John Daffy

Risk factors associated with acute hip prosthetic joint infections and outcome of treatment with a rifampin‐based regimen

Background and purpose Acute prosthetic infection is a serious problem. We report factors related to the incidence of acute infection and results of combined joint debridement and prolonged rifampicin-based antibiotic therapy. Patients and methods Between 1998 and 2004, 14 acute infections occurred after 819 primary hip arthroplasties. The association between patient-related and surgical factors and the risk of infection were analyzed. Infections were treated with multiple joint lavage, debridement, 2 weeks of antibiotic therapy, and then oral antibiotics for a minimum of 6 months. Results There was a correlation between having a body mass index (BMI) of ≥ 30, and also more than 2 co-morbidities, and an increased risk of infection. Diabetes was a potential risk factor. Following our regime of treatment, 11 of 14 patients retained their prosthesis. 2 of 3 who required resection arthroplasty underwent successful staged revision, while the third patient had no further surgery because of being deemed unfit. Interpretation Primary joint replacement was salvaged in 11 of 14 patients. When successful re-implanta-tion was included, 13 of 14 patients had a mobile prosthetic joint without further infection.

Risk factors for prosthetic hip and knee infections according to arthroplasty site.

Prosthetic joint infection is a devastating complication of arthroplasty. Previous epidemiological studies have assessed factors associated with arthroplasty infections but have not assessed the impact of comorbidity on infection at different arthroplasty locations. We used a case-control design to investigate risk factors for prosthetic joint infection with reference to the anatomical site. During an eight-year period at a single hospital, 63 patients developed a prosthetic joint infection (36 hips, 27 knees). Cases of prosthetic hip or knee joint infection were matched 1:2 to controls. The results suggest that factors associated with arthroplasty infections differ with anatomical location. Following knee arthroplasty, wound discharge was associated with an increased risk of prosthetic joint infection whereas the presence of a drain tube reduced the risk. By contrast, increased body mass index, increased drain tube loss and superficial incisional surgical site infections (SSIs) were associated with prosthetic hip infection. When analysed as a combined cohort, systemic steroid use, increased SSI drain tube losses, wound discharge, and superficial incisional SSIs were predictors of infection.

Gram-negative prosthetic joint infection treated with debridement, prosthesis retention and antibiotic regimens including a fluoroquinolone

Information is required about treatment outcomes of Gram-negative prosthetic joint infections treated with prosthesis retention and surgical debridement, especially where biofilm-active antibiotics such as fluoroquinolones are used. The outcome of 17 consecutive patients with an early Gram-negative prosthetic joint infection who had been treated with prosthesis retention and surgical debridement was analysed. Enterobacteriaceae were isolated in 16 patients and infections were mixed with other organisms in 13 (76%) patients. The median joint age was 17 days and the median duration of symptoms before debridement was 7 days. All patients initially received intravenous β-lactam antibiotic therapy and 14 patients were then treated with oral ciprofloxacin. Treatment failure occurred in two patients over a median period of follow-up of 28 months. In only one patient was a relapsed Gram-negative infection responsible for the failure and this patient had not been treated with ciprofloxacin. The 2-year survival rate free of treatment failure was 94% (95% CI, 63-99%). Prosthesis retention with surgical debridement, in combination with antibiotic regimens including ciprofloxacin, was effective and should be considered for patients with early Gram-negative prosthetic joint infection.

Outcome of Debridement and Retention in Prosthetic Joint Infections by Methicillin-Resistant Staphylococci, with Special Reference to Rifampin and Fusidic Acid Combination Therapy

ABSTRACT The management of prosthetic joint infections remains a clinical challenge, particularly infections due to methicillin-resistant staphylococci. Previously, this infection was considered a contraindication to debridement and retention strategies. This retrospective cohort study examined the treatment and outcomes of patients with arthroplasty infection by methicillin-resistant staphylococci managed by debridement and retention in conjunction with rifampin-fusidic acid combination therapy. Over an 11-year period, there were 43 patients with infection by methicillin-resistant staphylococci managed with debridement and retention. This consisted of close-interval repeated arthrotomies with pulsatile lavage. Rifampin was combined with fusidic acid for the majority of patients (88%). Patients were monitored for a median of 33.5 months (interquartile range, 20 to 54 months). Overall, 9 patients experienced treatment failure, with 12- and 24-month estimates of infection-free survival of 86% (95% confidence interval [CI], 71 to 93%) and 77% (95% CI, 60 to 87%), respectively. The following factors were associated with treatment failure: methicillin-resistant Staphylococcus aureus (MRSA) arthroplasty infection, a single surgical debridement or ≥4 debridements, and the receipt of less than 90 days of antibiotic therapy. Patients with infection by methicillin-resistant coagulase-negative staphylococci (MR-CNS) were less likely to fail treatment. The overall treatment success rate reported in this study is comparable to those of other treatment modalities for prosthetic joint infections by methicillin-resistant staphylococci. Therefore, the debridement and retention of the prosthesis and rifampin-based antibiotic therapy are a valid treatment option for carefully selected patients.

Australian football players' Achilles tendons respond to game loads within 2 days: an ultrasound tissue characterisation (UTC) study.

Background/aim The Achilles tendon is a tissue that responds to mechanical loads at a molecular and cellular level. In vitro and in vivo studies have shown that the expression of anabolic and/or catabolic proteins can change within hours of loading and return to baseline levels within 72 h. These biochemical changes have not been correlated with changes in whole tendon structure on imaging. We examined the nature and temporal sequence of changes in Achilles tendon structure in response to competitive game loads in elite Australian football players. Methods Elite male Australian football players with no history of Achilles tendinopathy were recruited. Achilles tendon structure was quantified using ultrasound tissue characterisation (UTC) imaging, a valid and reliable measure of intratendinous structure, the day prior to the match (day 0), and then reimaged on days 1, 2 and 4 postgame. Results Of the 18 participants eligible for this study, 12 had no history of tendinopathy (NORM) and 6 had a history of patellar or hamstring tendinopathy (TEN). Differences in baseline UTC echopattern were observed between the NORM and TEN groups, with the Achilles of the TEN group exhibiting altered UTC echopattern, consistent with a slightly disorganised tendon structure. In the NORM group, a significant reduction in echo-type I (normal tendon structure) was seen on day 2 (p=0.012) that returned to baseline on day 4. Summary There was a transient change in UTC echopattern in the Achilles tendon as a result of an Australian football game in individuals without a history of lower limb tendinopathy.

Posaconazole as first line treatment for disseminated zygomycosis

We describe the first case report of posaconazole use as first line agent in the treatment of disseminated zygomycosis with prosthetic hip joint and pulmonary involvement due to Rhizopus microsporus. This infection occurred in a heavily immunosuppressed patient with systemic lupus erythematosus.

Structural integrity is decreased in both Achilles tendons in people with unilateral Achilles tendinopathy

OBJECTIVES A high proportion of Achilles tendinopathy patients develop bilateral symptoms with human and animal studies showing bilateral histological changes associated with overuse/pathology in one tendon. The current study examined changes in tendon structure, assessed semi-quantitatively using ultrasound tissue characterisation, in both the symptomatic and asymptomatic tendon in unilateral Achilles tendinopathy patients in comparison to individuals with no history of tendinopathy. DESIGN Cross-sectional case-control study. METHODS Participants with Achilles tendinopathy (n=21), with varying severity and length of clinical symptoms, and six participants with no history of tendinopathy were recruited. Tendons were scanned using ultrasound tissue characterisation, which captures contiguous transverse ultrasound images every 0.2mm and renders a 3-dimensional image. Ultrasound tissue characterisation quantifies tendon structure by measuring the stability of echopattern over contiguous transverse images. Four echo-types were discriminated and expressed as a percentage. Antero-posterior diameter of all tendons was measured. RESULTS Significant differences were observed in the proportion of normal tendon structure between all three groups (p<0.01), with the symptomatic tendon containing the least amount of normal tendon structure (symptomatic - 79.5%, asymptomatic - 81.8%, control - 86.4%). The asymptomatic tendon contained significantly less normal tendon in comparison to the control tendon (p=0.008), suggesting the asymptomatic tendon is structurally compromised despite the absence of symptoms. CONCLUSIONS Both Achilles tendons are structurally compromised in patients with unilateral Achilles tendinopathy. Future studies need to investigate whether these changes increase the risk of developing symptoms.

Caspofungin as salvage monotherapy for invasive aspergillosis in patients with haematological malignancies or following allogeneic stem cell transplantation: efficacy and concomitant cyclosporin A

Caspofungin (CAS) has shown efficacy as salvage monotherapy for invasive aspergillosis (IA) in two open label non‐comparative trials. The association between hepatotoxicity and concomitant use of CAS and cyclosporin A (CsA) has not been fully elucidated. We report results on CAS efficacy in the first cohort from outside Europe and USA and the interaction between CAS and CsA. We retrospectively reviewed the charts of all patients with haematological malignancies or postallogeneic haematopoietic stem cell transplant (HSCT) who received ≥1 dose of CAS as salvage monotherapy for IA as part of the Australian Special Access Scheme (4/2001‐8/2002). Outcomes were assessed at the end of CAS therapy. Favourable response (FR) was defined as >50% clinical and radiological improvement. Risk factors for elevation of liver transaminases (LTs) were examined using multivariate models. 54 patients were included in the analysis with 47 neutropenic at study entry. Proven or probable IA occurred in 11 and refractory IA in 28. An FR occurred in 26 (48.1%) and predictors for a poor response to CAS were allogeneic HSCT, graft vs. host disease and treatment with CAS for <14 days. Concomitant CAS and CsA for >7 days was an independent risk factor for laboratory hepatoxicity. The CAS efficacy results from the Australian cohort confirm those of previous studies. Close monitoring of LTs is necessary on concomitant CAS and CsA but clinically relevant hepatotoxicity is rare.

Use of Pristinamycin for Infections by Gram-Positive Bacteria: Clinical Experience at an Australian Hospital

ABSTRACT Thirty-six patients were treated with pristinamycin for 46 different microbiological isolates between April 2007 and July 2009. Pathogens included 9 methicillin-resistant Staphylococcus aureus isolates, 13 methicillin-resistant coagulase negative staphylococci, and 9 vancomycin-resistant enterococci. Sites of infections included 12 osteomyelitis cases, 10 prosthetic joints, 4 other prostheses, and 1 epidural abscess. Five patients ceased treatment due to side effects. Ten patients were cured of their infections, and 21 patients had infections successfully suppressed.

Current concepts in the management of prosthetic joint infection

Prosthetic joint infection (PJI) is a serious complication of arthroplasty that is associated with significant mortality, morbidity and costs. PJI is difficult to cure because causative bacteria form and persist in biofilm adherent to the prosthesis surface. PJI can be classified into early, delayed or late according to the time of onset after insertion of the prosthesis, and this classification can help determine pathogenesis and appropriate management. Traditional treatment has been with prolonged intravenous antibiotics and prosthesis exchange, which has been successful in treating infection but is technically difficult and has high rates of associated morbidity. On the basis of in vitro and animal studies, interest has turned to the use of antimicrobials that are particularly active against biofilm‐associated bacteria. Recent clinical evidence shows success in more than 77% of early PJI with surgical debridement, retention of prosthesis and the use of rifampicin‐based combinations for staphylococcal PJI. Fluoroquinolones are preferred for Gram‐negative PJI. Optimal antimicrobial treatment duration and the management of polymicrobial, enterococcal, fungal and culture‐negative infections are still yet to be defined but will become more clear as the results of current research comes to hand.