0.02), complicated diabetes mellitus (P = 0.02), electrolyte disorders (P = 0.01), neurologic disease (P = 0.004), paralysis (P = 0.04), renal failure (P = 0.0001), and valvular disease (P = 0.0008) occurred more frequently in the PJI + IE group. Modified Duke's criteria were met for possible or definite IE in eight of the nine patients.

CONCLUSIONS

Concurrent PJIs and IE, although rare, are a potentially devastating disease state with increased length of hospital stay and 2-year mortality rates. This emphasizes the need for appropriate IE workups in patients who have a PJI. The modified Duke's criteria are effective in establishing a diagnosis for IE in this scenario.

Carbon-Infiltrated Carbon Nanotube Topography Reduces the Growth of Staphylococcus aureus Biofilms

Orthopedic implant-associated infections are a growing problem. These infections are often associated with bacterial biofilms, such as those formed by Staphylococcus aureus. Nanotextured surfaces can reduce or prevent the development of bacterial biofilms and could help reduce infection rates and severity. Previous work has shown that a carbon-infiltrated carbon nanotube (CICNT) surface reduces the growth of S. aureus biofilms. This work expands on previous experiments, showing that the topography of the CICNT, rather than its surface chemistry, is responsible for the reduction in biofilm growth. Additionally, the CICNT surface does not reduce biofilm growth by killing the bacteria or by preventing their attachment. Rather it likely slows cell growth, resulting in fewer cells and reduced biofilm formation.

Cutibacterium acnes and its complex host interaction in prosthetic joint infection: Current insights and future directions

Cutibacterium acnes is a commensal Gram-positive anaerobic bacterium that can also act as an opportunistic pathogen in various diseases, particularly in prosthetic joint infections (PJI). Throughout this review, we delve into the current understanding of the intricate interactions between C. acnes and host cells and discuss bacterial persistence in the host. C. acnes colonization and subsequent PJI set-up represent complex processes involving bacterial adhesion, immune recognition, and host response mechanisms. We highlight existing knowledge and gaps in specific host-pathogen interactions and stress the importance of acquiring additional information to develop targeted strategies for preventing and treating C. acnes-related PIJ.

One-stage exchange strategy with extensive debridement for chronic periprosthetic joint infection following total knee arthroplasty is associated with a low relapse rate in non-selected patients: a prospective single-center analysis

PURPOSE

This prospective clinical cohort was undertaken to determine the long-term risks of reinfection and all-cause aseptic failure after 1-stage exchange total knee arthroplasties (TKA) in a large series of consecutive patients with periprosthetic joint infection (PJI) following TKA.

HYPOTHESIS

One-stage exchange for chronic PJI is an effective strategy, even in a non-selected population.

PATIENTS AND METHODS

Non-selected patients (152 with 154 PJI) undergoing 1-stage-exchange TKA for PJI (January 2003-August 2015) were prospectively included and monitored for ≥2 years. PJI following TKA satisfying Musculoskeletal Infection Society diagnostic criteria were documented by microbiological culture results of preoperative joint aspirates and/or intraoperative samples. The cumulative incidences of total reinfections (i.e., relapses or new infections) and aseptic revisions were assessed. The mean follow-up (FU) duration was 7.5 years post-reimplantation.

RESULTS

At the last follow-up, 35 knees had developed reinfections: 7 relapses and 28 new infections, with respective 14-year cumulative incidences of 4.8% and 20.6%. The 2-, 5- and 14-year cumulative total reinfection incidences were 12.3%, 21.3% and 24.3%, respectively. Respective 2-, 5-, 10- and 14-year aseptic component-revision incidences were 0.7%, 3.2%, 5.4% and 13.4%. Multivariate analysis retained male sex (HR 3.27, p < 0.01) and preoperative atrial fibrillation (HR 3.03; p = 0.01) as being significantly associated with greater risk of reinfection.

CONCLUSIONS

One-stage-exchange TKA with aggressive debridement for chronic PJI is apparently a valid strategy, even for non-selected patients. It was associated with a low relapse rate, prevented morbidity and avoided economic social costs of 2-stage exchange. New infections with a different microorganism were observed more frequently and occurred even after years of FU.

LEVEL OF EVIDENCE

II; Therapeutic.

Bacteriological sampling in revision surgery: When, how, and with what therapeutic impact?

Bacteriological sampling in orthopedic revision surgery for arthroplasty or internal fixation raises several questions. 1) When? And should sampling be systematic? Sampling should not be systematic in revision surgery, but only in case of suspected infection, in which case empirical antibiotic regimen should be systematically implemented. 2) How? Which tissues, how many and what transport? Only deep samples, preferably taken without ongoing antibiotic therapy, allow reliable interpretation of results. The optimal number of intra-operative samples is 5, or 3 if the laboratory uses seeding in aerobic and anaerobic vials. Samples should be transported to the laboratory within 2 h, at room temperature. 3) What conclusions can be drawn, using what references? There are several classifications, leading to divergent interpretation. The EBJIS (European Bone and Joint Infection Society) classification showed the best sensitivity in a multicenter study. 4) What duration of antibiotic washout before revision, and how to proceed if it cannot be achieved? The antibiotic-free period before sampling should be 14 days, or 21 days in case of prior treatment by cyclins, clindamycin, rifampicin or drugs with a very long half-life such as lipoglycopeptides, except when surgical intervention is required urgently. 5) How to deal with microbiological sampling and antibiotic prophylaxis at the time of revision surgery? Pursuing prophylactic antibiotic therapy during bone and joint implant revision does not greatly impair the value of intra-operative sampling. However, evidence of benefit of continuing antibiotic prophylaxis during revision arthroplasty is lacking. 6) What samples for atypic infection? Atypic micro-organisms (mycobacteria, fungi, etc.) require specific screening, guided by the clinical context and discussed before sampling is carried out. LEVEL OF EVIDENCE: V; expert opinion.

Never mind the bug: no differences in infection-free survival after periprosthetic joint infections with Staphylococcus aureus, Coagulase-negative Staphylococcus, or Streptococcus

Background

Periprosthetic joint infection (PJI) is a devastating complication following arthroplasty of the hip or knee joint and can be challenging to treat, depending on the underlying pathogen. There is still a debate whether streptococcal PJI are more difficult to treat than those caused by staphylococci. We aimed to investigate if the treatment results after PJI caused by Staphylococci aureus (S. aureus), Coagulase-negative Staphylococci spp. (CoNS) or Streptococci differ.

Patients and methods

This study was designed as a retrospective observational study on patients with PJI caused by either streptococci or staphylococci in the hip or knee treated at a tertiary referral center between 1998 and 2021. Patients were identified in the local PJI register and data were collected by medical chart review performed minimum 1 year after the index PJI. Patients with polymicrobial infections or incomplete data were excluded, leaving 299 patients with streptococcal or staphylococcal PJI for final analysis. These patients were categorized according to the underlying pathogen: 114 were S. aureus 121 were CoNS, and 64 Streptococci. Infection-free survival was defined as the absence of (1) further surgery to the index joint due to PJI, (2) suppressive antibiotic therapy, and (3) death due to PJI and was assessed using the Kaplan-Meier method. Cox regression models were fitted to estimate the risk of infection relapse adjusted for relevant confounders.

Results

We found no statistically or clinically significant difference in unadjusted survival between the three groups. Infection-free survival at 2 years was 71% (95%CI: 63-80) for S. aureus, 75% (95%CI: 67-84) for CoNS, and 60% (95%CI: 60-84) for Streptococci. The adjusted hazard ratios (HR) for the risk of infection relapse with S. aureus as the reference were 1.2 (95%CI: 0.7-2.0) for CoNS and 1.1 (95%CI: 0.6-2.0) for Streptococci. For all three groups of bacteria, survival was lower when DAIR was performed in comparison to exchange surgery.

Discussion

In our cohort, there was no difference in infection-free survival between the three groups. Albeit limitations due to the study design, it seems that streptococcal PJI do not have to be considered more difficult to treat than their staphylococcal counterparts. Exchange surgery shows favorable results in all groups compared to DAIR.

Risk of orthopaedic implant infection during bacteraemia

Orthopaedic implant material can get infected via haematogenous spread from a distant source at any point after implantation. The sources of haematogenous orthopaedic implant infections have been studied only for prosthetic joints. The most common source of infection has varied, but it can be, for example from the skin and soft tissues, cardiovascular system and dental infections. The risk for developing a periprosthetic joint infection (PJI) during bacteraemia is dependent on the pathogen: it is highest for Staphylococcus aureus and beta-haemolytic streptococci, but low for gram-negative bacteria. The risk for developing a (PJI) during Staphylococcus aureus bacteraemia (SAB) has varied between 12 and 41%; the risk for developing an infection in any orthopaedic implant in the extremities during SAB is probably almost the same as for prosthetic joints, but data are very limited. The risk of developing an infection in spinal implants during bacteraemia is not known, as it has not been studied. Especially in the case of SAB, infected orthopaedic implants are usually symptomatic, so asymptomatic implants do not routinely require further diagnostic work-up, such as synovial fluid aspiration.

Preoperative MRSA screening using a simple questionnaire prior elective total joint replacement

INTRODUCTION

The purpose of this study was to evaluate the management and results of our standarized protocol for preoperative identification of MRSA colonisation in patients undergoing primary total hip and knee replacement procedures.

METHODS

Following hospital protocol, between January 2016 and June 2019 37,745 patients awaiting elective joint replacement underwent a standardized questionnaire to assess the risk of MRSA infection, identifying patients requiring preoperative MRSA screening. An evaluation of the questionnaire identified effective questions for identifying infected patients. Furthermore, an analysis evaluated the impact of comorbidities or Charlson Comorbidity Index scores on positive MRSA colonization. Additionally, we evaluated the cost savings of targeted testing compared to testing all surgery patients.

RESULTS

Of the 37,745 patients, 8.057 (21.3%) were swabbed, with a total of 65 (0.81%) positive tests. From this group 27 (36.48%) who were treated were negative before surgery. Some of the questionnaire results were consistently associated with a higher chance of colonization, including hospitalization during the past year (47,7%), previous history of MRSA (44,6%), and agriculture or cattle farming related work (15,4%). By selectively testing high-risk patients identified through the questionnaire, we achieved a 79% reduction in costs compared to universal MRSA screening.

CONCLUSION

Our results suggest that the simple and standardized questionnaire is a valuable tool for preoperative screening, effectively identifying high-risk patients prone to MRSA colonisation. The risk of periprosthetic joint infection (PJI) and its associated sequelae may be reduced by this approach.

Prosthetic Joint Infection Research Models in NZW Rabbits: Opportunities for Standardization-A Systematic Review

Prosthetic joint infection (PJI) is a major complication following total arthroplasty. Rising antimicrobial resistance (AMR) to antibiotics will further increase therapeutic insufficiency. New antibacterial technologies are being developed to prevent PJI. In vivo models are still needed to bridge the translational gap to clinical implementation. Though rabbit models have been used most frequently, there is no consensus about methodology and measured outcomes. The PubMed, Scopus, and EMBASE databases were searched for literature on PJI in rabbit models. Data extraction included bias control, experimental design, and outcome measures of the NZW rabbit models in the articles. A total of 60 articles were included in this systematic literature review. The articles were divided into six groups based on the PJI intervention: no intervention used (21%), revision surgery (14%), prevention with only antibiotics (21%), prevention with surface modifications (7%), prevention with coatings (23%), and others (14%). Despite the current availability of guidelines and recommendations regarding experimental design, bias control, and outcome measures, many articles neglect to report on these matters. Ultimately, this analysis aims to assist researchers in determining suitable clinically relevant methodologies and outcome measures for in vivo PJI models using NZW rabbits to test new antimicrobial technologies.

Musculoskeletal infections through direct inoculation

Musculoskeletal infections consist of different clinical conditions that are commonly encountered in daily clinical settings. As clinical findings and even laboratory tests cannot always be specific, imaging plays a crucial role in the diagnosis and treatment of these cases. Musculoskeletal infections most commonly occur secondary to direct inoculation into the skin involuntarily affected by trauma, microorganism, foreign bodies, or in diabetic ulcers; direct infections can also occur from voluntary causes due to surgery, vaccinations, or other iatrogenic procedures. Hematogenous spread of infection from a remote focus can also be a cause for musculoskeletal infections. Risk factors for soft tissue and bone infections include immunosuppression, old age, corticosteroid use, systemic illnesses, malnutrition, obesity, and burns. Most literature discusses musculoskeletal infections according to the diagnostic tools or forms of infection seen in different soft tissue anatomical planes or bones. This review article aims to evaluate musculoskeletal infections that occur due to direct inoculation to the musculoskeletal tissues, by focusing on the traumatic mechanism with emphasis on the radiological findings.

Dhvar5-chitosan nanogels and their potential to improve antibiotics activity

Infection is one of the main causes of orthopedic implants failure, with antibiotic-resistant bacteria playing a crucial role in this outcome. In this work, antimicrobial nanogels were developed to be applied in situ as implant coating to prevent orthopedic-device-related infections. To that regard, a broad-spectrum antimicrobial peptide, Dhvar5, was grafted onto chitosan via thiol-norbornene "photoclick" chemistry. Dhvar5-chitosan nanogels (Dhvar5-NG) were then produced using a microfluidic system. Dhvar5-NG (1010 nanogels (NG)/mL) with a Dhvar5 concentration of 6 μg/mL reduced the burden of the most critical bacteria in orthopedic infections - methicillin-resistant Staphylococcus aureus (MRSA) - after 24 h in medium supplemented with human plasma proteins. Transmission electron microscopy showed that Dhvar5-NG killed bacteria by membrane disruption and cytoplasm release. No signs of cytotoxicity against a pre-osteoblast cell line were verified upon incubation with Dhvar5-NG. To further explore therapeutic alternatives, the potential synergistic effect of Dhvar5-NG with antibiotics was evaluated against MRSA. Dhvar5-NG at a sub-minimal inhibitory concentration (109 NG/mL) demonstrated synergistic effect with oxacillin (4-fold reduction: from 2 to 0.5 μg/mL) and piperacillin (2-fold reduction: from 2 to 1 μg/mL). This work supports the use of Dhvar5-NG as adjuvant of antibiotics to the prevention of orthopedic devices-related infections.

Antibiotics with antibiofilm activity - rifampicin and beyond

The management of prosthetic joint infections is a complex and multilayered process that is additionally complicated by the formation of bacterial biofilm. Foreign material provides the ideal grounds for the development of an intricate matrix that hinders treatment and creates a difficult environment for antibiotics to act. Surgical intervention is often warranted but requires appropriate adjunctive therapy. Despite available guidelines, several aspects of antibiotic therapy with antibiofilm activity lack clear definition. Given the escalating challenges posed by antimicrobial resistance, extended treatment durations, and tolerance issues, it is essential to ensure that antimicrobials with antibiofilm activity are both potent and diverse. Evidence of biofilm-active drugs is highlighted, and alternatives to classical regimens are further discussed.

What Place Is There for Long-Acting Antibiotics in the Management of Gram-Positive Infections? A Qualitative Cross-Sectional Study

OBJECTIVES

To identify the current practices with long half-life lipoglycopeptides (LGPs) and potential use/position of oritavancin.

RESULTS

Despite their indication being limited to skin and soft tissue infections (SSTIs), long half-life lipoglycopeptides are mainly used off-label to treat bone and joint infections (BJIs) and infective endocarditis. Oritavancin and dalbavancin are both semisynthetic lipoglycopeptide antibiotics with activity against Gram-positive organisms. The game-changing property of these two antibiotics is their one-time dosing. Due to its shorter half-life, oritavancin might have an advantage over dalbavancin for a treatment duration of less than 2 weeks, as it could be used both in prolonged treatments of complicated patients in BJIs or administered as a single-dose treatment for Gram-positive cocci infections usually treated by a 5- to 10-day antibiotic course. These infections include urinary tract infections, bacteremias, catheter-related infections, etc. In addition to the possibility of being used as an end-of-treatment injection, oritavancin could be used as an empiric therapy treatment in the postoperative period in the context of device-associated especially prosthetic joint infections to allow for the early discharge of the patient.

METHODS

A qualitative survey was conducted in March 2022 including sixteen infectiologists, one internist, five hospital pharmacists, and one pharmacologist.

CONCLUSION

Long half-life lipoglycopeptides contribute to changing the paradigm in the management of acute bacterial infections, as infectiologists now consider a range of indications and patient profiles for one single drug. Oritavancin strengthens the therapeutic arsenal in numerous infections from BJIs to urinary tract infections and could help to manage specific clinical situations, on top of providing potential benefits for the hospital's budget.

Modern Microbiological Methods to Detect Biofilm Formation in Orthopedy and Suggestions for Antibiotic Therapy, with Particular Emphasis on Prosthetic Joint Infection (PJI)

Biofilm formation is a serious problem that relatively often causes complications in orthopedic surgery. Biofilm-forming pathogens invade implanted foreign bodies and surrounding tissues. Such a condition, if not limited at the appropriate time, often requires reoperation. This can be partially prevented by selecting an appropriate prosthesis material that prevents the development of biofilm. There are many modern techniques available to detect the formed biofilm. By applying them we can identify and visualize biofilm-forming microorganisms. The most common etiological factors associated with biofilms in orthopedics are: Staphylococcus aureus, coagulase-negative Staphylococci (CoNS), and Enterococcus spp., whereas Gram-negative bacilli and Candida spp. also deserve attention. It seems crucial, for therapeutic success, to eradicate the microorganisms able to form biofilm after the implantation of endoprostheses. Planning the effective targeted antimicrobial treatment of postoperative infections requires accurate identification of the microorganism responsible for the complications of the procedure. The modern microbiological testing techniques described in this article show the diagnostic options that can be followed to enable the implementation of effective treatment.

Outcomes in orthopedic device infections due to Streptococcus agalactiae: a retrospective cohort study

BACKGROUND

Group B streptococci (Streptococcus agalactiae) (GBS) is a rare cause of prosthetic joint infection (PJI) occurring in patients with comorbidities and seems to be associated with a poor outcome. Depiction of GBS PJI is scarce in the literature.

METHODS

A retrospective survey in 2 referral centers for bone joint infections was done Patients with a history of PJI associated with GBS between 2014 and 2019 were included. A descriptive analysis of treatment failure was done. Risk factors of treatment failure were assessed.

RESULTS

We included 61 patients. Among them, 41 had monomicrobial (67%) infections. The median duration of follow-up was 2 years (interquartile range 2.35) Hypertension, obesity, and diabetes mellitus were the most reported comorbidities (49%, 50%, and 36% respectively). Death was observed in 6 individuals (10%) during the initial management. The rate of success was 63% (26/41). Removal of the material was not associated with remission (p = 0.5). We did not find a specific antibiotic regimen associated with a better outcome.

CONCLUSION

The results show that S. agalactiae PJIs are associated with high rates of comorbidities and a high treatment failure rate with no optimal treatment so far.

Acute Haematogenous Revision Total Knee Arthroplasty Infection by Streptococcus canis Treated by Debridement, Antibiotics, and Implant Retention: A Case Report

Prosthetic joint infections (PJIs) are one of the most feared complications by orthopaedic surgeons. Haematogenous PJI represents an important part of PJI cases. Streptococcus canis is an extremely rare cause of haematogenous PJI and its medical and surgical treatment and prognosis are not well established. We present a 79-year-old female patient who had a revision total knee arthroplasty (rTKA) surgery three years before. She was admitted to the hospital referring to three days of knee pain, restricted range of motion, and fever. Blood tests demonstrated leukocyte and C-reactive protein elevation. Joint fluid aspiration showed elevated white blood cell count with a high neutrophil differential and its conventional culture was positive for Streptococcus canis. She did not have pets but she took care of her daughter's dog. An acute haematogenous infection of the rTKA was diagnosed and treated with debridement, antibiotics (eight weeks of IV ceftriaxone), and implant retention (DAIR). After one year, the patient remains clinically asymptomatic without changes on X-rays and with normal serum levels of inflammatory blood markers. Streptococcus canis has to be kept in mind as a possible cause of haematogenous TKA infection in patients who have contact with domestic pets and patients should be asked for this contact. We recommend DAIR as a viable treatment option for this type of infection, which may show excellent results.

How are Oral Antibiotics Being Used in Total Joint Arthroplasty? A Review of the Literature

While the role and benefit of perioperative intravenous (IV) antibiotics in patients undergoing total joint arthroplasty (TJA) is well-established, oral antibiotic use in TJA remains a controversial topic with wide variations in practice patterns. With this review, we aimed to better educate the orthopedic surgeon on when and how oral antibiotics may be used most effectively in TJA patients, and to identify gaps in the literature that could be clarified with targeted research. Extended oral antibiotic prophylaxis (EOAP) use in high-risk primary, aseptic revision, and exchange TJA for infection may be useful in decreasing periprosthetic joint infection (PJI) rates. When prescribing oral antibiotics either as EOAP or for draining wounds, patient factors, type of surgery, and type of infectious organisms should be considered in order to optimally prevent and treat PJI. It is important to maintain antibiotic stewardship by administering the proper duration, dose, and type of antibiotics and by consulting infectious disease when necessary.

Systemic Inflammatory Response Syndrome and Prosthetic Joint Infection

BACKGROUND

The development of systemic inflammatory response syndrome (SIRS) criteria leads to increased mortality. Little is known about development of SIRS in patients who have prosthetic joint infection (PJI). We aimed to determine the incidence, risk factors, clinical outcomes, and causative organisms in patients who develop SIRS with PJI.

METHODS

We retrospectively identified 655 patients (321 men, 334 women; 382 total hip, 273 total knee) who have hip or knee PJI at 1 institution between July 1, 2015 and December 31, 2020. We formed 2 groups: patients who have SIRS alert (PJI + SIRS) and patients who do not have SIRS alert (PJI). We analyzed clinical outcomes, comorbidities, and operating room culture results.

RESULTS

Of 655 patients, 63 developed SIRS with PJI (9.6%). Intensive care unit (ICU) admission rates (27.0 versus. 6.9%, P < .001) and length of stay (7.7 versus. 5.6 days, P = .003) were greater in PJI + SIRS. At 2 years, reoperation (36.5 versus. 22.3%, P = .01) and mortality rates (17.5 versus. 8.8%, P = .03) were greater in PJI + SIRS. Risk factors included deficiency anemia (P = .001), blood loss anemia (P = .013), uncomplicated diabetes (P = .006), diabetes with complication (P = .001), electrolyte disorder (P < .00001), neurological disorder (P = .0001), paralysis (P = .026), renal failure (P = .005), and peptic ulcer disease (P = .004). Staphylococcus aureus more commonly speciated on tissue cultures in PJI + SIRS (P = .002).

CONCLUSION

The incidence of SIRS is 10% among patients who have PJI. Development of PJI + SIRS is associated with increased lengths of stay, ICU admissions, and 2-year reoperation and mortality rates. Identifying certain comorbidities can stratify patients' risk of developing PJI + SIRS.

Piezoelectric ultrasonic debridement as new tool for biofilm removal from orthopedic implants: A study in vitro

Pulse lavage (PL) debridement is the standard treatment used in Debridement, Antibiotics and Implant Retention (DAIR) for bacterial biofilm removal during acute and early postoperative cases of periprosthetic joint infection (PJI). The failure rate of DAIR is still high due to the inadequacy of PL in removing the biofilm. Ultrasound-based techniques are a well-established tool for PJI diagnosis due to their ability to completely eradicate the biofilm from implant surfaces. Hence, this study investigates the efficiency of a piezoelectric ultrasonic scalpel (PUS) in removing bacterial biofilm from different orthopedic implant materials in vitro and compares the results with PL. Biofilms of methicillin-resistant Staphylococcus aureus strains were grown on titanium alloy (Ti6Al4V ELI), stainless steel (AISI 316L), and ultrahigh molecular weight polyethylene (UHMWPE) disks for 24 h. The disks of each material were divided into three groups: (i) a control group (no lavage/debridement), (ii) a group treated with PL, (iii) a group treated with PUS. The disks were then sonicated for viable cell count to measure the residual biofilm content. Compared to the initial cell count (105  CFU/mL for each material), PL showed a two-log reduction of CFU/mL (p < 0.001 for each material), while for PUS a four-log reduction was found (p < 0.001 for each material). The comparison between the two lavage/debridement displayed a two-log reduction of CFU/mL (p < 0.001 for each material) of PUS compared with PL. Its increased efficiency compared with PL promotes the use of PUS in removing bacterial biofilm from orthopedic implants, suggesting its implementation to improve the success rate of DAIR.

High treatment failure rate in haematogenous compared to non-haematogenous periprosthetic joint infection

Aims

A higher failure rate has been reported in haematogenous periprosthetic joint infection (PJI) compared to non-haematogenous PJI. The reason for this difference is unknown. We investigated the outcome of haematogenous and non-haematogenous PJI to analyze the risk factors for failure in both groups of patients.

Methods

Episodes of knee or hip PJI (defined by the European Bone and Joint Infection Society criteria) treated at our institution between January 2015 and October 2020 were included in a retrospective PJI cohort. Episodes with a follow-up of > one year were stratified by route of infection into haematogenous and non-haematogenous PJI. Probability of failure-free survival was estimated using the Kaplan-Meier method, and compared between groups using log-rank test. Univariate and multivariate analysis was applied to assess risk factors for failure.

Results

A total of 305 PJI episodes (174 hips, 131 knees) were allocated to the haematogenous (n = 146) or the non-haematogenous group (n = 159). Among monomicrobial infections, Staphylococcus aureus was the dominant pathogen in haematogenous PJI (76/140, 54%) and coagulase-negative staphylococci in non-haematogenous PJI (57/133, 43%). In both groups, multi-stage exchange (n = 55 (38%) in haematogenous and n = 73 (46%) in non-haematogenous PJI) and prosthesis retention (n = 70 (48%) in haematogenous and n = 48 (30%) in non-haematogenous PJI) were the most common surgical strategies. Median duration of antimicrobial treatment was 13.5 weeks (range, 0.5 to 218 weeks) and similar in both groups. After six years of follow-up, the probability of failure-free survival was significantly lower in haematogenous compared to non-haematogenous PJI (55% vs 74%; p = 0.021). Infection-related mortality was significantly higher in haematogenous than non-haematogenous PJI (7% vs 0% episodes; p = 0.001). Pathogenesis of failure was similar in both groups. Retention of the prosthesis was the only independent risk factor for failure in multivariate analysis in both groups.

Conclusion

Treatment failure was significantly higher in haematogenous compared to non-haematogenous PJI. Retention of the prosthesis was the only independent risk factor for failure in both groups.

One-stage revision for infected shoulder arthroplasty: prospective, observational study of 37 patients

Background

Periprosthetic joint infection is a severe complication of joint replacement surgery. Thus two-stage exchange remains the gold standard, one-stage exchange is now widely recommended. We hypothesized that, for patients with chronic periprosthetic shoulder infection (PSI), treatment with a one-stage exchange would be an effective approach to eradicate infection, relieve pain, and restore function to the involved shoulder.

Materials and methods

This monocenter cohort study in a Bone and Joint Infection Referral Center (11/2003-05/2020) included all patients with confirmed PSI treated by one-stage revision. Data were extracted from the prospective database, including demographics, infection characteristics, and functional evaluations (range of motion and Constant Score at admission and last follow-up). The primary outcome was the 2-year reinfection-free rate.

Results

We included 37 patients. The refection-free rate was 5%. The most commonly isolated pathogen was Cutibacterium acnes (68%), isolated alone (15 patients, 41%) or as polymicrobial infections (10 patients, 27%). The Constant Score increased significantly from 24 to 53 (P = .001). Range of motion (forward elevation, abduction) was also significantly improved after surgery. Mean active forward elevation increased significantly by 45° from 60° to 105° postoperatively (P < .001), mean abduction increased by 42° from 55° to 97° (P < .001).

Discussion

Results from our prospective cohort-extracted series suggest that one-stage revision is a reliable treatment with a low infection recurrence rate. Improved functional outcomes can be achieved with one-stage exchange. Our patients' overall functional results were similar to those previously reported for one-stage revision and better than those reported after two-stage exchange. Patients with multiple previous surgeries seem to have worse functional outcomes than the subgroup without surgery before the index arthroplasty.

Conclusions

Our results and literature search findings suggest that one-stage revisions effectively eradicate PSIs, with good functional outcomes.

Clinical presentation of group B Streptococcus-infected diabetic foot ulcers

OBJECTIVE

Group B Streptococcus (GBS) is a common pathogen in diabetic foot ulcers (DFUs), where it has been found to result in higher rates of soft tissue infection and amputation despite appropriate treatment. In this study, we aim to investigate clinical characteristics and prognosis of GBS DFU infections, especially those with tenosynovial involvement. We hypothesise that GBS-infected DFUs with tenosynovial involvement leads to an increased number of recurrent infections and unexpected returns to the operating room.

METHOD

Data were retrospectively collected from GBS-infected DFU patients surgically treated by an orthopaedic foot and ankle surgeon over a four-year period. Demographics, comorbidities, initial laboratory values and culture results from infected bone samples were recorded. Clinical outcome was assessed by recurrent infection and unplanned reoperation(s) within 3 months following the initial surgery.

RESULTS

In total, 72 patients were treated for GBS-infected DFUs. Intra-operative culture of infected bone identified GBS in 16 patients (22.2%). Significantly more black patients (p=0.017) were afflicted by GBS DFUs. Patients with GBS DFUs had higher initial haemoglobin A1C levels (p=0.019), and those with tenosynovial involvement were likely to require reoperation (p=0.036) and had a greater total number of surgeries (p=0.015) than those without.

CONCLUSION

GBS-infected DFUs are more common in black patients and those with elevated haemoglobin A1Cs. GBS infections with tenosynovial involvement are particularly destructive and require aggressive treatment by surgeons.

Antibiotic Prophylaxis is Often Unnecessary for Screening Colonoscopies Following Total Knee Arthroplasty

INTRODUCTION

Incidence of bacteremia following screening colonoscopy is low, but risk of hematogenous spread causing prosthetic joint infection (PJI) may exist in total knee arthroplasty (TKA) patients. In multivariate analyses, we examined PJI risk among three TKA cohorts: (1) colonoscopy recipients given antibiotic prophylaxis; (2) colonoscopy recipients not given antibiotic prophylaxis; and (3) no colonoscopy. We assessed: 90-day to one-year (A) PJI risk, and (B) risk factors for post-colonoscopy PJI.

METHODS

We queried a national, all-payer database for primary TKA recipients from 2010 to 2020. Patients who had colonoscopies and who did (n=2,558) or did not have antibiotic prophylaxis (n=20,000) were identified. These were compared those who did not undergo colonoscopy (n=20,000). The 20,000 patients were randomly selected to mitigate type 1 errors. Multivariate regressions compared PJI risk factors, such as alcohol abuse (AA), rheumatoid arthritis (RA), and diabetes.

RESULTS

Both colonoscopy cohorts had no increased PJI risk compared to non-colonoscopy (odds ratio (OR)<2.20, P≥0.064). Alcohol abuse, diabetes, and RA were found to be risk factors further enhancing likelihood of PJI for TKA patients not receiving antibiotics undergoing colonoscopies (OR>1.35, P≤0.044).

CONCLUSION

Overall, antibiotic prophylaxis does not decrease PJI risk following colonoscopy TKA recipients. After adjusting for known risk factors, both colonoscopy cohorts demonstrated similar PJI risks compared to the non-colonoscopy cohort. However, AA, diabetes, and RA were associated with further increased PJI risk for TKA patients undergoing colonoscopies compared to those who did not. Therefore, if undergoing colonoscopy after TKA, our findings suggest that most patients do not need to have antibiotics except for these high-risk patients.

Poor outcome after debridement and implant retention for acute hematogenous periprosthetic joint infection: a cohort study of 43 patients

BACKGROUND AND PURPOSE

The management of acute hematogenous periprosthetic joint infection (AHI) is challenging and the optimal treatment is not clearly defined. The aim of this study was to evaluate the treatment outcome of AHI, and secondarily to investigate potential risk factors that affect outcome.

PATIENTS AND METHODS

We retrospectively analyzed 43 consecutive AHIs in a total hip or knee arthroplasty between 2013 and 2020 at a single center. We used the Delphi international consensus criteria to define infection. Patients were treated by either debridement, antibiotics, and implant retention (DAIR) (n = 25), implant exchange/removal (n = 15), or suppressive antibiotics only (n = 3). AHI was defined as abrupt symptoms of infection ≥ 3 months after implantation in an otherwise well-functioning arthroplasty.

RESULTS

AHI was most often caused by Staphylococcus aureus (16/43) and streptococcal species (13/43), but a broad spectrum of microbes were identified. 25 of 43 were treated with DAIR, with success in 10 of 25, which was significantly lower than in patients treated with removal of the implant with success in 14 of 15. S. aureus infection, knee arthroplasty, and implant age < 2 years were associated with treatment failure. The 2-year mortality rate was 8 of 43.

CONCLUSION

The outcome following DAIR in AHIs was poor. The majority of infections were caused by virulent microbes, and we found a high mortality rate. Removal of the implant should more often be considered.

Increased Incidence of Methicillin-Resistant Staphylococcus aureus in Knee and Hip Prosthetic Joint Infection

BACKGROUND

Periprosthetic joint infection (PJI) is a devastating complication of knee and hip arthroplasty. Past literature has shown that gram-positive bacteria are commonly responsible for these infections, although limited research exists studying the changes in the microbial profile of PJIs over time. This study sought to analyze the incidence and trends of pathogens responsible for PJI over three decades.

METHODS

This is a multi-institutional retrospective review of patients who had a knee or hip PJI from 1990 to 2020. Patients with a known causative organism were included and those with insufficient culture sensitivity data were excluded. There were 731 eligible joint infections from 715 patients identified. Organisms were divided into multiple categories based on genus/species and 5-year increments were used to analyze the study period. The Cochran-Armitage trend tests were used to evaluate linear trends in microbial profile over time and a P-value <.05 was considered statistically significant.

RESULTS

There was a statistically significant positive linear trend in the incidence of methicillin-resistant Staphylococcus aureus over time (P = .0088) as well as a statistically significant negative linear trend in the incidence of coagulase-negative staphylococci over time (P = .0018). There was no statistical significance between organism and affected joint (knee/hip).

CONCLUSION

The incidence of methicillin-resistant Staphylococcus aureus PJI is increasing over time, whereas, coagulase-negative staphylococci PJI is decreasing, paralleling the global trend of antibiotic resistance. Identifying these trends may help with the prevention and treatment of PJI through methods such as remodeling perioperative protocols, modifying prophylactic/empiric antimicrobial approaches, or transitioning to alternative therapeutic strategies.

Comparative analysis of pathogen distribution in patients with fracture-related infection and periprosthetic joint infection: a retrospective study

BACKGROUND

The purpose of this study is to investigate the microbial patterns of periprosthetic joint infection (PJI) and fracture-related infection (FRI), and guide for the formulation of more accurate empirical antimicrobial regimens based on the differences in pathogen distribution.

METHODS

A comparative analysis of pathogen distribution was conducted between 153 patients (76 with PJI and 77 with FRI). Predicted analyses against isolated pathogens from two cohorts were conducted to evaluate the best expected efficacy of empirical antimicrobial regimens (imipenem + vancomycin, ciprofloxacin + vancomycin, and piperacillin/tazobactam + vancomycin).

RESULTS

Our study found significant differences in pathogen distribution between the PJI and FRI cohorts. Staphylococci (61.3% vs. 31.9%, p = 0.001) and Gram-negative bacilli (GNB, 26.7% vs. 56.4%, p < 0.001) were responsible for the majority of infections both in the PJI and FRI cohorts, and their distribution in the two cohorts showed a significant difference (p < 0.001). Multi-drug resistant organisms (MDRO) were more frequently detected in the FRI cohort (29.3% vs. 44.7%, p = 0.041), while methicillin-resistant coagulase-negative Staphylococci (MRCoNS, 26.7% vs. 8.5%, p = 0.002) and Canidia albicans (8.0% vs. 1.1%, p = 0.045) were more frequently detected in the PJI cohort. Enterobacter spp. and Acinetobacter baumannii were detected only in the FRI cohort (11.7% and 8.5%, respectively).

CONCLUSIONS

Staphylococci and GNB were responsible for the majority of infections in both PJI and FRI. Empirical antimicrobial therapy should focus on the coverage of Staphylococci in PJI and GNB in FRI, and infections caused by MDROs should be more vigilant in FRI, while the high incidence of MRCoNS in PJI should be noted, which could guide for the formulation of more accurate empirical antimicrobial regimens. Targeted therapy for FRI caused by A. baumannii and PJI caused by C. albicans needs to be further investigated. Our study reports significant differences in pathogen distribution between the two infections and provides clinical evidence for studies on the mechanism of implant-associated infection.

Are There Any Changes in the Causative Microorganisms Isolated in the Last Years from Hip and Knee Periprosthetic Joint Infections? Antimicrobial Susceptibility Test Results Analysis

BACKGROUND

PJIs following total hip and knee arthroplasty represent severe complications with broad implications, and with significant disability, morbidity, and mortality. To be able to provide correct and effective management of these cases, an accurate diagnosis is needed. Classically, acute PJIs are characterized by a preponderance of virulent microorganisms, and chronic PJIs are characterized by a preponderance of less-virulent pathogens like coagulase-negative staphylococci or Cutibacterium species. This paper aims to analyze if there are any changes in the causative microorganisms isolated in the last years, as well as to provide a subanalysis of the types of PJIs.

METHODS

In this single-center study, we prospectively included all retrospectively consecutive collected data from patients aged over 18 years that were hospitalized from 2016 through 2022, and patients that underwent a joint arthroplasty revision surgery. A standardized diagnostic protocol was used in all cases, and the 2021 EBJIS definition criteria for PJIs was used.

RESULTS

114 patients were included in our analysis; of them, 67 were diagnosed with PJIs, 12 were acute/acute hematogenous, and 55 were chronic PJIs. 49 strains of gram-positive aerobic or microaerophilic cocci and 35 gram-negative aerobic bacilli were isolated. Overall, Staphylococcus aureus was the most common isolated pathogen, followed by coagulase-negative staphylococci (CoNS). All cases of acute/acute hematogenous PJIs were caused by gram-positive aerobic or microaerophilic cocci pathogens. Both Staphylococcus epidermidis and methicillin-resistant S. aureus were involved in 91.66% of the acute/acute hematogenous PJIs cases. 21.8% of the chronic PJIs cases were caused by pathogens belonging to the Enterobacterales group of bacteria, followed by the gram-negative nonfermenting bacilli group of bacteria, which were involved in 18.4% of the cases. 12 chronic cases were polymicrobial.

CONCLUSION

Based on our findings, empiric broad-spectrum antibiotic therapy in acute PJIs could be focused on the bacteria belonging to the gram-positive aerobic or microaerophilic cocci, but the results should be analyzed carefully, and the local resistance of the pathogens should be taken into consideration.

The Clinical Outcome of Early Periprosthetic Joint Infections Caused by Staphylococcus epidermidis and Managed by Surgical Debridement in an Era of Increasing Resistance

INTRODUCTION

A risk factor for the failure of surgical debridement in patients with early periprosthetic joint infections (PJI) is the presence of multidrug-resistant microorganisms. Staphylococcus epidermidis is one of the most isolated microorganisms in PJI and is associated with emerging resistance patterns. We aimed to assess the antibiotic resistance patterns of S. epidermidis in early PJIs treated with surgical debridement and correlate them to clinical outcomes.

MATERIAL AND METHODS

A retrospective multicentre observational study was conducted to evaluate patients with an early PJI (within 3 months after the index arthroplasty) by S. epidermidis with at least two positive intraoperative cultures. Clinical failure was defined as the need for additional surgical intervention or antibiotic suppressive therapy to control the infection.

RESULTS

A total of 157 patients were included. The highest rate of resistance was observed for methicillin in 82% and ciprofloxacin in 65% of the cases. Both were associated with a higher rate of clinical failure (41.2% vs. 12.5% (p 0.048) and 47.3% vs. 14.3% (p 0.015)), respectively. Furthermore, 70% of the cases had reduced susceptibility to vancomycin (MIC ≥ 2), which showed a trend towards a higher failure rate (39.6% vs. 19.0%, NS). Only 7% of the cases were rifampin-resistant. Only the resistance to fluoroquinolones was an independent risk factor for clinical failure in the multivariate analysis (OR 5.45, 95% CI 1.67-17.83).

CONCLUSION

S. epidermidis PJIs show a high rate of resistance. Resistance to fluoroquinolones is associated with clinical failure. Alternative prophylactic antibiotic regimens and optimising treatment strategies are needed to improve clinical outcomes.

Cutibacterium acnes Prosthetic Joint Infections: Is Rifampicin-Combination Therapy Beneficial?

No consensus has been reached on the optimal antibiotic regimen to treat Cutibacterium acnes PJIs (Ca-PJIs). In vitro studies showed excellent rifampicin efficacy against biofilm-associated C. acnes infections, but clinical studies did not confirm the superiority of rifampicin-combined therapy over monotherapy. This prospective cohort study was undertaken to analyze the outcomes of 70 patients who underwent exchange arthroplasty for chronic monomicrobial Ca-PJI and were treated with rifampicin or without between 2004 and 2019. The 37 patients treated from January 2004 to August 2014 were prescribed rifampicin-combination therapy and the 33 treated from September 2014 to December 2019 received monotherapy without rifampicin. The primary endpoint was the 2-year Kaplan-Meier-estimated reinfection-free probability, including relapses and new-pathogen PJIs. The 2-year reinfection-free rate was high and not different for patients who had received rifampicin or not (89.2% vs. 93.8%, respectively; p = 0.524). None of the patients relapsed and six developed new-pathogen PJIs. Our results do not support a benefit of rifampicin-combination therapy for patients who underwent exchange arthroplasty for chronic Ca-PJIs.

Pseudomonas aeruginosa prosthetic joint-infection outcomes: Prospective, observational study on 43 patients

Objectives

Analysis the outcomes of Pseudomonas aeruginosa prosthetic joint infection (PJI), and of their clinical and microbiological characteristics, surgical strategies and antibiotic treatments.

Methods

Monocenter cohort study in a Bone-and-Joint-Infection Referral Center (08/2004 to 10/2018) including all consecutive P. aeruginosa PJIs. Data were extracted from the prospective database, including the following events: relapses, new PJIs, related deaths.

Results

Median [IQR]: among the 43 patients included (28 females; 72 [63-80] years old; 27 hip, 15 knee, and 1 shoulder PJIs), 29 (67%) had underlying comorbidities, 12 (28%) had previously been treated for another PJI and 9 (21%) had undergone previous surgeries for their P. aeruginosa PJI. Eleven (26%) PJIs were polymicrobial, 16 (37%) strains were wild type, 8 (19%) ciprofloxacin-resistant. PJIs were classified as late chronic (n = 33), early postoperative (n = 9) or acute hematogenous infection (n = 1). Forty patients underwent surgery: 27 one-stage and 5 two-stage exchanges, 3 debridement and implant retention, and 5 other surgical strategies. Antibiotic treatments were: 29 received 41 [37-43] days of combination therapy (IV anti-pseudomonal β-lactam and 3-5 days of amikacin, then β-lactam and oral ciprofloxacin), followed by oral ciprofloxacin for a total of 12 weeks; 10 received only IV antibiotics for 83 [77-86] days, including 37 [32-46] days of combination therapy; 49 days of ceftazidime alone for 1. During follow-up lasting 33 [24-64.5] months, 2 relapses, 3 new PJIs, and 2 related deaths occurred. Thirty-three (82%) patients and 93% of those managed with one-stage exchange experienced no event.

Conclusion

Outcomes of our cohort's P. aeruginosa PJIs-predominantly monomicrobial, chronic, ciprofloxacin-susceptible, treated with one-stage exchange and prolonged IV antibiotics-were 82% favorable.

Development of an innovative in vivo model of PJI treated with DAIR

Introduction

Prosthetic Joint Infection (PJI) are catastrophic complications of joint replacement. Debridement, implant retention, and antibiotic therapy (DAIR) is the usual strategy in acute infections but fails in 45% of MRSA infections. We describe the development of a model of infected arthroplasty in rabbits, treated with debridement and a course of vancomycin with clinically relevant dosage.

Materials and methods

A total of 15 rabbits were assigned to three groups: vancomycin pharmacokinetics (A), infection (B), and DAIR (C). All groups received a tibial arthroplasty using a Ti-6Al-4V implant. Groups B and C were infected per-operatively with a 5.5 log10 MRSA inoculum. After 1 week, groups C infected knees were surgically debrided. Groups A and C received 1 week of vancomycin. Pharmacokinetic profiles were obtained in group A following 1st and 5th injections. Animals were euthanized 2 weeks after the arthroplasty. Implants and tissue samples were processed for bacterial counts and histology.

Results

Average vancomycin AUC_{0–12 h} were 213.0 mg*h/L (1st injection) and 207.8 mg*h/L (5th injection), reaching clinical targets. All inoculated animals were infected. CFUs were reproducible in groups B. A sharp decrease in CFU was observed in groups C. Serum markers and leukocytes counts increased significantly in infected groups.

Conclusion

We developed a reproducible rabbit model of PJI treated with DAIR, using vancomycin at clinically relevant concentrations.

The Role of Staphylococcal Biofilm on the Surface of Implants in Orthopedic Infection

Despite advanced implant sterilization and aseptic surgical techniques, implant-associated infection remains a major challenge for orthopedic surgeries. The subject of bacterial biofilms is receiving increasing attention, probably as a result of the wide acknowledgement of the ubiquity of biofilms in the clinical environment, as well as the extreme difficulty in eradicating them. Biofilm can be defined as a structured microbial community of cells that are attached to a substratum and embedded in a matrix of extracellular polymeric substances (EPS) that they have produced. Biofilm development has been proposed as occurring in a multi-step process: (i) attachment and adherence, (ii) accumulation/maturation due to cellular aggregation and EPS production, and (iii) biofilm detachment (also called dispersal) of bacterial cells. In all these stages, characteristic proteinaceous and non-proteinaceous compounds are expressed, and their expression is strictly controlled. Bacterial biofilm formation around implants shelters the bacteria and encourages the persistence of infection, which could lead to implant failure and osteomyelitis. These complications need to be treated by major revision surgeries and extended antibiotic therapies, which could lead to high treatment costs and even increase mortality. Effective preventive and therapeutic measures to reduce risks for implant-associated infections are thus in urgent need.

Epidemiology and antibiotic resistance of prosthetic joint infections according to time of occurrence, a 10-year study

OBJECTIVES

To describe the microorganisms responsible for prosthetic joint infections (PJIs) and their antimicrobial susceptibilities, and to propose appropriate empirical antimicrobial treatments (EATs) according to time of occurrence METHODS: : This 10-year retrospective study presents the bacterial etiology of 282 consecutive PJIs in a French hospital according to time of occurrence (adapted from Zimmerli's classification: early, <3 months; delayed, 3-12 months; late acute, >12 months with hematogenous seeding or contiguous spread; late chronic, >12 months without hematogenous seeding). The expected efficacy of various EATs was analyzed for each PJI.

RESULTS

Staphylococci were the most commonly found bacteria (S. aureus (44.3%), coagulase-negative staphylococci (25.2%) with 15.2% and 49.3% methicillin resistance respectively), followed by Gram-negative bacilli (GNB) (17.7%) and streptococci (14.9%). The distribution of species varied between categories, but antibiotics targeting GNBs were required in all categories. Imipenem-vancomycin was the most effective combination (99.3%) but should be reserved for patients with suspected resistant GNB. Cefotaxime-vancomycin was less effective in early/delayed and late PJIs (91.1% and 86.1% respectively), due to resistant GNB and polymicrobial infections. Piperacillin/tazobactam-vancomycin appeared to be appropriate in all situations (>96% efficacy).

CONCLUSION

Proposing universal recommendations remains challenging, but a good understanding of the local epidemiology is important for optimizing EATs.

Antibiotic Prophylaxis for Prosthetic Joint Patients Undergoing Invasive Dental Procedures: Time for a Rethink?

BACKGROUND

In the United States, it has been common practice to recommend that dentists provide antibiotic prophylaxis (AP) before invasive dental procedures (IDPs) to prevent late periprosthetic joint infections (LPJIs) in patients who have prosthetic arthroplasties despite lack of evidence for a causal relationship between IDP and LPJI and a lack of evidence for AP efficacy.

METHODS

A recent study quantified the IDP incidence over the 15-month period prior to LPJI hospital admissions in the United Kingdom for which dental records were available. A case-crossover analysis compared IDP incidence in the 3 months before LPJI admission with the preceding 12 months. The English population was used because guidelines do not recommend AP and any relationship between IDPs and LPJI should be fully exposed.

RESULTS

No significant positive association was identified between IDPs and LPJI. Indeed, the incidence of IDPs was lower in the 3 months before LPJI hospital admission than that in the preceding 12 months.

CONCLUSION

In the absence of a significant positive association between IDPs and LPJI, there is no rationale to administer AP before IDPs in patients with prosthetic joints, particularly given the cost and inconvenience of AP, the risk of adverse drug reactions, and the potential for unnecessary AP use that promotes antibiotic resistance. These results should reassure orthopedic surgeons and their patients that dental care of patients who have prosthetic joints should focus on maintaining good oral hygiene rather than on recommending AP for IDPs. Moreover, it should also reassure those in other countries where AP is not recommended that such guidance is sufficient.

Skeletal infections: microbial pathogenesis, immunity and clinical management

Osteomyelitis remains one of the greatest risks in orthopaedic surgery. Although many organisms are linked to skeletal infections, Staphylococcus aureus remains the most prevalent and devastating causative pathogen. Important discoveries have uncovered novel mechanisms of S. aureus pathogenesis and persistence within bone tissue, including implant-associated biofilms, abscesses and invasion of the osteocyte lacuno-canalicular network. However, little clinical progress has been made in the prevention and eradication of skeletal infection as treatment algorithms and outcomes have only incrementally changed over the past half century. In this Review, we discuss the mechanisms of persistence and immune evasion in S. aureus infection of the skeletal system as well as features of other osteomyelitis-causing pathogens in implant-associated and native bone infections. We also describe how the host fails to eradicate bacterial bone infections, and how this new information may lead to the development of novel interventions. Finally, we discuss the clinical management of skeletal infection, including osteomyelitis classification and strategies to treat skeletal infections with emerging technologies that could translate to the clinic in the future.

Streptococcal and Staphylococcus aureus prosthetic joint infections: are they really different?

Background

Staphylococci and streptococci are the most frequent pathogens isolated from prosthetic joint infections (PJIs). The aim of this study was to analyze the outcome of streptococcal and methicillin-susceptible Staphylococcus aureus (MSSA) PJIs.

Methods

All monomicrobial streptococcal and MSSA PJIs managed in a French Referral Center (2010–2017) were sampled from the prospective PJIs cohort study. The primary outcome of interest was the cumulative reinfection-free survival at a 2-year follow-up.

Results

Two hundred and nine patients with 91 streptococcal and 132 staphylococcal infections were analyzed. Patients with streptococcal PJI were older, and infection was more frequently hematogenous. Reinfection-free survival rates at 2-years after all treatment strategies were higher for patients with streptococcal PJI (91% vs 81%; P = .012), but differed according to the strategy. After exchange arthroplasty, no outcome differences were observed (89% vs 93%; P = .878); after debridement, antibiotics and implant retention (DAIR), the reinfection-free survival rate was higher for patients with streptococcal PJI (87% vs 60%; P = .062). For patients managed with prolonged suppressive antibiotic therapy (SAT) alone, those with streptococcal PJIs had a 100% infection-free survival (100% vs 31%; P < .0001).

Conclusions

Reinfection-free survival after DAIR and SAT was better for patients with streptococcal than those with MSSA PJIs. No difference was observed after prosthesis exchange.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12879-022-07532-x.

Tissue sampling is non-inferior in comparison to sonication in orthopedic revision surgery

BACKGROUND

The aim of this study was to assess the role of sonication fluid cultures in detecting musculoskeletal infections in orthopedic revision surgery in patients suspected of having peri-prosthetic joint infection (PJI), fracture-related infections (FRI), or postoperative spinal implant infections (PSII).

METHODS

Between 2016 and 2019, 149 cases with a data set including sonication fluid cultures and tissue specimen and histological analysis were included. Accuracy of each diagnostic tool as well as the influence of antibiotic therapy was analyzed. Pathogens identified in the sonication cultures and in the associated tissue samples were compared based on the matching of the antibiograms. Therapeutic benefits were then assessed.

RESULTS

Of 149 cases, 43.6% (n = 65) were identified as PJI, 2.7% (n = 4) as FRI, 12.8% (n = 19) as PSII, 6.7% (n = 10) as aseptic non-union, and 34.2% (n = 51) as aseptic implant loosening. The sensitivity and specificity of tissue and synovial specimens showed no significant difference with respect to sonication fluid cultures (sensitivity/specificity: tissue: 68.2%/96.7%; sonication fluid cultures: 60.2%/98.4%). The administration of antibiotics over 14 days prior to microbiological sampling (n = 40) resulted in a lower sensitivity of 42.9% each. Histological analysis showed a sensitivity 86.3% and specificity of 97.4%. In 83.9% (n = 125) of the cases, the results of sonication fluid cultures and tissue specimens were identical. Different microorganisms were found in only four cases. In 17 cases, tissue samples (n = 5) or sonication (n = 12) were false-negatives.

CONCLUSION

Sonication fluid culture showed no additional benefit compared to conventional microbiological diagnostics of tissue and synovial fluid cultures. Preoperative administration of antibiotics had a clearly negative effect on microbiologic test accuracy. In over 83.9% of the cases, sonication fluid and tissue cultures showed identical results. In the other cases, sonication fluid culture did not further contribute to the therapy decision, whereas other factors, such as fistulas, cell counts, or histological analysis, were decisive in determining therapy.

Arthroplasty after septic arthritis of the native hip and knee: retrospective analysis of 49 joints

Abstract. Background: Arthroplasty after septic arthritis (SA) treatment raises diagnostic and therapeutic questions. The main objective was to evaluate infection-free survival of patients undergoing total knee arthroplasty (TKA) or total hip arthroplasty (THA) post-SA. Other objectives were to describe the population's characteristics, surgical strategies, results of preoperative examinations and cultures of intraoperative samples taken at implantation, and postoperative antibiotic therapy. Methods: This is a retrospective, observational, monocenter study, from January 2005 to May 2019, including all patients undergoing TKA or THA with prior or ongoing SA in the same joint. Infection–free survival was analyzed and reported. Results: Forty-seven patients, 29 men, 49 joints operated on (30 knees, 19 hips), were included. Median SA-to-arthroplasty interval was 32 [1–216] weeks. It was <2 years for 43 joints and <6 months for 19 joints. Six patients underwent arthroplasty while still on SA treatment. One-stage arthroplasty was done for 43 joints and two-stage arthroplasty for 6 joints. Eight (16 %) cultures of intraoperative specimens were positive. Median durations of postoperative antibiotic therapy were 10 d for sterile cultures and 82 d for those that were positive. At 2 years, infection-free survival rate was 95.9 % (±0.02). After a median follow-up of 47 [18–142] months, no SA relapse was observed, but five patients developed new periprosthetic joint infections (PJIs) with a different microorganism. Conclusion: Arthroplasty may be a post-SA option, even within a short period of time. One-stage arthroplasty can be done if synovectomy is thorough, intraoperative samples are taken and antibiotics are administered until those culture results become available. We observed no SA relapse, but new PJIs occurred.

Outcomes of Concurrent Endocarditis and Periprosthetic Joint Infection: A Retrospective Case Series of 16 Patients

Introduction

Concurrent diagnosis of periprosthetic joint infection (PJI) of total hip arthroplasty (THA) or total knee arthroplasty (TKA) with infectious endocarditis is a devastating clinical scenario infrequently documented in the literature. To date, no studies have fully described the orthopedic and infectious outcomes of patients with these concurrent diagnoses. The purpose of this study was to conduct a case series of patients with these diagnoses and document the orthopedic and infectious outcomes so that surgeons may effectively counsel patients regarding the gravity of the condition and the expected course of treatment.

Methods

This study is a retrospective case series using patient data from five hospitals within an academic healthcare system in the northeastern United States. Cases of concurrent endocarditis and THA or TKA PJI with a minimum of one-year follow-up were identified from January 2000 to January 2021. Basic statistics such as means, standard deviations, and percentages were used to identify trends within our series. Kaplan-Meier survivorship curves with log-rank tests were performed to determine if there were any differences in two-year mortality and joint survival (defined as needing explant) between patients who had cardiac surgery prior to surgical management for their PJI and those who had surgical management for PJI prior to cardiac surgery.

Results

A total of 18 joints in 16 patients with endocarditis and concurrent TKA or THA PJI were identified. All PJIs were managed surgically, with 14/18 (77.77%) of joint infections initially being managed by debridement, antibiotics, and implant retention (DAIR) and 4/18 (22.22%) of joint infections initially being managed by explant. Within the first six months of PJI diagnosis, 25% (4/16) of patients died of complications related to their infection, and one additional patient died of bacteremia just over a year after the initial PJI diagnosis. Of the 18 PJIs, 72.23% (13/18) had treatment failure, defined as any outcome equal to or worse than requiring chronic suppressive antibiotics for the infection. Due to low statistical power, we were not able to identify any differences in two-year mortality from PJI diagnosis (p=0.311) or joint survival (in terms of requiring explant) (p=0.420) depending on whether cardiac surgery or DAIR was performed first.

Conclusions

Concurrent infectious endocarditis and prosthetic joint infection is associated with high morbidity and mortality. Patients with these concurrent infections should be counseled that not only the associated mortality rate is high, but also the surgical treatment of their PJI has a high rate of treatment failure, including an explant following an initial DAIR, an explant with retained spacer, or a requirement of lifelong antibiotic suppression.

Antibiotic Therapy for Prosthetic Joint Infections: An Overview

Prosthetic joint infection (PJI) is a severe complication after arthroplasty. Its management combines surgical intervention, whose type depends on the clinical situation, and prolonged high-dose antibiotics adapted to the responsible microorganism(s) and the patient. Antibiotics are only one part of the therapeutic regimen and are closely related to the surgical strategy. Their efficacy depends to a large extent on the choice and quality of the surgical procedure, and the quality of the microbiological diagnosis. Although guidelines have been published, many aspects of antibiotic therapy remain poorly established. Choosing the optimal agent(s) is one aspect, with others being optimization of drugs' pharmacokinetic/pharmacodynamic parameters, the choice of administration route, use of monotherapy or combination regimens, therapeutic drug-monitoring and patient education to improve compliance and tolerance. Herein, we address PJI management based on recent literature data, guidelines and the experience of our referral center for complex bone-and-joint infections.

Outcome and failure analysis of 132 episodes of haematogenous periprosthetic joint infections – a cohort study

Background

Outcome of haematogenous periprosthetic joint infection (PJI) and reasons for failure are largely unknown.

Methods

Outcome of consecutive patients with haematogenous PJI treated at our institution between 2010 and 2019 was evaluated. Failure was classified as persistence or relapse of infection or new infection. Failure-free survival was assessed using Kaplan-Meier analysis. Proportions between groups were compared with Fisher's exact test.

Results

132 haematogenous PJI episodes involving knee (n=76), hip (n=54), shoulder (n=1) or elbow (n=1) prostheses experienced by 110 patients were included. Median follow-up was 20.7 months (range, 0.2-89.9 months). Haematogenous PJI were caused by Staphylococcus aureus (n=49), Streptococcus spp. (n=36), Enterococcus faecalis (n=17), Enterobacterales (n=16), coagulase-negative staphylococci (n=9) and others (n=6). Debridement and implant retention were performed in 50 (38%), prosthesis exchange or removal in 79 (60%) and no surgery in 3 episodes (2%). Treatment failed in 42 episodes (32%), including 6 infection-related deaths. Among 36 non-fatal failures, 21 were caused by a new pathogen and 8 by the same pathogen, in 7 episodes no pathogen was isolated. Of all non-fatal failures, 19 (53%) PJI were of haematogenous origin. Identification of the primary focus, causative pathogen and CRIME80-Score did not influence treatment outcome, but failure rate was higher following prosthesis retention compared to multi-stage exchange.

Conclusions

Persistence-/relapse-free survival after treatment of haematogenous PJI was high (84%). New haematogenous PJI due to the same or a new pathogen occurred frequently, reducing the treatment success to 62% after 4 years of follow-up, suggesting an individual predisposition to haematogenous PJI. The outcome was similar for different pathogens, but worse in episodes treated with prosthesis retention compared to multi-stage exchange.

How to Handle Concomitant Asymptomatic Prosthetic Joints During an Episode of Hematogenous Periprosthetic Joint Infection, a Multicenter Analysis

BACKGROUND

Prosthetic joints are at risk of becoming infected during an episode of bacteremia, especially during Staphylocococcus aureus bacteremia. However, it is unclear how often asymptomatic periprosthetic joint infection (PJI) occurs, and whether additional diagnostics should be considered.

METHODS

In this multicenter study, we retrospectively analyzed a cohort of patients with a late acute (hematogenous) PJI between 2005-2015 who had concomitant prosthetic joints in situ. Patients without at least 1 year of follow-up were excluded.

RESULTS

We included 91 patients with a hematogenous PJI and 108 concomitant prosthetic joints. The incident PJI was most frequently caused by Staphylococcus aureus (43%), followed by streptococci (26%) and Gram-negative rods (18%). Of 108 concomitant prosthetic joints, 13 were symptomatic, of which 10 were subsequently diagnosed as a second PJI. Of the 95 asymptomatic prosthetic joints, 1 PJI developed during the follow-up period and was classified as a "missed" PJI at the time of bacteremia with S. aureus (1.1%). Infected prosthetic joints were younger than the noninfected ones in 67% of cases, and prosthetic knees were affected more often than prosthetic hips (78%).

CONCLUSIONS

During an episode of hematogenous PJI, concomitant asymptomatic prosthetic joints have a very low risk of being infected, and additional diagnostic work-up for these joints is not necessary.

What Is the Mid-term Survivorship of Infected Rotating-hinge Implants Treated with One-stage-exchange?

BACKGROUND

Despite the growing number of studies reporting on periprosthetic joint infection (PJI), there is little information on one-stage exchange arthroplasty for the revision of infected rotating-hinge prostheses, which can be among the most difficult PJI presentations to treat.

QUESTIONS/PURPOSES

After one-stage direct exchange revision for an infected rotating-hinge TKA prosthesis, and using a multimodal approach for infection control, we asked: (1) What is the survivorship free from repeat revision for infection and survivorship free from reoperation for any cause? (2) What is the clinical outcome, based on the Oxford Knee Score, of these patients at the latest follow-up?

METHODS

Between January 2011 and December 2017, we treated 101 patients with infected rotating-hinge knee prostheses at our hospital. All patients who underwent a one-stage exchange using another rotating-hinge implant were potentially eligible for this retrospective study. During that period, we generally used a one-stage approach when treating PJIs. Eighty-three percent (84 of 101) of patients were treated with one-stage exchange, and the remainder were treated with two-stage exchange. Of the 84 treated with one-stage exchange, eight patients died of unrelated causes and were therefore excluded, one patient declined to participate in the study, and another eight patients were lost before the minimum study follow-up of 2 years or had incomplete datasets, leaving 80% (67 of 84) for analysis in this study. The included study population consisted of 60% males (40 of 67) with a mean age of 64 ± 8 years and a mean (range) BMI of 30 ± 6 kg/m2 (21 to 40). The mean number of prior surgeries was 4 ± 2 (1 to 9) on the affected knee. Fifteen percent (10 of 67) of knees had a preoperative joint communicating sinus tract, and 66% (44 of 67) had experienced a prior PJI on the affected knee. The antimicrobial regimen was chosen based on the advice of our infectious disease consultant and individually adapted for the organism cultured. The mean follow-up duration was 6 ± 2 years. Kaplan-Meier survivorship analysis was performed using the endpoints of survivorship free from repeat revision for infection and survivorship free from all-cause revision. The functional outcome was assessed using the Oxford Knee Score (on a 12- to 60-point scale, with lower scores representing less pain and greater function), obtained by interviewing patients for this study at their most recent follow-up visit. Preoperative scores were not obtained.

RESULTS

The Kaplan-Meier analysis demonstrated an overall survivorship free from reoperation for any cause of 75% (95% CI 64% to 87%) at the mean follow-up of 6 years postoperatively. Survivorship free from any repeat operative procedure for infection was 90% (95% CI 83% to 97%) at 6 years. The mean postoperative Oxford Knee Score was 37 ± 11 points.

CONCLUSION

With an overall revision rate of about 25% at 6 years and the limited functional results based on the poor Oxford Knee Scores, patients should be counseled to have modest expectations concerning postoperative pain and function level after one-stage exchange of an infected rotating-hinge arthroplasty. Nevertheless, patients may be informed about a reasonable chance of PJI eradication and might opt for this approach as a means to try to avoid high transfemoral amputation or joint arthrodesis, which in this population often is associated with the inability to ambulate at all. Regarding the relatively high number of patients with aseptic loosening, future studies might focus on implant design of revision knee systems as well. A longer course of oral antibiotics after such procedures may also be warranted to limit the chance of reinfection but requires further study.

LEVEL OF EVIDENCE

Level IV, therapeutic study.

Outcomes and Risk Factors Associated With Failures of Debridement, Antibiotics, and Implant Retention in Patients With Acute Hematogenous Periprosthetic Joint Infection

BACKGROUND

Acute hematogenous periprosthetic joint infections (PJI) accounts for 20% to 35% of all PJI cases. Treatment options include débridement, antibiotics, and implant retention (DAIR) or implant revision (single-stage/two-stage revision). Because the reported success rates of DAIR for acute PJIs as reported in the literature varies widely, this study aimed to investigate (1) the outcome of DAIR as revision surgery procedure and (2) the potential risk factors for treatment failure of DAIR in patients with acute hematogenous PJI.

METHODS

We reviewed 106 consecutive cases of total joint arthroplasty patients who underwent DAIR for the diagnosis of acute hematogenous PJI. Outcomes of the cohort including infection free survival was investigated. Mean follow-up was 4.9 years. Demographics, case data, comorbidities, and extremity score were analyzed by univariate and multivariate regressions to identify risk factors for failure of DAIR.

RESULTS

The failure rate of patients who underwent DAIR was 23.6% (25 of 106 patients). Univariate regression demonstrated that diabetes mellitus (P = 0.01) and polymicrobial infections (P < 0.01) are associated with failure of DAIR. Multivariate regression confirmed diabetes mellitus and polymicrobial infections as independent risk factors for failure of DAIR.

DISCUSSION

Debridement, antibiotics, and implant retention may be a viable treatment option with moderate failure rates at the midterm follow-up in cases of acute hematogenous PJI. The study also identified diabetes mellitus and polymicrobial infections as independent risk factors for failure of DAIR. The findings of this study provide clinically useful information for surgeons in treatment of patients with acute hematogenous PJI.

Different microbial and resistance patterns in primary total knee arthroplasty infections - a report on 283 patients from Lithuania and Sweden

Background

The microbiology and the susceptibility patterns of infected total knee arthroplasties (TKAs) vary depending on demographic, local antimicrobial stewardship, and surgical factors. We wanted to compare the recent microbial profile and antimicrobial resistance pattern in revisions due to infections after primary TKAs in Sweden and Lithuania. Our hypothesis was that there is a difference in bacteriology and resistance pattern based on patient related, societal and local hospital factors as almost similar praxis have been applied for TKA surgery, short term systemic prophylaxis and routine use of local gentamicin containing bone cement.

Methods

Primary TKAs revised for the first time due to verified or suspected infection were collected nationwide in Sweden during 2018, and in Lithuania between 2011 and 2020 from a single major TKA revision centre in Kaunas. We identified 202 TKAs in Sweden from the Swedish Knee Arthroplasty Register and 84 from Kaunas revised due to infection. We collected available culture reports and evaluated the type of microorganisms with antimicrobial resistance pattern at revision.

Results

The majority of the infected cases in Sweden were early-type prosthetic joint infection (PJI) (44%), whereas late-type PJI (52%) were more common in the Kaunas cases. Gram-positive bacteria prevailed in both Sweden (55%) and Lithuania (80%). Staphylococcus aureus was the most frequent organism identified in both countries (33% in Sweden and 34% in Lithuania). More polymicrobial infections were observed in Sweden than in Lithuania (16 and 6% respectively). Methicillin resistance in Staphylococcus aureus and coagulase-negative staphylococci were higher in Lithuania (4/28 and 19/29) than in Sweden (1/42 and 9/41).

Conclusions

The type of infections, microbial profile, and drug resistance pattern differed between Sweden and Lithuania. Societal and local hospitals factors with emerging resistance in Lithuania are the most plausible explanation for the difference. Lack of complete data on a national level in Lithuania underlines the importance of adding microbiology of PJIs in implant registers for national aggregation and allow cross country comparisons.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12891-021-04689-5.

Predilection for developing a hematogenous orthopaedic implant-associated infection in older versus younger mice

Background

The pathogenesis of hematogenous orthopaedic implant-associated infections (HOIAI) remains largely unknown, with little understanding of the influence of the physis on bacterial seeding. Since the growth velocity in the physis of long bones decreases during aging, we sought to evaluate the role of the physis on influencing the development of Staphylococcus aureus HOIAI in a mouse model comparing younger versus older mice.

Methods

In a mouse model of HOIAI, a sterile Kirschner wire was inserted retrograde into the distal femur of younger (5–8-week-old) and older (14–21-week-old) mice. After a 3-week convalescent period, a bioluminescent Staphylococcus aureus strain was inoculated intravenously. Bacterial dissemination to operative and non-operative legs was monitored longitudinally in vivo for 4 weeks, followed by ex vivo bacterial enumeration and X-ray analysis.

Results

In vivo bioluminescence imaging and ex vivo CFU enumeration of the bone/joint tissue demonstrated that older mice had a strong predilection for developing a hematogenous infection in the operative legs but not the non-operative legs. In contrast, this predilection was less apparent in younger mice as the infection occurred at a similar rate in both the operative and non-operative legs. X-ray imaging revealed that the operative legs of younger mice had decreased femoral length, likely due to the surgical and/or infectious insult to the more active physis, which was not observed in older mice. Both age groups demonstrated substantial reactive bone changes in the operative leg due to infection.

Conclusions

The presence of an implant was an important determinant for developing a hematogenous orthopaedic infection in older but not younger mice, whereas younger mice had a similar predilection for developing periarticular infection whether or not an implant was present. On a clinical scale, diagnosing HOIAI may be difficult particularly in at-risk patients with limited examination or other data points. Understanding the influence of age on developing HOIAI may guide clinical surveillance and decision-making in at-risk patients.

Direct-Contact Low-Frequency Ultrasound and Pulse Lavage Eradicates Biofilms on Implant Materials In Vitro

Pulse lavage (PL) debridement and ultrasound are both known to be the treatment of biofilm-related periprosthetic joint infection (PJI). However, the efficacy of these in combination is unknown in eradicating biofilm from the orthopaedic metal implant surface. This study was conducted to understand the efficacy of PL and ultrasound in combination in eradicating bacterial biofilms on titanium alloy in vitro. Biofilms of Staphylococcus aureus strains were grown on titanium alloy coupons for 24 h. Then, the coupons were taken to each treatment group: (i) debrided with PL, (ii) exposed to ultrasound, or (iii) exposed to both. An untreated biofilm was set as a control group. Viable plate count and confocal microscopy using live/dead staining was used to measure the amount of biofilm. Viable plate count showed an approximate two-log reduction in CFU/cm² in PL alone, from an initial cell count on the mental surface of approximately 10⁹ CFU/cm². The ultrasound caused an approximate seven-log reduction, and the combination group eradicated viable biofilm bacteria completely. Confocal imaging corroborated the CFU data. Our results indicate that PL and ultrasound both are remarkably in eradicating biofilm, and the combination of PL and ultrasound is more effective than alone in reducing biofilm.