In an effort to improve mobility and alleviate pain from degenerative and connective tissue joint disease, an increasing number of individuals are undergoing prosthetic joint replacement in the United States. Joint replacement is a highly effective intervention, resulting in improved quality of life and increased independence [1]. By 2030, it is predicted that approximately 4 million total hip and knee arthroplasties will be performed yearly in the United States [2]. One of the major complications associated with this procedure is prosthetic joint infection (PJI), occurring at a rate of 1-2% [3-7]. In 2011, the Musculoskeletal Infectious Society created a unifying definition for prosthetic joint infection [8]. The following year, the Infectious Disease Society of America published practice guidelines that focused on the diagnosis and management of PJI. These guidelines focused on the management of commonly encountered organisms associated with PJI, including staphylococci, streptococci and select aerobic Gram-negative bacteria. However, with the exception of Propionibacterium acnes, management of other anaerobic organisms was not addressed in these guidelines [1]. Although making up approximately 3-6% of PJI [9,10], anaerobic microorganisms cause devastating complications, and similar to the more common organisms associated with PJI, these bacteria also result in significant morbidity, poor outcomes and increased health-care costs. Data on diagnosis and management of anaerobic PJI is mostly derived from case reports, along with a few cohort studies [3]. There is a paucity of published data outlining factors associated with risks, diagnosis and management of anaerobic PJI. We therefore reviewed available literature on anaerobic PJI by systematically searching the PubMed database, and collected data from secondary searches to determine information on pathogenesis, demographic data, clinical features, diagnosis and management. We focused our search on five commonly encountered anaerobic organisms associated with PJI. Since anaerobic PJI has also been linked to dental procedures, we also reviewed information on the use of dental procedures and prophylaxis, when available.

Clinical and microbiological characteristics of patients with Bacteroides prosthetic joint infection (PJI) have not been well described in the literature. The aim of this retrospective cohort study was to assess the outcome of patients with Bacteroides PJI and to review risk factors associated with failure of therapy. Between 1/1969 and 12/2012, 20 episodes of Bacteroides PJI in 17 patients were identified at our institution. The mean age of the patients in this cohort at the time of diagnosis was 55.6 years; 59% (n=10) had knee involvement. Twenty four percent (n=4) had diabetes mellitus, and 24% had a history of either gastrointestinal (GI) or genitourinary (GU) pathology prior to the diagnosis of PJI. Thirty five percent (n=6) were immunosuppressed. The initial medical/surgical strategy was resection arthroplasty (n=9, 50%) or debridement and implant retention (n=5, 28%). Thirty seven percent (n=7) were treated with metronidazole. Eighty percent (n=4) of patients that failed therapy had undergone debridement and retention of their prosthesis, as compared to none of those treated with resection arthroplasty. Seventy percent (n=14) of patient episodes were infection free at their last date of follow up. In conclusion, a significant proportion of patients with Bacteroides PJI are immunosuppressed and have an underlying GI or GU tract pathology. Retention and debridement of the prosthesis is associated with a higher risk of treatment failure.

Abstract. Background: The outcome of patients with Pseudomonas prosthetic joint infection (PS PJI) has not been well studied. The aim of this retrospective cohort study was to assess the outcome of patients with Pseudomonas PJI and to review risk factors associated with failure of therapy.Methods: Between 1/1969 and 12/2012, 102 episodes of PS PJI in 91 patients were identified.Results: The mean age at the time of diagnosis was 67.4 years; forty three percent had knee involvement. Over 40 percent had either diabetes mellitus or a history of gastrointestinal or genitourinary surgery. Nearly half (48 out of 102 episodes) received aminoglycoside monotherapy, while 25% received an anti-pseudomonal cephalosporin. The 2-year cumulative survival free from failure was 69% (95% CI, 56%-82%). Patients treated with resection arthroplasty, two-stage exchange, and debridement with implant retention had a 2-year cumulative survival free from failure of 80% (95% CI, 66%-95%), 83% (95% CI, 60%-100%), and 26% (95% CI, 23%-29%) respectively (P=0.0001).Conclusions: PS PJI's are associated with a high failure rate. Patients treated with debridement and implant retention had a worse outcome.

BACKGROUND: Total knee arthroplasty (TKA) periprosthetic joint infection (PJI) can be managed with debridement, antibiotic therapy, and implant retention (DAIR). Oral antibiotics can be used after DAIR for an extended time period to improve outcomes. The objective of this study was to compare DAIR failure rates and adverse events between an initial course of intravenous antibiotic therapy and the addition of extended treatment with oral antibiotics. METHODS: A multicenter observational study of patients diagnosed with a TKA PJI who underwent DAIR was performed. The primary outcome of interest was the failure rate derived from the survival time between the DAIR procedure and future treatment failure. RESULTS: One hundred eight patients met inclusion criteria; 47% (n = 51) received an extended course of oral antibiotics. These patients had a statistically significant lower failure rate compared to those who received only intravenous antibiotics (hazard ratio, 2.47; P = .009). Multivariable analysis demonstrated that extended antibiotics independently predicted treatment success, controlling for other variables. There was no significant difference in failure rates between an extended course of oral antibiotics less or more than 12 months (P = .23). No significant difference in the rates of adverse events was observed between patients who received an initial course of antibiotics alone and those who received a combination of initial and extended antibiotic therapy (P = .59). CONCLUSIONS: Extending therapy with oral antibiotics had superior infection-free survival for TKA PJI managed with DAIR. There was no increase in adverse events, demonstrating safety. After 1 year, there appears to be no significant benefit associated with continued antibiotic therapy.

Background In total knee arthroplasty (TKA) periprosthetic joint infection (PJI), irrigation and debridement (I&D) with component retention is a treatment option with a wide variation in reported failure rates. The purpose of this study was to determine failure rates, outcomes, and factors that predict failure in I&D for TKA PJI. Methods A multicenter observational study of patients with a TKA PJI and subsequently undergoing an I&D with retention of components was conducted. The primary outcome was failure rate of I&D, where failure was defined as any subsequent surgical procedures. Results Two hundred sixteen cases of I&D with retention of components performed on 206 patients met inclusion criteria. The estimated long-term failure rate at 4 years was 57.4%. Time-to-event analyses revealed that the median survival time was 14.32 months. Five-year mortality was 19.9%. Multivariable modeling revealed that time symptomatic and organism were independent predictors of I&D failure. Culture-negative status had a higher hazard for failure than culture-positive patients. When primary organism and time symptomatic were selected to produce an optimized scenario for an I&D, the estimated failure rate was 39.6%. Conclusion I&D with retention of components has a high failure rate, and there is a high incidence of more complex procedures after this option is chosen. The patient comorbidities we investigated did not predict I&D success. Our results suggest that I&D has a limited ability to control infection in TKA and should be used selectively under optimum conditions.

Background Periprosthetic joint infection (PJI) mortality rate is approximately 20%. The etiology for high mortality remains unknown. The objective of this study was to determine whether mortality was associated with preoperative morbidity (frailty), sequalae of treatment, or the PJI disease process itself. Methods A multicenter observational study was completed comparing 184 patients treated with septic revision total knee arthroplasty (TKA) to a control group of 38 patients treated with aseptic revision TKA. Primary outcomes included time and the cause of death. Secondary outcomes included preoperative comorbidities and Charlson Comorbidity Index (CCMI) measured preoperatively and at various postoperative timepoints. Results The septic revision TKA cohort experienced earlier mortality compared to the aseptic cohort, with a higher mortality rate at 90 days, 1, 2, and 3 years after index revision surgery (P = .01). There was no significant difference for any single cause of death (P > .05 for each). The mean preoperative CCMI was higher (P = .005) in the septic revision TKA cohort. Both septic and aseptic cohorts experienced a significant increase in CCMI from the preoperative to 3 years postoperative (P < .0001 and P = .002) and time of death (P < .0001 both) timepoints. The septic revision TKA cohort had a higher CCMI 3 years postoperatively (P = .001) and at time of death (P = .046), but not one year postoperatively (P = .119). Conclusion Compared to mortality from aseptic revision surgery, septic revision TKA is associated with earlier mortality, but there is no single specific etiology. As quantified by changes in CCMI, PJI mortality was associated with both frailty and the PJI disease process, but not treatment.