Bridget L. Atkins

The diagnosis and management of prosthetic joint infections

A host of technical and operative improvements have seen the rates of infection associated with joint replacement reach historic lows. However, the increasing number of operations being performed means that the absolute number of such infections remains significant. Diagnosis may be challenging and delaying appropriate treatment can lead to reduced joint function and the need for more complex, perhaps multiple, procedures. Individual centres tend to see small numbers of such cases, and in the absence of large clinical trials management varies. Early diagnosis, selection of an appropriate surgical strategy, accurate identification of the responsible microorganisms and construction of an appropriate antibiotic regimen are essential elements of any management strategy. Such packages of care are best delivered by a multidisciplinary team composed of orthopaedic and plastic surgeons, microbiologists, infectious disease physicians, specialist nurses, physiotherapists and occupational therapists. Each treatment plan must be developed in consultation with the patient, taking into account their aims and realistic goals. This review provides an overview of current understanding regarding diagnosis and treatment of prosthetic joint infections and suggests a treatment algorithm.

Two-stage revision for prosthetic joint infection: predictors of outcome and the role of reimplantation microbiology

Objectives We describe rates of success for two-stage revision of prosthetic joint infection (PJI), including data on reimplantation microbiology. Methods We retrospectively collected data from all the cases of PJI that were managed with two-stage revision over a 4 year period. Patients were managed with an antibiotic-free period before reimplantation, in order to confirm, clinically and microbiologically, that infection was successfully treated. Results One hundred and fifty-two cases were identified. The overall success rate (i.e. retention of the prosthesis over 5.75 years of follow-up) was 83%, but was 89% for first revisions and 73% for re-revisions [hazard ratio = 2.9, 95% confidence interval (CI) 1.2–7.4, P = 0.023]. Reimplantation microbiology was frequently positive (14%), but did not predict outcome (hazard ratio = 1.3, 95% CI 0.4–3.7, P = 0.6). Furthermore, most unplanned debridements following the first stage were carried out before antibiotics were stopped (25 versus 2 debridements). Conclusions We did not identify evidence supporting the use of an antibiotic-free period before reimplantation and routine reimplantation microbiology. Re-revision was associated with a significantly worse outcome.

The use of a biodegradable antibiotic-loaded calcium sulphate carrier containing tobramycin for the treatment of chronic osteomyelitis: a series of 195 cases

We report our experience using a biodegradable calcium sulphate antibiotic carrier containing tobramycin in the surgical management of patients with chronic osteomyelitis. The patients were reviewed to determine the rate of recurrent infection, the filling of bony defects, and any problems with wound healing. A total of 193 patients (195 cases) with a mean age of 46.1 years (16.1 to 82.0) underwent surgery. According to the Cierny-Mader classification of osteomyelitis there were 12 type I, 1 type II, 144 type III and 38 type IV cases. The mean follow-up was 3.7 years (1.3 to 7.1) with recurrent infection occurring in 18 cases (9.2%) at a mean of 10.3 months post-operatively (1 to 25.0). After further treatment the infection resolved in 191 cases (97.9%). Prolonged wound ooze (longer than two weeks post-operatively) occurred in 30 cases (15.4%) in which there were no recurrent infection. Radiographic assessment at final follow-up showed no filling of the defect with bone in 67 (36.6%), partial filling in 108 (59.0%) and complete filling in eight (4.4%). A fracture occurred in nine (4.6%) of the treated osteomyelitic segments at a mean of 1.9 years (0.4 to 4.9) after operation. We conclude that Osteoset T is helpful in the management of patients with chronic osteomyelitis, but the filling of the defect in bone is variable. Prolonged wound ooze is usually self-limiting and not associated with recurrent infection.

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

The diagnosis of prosthetic joint infection (PJI) in the routine microbiology laboratory is labour-intensive, but semi-automated methods may be appropriate. We prospectively compared four microbiological culture methods on samples taken at prosthetic joint revision surgery. Automated BACTEC blood culture bottles and cooked meat enrichment broth were the most sensitive methods (87% and 83%, respectively, as compared with fastidious anaerobic broth (57%) and direct plates (39%)); all were highly specific (97-100%). To our knowledge, this is the first prospective study aimed at comparing culture methods in routine use in UK clinical laboratories for the diagnosis of PJI.

Skin and soft tissue infections caused by nontuberculous mycobacteria.

Purpose of review Skin and soft tissues infections (SSTIs) caused by nontuberculous mycobacteria (NTM) are underrecognized and difficult to treat. Controversies exist for optimal medical management and the role of surgery. Defining the epidemiology in the environment, in animals and in healthcare aids disease prevention. This review focuses on recent advances in epidemiology, risk factors, diagnostics and therapy. Recent findings The increasing consumer appetite for cosmetic and body-modifying procedures (e.g. tattooing, mesotherapy, liposuction) has been associated with rises in sporadic cases and outbreaks of NTM SSTIs. In mainstream healthcare, recent epidemiological studies have helped to quantify the increased risk of NTM infection related to anti-tumour necrosis factor-&agr; monoclonal antibody therapy. Cervicofacial lymphadenitis in children poses management dilemmas, but recent studies and resultant algorithms have simplified decision-making. Molecular studies have led to a better understanding of the epidemiology, therapy and course of Mycobacterium ulcerans infection (Buruli ulcer) that remains prevalent in many areas including sub-Saharan Africa and southeastern Australia. Apart from molecular methods, the widespread adoption of matrix-assisted laser desorption ionization-time of flight mass spectrometry by routine laboratories has potential to simplify and expedite the laboratory identification of NTMs. Summary An improved understanding of the epidemiology of NTM SSTIs indicates a need to apply effective infection control and ensure regulation of cosmetic and related procedures associated with nonsterile fluids. Broader access to newer diagnostic methods will continue to improve recognition of NTM disease. Along with a paucity of therapeutic agents, there is need for more reliable methods to assess susceptibility and selection of effective combination therapy.

Molecular Diagnosis of Orthopedic-Device-Related Infection Directly from Sonication Fluid by Metagenomic Sequencing

ABSTRACT Culture of multiple periprosthetic tissue samples is the current gold standard for microbiological diagnosis of prosthetic joint infections (PJI). Additional diagnostic information may be obtained through culture of sonication fluid from explants. However, current techniques can have relatively low sensitivity, with prior antimicrobial therapy and infection by fastidious organisms influencing results. We assessed if metagenomic sequencing of total DNA extracts obtained direct from sonication fluid can provide an alternative rapid and sensitive tool for diagnosis of PJI. We compared metagenomic sequencing with standard aerobic and anaerobic culture in 97 sonication fluid samples from prosthetic joint and other orthopedic device infections. Reads from Illumina MiSeq sequencing were taxonomically classified using Kraken. Using 50 derivation samples, we determined optimal thresholds for the number and proportion of bacterial reads required to identify an infection and confirmed our findings in 47 independent validation samples. Compared to results from sonication fluid culture, the species-level sensitivity of metagenomic sequencing was 61/69 (88%; 95% confidence interval [CI], 77 to 94%; for derivation samples 35/38 [92%; 95% CI, 79 to 98%]; for validation samples, 26/31 [84%; 95% CI, 66 to 95%]), and genus-level sensitivity was 64/69 (93%; 95% CI, 84 to 98%). Species-level specificity, adjusting for plausible fastidious causes of infection, species found in concurrently obtained tissue samples, and prior antibiotics, was 85/97 (88%; 95% CI, 79 to 93%; for derivation samples, 43/50 [86%; 95% CI, 73 to 94%]; for validation samples, 42/47 [89%; 95% CI, 77 to 96%]). High levels of human DNA contamination were seen despite the use of laboratory methods to remove it. Rigorous laboratory good practice was required to minimize bacterial DNA contamination. We demonstrate that metagenomic sequencing can provide accurate diagnostic information in PJI. Our findings, combined with the increasing availability of portable, random-access sequencing technology, offer the potential to translate metagenomic sequencing into a rapid diagnostic tool in PJI.

Native hip joint septic arthritis in 20 adults: Delayed presentation beyond three weeks predicts need for excision arthroplasty

OBJECTIVES Septic arthritis of native hip joints is an uncommon condition in adults in Western Europe, but continues to present a challenge to medical and surgical management. We set out to study the natural history and bacteriology of the disease in this group, with a particular focus on patients requiring excision arthroplasty (EA). METHODS We retrospectively studied 26 secondary referral cases (20 adults) managed by a specialist bone infection unit over a 12 year period. RESULTS Our patient cohort was diverse, affecting all age groups in the presence and absence of co-morbid conditions. The commonest pathogen was Staphylococcus aureus. Of 20 adults studied, five (25%) required EA. Symptom duration prior to presentation was a statistical predictor of the requirement for EA (p<0.003); in particular, symptom duration of over three weeks was strongly associated with requirement for this procedure (p<0.0003). CONCLUSIONS In cases that present promptly, combined surgical drainage and intravenous antibiotics should be expected to eradicate infection and to salvage the femoral head. Cases presenting following a delay are more likely to require EA and subsequent hip reconstruction.

Single-stage treatment of chronic osteomyelitis with a new absorbable, gentamicin-loaded, calcium sulphate/hydroxyapatite biocomposite: a prospective series of 100 cases.

AIMS Chronic osteomyelitis may recur if dead space management, after excision of infected bone, is inadequate. This study describes the results of a strategy for the management of deep bone infection and evaluates a new antibiotic-loaded biocomposite in the eradication of infection from bone defects. PATIENTS AND METHODS We report a prospective study of 100 patients with chronic osteomyelitis, in 105 bones. Osteomyelitis followed injury or surgery in 81 patients. Nine had concomitant septic arthritis. 80 patients had comorbidities (Cierny-Mader (C-M) Class B hosts). Ten had infected nonunions. All patients were treated by a multidisciplinary team with a single-stage protocol including debridement, multiple sampling, culture-specific systemic antibiotics, stabilisation, dead space filling with the biocomposite and primary skin closure. RESULTS Patients were followed up for a mean of 19.5 months (12 to 34). Infection was eradicated in 96 patients with a single procedure and all four recurrences were successfully managed with repeat surgery. Adverse events were uncommon, with three fractures, six wound leaks and three unrelated deaths. Outcome was not dependant on C-M host class, microbial culture, wound leakage or presence of nonunion. CONCLUSION This single-stage protocol, facilitated by the absorbable local antibiotic, is effective in the treatment of chronic osteomyelitis. It offers a more patient-friendly treatment compared with other published treatment options. Cite this article: Bone Joint J 2016;98-B:1289-96.

Serial measurement of the C-reactive protein is a poor predictor of treatment outcome in prosthetic joint infection

OBJECTIVES Prosthetic joint infection is usually treated using surgery and antibiotics. The response to the treatment regimen is often evaluated using serial monitoring of plasma C-reactive protein (CRP) concentrations. In order to examine how useful this monitoring is, we calculated the sensitivity and specificity of CRP concentrations for predicting treatment failure. PATIENTS AND METHODS We examined 3732 CRP measurements from 260 patients who were treated by either two-stage revision or debridement and retention. We tested the association between CRP concentration and outcome using logistic regression models, and assessed sensitivity and specificity by using receiver operator curves. RESULTS The areas under receiver operator curves for CRP concentrations predicting outcome ranged from 0.55 to 0.65. CONCLUSIONS CRP concentrations did not accurately predict treatment failure. Serial monitoring may not be of benefit.

Pristinamycin as adjunctive therapy in the management of Gram-positive multi-drug resistant organism (MDRO) osteoarticular infection

OBJECTIVE Osteoarticular infection often requires prolonged antibiotic therapy as an adjunct to surgery. We report our experience using pristinamycin, an oral streptogramin, when conventional antibiotics were poorly tolerated or inappropriate because of multi-drug resistant organisms (MDROs). METHODS We retrospectively identified, from pharmacy records, all patients prescribed pristinamycin between 1/1/2004 and 31/12/2006. We collected clinical and microbiological data. RESULTS Twenty-one patients were identified (13 male and eight female patients, age range 18-83 years). Sixteen patients (76%) had infection due to MDROs and five (24%) were intolerant of conventional antibiotics. Ten patients received other concurrent oral antibiotics. Eleven of 21 (52%) patients remained free of recurrent infection off antibiotics at a mean follow up duration of 13 months, (range 4-25 months). Suppression of infection while still on therapy was achieved in a further four patients (19%) with a mean follow up of 11.5 months (range 5-15 months). Six patients (29%) failed therapy, all requiring a further surgical procedure. CONCLUSION Oral pristinamycin was a well tolerated and useful adjunctive treatment in this group with complex orthopaedic infection. Pristinamycin can be considered in patients with osteoarticular infection due to Gram-positive organisms when antibiotic multi-resistance or intolerance makes conventional therapies impossible. SUMMARY We report our experiences of using pristinamycin in the management of 21 patients with Gram-positive MDRO osteoarticular infection or who were unable to tolerate more conventional regimens. Our results show that pristinamycin is well tolerated with outcomes comparable to those of other agents described in the literature on osteoarticular infection.