Bacterial epidemiology of osteoarticular infections in a referent center: 10-year study

Effect of achieving bone sterilisation on bone architecture and bone marrow, in an experimental rabbit model of osteomyelitis caused by carbapenemase-producing Enterobacterales

OBJECTIVES

Natural history and treatment of bone infections caused by carbapenemase-producing Enterobacterales (CPE) are poorly defined. We evaluated the effect of treatment on the progression of subacute osteomyelitis in a rabbit model.

METHODS

Two isolates were used: a KPC-producing Klebsiella pneumoniae and an Escherichia coli harbouring blaOXA-48 and blaCTX-M15 inserts, both susceptible to gentamicin, colistin, fosfomycin, and ceftazidime-avibactam. Osteomyelitis was induced in rabbits by tibial injection of 2 × 108 colony-forming units/mL. Antibiotics were started 14 d later, for 7 d, in 6 groups of 12 rabbits. Three days after treatment completion (D24), rabbits were euthanised and bones were cultured. Bone marrow and bone architecture macroscopic changes were evaluated through analysis of pictures by investigators unaware of the rabbit treatment group and microbiological outcome, using scales ranging from 0 (normal) to 3 (severe lesions) depending on modifications.

RESULTS

Bone marrow modifications induced by local infection were similar between prematurely deceased animals and non-sterilised animals (P = 0.14) but differed significantly from animals that achieved bone sterilisation after treatment (P = 0.04). Conversely, when comparing bone deformity, rabbits who died early (n = 13) had similar bone architecture as those achieving bone sterilisation (P = 0.12), as opposed to those not sterilised after treatment (P = 0.04). After a multivariate logistic regression, bone marrow scale ≤2 was associated with bone sterilisation (P < 0.001), and bone architecture scale ≤2 was associated with bone sterilisation (adjusted odds ratio = 2.7; 95% confidence interval 1.14-6.37) and KPC infection (adjusted odds ratio = 5.1; 95% confidence interval 2.17-12.13).

CONCLUSION

Effective antibacterial treatment reduces bone architecture distortion and bone marrow changes. These variables may be used as proxy for bone sterilisation.

Evolution of antibiotic susceptibility profiles of staphylococci from osteoarticular infections: A 10-year retrospective study

BACKGROUND

Knowledge of the antibiotic susceptibility profiles of the bacteria responsible for osteoarticular infections is crucial for choosing the appropriate empirical antibiotic regimen. Wide use of broad spectrum antibiotics in these infections may have lead to selection of resistant bacteria. The aim of our study was to answer to these questions: (1) Did the bacterial pathogens isolated from osteoarticular infections (OAIs) and their antibiotic susceptibility profile change over the 10-year period in our University Hospital, particularly for Staphylococcus aureus and Coagulase negative staphylococci? (2) Are the antibiotics used for post-operative antibiotic therapy still effective against staphylococci involved in OAIs? (3) Are the antibiotics used for documented therapy still effective against staphylococci involved in OAIs?

HYPOTHESIS

We hypothetise that bacterial epidemiology and antibiotic resistance rates have changed little thanks to a reasoned prescription of antibiotics in our Center.

MATERIALS AND METHODS

We performed a retrospective study describing the antibiotic susceptibility profile of bacteria isolated from osteoarticular infections over 10years in our University Hospital, with a focus on the Staphylococcus genus.

RESULTS

A total of 3474 staphylococci were included (2373 coagulase negative staphylococci and 1101 S. aureus), 34.8% (1207/3469) of which were resistant to methicillin. Antibiotic susceptibility profiles remained quite stable between 2010 and 2019, except for rifampicin (14.1% (45/318) versus 5.7% (23/401), p=0.0001) and fluoroquinolones (35.3% (109/309) versus 20.3% (81/399), p=0.000008) for which resistance rates significantly decreased even among methicillin-resistant strains.

DISCUSSION

In spite of wide use of antibiotics in orthopaedic units, overall resistance rates did not increase over the last 10years. The prescription of these molecules in combination regimens guided by the antibiotic susceptibility patterns performed on reliable samples and on the basis of multidisciplinary discussions may explain these results.

LEVEL OF EVIDENCE

IV, retrospective study.

Carbapenem-resistant Klebsiella pneumoniae Osteoarthritis in Two Preterm Infants Treated With Ceftazidime-avibactam

BACKGROUND

The emergence of carbapenem-resistant Klebsiella pneumoniae (CRKP) poses a major threat to global public health. CRKP infections are challenging to treat owing to the limited number of antibiotic species, especially in preterm infants. Ceftazidime-avibactam (CAZ-AVI) is a novel antibiotic with activity against CRKP. At present, there have been no reports of using CAZ-AVI to treat osteoarthritis in premature infants.

METHODS

We describe 2 preterm infants with CRKP osteoarthritis treated with CAZ-AVI in a tertiary children's hospital in China. Clinical characteristics, laboratory and microbiologic data, treatment and follow-up information were retrospectively collected and analyzed.

RESULTS

The 2 cases were both premature infants who contracted sepsis and CRKP osteoarthritis. Meropenem and polymyxin B were initially chosen for the first infant. CAZ-AVI was then used due to persistent infection. The second infant was commenced immediately on CAZ-AVI after receipt of antimicrobial susceptibility on the 4th day after admission. Both recovered with CAZ-AVI (50 mg/kg q8h) and surgical incision and drainage. Neither had a joint deformity or limb length discrepancy at 36 and 34 months, respectively.

CONCLUSIONS

This is the first report on the use of CAZ-AVI to treat CRKP osteoarthritis in premature infants. Successful treatment depends on prompt recognition of the pathogen and treatment with a combination of antibiotics with or without surgery. Further study is needed to determine the pharmacokinetics and pharmacodynamics of CAZ-AVI for treating preterm infants with serious CRKP osteoarthritis.

Ceftazidime-Avibactam as Osteomyelitis Therapy: A Miniseries and Review of the Literature

Bone and joint infections (BJIs) caused by multidrug-resistant gram-negative bacteria are becoming a concern due to limited therapeutic options. Although not approved for these indications, an ever-growing amount of evidence supports the efficacy and safety of ceftazidime-avibactam as a therapy for osteomyelitis and prosthetic joint infections. Here, we present three cases of difficult-to-treat resistant Pseudomonas aeruginosa osteomyelitis that were successfully treated with ceftazidime-avibactam alone or in combination therapy with fosfomycin and amikacin. Ceftazidime-avibactam was prescribed at a daily dose of 2.5 g every 8 h for 42 days in all cases. One potential drug-related adverse effect was observed, i.e., Clostridioides difficile infection, which occurred after fourteen days of treatment with ceftazidime-avibactam.

Treating osteoarticular infections in a Role 2 in Chad: a bacterial epidemiological study

INTRODUCTION

The treatment of osteoarticular infections in Africa is a medical and surgical challenge due to the difficulties in managing antibiotic therapy after the surgical procedure. The objectives of this study were to identify the types of bacteria in osteoarticular lesions in patients treated in Chad and to determine the spectrum of resistance encountered and the efficacy of available antibiotics.

MATERIAL AND METHODS

This is a retrospective study of all intraoperative osteoarticular and soft tissue samples taken in a French Role 2 Medical Treatment Facility of N'Djamena during surgery for chronic osteoarticular infections, in Chad, for 1 year.

RESULTS

A total of 160 bacterial strains were identified, with a predominance of Gram-negative bacillus (GNB) and staphylococcus infections. Among staphylococci, 80% were methicillin-sensitive streptococci which were generally multidrug-sensitive. Enterococci were resistant to third-generation cephalosporins, first-generation fluoroquinolones and gentamycin. Among GNB, there was a predominance of enterobacteria compared with non-fermenting GNB, of which 52% were multidrug-resistant and produced extended spectrum beta-lactamases (ESBL).

CONCLUSION

Staphylococcus aureus infections are most often sensitive to available antibiotics and therefore have better prognoses than infections caused by other bacteria. In contrast, in half of the cases of GNB, infections were caused by bacteria producing ESBL, thus posing the problem of multidrug-resistance, the risks of which are increased in precarious situations. Therefore, the type of bacteria appears to be a major prognostic factor in the treatment of osteoarticular infections in a Role 2 in Chad. This criterion will need to be considered before any treatment decisions are made.

Efficacy of ceftazidime-avibactam in various combinations for the treatment of experimental osteomyelitis due to Klebsiella pneumoniae carbapenemase (KPC)-producing Klebsiella pneumoniae

BACKGROUND

Optimal treatment of carbapenemase-producing Enterobacterales (CPE) bone infections is poorly defined. This study evaluated the efficacy of the novel beta-lactam-beta-lactamase inhibitor-ceftazidime-avibactam (CAZ-AVI)-with different antibiotic combinations in an experimental model of CPE osteomyelitis.

METHODS

KPC-99YC is a clinical strain of Klebsiella pneumoniae carbapenemase (KPC)-producing Klebsiella pneumoniae with intermediate susceptibility to meropenem (MIC 4 mg/L), gentamicin (MIC 0.25 mg/L), colistin (MIC 0.25 mg/L), fosfomycin (MIC 4 mg/L) and ceftazidime-avibactam (MIC 1 mg/L). Time-kill curves were performed at 4x MIC. Osteomyelitis was induced in rabbits by tibial injection of 2×10⁸ CFU of KPC-99YC. Six groups started treatment 14 days later for 7 days: control, colistin, CAZ-AVI, CAZ-AVI plus gentamicin, CAZ-AVI plus colistin and CAZ-AVI plus fosfomycin. Antibiotic dosages were selected to simulate plasma concentrations obtained in humans. Treatment was evaluated according to bone cultures quantified in log₁₀ CFU.

RESULTS

In vitro, CAZ-AVI plus colistin or gentamicin were rapidly bactericidal in contrast with CAZ-AVI plus fosfomycin. In vivo, compared with controls, colistin alone (P = 0.045) and CAZ-AVI alone or in combination significantly lowered bone bacterial counts (P < 0.001). Bone sterilisation was achieved in 67% and 100% of animals with combinations of CAZ-AVI plus colistin or gentamicin (P = 0.001 and P < 0.001, respectively) whereas other treatments were no different from controls. CAZ-AVI plus gentamicin provided greater bone bacterial reduction than CAZ-AVI plus colistin (P = 0.033). No CAZ-AVI-resistant strains emerged in treated rabbits, regardless of combination.

CONCLUSIONS

CAZ-AVI plus gentamicin was the best effective combination therapy. Combinations with CAZ-AVI appear to be a promising treatment of KPC-producing Klebsiella pneumoniae osteomyelitis.

Osteosynthesis-associated infection of the lower limbs by multidrug-resistant and extensively drug-resistant Gram-negative bacteria: a multicentre cohort study

Purpose: The purpose of this study was the clinical and therapeutic assessment of lower-limb osteosynthesis-associated infection (OAI) by multidrug-resistant (MDR) and extensively drug-resistant (XDR) Gram-negative bacteria (GNB), which have been poorly studied to date. Methods: A prospective multicentre observational study was conducted on behalf of ESGIAI (the European Society of Clinical Microbiology and Infectious Diseases (ESCMID) Study Group on Implant-Associated Infections). Factors associated with remission of the infection were evaluated by multivariate and Cox regression analysis for a 24-month follow-up period. Results: Patients ( n = 57 ) had a history of trauma (87.7 %), tumour resection (7 %) and other bone lesions (5.3 %). Pathogens included Escherichia coli ( n = 16 ), Pseudomonas aeruginosa ( n = 14 ; XDR 50 %), Klebsiella spp. ( n = 7 ), Enterobacter spp. ( n = 9 ), Acinetobacter spp. ( n = 5 ), Proteus mirabilis ( n = 3 ), Serratia marcescens ( n = 2 ) and Stenotrophomonas maltophilia ( n = 1 ). The prevalence of ESBL (extended-spectrum β -lactamase), fluoroquinolone and carbapenem resistance were 71.9 %, 59.6 % and 17.5 % respectively. Most patients ( n = 37 ; 64.9 %) were treated with a combination including carbapenems ( n = 32 ) and colistin ( n = 11 ) for a mean of 63.3 d. Implant retention with debridement occurred in early OAI (66.7 %), whereas the infected device was removed in late OAI (70.4 %) ( p = 0.008 ). OAI remission was achieved in 29 cases (50.9 %). The type of surgery, antimicrobial resistance and duration of treatment did not significantly influence the outcome. Independent predictors of the failure to eradicate OAI were age > 60  years (hazard ratio, HR, of 3.875; 95 % confidence interval, CI95 %, of 1.540-9.752; p = 0.004 ) and multiple surgeries for OAI (HR of 2.822; CI95 % of 1.144-6.963; p = 0.024 ). Conclusions: Only half of the MDR/XDR GNB OAI cases treated by antimicrobials and surgery had a successful outcome. Advanced age and multiple surgeries hampered the eradication of OAI. Optimal therapeutic options remain a challenge.

Seventeen Cases of Daptomycin-Induced Eosinophilic Pneumonia in a Cohort of Patients Treated for Bone and Joint Infections: Proposal for a New Algorithm

BACKGROUND

Daptomycin is increasingly used in the treatment of bone and joint infections (BJIs) and may be responsible for daptomycin-induced eosinophilic pneumonia (DIEP), a potentially severe adverse drug reaction. The aim of this study was to describe DIEP in patients treated at a referral center for the management of BJI, and to revisit current definitions of this disease.

METHODS

Patients treated from 1 January 2012 to 31 March 2021 were included in a prospective cohort (NCT02817711), in which all potential serious adverse events are prospectively recorded. Patients diagnosed with DIEP were retrospectively analyzed using different definitions.

RESULTS

In a total of 4664 patients included in the cohort during the study period, 1021 patients (21.9%) received daptomycin, of whom 17 (1.7%) were diagnosed with DIEP. Most patients were male (n = 11 [64.7%]), and periprosthetic joint infection was the commonest BJI (n = 12 [70.6%]). Only 1 patient had bronchoalveolar lavage (BAL) eosinophil count ≥25%, while most patients had peripheral blood eosinophilia (n = 15 [88.2%]). Chest computed tomography (CT) was compatible with eosinophilic pneumonia in 13 of 14 cases (92.9%). All patients recovered upon discontinuation of daptomycin. Using the different definitions available, only a minority of cases fulfilled existing criteria for DIEP. We propose a new algorithm that includes specific CT scan signs, and systemic instead of BAL eosinophilia.

CONCLUSIONS

DIEP is a rare event that requires prompt discontinuation of the causative antibiotic. Current criteria to diagnose definite DIEP are too restrictive and not easily applicable in clinical practice. A new algorithm is proposed here (Lyon algorithm) to facilitate the early identification of DIEP.

Short-term Clinical Outcomes of Unexpected Culture-positive Cutibacterium acnes (Formerly Propionibacterium acnes) in Open Orthopaedic Surgery

INTRODUCTION

The clinical significance and treatment recommendations for an unexpected positive Cutibacterium acnes (C acnes) culture remain unclear. The purpose of our study was to evaluate the clinical effect of a C acnes positive culture in patients undergoing open orthopaedic surgery.

METHODS

Patients with a minimum of one positive C acnes intraoperative culture were retrospectively reviewed over a 7-year period. True C acnes infection was defined as culture isolation from ≥1 specimens in the presence of clinical or laboratory indicators of infection.

RESULTS

Forty-eight patients had a positive intraoperative C acnes culture. 4.2% had a C acnes monoinfection, and 12.5% of the patients had a coinfection. The remainder was classified as indeterminate. Significant differences were identified between the indeterminate and true C acnes infection groups, specifically in patients with surgery history at the surgical site (P = 0.04), additional antibiotic therapy before surgery (P < 0 .001), and postoperative clinical signs of infection (P < 0 .001).

DISCUSSION

Suspicion for true C acnes infection should be raised in patients with surgery site history, antibiotic therapy before surgery, and clinical infectious signs. The indeterminate unexpected positive culture patients had a low risk of developing a true clinical infection that required antibiotic therapy.

Hip joint infections caused by multidrug-resistant Enterobacterales among patients with spinal cord injury: experience of a reference center in the Greater Paris area

Introduction

We aimed to describe the management and treatment of hip joint infections caused by multidrug-resistant Enterobacterales among patients with spinal cord injury (SCI).

Methods

We included all hip joint infections associated with grade IV decubitus ulcers caused by Extended-Spectrum Beta-Lactamase producing Enterobacterales (ESBL-PE) and Carbapenemase-Producing Enterobacterales (CPE) treated in a reference center for bone and joint infections (BJIs) over 9 years in a retrospective study.

Results

Seventeen SCI patients with ischial pressure ulcers breaching the hip capsule (mean age 52 ± 15 years) were analyzed. In 16 patients, paraplegia was secondary to trauma and one was secondary to multiple sclerosis. Infections were mostly polymicrobial (n=15; 88.2%), notably caused by Klebsiella pneumoniae (n=10) and S. aureus (n=10). The carbapenemases identified were exclusively OXA-48-type (n=3) including 2 isolates co-expressed with ESBL-PE within the same bacterial host.

Multidrug-resistant Enterobacterales were commonly resistant to fluoroquinolones (n=12; 70.6%). Most therapies were based on carbapenems (n=10) and combination therapies (n=13). Median duration of treatment was 45 (6-60) days. Of 17 cases of hip joint infections, 94.1% (n=16) benefited from a femoral head and neck resection.

Infection control was initially achieved in 58.8% (n=10) of cases and up to 88.2% after revision surgeries, after a median follow-up of 3 (1-36) months.

Conclusion

Hip infections among SCI patients caused by multidrug-resistant Enterobacterales are often polymicrobial and fluoroquinolones-resistant infections caused by K. pneumoniae and S. aureus, highlighting the need for expert centers with pluridisciplinary meetings associating experienced surgeons, clinical microbiologists and infectious disease specialists.

Native bone and joint infections caused by extended-spectrum β-lactamase-producing Enterobacterales: experience of a reference centre in the Greater Paris area

Antibiotic treatment of native osteomyelitis caused by extended-spectrum β-lactamase-producing Enterobacterales (ESBL-PE) is a challenge. Limited epidemiological and outcome data are available. This retrospective cohort study included osteomyelitis patients with ESBL-PE infections treated in a reference centre for bone and joint infections (BJIs) between 2011-2019. Twenty-nine patients with native BJI (mean age, 44.4 ± 15.7 years) were analysed. Fifteen cases were paraplegic patients with ischial pressure sores breaching the hip capsule. Other cases included eight other hip infections, four tibial infections and two foot infections. Infections were mostly polymicrobial (n = 23; 79.3%), including Staphylococcus aureus (n = 13; 8 methicillin-resistant). Klebsiella pneumoniae (n = 13) was the most frequent ESBL-producing species identified, followed by Escherichia coli (n = 10), including 3 E. coli/K. pneumoniae co-infections, and Enterobacter spp. (n = 9). ESBL-PE were rarely susceptible to fluoroquinolones (n = 4; 13.8%). Most therapies were based on carbapenems (n = 22) and combination therapies (n = 19). The median duration of treatment was 41 (5-60) days. Primary control of the infection was achieved in 62.1% (18/29) of cases and up to 86.2% after second look surgeries, after a median follow-up of 6 (1-36) months. Infection with ESBL-producing K. pneumoniae was associated with failure (P = 0.001), whereas age, infection location, prior colonisation and antimicrobial therapy were not found to be predictors of outcome. ESBL-PE native BJIs are often polymicrobial and fluoroquinolone-resistant infections caused by K. pneumoniae, highlighting the need for expert centres with pluridisciplinary meetings with experienced surgeons.

Cost of off-label antibiotic therapy for bone and joint infections: a 6-year prospective monocentric observational cohort study in a referral centre for management of complex osteo-articular infections

Introduction: Costs related to bone and joint infection (BJI) management are increasing worldwide, particularly due to the growing use of off-label antibiotics that are expensive treatments (ETs), in conjunction with increasing incidence of multi-drug-resistant pathogens. The aim of this study was to evaluate the whole costs related to these treatments during the patient route, including those attributed to the rehabilitation centre (RC) stay in one regional referral centre in France. The total annual cost of ETs for managing complex BJIs in France was then estimated.

Material and methods: A prospective monocentric observational study was conducted from 2014 to 2019 in a referral centre for BJI management (CRIOAc – Centre de Référence des Infections OstéoArticulaires complexes). Costs related to expensive treatments (“old” ETs, i.e. ceftaroline, ertapenem, daptomycin, colistin, tigecycline, and linezolid and “new” ETs, defined as those used since 2017, including ceftobiprole, ceftazidime-avibactam, ceftolozane-tazobactam, tedizolid, and dalbavancin) were prospectively recorded. In all cases, the use of these ETs was validated during multidisciplinary meetings.

Results: Of the 3219 patients treated, 1682 (52.3 %) received at least one ET, and 21.5 % of patients who received ET were managed in RCs. The overall cost of ETs remained high but stable (EUR 1 033 610 in 2014; EUR 1 129 862 in 2019), despite the increase of patients treated by ETs (from 182 in 2014 to 512 in 2019) and in the cumulative days of treatment (9739 to 16 191 d).

Daptomycin was the most prescribed molecule (46.2 % of patients in 2014 and 56.8 % in 2019, with 53.8 % overall), but its cost has decreased since this molecule was genericized in 2018; the same trend was observed for linezolid. Thus, costs for old ETs decreased overall, from EUR 1 033 610 in 2014 to EUR 604 997 in 2019, but global costs remained stable due to new ET utilization accounting for 46.5 % of overall costs in 2019. Tedizolid, used as suppressive antimicrobial therapy, represented 77.5 % of total new ET costs. In our centre, dalbavancin was never used.

The cost paid by RCs for ETs and the duration of ET remained stable overall between 2016 and 2019.

Conclusions: A high consumption of off-label ET is required to treat patients with BJIs in a CRIOAc, and the consequence is a high cost of antimicrobial therapy for these patients, estimated to be almost EUR 10 million in France annually. Costs associated with ET utilization remained stable over the years. On the one hand, the introduction of the generic drugs of daptomycin and linezolid has significantly decreased the share of old ETs, but, on the other hand, the need for new ETs to treat infections associated with more resistant pathogens has not led to decrease in the overall costs. A drastic price reduction of generic drugs is essential to limit the costs associated with more complex BJIs.

Safety of Tedizolid as Suppressive Antimicrobial Therapy for Patients With Complex Implant-Associated Bone and Joint Infection due to Multidrug-Resistant Gram-Positive Pathogens: Results From the TediSAT Cohort Study

A prospective cohort study was conducted to evaluate long-term safety of tedizolid as suppressive antimicrobial treatment in patients with implant-associated bone and joint infection caused by multidrug-resistant gram-positive pathogens. Seventeen patients received tedizolid with a median duration of treatment of 6 months. No patients developed a serious adverse event.

Diagnostic accuracy of the BJI InoPlex™ (Diaxonhit) immunoassay on blood samples for periprosthetic joint infection in complex microbiological situations. Preliminary results of 24 cases in a French Reference Center for Complex Bone and Joint Infection (CRIOAC)

BACKGROUND

While joint aspiration is the benchmark for diagnosing periprosthetic joint infections (PJI), the results can be flawed because certain bacteria are difficult to culture, the patient is on concurrent antibiotic therapy or in some cases, repeated joint aspirations confer conflicting results. The BJI InoPlex™ (Diaxonhit) is a multiplex ELISA (Enzyme Linked Immunosorbent Assay) that measures the immune response (presence of specific IgG) to certain bacterial species from three families: Staphylococcus (8 antigens) epidermidis, aureus and lugdunensis, Streptococcus B (4 antigens) and Cutibacterium acnes (4 antigens). This assay is done with peripherally collected blood. However, there are few published studies about this assay, especially if the microbiological diagnosis is in doubt in cases of suspected chronic PJI. This led us to conduct a retrospective study in a French tertiary care center to determine 1) the sensitivity and specificity of the BJI InoPlex™, 2) its positive (PPV) and negative predictive value (NPV) and 3) what causes diagnostic errors.

HYPOTHESIS

The BJI InoPlex has a sensitivity/specificity and PPV/NPV above 75%.

MATERIALS AND METHODS

The BJI InoPlex was used 24 times on 24 patients between January 2016 and January 2017 in scenarios where the microbiological diagnosis was difficult: 1 with on-going antibiotic therapy, 13 conflicting repeat joint aspirations, 10 negative cultures with history of infection and/or clinical evidence of a PJI. The series consisted of 11 hip arthroplasty and 13 knee arthroplasty cases. The results of the BJI InoPlex test were compared to the MusculoSkeletal Infection Society (MSIS) the criteria for a joint infection.

RESULTS

For the bacterial species covered by the test, the sensitivity of the BJI InoPlex for diagnosing a chronic PJI based on the 2018 MSIS criteria was 50%, the specificity was 56%, the PPV was 36% and the NPV was 69%.

DISCUSSION

While innovative, minimally invasive, and rapid (results in a few hours), the BJI InoPlex does not provide an effective diagnosis of chronic PJI in complex microbiological situations. In this study, we used the test in the most difficult situations possible and on a small number of patients, which may explain why the results were not as good as in other studies. Its current performance and cost mean there is no role for it in our algorithm for treating patients with a suspected PJI, contrary to other biomarkers. Its spectrum must include other bacterial strains involved in chronic PJI. Knowledge of the specific infectious agent increases its diagnostic value, it could be used to monitor the outcome of a PJI, although other studies would be needed to support this use.

LEVEL OF EVIDENCE

IV-Retrospective diagnostic study.

Treatment of bone and joint infections by ceftazidime/avibactam and ceftolozane/tazobactam: a cohort study

OBJECTIVES

Ceftazidime/avibactam (C/A) and ceftolozane/tazobactam (C/T) are two novel antibacterials with known efficacy against Gram-negative bacteria (GNB). We aimed to describe the efficacy and safety of surgical management combined with C/A or C/T treatment for bone and joint infections (BJIs).

METHODS

We conducted an observational, bicentric study of patients treated with C/A or C/T for a BJI between May 2016 and June 2019. Failure was defined as the need for unplanned additional antibiotic treatment or orthopaedic surgery, or death due to the BJI up to the patient's latest visit.

RESULTS

Overall, 15 patients were included. Nine patients were treated with C/A, mainly for polymicrobial BJI due to multidrug-resistant (MDR) bacteria (Enterobacteriaceae, n = 7). Six patients were male, the median age was 66 years and the median Charlson comorbidity index (CCI) was 5. It was the first septic episode at the site in 3/9 patients. The cure rate was 7/9 (median follow-up, 272 days). Two patients showed C/A-related confusion. Five patients were treated with C/T for BJI involving MDR Pseudomonas aeruginosa. Four patients were male, the median age was 53 years and the median CCI was 2. All patients had previous septic episodes at the infection site. The cure rate was 3/5 (median follow-up, 350 days). One patient was successfully treated by C/T then C/A for multistage spondylodiscitis.

CONCLUSION

In our experience, C/A and C/T are two effective and safe options, even as salvage treatment for BJI due to MDR-GNB despite the absence of label, however more data are warranted.

The Topical Tranexamic Acid Have Potential Hazard of Promoting Biofilm Formation of Staphylococcus aureus in Microenvironment of the Prosthetic Joint

Background. Perioperative topical tranexamic acid as antifibrinolytic agent is often used for total joint replacement to reduce bleeding currently. Staphylococcus aureus was the most common isolates from perioperative infection of prosthetic joint. The influence of topical application with tranexamic acid on the incidence of acute prosthetic joint infection of Staphylococcus aureus has not been clarified. Methods. Mouse model of Staphylococcus aureus knee prosthesis infection was constructed. Tranexamic acid was intra-articular injected during the perioperative period. CFU counting from tissue and implant sample was evaluated 3 days and 7 days after inoculating of Staphylococcus aureus. Bacterial growth curve, biofilm formation, aggregation, and plasmin inhibition of Staphylococcus aureus were tested with tranexamic acid added to the synovial culture medium. Results. There were no significant differences of CFU counting from tissue and implant samples in knee prosthesis infection after a single local injection of tranexamic acid at the postoperative 3 or 7 days. The amount of bacterial colonization on the surface of implant increased after 3 days’ continuous local injection of tranexamic acid. Tranexamic acid has no effect on bacterial growth at the concentration (10 mg/ml) of clinical application, but it can inhibit bacterial aggregation and mildly inhibit biofilm formation. Plasmin can significantly inhibit biofilm formation which can be revised by adding tranexamic acid. Conclusion. Although continuous local injection of tranexamic acid can promote the biofilm formation of Staphylococcus aureus on the surface of articular implant, it has clinical safety for using one single local injection of tranexamic acid during the perioperative period.

Tolerance of Prolonged Oral Tedizolid for Prosthetic Joint Infections: Results of a Multicentre Prospective Study

Objectives: Data on clinical and biological tolerance of tedizolid (TZD) prolonged therapy are lacking. Methods: We conducted a prospective multicentre study including patients with prosthetic joint infections (PJIs) who were treated for at least 6 weeks but not more than 12 weeks. Results: Thirty-three adult patients of mean age 73.3 ± 10.5 years, with PJI including hip (n = 19), knee (n = 13) and shoulder (n = 1) were included. All patients were operated, with retention of the infected implants and one/two stage-replacements in 11 (33.3%) and 17/5 (51.5%/15.2%), respectively. Staphylococci and enterococci were the most prevalent bacteria identified. The mean duration of TZD therapy was 8.0 ± 3.27 weeks (6–12). TZD was associated with another antibiotic in 18 patients (54.5%), including rifampicin in 16 cases (48.5). Six patients (18.2%) had to stop TZD therapy prematurely because of intolerance which was potentially attributable to TZD (n = 2), early failure of PJI treatment (n = 2) or severe anaemia due to bleeding (n = 2). Regarding compliance with TZD therapy, no cases of two or more omissions of medication intake were recorded during the whole TZD treatment duration. Conclusions: These results suggest good compliance and a favourable safety profile of TZD, providing evidence of the potential benefit of the use of this agent for the antibiotic treatment of PJIs.

[Recurrence of septic arthritis of the wrist by Pseudomonas aeruginosa due to colonization of a central venous indwelling catheter]

A diabetic patient, wearer of a port and with a history of gonarthritis due to Pseudomonas aeruginosa presented with subacute arthritis of a wrist. After a protracted interval P. aeruginosa was detected by microbial culture from the explanted port and the affected joint. This case shows that in patients with unclear arthritis of the wrist, a history of septic arthritis with P. aeruginosa and risk factors for hematogenous spread, a recurrent infection should be excluded. The treatment consisted of explantation of the port, débridement with synovectomy of the joint and adequate antibiotic treatment.

First case report of Cryptococcus laurentii knee infection in a previously healthy patient

Background

The purpose of this case report was to report a case of Cryptococcus laurentii infection in the left knee of a previously healthy 29 year old male patient.

Case presentation

After an initial misdiagnosis and 7 months of failed treatment, the patient received nearly a month of treatment with voriconazole (200 mg IV q12 h) and knee irrigation with amphotericin B until the infection was controlled. The treatment continued with fluconazole for nearly 7 months and approximately 5 weeks of antibiotic treatment for a skin bacterial coinfection. In the end, the patient’s symptoms disappeared completely, the left knee recovered well, and there was no recurrence of infection.

Conclusion

The key points of successful treatment in this case were the thorough debridement, the adequate course of knee irrigation with antifungal drugs and more than 6 months of oral antifungal drugs that were able to eradicate the infection.

Case series of carbapenemase-producing Enterobacteriaceae osteomyelitis: Feel it in your bones

OBJECTIVES

Limited data have been reported regarding osteomyelitis due to carbapenemase-producing Enterobacteriaceae (CPE), including co-infections with extended-spectrum β-lactamase (ESBL)-producing micro-organisms.

METHODS

We conducted a retrospective study in a reference centre for bone and joint infections from 2011 to 2019 among patients infected with CPE.

RESULTS

Nine patients (mean age 46.8 ± 16.6 years), including three with infected implants, were identified. Infections were mostly polymicrobial (n = 8/9), including Staphylococcus aureus (n = 6/9). CPE were mainly OXA-48-type, associated with ESBL-producing Enterobacteriaceae (n = 8/9), of which 5/9 isolates were Klebsiella pneumoniae. Control of the infection was achieved in seven cases.

CONCLUSIONS

CPE osteomyelitides are essentially polymicrobial and fluoroquinolone-resistant infections, highlighting the need for efficient surgery with implant removal.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSION

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

Efficacy of cotrimoxazole (Sulfamethoxazole-Trimethoprim) as a salvage therapy for the treatment of bone and joint infections (BJIs)

INTRODUCTION

Cotrimoxazole (Sulfamethoxazole-Trimethoprim, SXT) has interesting characteristics for the treatment of bone and joint infection (BJI): a broad spectrum of activity with adequate bone diffusion and oral and intravenous formulations. However, its efficacy and safety in BJIs are poorly documented and its use remains limited.

METHODS

We conducted a retrospective study in 2 reference centers for BJIs from 2013 to 2018 among patients treated with SXT for a BJI. Data were collected from patient's medical charts. Outcomes and adverse events were evaluated at day (D)7, D45 and D90.

RESULTS

We analyzed 51 patients with a mean age of 60 ± 20 (SD) years of which 76% presented with an orthopedic device infection (ODI). Gram-negative bacilli (GNB) were involved in 47% of BJIs (n = 24). Moreover, they were often polymicrobial infections (41%). Doses of SXT ranged from 800/160mg bid (61%; n = 31) to 800/160mg tid (39%; n = 20). Median SXT treatment duration was 45 days (IQR 40-45). SXT was part of a dual therapy in 84% of patients (n = 43), associated mainly with fluoroquinolones (n = 17) or rifampicin (n = 14). Outcome was favorable at D7 in 98% (n = 50), at D45 in 88.2% (n = 45) and at D90 in 78.4% (n = 40). The second agent combined with SXT was not an independent factor of favorable outcome (p = 0.97). Adverse events were reported in 8% (n = 4) of patients, with a median of 21 days (IQR 20-30) from SXT initiation and led to discontinuation (n = 3).

CONCLUSION

SXT appears to be effective for treatment of BJIs as a salvage therapy, even in GNB or polymicrobial infection, including ODI. Further data are needed to confirm SXT efficacy as an alternative oral regimen in BJIs.

Oral versus Intravenous Antibiotics for Bone and Joint Infection

BACKGROUND

The management of complex orthopedic infections usually includes a prolonged course of intravenous antibiotic agents. We investigated whether oral antibiotic therapy is noninferior to intravenous antibiotic therapy for this indication.

METHODS

We enrolled adults who were being treated for bone or joint infection at 26 U.K. centers. Within 7 days after surgery (or, if the infection was being managed without surgery, within 7 days after the start of antibiotic treatment), participants were randomly assigned to receive either intravenous or oral antibiotics to complete the first 6 weeks of therapy. Follow-on oral antibiotics were permitted in both groups. The primary end point was definitive treatment failure within 1 year after randomization. In the analysis of the risk of the primary end point, the noninferiority margin was 7.5 percentage points.

RESULTS

Among the 1054 participants (527 in each group), end-point data were available for 1015 (96.3%). Treatment failure occurred in 74 of 506 participants (14.6%) in the intravenous group and 67 of 509 participants (13.2%) in the oral group. Missing end-point data (39 participants, 3.7%) were imputed. The intention-to-treat analysis showed a difference in the risk of definitive treatment failure (oral group vs. intravenous group) of -1.4 percentage points (90% confidence interval [CI], -4.9 to 2.2; 95% CI, -5.6 to 2.9), indicating noninferiority. Complete-case, per-protocol, and sensitivity analyses supported this result. The between-group difference in the incidence of serious adverse events was not significant (146 of 527 participants [27.7%] in the intravenous group and 138 of 527 [26.2%] in the oral group; P=0.58). Catheter complications, analyzed as a secondary end point, were more common in the intravenous group (9.4% vs. 1.0%).

CONCLUSIONS

Oral antibiotic therapy was noninferior to intravenous antibiotic therapy when used during the first 6 weeks for complex orthopedic infection, as assessed by treatment failure at 1 year. (Funded by the National Institute for Health Research; OVIVA Current Controlled Trials number, ISRCTN91566927 .).

Comparison between the Staphylococci aureus and coagulase-negative staphylococci infected total joint arthroplasty treated by two-stage revision: A retrospective study with two year minimum follow-up

BACKGROUND

Staphylococcus species are major pathogens of peri-prosthetic joint infection (PJI). Coagulase-positive staphylococci and coagulase-negative staphylococci have different intrinsic virulences. However, few studies have specifically compared the clinical manifestations and two-stage revision outcomes of PJI caused by these two species.

METHODS

We retrospectively collected 260 arthroplasty patients who underwent a two-stage revision because of PJI from January 2003 to June 2015 in our institute because of PJI. Sixty-four patients (36 hips and 28 knees) and 23 patients (13 hips and 10 knees) were infected by coagulase-negative staphylococci (CoNS) and SA, respectively.

RESULTS

The preoperative mean ESR value of the SA group was higher than that of the CoNS group (median, 60.9 VS 35.9; P < 0.001). Seventeen (73.9%) of the 23 SA infected patients had a sinus tract, while only 12 (18.8%) of the 64 CoNS-infected patients had this symptom (73.9% VS 18.8%; P < 0.001). At the time of follow-up, 58 (90.6%) of the 64 CoNS-infected patients had successfully controlled the infection. In the SA group, 20 (87.0%) patients ultimately acquired successful control (90.6% VS 87.0%; P = 0.923). Surgical history was identified as a potential risk factor (OR = 6.2, 95%CI 1.17-32.4) for prognosis when potential covariates were adjusted.

CONCLUSIONS

SA infection has a higher ESR value and a more frequent occurrence of sinus tract. The infection control rate of the two-stage revision protocol was close to 90% for both SA and CoNS species, and there is no statistically significant difference in the eradication rate of infection between the SA and CoNS groups. Surgical history may be a good predictor of failure for PJI patients treated with two-stage revision.

Species and antimicrobial susceptibility testing of coagulase-negative staphylococci in periprosthetic joint infections

The objective was to evaluate the distribution of coagulase-negative staphylococci (CNS) involved in periprosthetic-joint infections (PJIs) and to describe their susceptibility profile to antibiotics. We conducted a multicentre retrospective study in France, including 215 CNS PJIs between 2011 and 2015. CNS PJIs involved knees in 54% of the cases, hips in 39%, other sites in 7%. The distribution of the 215 strains was: Staphylococcus epidermidis 129 (60%), Staphylococcus capitis 24 (11%), Staphylococcus lugdunensis 21 (10%), Staphylococcus warneri 8 (4%), Staphylococcus hominis 7 (3%), Staphylococcus haemolyticus 7 (3%). More than half of the strains (52.1%) were resistant to methicillin, 40.9% to ofloxacin, 20% to rifampicin. The species most resistant to antibiotics were S. hominis, S. haemolyticus, S. epidermidis, with 69.7% of the strains resistant to methicillin and 30% simultaneously resistant to clindamycin, cotrimoxazole, ofloxacin and rifampicin. No strain was resistant to linezolid or daptomycin. In this study on CNS involved in PJIs, resistance to methicillin is greater than 50%. S. epidermidis is the most frequent and resistant species to antibiotics. Emerging species such S. lugdunensis, S. capitis and Staphylococcus caprae exhibit profiles more sensitive to antibiotics. The antibiotics most often active in vitro are linezolid and daptomycin.

Bacteriological relevance of linezolid vs. vancomycin in postoperative empirical treatment of osteoarticular infections: a retrospective single-center study

BACKGROUND

In 2015, our center replaced vancomycin with linezolid for the postoperative empirical treatment of osteoarticular infections (OAI).

OBJECTIVES

To assess the bacteriological relevance of linezolid for orthopedic postoperative probabilistic antibiotic therapy.

METHODS

Analysis of an observational cohort of patients empirically treated with a combination of linezolid and piperacillin/tazobactam during the immediate postoperative stage for an OAI between July 1^st 2015 and July 1^st 2016, in a French reference center.

RESULTS

Seventy-seven of 126 patients who received a probabilistic postoperative combination of linezolid with piperacillin/tazobactam had microbiological proof of infection. Sixty-six of 77 OAI involved material, including an osteosynthesis in 45 cases (68%) and prosthesis in 21 cases (32%). Infection was due to Gram-positive bacteria in 62 cases (80.5%), mostly S. aureus (n=32, 41.6%), and S. epidermidis (n=14, 18.2%) accounting for 74.2% of Gram-positive bacteria. Among 14 OAI due to S. epidermidis, 11 (78.6%) were due to methicillin-resistant strains. All the S. aureus and S. epidermidis strains were susceptible to linezolid (MICs ≤ 4 mg/L), except in one patient previously treated with linezolid who was infected with a linezolid-resistant S. epidermidis strain (MIC > 256 mg/L).

CONCLUSION

Linezolid can be used empirically in postoperative antibiotic therapy of OAI before obtaining definitive microbial results. Although linezolid resistance is rare in this population, previous oxazolidinone treatment should be documented before initiation of probabilistic postoperative treatment to highlight potential linezolid resistance.

Characteristics of spontaneous coagulase-negative staphylococcal spondylodiscitis: a retrospective comparative study versus Staphylococcus aureus spondylodiscitis

Background

Coagulase-negative staphylococci (CoNS) are increasingly implicated in recent patient series of spondylodiscitis, but there are no series of CoNS-spondylodiscitis available. The objective of this study was to compare the characteristics of patients with spontaneous CoNS-spondylodiscitis with those patients with Staphylococcus aureus (SA) spondylodiscitis.

Methods

This was a retrospective single center study involving 147 spontaneous infectious spondylodiscitis cases observed between 2000 and 2015. The 26 cases of CoNS-spondylodiscitis (15 confirmed) were compared with 30 cases of SA-spondylodiscitis. CoNS infection was considered confirmed if the same CoNS was isolated in at least two samples at two different times.

Result

Patients with CoNS-spondylodiscitis were older (70 vs. 61 years of age; p = 0.01), had associated cancer more often (15% vs. 0%; p = 0.04) and had a longer diagnostic delay (>15 days in 88% vs. 60%; p = 0.01); experienced fever less often (19% vs. 50%; p = 0.01), and had lower white blood cell (7.6 vs. 9.9G/L; p = 0.01) and polymorphonuclear leucocyte counts (5.6 vs. 7.5G/L; p = 0.04). Patients with CoNS spondylodiscitis had less pronounced inflammatory syndrome (erythrocyte sedimentation rate [ESR]: 62 vs. 81 mm at 1 h; p = 0.03; CRP: 60 vs. 147 mg/L; p = 0.0003) and less common (ESR < 30 mm: 23% vs. 0%; p = 0.01; CRP < 10 mg/L: 23% vs. 0%; p = 0.005) in comparison with patients with SA infection. The infection entry site was most often an intravascular catheter (20% vs. 3%; p = 0.008). The level of positive percutaneous needle biopsies was comparable between CoNS and SA. Two patients who died both had SA infections.

Conclusion

CoNS-spondylodiscitis involved at least 10% of spontaneous spondylodiscitis cases and was more common in elderly patients, afflicted by comorbidities, and its presentation was less virulent than that of those with SA-spondylodiscitis.

Clinical impact of positive Propionibacterium acnes cultures in orthopedic surgery

BACKGROUND

The clinical significance of a positive culture to Propionibacterium acnes in orthopedic specimens remains unclear, whether about its role as a contaminant or a pathogen, or its impact as a coinfectant. Therefore, we performed a retrospective study to provide a more accurate description of the clinical impact of P. acnes in an orthopedic population aiming to determine: 1) if there is a clinical difference between P. acnes infection and contamination? 2) If there is a clinical difference between P. acnes monoinfection, and coinfection.

HYPOTHESIS

There is a clinical difference between P. acnes infection and contamination.

MATERIALS AND METHODS

Patients were selected over a five-year period, and those with a minimum of one positive culture for P. acnes, from any intraoperative orthopedic tissue sample, were included in the study. P. acnes infection was defined as the isolation of P. acnes from≥2 specimens, or in only one specimen, in the presence of typical perioperative findings and/or local signs of infection.

RESULTS

A total of 68 patients had a positive P. acnes culture, 35 of which were considered to be infected. The infections affected mostly males (29/35-83%), occurred mostly in shoulders (22/35-63%), and at a site already containing an orthopedic implant (32/35-91%). Local inflammatory signs were present in half of the cases when an infection was diagnosed. Coinfection with other pathogens was present in 31% of patients (11/35). When comparing patients coinfected with P. acnes, and those who were monoinfected, the latter presented less often with local inflammatory signs. Recurrence rate was 24% (8/35) and the only risk factor for recurrence was the presence of a monoinfection.

DISCUSSION

This study confirms the pathogenicity of P. acnes in an orthopedic population, as it is present in multiple samples in the same patient, and because it is present in cultures from cases with clinical recurrence. Our study showed that monoinfections differ from coinfections mainly by their higher risk of recurrence.

LEVEL OF EVIDENCE

Level IV retrospective case series.

Old antimicrobials and Gram-positive cocci through the example of infective endocarditis and bone and joint infections

The management of some serious infections such as infective endocarditis (IE) and bone and joint infections (BJIs) caused by Gram-positive cocci (GPC) is complex and requires great responsiveness and effective antimicrobials with high bioavailability in heart valves or bone tissues. Treatment of these infections requires the use of a higher dosage that may result in increased toxicity or the use of new promising antimicrobials to control the infection. However, use of these new antimicrobials could still bring about new toxicity and resistance. Another approach may be the 'comeback' of old antimicrobials, which is evaluated in this review in the treatment of IE and BJIs caused by GPC.

Epidemiology of patients with MSSA versus MRSA infections of orthopedic implants: Retrospective study of 115 patients

Factors that predict the occurrence of a surgical site infection due to methicillin-resistant Staphylococcus aureus (MRSA) are not well known; however this information could be used to modify the recommended antimicrobial prophylaxis. We carried out a retrospective study of S. aureus infections on orthopedic implants to determine: (1) whether epidemiological factors can be identified that predict a MRSA infection, (2) the impact of these factors as evidenced by the odds ratio (OR).

HYPOTHESIS

Risk factors for a MRSA infection can be identified from a cohort of patients with S. aureus infections.

MATERIALS AND METHODS

We identified 244 patients who experienced a S. aureus surgical site infection (SSI) in 2011-2012 documented by intraoperative sample collection. Of these 244 patients, those who had a previous SSI (n=44), those with a SSI but no orthopedic implant (n=80) or those who had the infection more than 1-year after the initial surgery (n=5) were excluded. This resulted in 115 patients (53 arthroplasty, 62 bone fixation) being analyzed for this study. There were 24 MRSA infections and 91 MSSA infections. The following factors were evaluated in bivariate and multifactorial analysis: age, sex, type of device (prosthesis/bone fixation), predisposition (diabetes, obesity, kidney failure), and environmental factors (hospitalization in intensive care unit within past 5 years, nursing home stay).

RESULTS

Two factors were correlated with the occurrence of MRSA infections. (1) Nursing home patients had a higher rate of MRSA infections (67% vs. 18%, P=0.017) with an OR of 8.42 (95% CI: 1.06-66.43). (2) Patients who had undergone bone fixation had a lower rate of MRSA infections than patients who had undergone arthroplasty (13% vs. 30%, P=0.023), OR 0.11 (95% CI: 0.02-0.56). Although the sample size was too small to be statistically significant, all of the patients with kidney failure (n=4) had a MRSA infection.

DISCUSSION

Since these MRSA infection risk factors are easy to identify, the antimicrobial prophylaxis could be adapted in these specific patient groups.

Temporal trends of β-haemolytic streptococcal osteoarticular infections in western Norway

BACKGROUND

Beta-haemolytic streptococci are important contributors to the global burden of osteoarticular infections (OAI). Knowledge on the disease traits specific for streptococcal OAI, however, remains scarce. We wished to explore temporal trends of OAI caused by Group A Streptococci (GAS), Group B Streptococci (GBS) and Group C and G Streptococci (GCGS), and furthermore, to describe the associated host and pathogen characteristics.

METHODS

All cases of microbiologically verified β-haemolytic streptococcal OAI in Health Region Bergen, Norway, in the period 1999-2013 were retrospectively identified. Clinical data were extracted from medical records. Microbial isolates were submitted to antibiotic susceptibility testing and molecular typing.

RESULTS

A total of 24 GAS, 45 GBS and 42 GCGS acute OAI were identified. The cumulative incidence of GCGS OAI, but not GAS or GBS OAI, increased significantly from the first to the last 5-year period (IRR 5.7, p = 0.0003), with the annual incidence peaking at 1.9/100 000 in 2013. GAS OAI generally produced the most acute and severe clinical presentation, whereas GBS and GCGS predominantly affected the elderly, and were significantly associated with the presence of host risk factors of systemic and focal origin, respectively.

CONCLUSIONS

We found a significantly increasing incidence of GCGS OAI, likely related to the presence of host susceptibility factors, including prosthetic material and pre-existing joint disease. With an increasing application of therapeutic and diagnostic bone and joint procedures, the rising trend of OAI caused by GCGS is likely to continue. Sustained epidemiological attentiveness to GCGS seems warranted.

Is the prognosis the same for periprosthetic joint infections due to Staphylococcus aureus versus coagulase-negative staphylococci? A retrospective study of 101 patients with 2-year minimum follow-up

BACKGROUND

Staphylococcus aureus (SA) and Coagulase-negative staphylococci (CoNS) are often responsible for infections of total hip arthroplasty (THA) and total knee arthroplasty (TKA). One of the main differences between these two microorganisms is their virulence, with SA presumed to be more virulent; however, few studies have specifically investigated the impact of this virulence. This inspired us to carry out a retrospective study to evaluate whether the healing rate differed between SA and CoNS infections.

HYPOTHESIS

We hypothesised that the healing rate is lower for SA prosthetic joint infections.

MATERIALS AND METHODS

This was a retrospective study of 101 consecutive Staphylococcus infection cases that occurred between 2007 and 2011. There were 56 men and 45 women with an average age of 69 years (range 23-95). The infection was associated with TKA in 38 cases and THA in 63 cases. Thirty-two percent of patients had one or more comorbidities with infectious potential. In our cohort, there were 32 SA infections (31.7 %) and 69 CoNS infections (68.3 %) with 58 of the infections being methicillin-resistant (15 SA and 43 CoNS); there were 27 polymicrobial infections (26.7 %).

RESULTS

With a minimum 24-month follow-up after the end of antibiotic treatment, the healing rate was 70.3 % overall (71 patients). The healing rate was 75 % in the SA group (24 patients) versus 68.1 % (47 patients) in the CoNS group (P = 0.42).

CONCLUSION

Our hypothesis was not confirmed: the healing rate of SA prosthetic joint infections was not lower than that of CoNS infections.

LEVEL OF EVIDENCE

III, retrospective case-control study.

De novo Propionibacterium acnes septic arthritis

We report the third identifiable case of septic arthritis due to Propionibacterium acnes arising in the absence of prior surgical intervention. This anaerobic Gram-positive bacillus is now recognised as an important cause of postoperative infections, typically presenting in an indolent fashion some months after surgery. Reports of de novo septic arthritis due to P. acnes are exceedingly rare. Our case adds to the literature and significantly broadens the reported pathogenic potential of the organism, which in this instance has caused rapid and serious joint destruction.

Time trends in the aetiology of prosthetic joint infections: a multicentre cohort study

It is important to know the spectrum of the microbial aetiology of prosthetic joint infections (PJIs) to guide empiric treatment and establish antimicrobial prophylaxis in joint replacements. There are no available data based on large contemporary patient cohorts. We sought to characterize the causative pathogens of PJIs and to evaluate trends in the microbial aetiology. We hypothesized that the frequency of antimicrobial-resistant organisms in PJIs has increased in the recent years. We performed a cohort study in 19 hospitals in Spain, from 2003 to 2012. For each 2-year period (2003-2004 to 2011-2012), the incidence of microorganisms causing PJIs and multidrug-resistant bacteria was assessed. Temporal trends over the study period were evaluated. We included 2524 consecutive adult patients with a diagnosis of PJI. A microbiological diagnosis was obtained for 2288 cases (90.6%). Staphylococci were the most common cause of infection (1492, 65.2%). However, a statistically significant rising linear trend was observed for the proportion of infections caused by Gram-negative bacilli, mainly due to the increase in the last 2-year period (25% in 2003-2004, 33.3% in 2011-2012; p 0.024 for trend). No particular species contributed disproportionally to this overall increase. The percentage of multidrug-resistant bacteria PJIs increased from 9.3% in 2003-2004 to 15.8% in 2011-2012 (p 0.008), mainly because of the significant rise in multidrug-resistant Gram-negative bacilli (from 5.3% in 2003-2004 to 8.2% in 2011-2012; p 0.032). The observed trends have important implications for the management of PJIs and prophylaxis in joint replacements.

Clinical features and outcome of bone and joint infections with streptococcal involvement: 5-year experience of interregional reference centres in the south of France

Streptococcal bone and joint infections are less common than staphylococcal cases. Few studies have reported the cases with well-identified Streptococcus species. Their clinical features and prognosis are not clearly known to date. Moreover, no treatment regimen has yet been clarified. We reviewed the streptococcal bone and joint infection cases managed in our centres from January 2009 to December 2013. We described the epidemiology, clinical and microbiologic characteristics, treatment approach and outcome. Among the 93 cases, 83% of patients were men with a median age of 60 years, and 90% of patients had comorbidities or risk factors. Bacteraemia occurred in 14% of cases. Serious complications occurred in six patients, including severe sepsis (two cases) and infective endocarditis (two cases). Orthopaedic device infections were observed in 35% of cases, including 17 patients with internal osteosynthesis device infection, 14 with prosthetic joint infection and three with vertebral osteosynthesis device infection. The median time between orthopaedic device implantation and onset of infection was 447 days. Fourteen species of Streptococcus were identified, including 97 isolates using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry and three isolates using molecular identification. The five most represented species included S. agalactiae (37%), S. dysgalactiae (12%), S. anginosus (11%), S. constellatus (10%) and S. pneumoniae (9%). Streptococci isolates were susceptible to amoxicillin, with the exception of one S. mitis isolate. Remission 1 year after the end of treatment was recorded in 83%. One patient died of infection; eight patients had infections that failed to respond to treatment; and seven patients experienced relapse. Twenty patients (22%) had an unfavourable functional outcome, including 19 amputations and one arthrodesis. Five significant prognostic factors associated with an unfavourable clinical outcome were identified, including peripheral neuropathy (p 0.009), peripheral arterial disease (p 0.019), diabetes mellitus (p 0.031), location in the femur (p 0.0036), location in the foot (p 0.0475), osteitis without an orthopaedic device (p 0.041) and infection caused by S. dysgalactiae (p 0.020). The rate of poor outcomes remains high despite the low number of Streptococcus isolates resistant to antibiotics. Some prognostic factors, such as the presence of S. dysgalactiae, are associated with an unfavourable clinical outcome. Antibiotic regimens of streptococcal bone and joint infections are not standardized and need to be further investigated.

Trends in surgical site infections following orthopaedic surgery

PURPOSE OF REVIEW

This review presents an update on recent findings relating to the prevention, control and epidemiology of infections following orthopaedic surgery.

RECENT FINDINGS

Trends in population rates and characteristics of patients undergoing hip and knee replacement surgery, coupled with the reported excess infection risk in obese patients, emphasize the current and future impact of increasing population obesity on healthcare delivery.

SUMMARY

Prevention of orthopaedic infection is dependent on elimination or optimal management of documented risk factors. Guidelines and quality standards play a key role in translating this evidence base into a framework of practices for the prevention of surgical site infections. Increasing levels of orthopaedic infection due to Enterobacteriaceae, coupled with an increasingly obese surgical population may necessitate a reassessment of antimicrobial prophylaxis strategies.

Susceptibility Pattern of Microorganisms Isolated by Percutaneous Needle Biopsy in Nonbacteremic Pyogenic Vertebral Osteomyelitis

Pyogenic vertebral osteomyelitis (VO) is diagnosed according to several lines of evidence: clinical, biological, radiological, and histological. Definitive diagnosis requires the isolation of a causative pathogen or histological confirmation. The aim of our study was to describe the microorganisms isolated by percutaneous needle biopsy (PNB) and to analyze their susceptibility patterns, in order to assess the possibility of empirical combination therapy for the treatment of nonbacteremic patients without resorting to PNB. Based on a French prospective multicenter study of 351 patients with VO, we compiled clinical, biological, and radiological findings for 101 patients with microbiologically confirmed VO. Based on antibiotic susceptibility testing of PNB isolated pathogens, the suitabilities of four antibiotic combinations were analyzed: ofloxacin plus rifampin, levofloxacin plus rifampin, ciprofloxacin plus clindamycin, and ciprofloxacin plus amoxicillin-clavulanate. The main causative pathogens identified were coagulase-negative Staphylococcus spp. (26% of isolates), followed by Staphylococcus aureus (21%), Streptoccocus spp. (13%), and enterobacteria (21%). Empirical antibiotic combination therapy was effective in nearly 75% of cases, and the different combinations gave similar results, except for ofloxacin-rifampin, which was effective in only 58% of cases. A "perfect" empirical antibiotic therapy does not exist. If PNB is not possible, a combination of a fluoroquinolone with clindamycin or rifampin can be used, but the high risk of microbiological failure does not allow the exclusion of PNB. (This study has been registered with EudraCT, number 2006-000951-18, and ClinicalTrials.gov, number NCT00764114.).

Effects of antibiotics on biofilm and unattached cells of a clinical Staphylococcus aureus isolate from bone and joint infection

Treatment of orthopaedic infections remains challenging owing to the inability of antibiotics to eradicate biofilms and prevent their regrowth. The present study characterized the effects of 12 antibiotics on in vitro biofilm formed by a representative strain of meticillin-susceptible Staphylococcus aureus (MSSA) isolated from a bone infection. Determination of the minimum biofilm eradication concentrations indicated that in vitro eradication of 24 h-old biofilms required concentrations up to 51,200 times higher than MICs. The influence of the same panel of antibiotics was also investigated on biofilm formation at concentrations including the breakpoints, by numbering viable cells in the suspensions (individual cells) and the biofilm biomass. Except for fusidic acid, the presence of antibiotics during the initial steps of biofilm formation resulted in significant decreases in the number of sessile viable bacteria at the highest concentrations tested. Ceftarolin, daptomycin, fosfomycin, gentamicin, ofloxacin, rifampicin and vancomycin were the most effective drugs. Confocal microscopy analysis indicated that daptomycin was more efficient at bacteria lysis than gentamicin and vancomycin. However, viable individual cells were still detectable in the assays performed with ceftarolin, fosfomycin, ofloxacin, rifampicin and vancomycin at concentrations for which no sessile cells were detected. Although none of the molecules tested was effective at classical therapeutic concentrations against 24 h-old MSSA biofilms, all except fusidic acid were able to impair biofilm formation at concentrations near the breakpoints. However, presence of viable individual unattached cells could imply a significant risk of microbial dissemination and increased risk of infections.

Reversion of antibiotic resistance by inhibiting mecA in clinical methicillin-resistant Staphylococci by antisense phosphorothioate oligonucleotide

Methicillin-resistant Staphylococci (MRS), methicillin-resistant Staphylococcus aureus (MRSA) and methicillin-resistant Staphylococcus epidermidis (MRSE) have become a challenging problem in nosocomial infections and are connected with high morbidity and mortality rates. This is due to the increasing incidence of resistance to virtually all β-lactams and a wide variety of antimicrobials. The spread of MRS severely limits therapeutic options and generates the need for novel antibiotics that are able to combat MRS infections. One method of inhibiting bacterial growth is by blocking the expression of conserved bacterial genes and provides potential new avenues for generating a new generation of antimicrobials. The mecA gene is highly conserved among Staphylococcal species, and this makes it an ideal target for antisense inhibition. We had identified a target sequence (854-871 nt) within the mecA mRNA coding region that is particularly sensitive to antisense inhibition. The anti-mecA PS-ODN04 oligonucleotide was encapsulated into an anionic liposome. MRSA01 and MRSE01 clinical strains treated with this antisense sequence became susceptible to existing β-lactam antibiotics, and their growth was inhibited by oxacillin in vitro and in vivo. PS-ODN04 reduced the bacterial titers in the blood of mice infected with MRSA01 and MRSE01 and significantly improved their survival rate. Our data offer a possible new strategy for treating MRS infections.