Short Course of Oral Antibiotic Treatment After Two-Stage Exchange Arthroplasty Appears to Decrease Early Reinfection.

BACKGROUND: Recent evidence has suggested a benefit to extended postoperative prophylactic oral antibiotics after two-stage exchange arthroplasty for treatment of periprosthetic joint infections. We sought to determine reinfection rates with and without a short course of oral antibiotics after two-stage exchange procedures. METHODS: A retrospective review identified patients undergoing two-stage exchange arthroplasty for periprosthetic joint infection of the hip or knee. Patients were excluded if they failed a prior two-stage exchange, had positive cultures at reimplantation, prolonged intravenous antibiotics postoperatively, and/or life-long suppression. This resulted in 444 reimplantations (210 hips and 234 knees). Patients were divided into three cohorts based on the duration of oral antibiotics after reimplantation: no antibiotics (102), ≤2 weeks (266), or >2 weeks (76). The primary endpoint was reinfection within 1 year of reimplantation. RESULTS: Within 1 year of reimplantation, there were 34 reinfections. In the no-antibiotic, ≤ 2-week, and >2-week cohorts the reinfection rates were 14.1, 7.0, and 6.4%, respectively. Multivariate Cox regression showed a reduced reinfection rate in the ≤2-week cohort relative to no antibiotics (hazard ratio [HR]: 0.38, P = .01). While the smaller cohort with >2 weeks of antibiotics did not significantly reduce the reinfection rate (HR: 0.41, P = .12), when combined with the ≤2-week cohort, use of oral antibiotics had an overall reduction of the reinfection rate (HR: 0.39, P = .01). CONCLUSIONS: These data support the hypothesis that a short course of oral antibiotics after reimplantation decreases the 1-year reinfection rate. Future randomized studies should seek to examine the efficacy of different durations of oral antibiotics to reduce reinfection. LEVEL OF EVIDENCE: Prognostic Level IV.

Irrigation and Debridement With Chronic Antibiotic Suppression for the Management of Acutely Infected Aseptic Revision Total Joint Arthroplasties.

BACKGROUND: Most data on irrigation and debridement with component retention (IDCR) as a treatment for acute periprosthetic joint infections (PJIs) focuses on primary total joint arthroplasties (TJAs). However, the incidence of PJI is greater after revisions. We investigated the outcomes of IDCR with suppressive antibiotic therapy (SAT) following aseptic revision TJAs. METHODS: Through our total joint registry, we identified 45 aseptic revision TJAs (33 hips, 12 knees) performed from 2000 to 2017 that were treated with IDCR for acute PJI. Acute hematogenous PJI was present in 56%. Sixty-four percent of PJIs involved Staphylococcus. All patients were treated with 4 to 6 weeks of intravenous antibiotics with the intention to treat with SAT (89% received SAT). The mean age was 71 years (range, 41 to 90), with 49% being women and a mean body mass index of 30 (range, 16 to 60). The mean follow-up was 7 years (range, 2 to 15). RESULTS: The 5-year survivorships free from re-revision for infection and reoperation for infection were 80% and 70%, respectively. Of the 13 reoperations for infection, 46% involved the same species as the initial PJI. The 5-year survivorships free from any revision and any reoperation were 72% and 65%, respectively. The 5-year survivorship free from death was 65%. CONCLUSION: At 5 years following IDCR, 80% of implants were free from re-revision for infection. As the penalty for implant removal is often high in revision TJAs, IDCR with SAT is a viable option for acute infection after revision TJAs in select patients. LEVEL OF EVIDENCE: IV.

Laboratory Value Effectiveness in Predicting Early Postoperative Periprosthetic Joint Infection After Total Hip Arthroplasty.

BACKGROUND: Diagnosing early periprosthetic joint infection (PJI) after primary total hip arthroplasty (THA) remains challenging. We sought to validate optimal laboratory value cutoffs for detecting early PJIs in a series of primary THAs from one institution. METHODS: We retrospectively identified 22,795 primary THAs performed between 2000 and 2019. Within 12 weeks, 43 hips (43 patients) underwent arthrocentesis. Patients were divided into 2 groups: evaluation ≤6 weeks or 6-12 weeks following THA. The 2011 Musculoskeletal Infection Society major criteria for PJI diagnosed PJI in 15 patients. Mann-Whitney U-tests were used to compare median laboratory values and receiver operating characteristic curve analysis was used to evaluate optimal cutoff values. RESULTS: Both within 6 weeks and between 6 and 12 weeks postoperatively, median C-reactive protein (CRP), erythrocyte sedimentation rate, synovial white blood cell (WBC) count, neutrophil percentage, and absolute neutrophil count (ANC) values were significantly higher in infected THAs. Optimal cutoffs within 6 weeks were: CRP ≥100 mg/L, synovial WBCs ≥4390 cells/µL, neutrophil percentage ≥74%, and ANC ≥3249 cells/µL. Between 6 and 12 weeks, optimal cutoffs were: CRP ≥33 mg/L, synovial WBCs ≥26,995 cells/µL, neutrophil percentage ≥93%, and ANC ≥25,645 cells/µL. CONCLUSION: Early PJI following THA should be suspected within 6 weeks with CRP ≥100 mg/L or synovial WBCs ≥4390 cells/µL. Between 6 and 12 weeks postoperatively, cutoffs of CRP ≥33 mg/L, synovial fluid WBC ≥26,995 cells/µL, and neutrophil percentage ≥93% diagnosed PJI with high accuracy. LEVEL OF EVIDENCE: Level IV Diagnostic.

Recent Antibiotic Treatment Impacts Serum and Synovial Laboratory Values in Early Periprosthetic Joint Infection Workup.

BACKGROUND: Accurately detecting early postoperative periprosthetic joint infection (PJI) following total hip arthroplasty (THA) and total knee arthroplasty (TKA) remains challenging. The purpose of our study was to determine the impact of antibiotics given prior to laboratory evaluation on the reliability of serologic and synovial fluid tests to identify PJI in the early postoperative period. METHODS: We identified 49,861 primary total hip arthroplasties and total knee arthroplasties performed between 2000 and 2019. Among these patients, 21 hips and 28 knees that underwent arthrocentesis within 12 weeks of their arthroplasty were identified as infected. Patients who had received antibiotics within 2 weeks prior to laboratory evaluation were compared to those who had not. Median values of C-reactive protein, erythrocyte sedimentation rate, synovial white blood cell (WBC) count, synovial neutrophil percentage, and synovial absolute neutrophil count were compared between groups. The false negative rate for detecting PJI using laboratory values was compared using published cutoffs for PJI in the early postoperative period. RESULTS: Median values of C-reactive protein (105 vs 22 mg/L; P = .006), synovial WBC count (57,591 vs 4,473 cells/µL; P = .003), synovial neutrophil percentage (94% vs 76%; P = .004), and synovial absolute neutrophil count (50,748 vs 2,804 cells/µL; P < .001) were significantly lower in patients who received antibiotics compared to those who did not. False negative rates for detecting PJI were significantly higher for synovial WBC and synovial neutrophil percentage in patients treated with antibiotics compared to untreated patients. CONCLUSION: False negative rates for detecting early PJI when using published cutoffs were markedly higher in antibiotic-treated patients compared to untreated patients for synovial WBC count and synovial neutrophil percentage. LEVEL OF EVIDENCE: Level IV retrospective review.

Extended Oral Antibiotic Prophylaxis After Aseptic Revision Total Hip Arthroplasty: Does It Decrease Infection Risk?

BACKGROUND: Extended oral antibiotic prophylaxis (EOA) has been shown to reduce infection after high-risk primary total hip arthroplasties (THAs) and reimplantations. However, data are limited regarding EOA after aseptic revision THAs. This study evaluated the impact of EOA on infection-related outcomes after aseptic revision THAs. METHODS: We retrospectively identified 1,107 aseptic revision THAs performed between 2014 and 2019. Patients who received EOA >24 hours perioperatively (n = 370) were compared to those who did not (n = 737) using an inverse probability of treatment weighting model. Their mean age was 65 years (range, 19-98 years), mean body mass index was 30 kg/m2 (range, 16-72), and 54% were women. Outcomes included cumulative probabilities of any infection, periprosthetic joint infection (PJI), and re-revision or reoperation for infection. Mean follow-up was 4 years (range, 2-8 years). RESULTS: The cumulative probability of any infection after aseptic revision THA was 2.3% at 90 days, 2.7% at 1 year, and 3.5% at 5 years. The cumulative probability of PJI was 1.7% at 90 days, 2.1% at 1 year, and 2.8% at 5 years. There was a trend toward an increased risk of any infection (hazards ratio [HR] = 2.6; P = .058), PJI (HR = 2.6; P = .085), and re-revision (HR = 6.5; P = .077) or reoperation (HR = 2.3; P = .095) for infection in patients who did not have EOA at the final clinical follow-up. CONCLUSIONS: EOA after aseptic revision THA was not associated with a statistically significant decreased risk of any infection, PJI, or re-revision or reoperation for infection at all time points. LEVEL OF EVIDENCE: Level III.

Extended Oral Antibiotic Prophylaxis After Aseptic Revision TKA: Does It Decrease Infection Risk?

BACKGROUND: Extended oral antibiotic prophylaxis (EOA) has been shown to potentially reduce infection rates after high-risk primary total knee arthroplasties (TKAs) and reimplantations. However, data is limited regarding EOA after aseptic revision TKAs. This study evaluated the impact of EOA on infection-related outcomes after aseptic revision TKAs. METHODS: 904 aseptic revision TKAs from 2014-2019 were retrospectively identified. Patients who received EOA >24 hours perioperatively (n = 267) were compared to those who did not (n = 637) using an inverse probability of treatment weighting model. Mean age was 66 years, mean BMI was 33 kg/m2, and 54% were female. Outcomes included cumulative probabilities of any infection, periprosthetic joint infection (PJI), superficial infection, and re-revision or reoperation for infection. RESULTS: The cumulative probability of any infection after aseptic revision TKA was 1.9% at 90 days, 3.5% at 1 year, and 8.1% at 5 years. Patients without EOA had a higher risk of any infection at 90 days (HR = 7.1; P = .01), but not other time points. The cumulative probability of PJI after aseptic revision TKA was 0.8% at 90 days, 2.3% at 1 year, and 6.5% at 5 years. Patients without EOA did not have an increased risk of PJI. There were no differences in re-revision or reoperation for infection at any time point between groups. CONCLUSION: Extended oral antibiotics after aseptic revision TKA were associated with a 7-fold decreased risk of any infection at 90 days. The results suggest a potential role for EOA after aseptic revision TKA and warrant additional prospective studies. LEVEL OF EVIDENCE: Level III.

Safety and Tolerability of Fluoroquinolones in Patients with Staphylococcal Periprosthetic Joint Infections.

BACKGROUND: Fluoroquinolones (FQs) are known to be accompanied by significant risks. However, the incidence of adverse events (ADEs) resulting in unplanned drug discontinuation when used for periprosthetic joint infections (PJIs) is currently unknown. METHODS: This study included 156 patients over the age of 18 treated for staphylococcal PJI with debridement, antibiotics, and implant retention between 1 January 2007 and 21 November 2019. Of the 156 patients, 64 had total hip arthroplasty (THA) and 92 had total knee arthroplasty (TKA) infections. The primary outcome was rate of unplanned drug discontinuation. Secondary outcomes included incidence of severe ADEs, unplanned rifamycin discontinuation, mean time to unplanned regimen discontinuation, and all-cause mortality. RESULTS: Overall, unplanned drug discontinuation occurred in 35.6% of patients in the FQ group and 3% of patients in the non-FQ group. The rate of unplanned discontinuation of FQ regimens as compared with non-FQ regimens was 27.5% vs 4.2% (P = .021) in THA infections and 42% vs 2.4% (P < .001) in TKA infections. There was no significant difference in severe ADEs between FQ and non-FQ regimens in both THA and TKA infections. The overall rate of nonsevere ADEs in FQ compared with non-FQ regimens was 43.3% vs 6.1% (P < .001). FQs were associated with tendinopathy, myalgia, arthralgia, and nausea. CONCLUSIONS: A significantly higher rate of unplanned drug discontinuation was associated with FQ as compared with non-FQ regimens. This provides a real-world view of the implications of FQ-related ADEs on unplanned discontinuation when used in prolonged durations for the management of staphylococcal PJIs.

Renal Toxicity Associated With Resection and Spacer Insertion for Chronic Hip PJI.

BACKGROUND: Two-stage exchange arthroplasty with high-dose antibiotic-loaded bone cement spacer and intravenous (IV) antibiotics is the most common method of managing infected total hip arthroplasties. However, the contemporary incidence, risk factors, and outcomes of acute kidney injuries (AKIs) in this cohort are unknown. METHODS: We identified 227 patients treated with 256 antibiotic-loaded bone cement spacers after resection of an infected primary total hip arthroplasty between 2000 and 2017. Mean age was 65 years, mean body mass index was 30 mg/kg2, 55% were men, and 16% had pre-existing chronic kidney disease (CKD). Spacers were in situ for a mean of 15 weeks, concomitantly associated with IV or oral antibiotics for a mean of 6 weeks. AKI was defined as a creatinine ≥1.5X baseline or ≥0.3 mg/dL. Mean follow-up was 8 years. RESULTS: AKI occurred in 13 patients without pre-existing CKD (7%) vs 10 patients with CKD (28%; OR 5; P = .0001). None required acute dialysis. Postoperative fluid depletion (ß = 0.31; P = .0001), ICU requirement (ß = 0.40; P = .0001), and acute atrial fibrillation (ß = 0.43; P = .0001) were independent predictors for AKI in patients without pre-existing CKD. Duration of in situ spacer, mean antibiotic dose in cement, use of amphotericin B, and type of IV antibiotics were not significant risk factors. At last follow-up, 8 AKIs progressed to CKD, with one receiving dialysis 7 years later. CONCLUSION: AKIs occurred in 7% of patients with normal renal function, with 5-fold greater risk in those with CKD, and 4% did develop CKD. Importantly, causes of acute renal blood flow impairment were independent predictors for AKI. LEVEL OF EVIDENCE: Level III, comparative study.

Automated Detection of Periprosthetic Joint Infections and Data Elements Using Natural Language Processing.

BACKGROUND: Periprosthetic joint infection (PJI) data elements are contained in both structured and unstructured documents in electronic health records and require manual data collection. The goal of this study is to develop a natural language processing (NLP) algorithm to replicate manual chart review for PJI data elements. METHODS: PJI was identified among all total joint arthroplasty (TJA) procedures performed at a single academic institution between 2000 and 2017. Data elements that comprise the Musculoskeletal Infection Society (MSIS) criteria were manually extracted and used as the gold standard for validation. A training sample of 1208 TJA surgeries (170 PJI cases) was randomly selected to develop the prototype NLP algorithms and an additional 1179 surgeries (150 PJI cases) were randomly selected as the test sample. The algorithms were applied to all consultation notes, operative notes, pathology reports, and microbiology reports to predict the correct status of PJI based on MSIS criteria. RESULTS: The algorithm, which identified patients with PJI based on MSIS criteria, achieved an f1-score (harmonic mean of precision and recall) of 0.911. Algorithm performance in extracting the presence of sinus tract, purulence, pathologic documentation of inflammation, and growth of cultured organisms from the involved TJA achieved f1-scores that ranged from 0.771 to 0.982, sensitivity that ranged from 0.730 to 1.000, and specificity that ranged from 0.947 to 1.000. CONCLUSION: NLP-enabled algorithms have the potential to automate data collection for PJI diagnostic elements, which could directly improve patient care and augment cohort surveillance and research efforts. Further validation is needed in other hospital settings. LEVEL OF EVIDENCE: Level III, Diagnostic.

Novel Use of Rifabutin and Rifapentine to Treat Methicillin-Resistant Staphylococcus aureus in a Rat Model of Foreign Body Osteomyelitis.

BACKGROUND: Owing to patient intolerance or drug interactions, alternative agents to rifampin are needed for management of staphylococcal periprosthetic joint infection. In the current study, we evaluated rifabutin, rifapentine and rifampin, with and without vancomycin, in a rat model of foreign body osteomyelitis. METHODS: Proximal tibiae were inoculated with methicillin-resistant Staphylococcus aureus (MRSA) and a Kirschner wire (K-wire) implanted in each. After 4 weeks of infection, rifampin, rifabutin, or rifapentine were administered, alone or with vancomycin. Tibiae and K-wires were cultured, and medians were reported as log10 colony-forming units (CFUs) per gram of bone or log10 CFUs per K-wire, respectively. RESULTS: Rifampin, rifabutin or rifapentine administered with vancomycin yielded less MRSA from bones (0.10, 3.02, and 0.10 log10 CFUs/g, respectively) than did no treatment (4.36 log10 CFUs/g) or vancomycin alone (4.64 log10 CFUs/g) (both P ≤ .02). The K-wires of animals receiving no treatment or vancomycin monotherapy recovered medians of 1.76 and 2.91 log10 CFUs/g per K-wire, respectively. In contrast, rifampin, rifabutin and rifapentine administered with vancomycin yielded medians of 0.1 log10 CFUs per K-wire, respectively. Rifampin resistance was detected in a single animal in the rifampin monotherapy group. CONCLUSIONS: Rifabutin or rifapentine with vancomycin were as active as rifampin with vancomycin against MRSA in rat foreign body osteomyelitis, suggesting that rifabutin and/or rifapentine may be alternatives to rifampin in the clinical management of staphylococcal periprosthetic joint infections.

The Lawrence D. Dorr Surgical Techniques & Technologies Award: Aseptic Reoperations Within One Year of Primary Total Hip Arthroplasty Markedly Increase the Risk of Later Periprosthetic Joint Infection.

BACKGROUND: Despite the success of primary total hip arthroplasties (THAs), some patients will require an aseptic reoperation within 1 year of the index THA. The goal of this study is to evaluate the risk of subsequent periprosthetic joint infection (PJI) in patients undergoing an aseptic reoperation within 1 year of a primary THA. METHODS: A retrospective review utilizing our institutional joint registry identified 211 primary THAs requiring aseptic reoperation within 1 year following index arthroplasty. A control group of 15,357 primary THAs not requiring reoperation within 1 year was identified. Patients were divided into groups based on time from primary THA to reoperation: (1) within 90 days (n = 112 THAs; 40% for dislocation, 34% for periprosthetic fracture) or (2) 91-365 days (n = 99 THAs; 37% for dislocation, 29% for periprosthetic fracture). Mean follow-up was 7 years. RESULTS: Patients undergoing an aseptic reoperation within 90 days had a PJI rate of 4.8% at 2 years, while the 91-365 day group had a PJI rate of 3.2% at 2 years. The control group had a PJI rate of 0.2% at 2 years. Employing a multivariate analysis, reoperation within 90 days of index arthroplasty had an elevated risk of PJI (hazard ratio 8, P < .001) as did a reoperation between 91 and 365 days (hazard ratio 13, P < .001). CONCLUSION: Aseptic reoperations within 1 year following primary THA resulted in an 8- to 13-fold increased risk of subsequent PJI. The risk was similar whether the aseptic reoperation was early (within 90 days) or later (91-365 days). LEVEL OF EVIDENCE: Level III (Prognostic).

Aseptic Reoperations Within 1 Year of Primary Total Knee Arthroplasty Markedly Increase the Risk of Later Periprosthetic Joint Infection.

BACKGROUND: Despite the high rate of success of primary total knee arthroplasty (TKA), some patients are candidates for early aseptic reoperation. The goal of this study is to evaluate the risk of subsequent periprosthetic joint infection (PJI) in patients treated with an aseptic reoperation within 1 year of primary TKA. METHODS: A retrospective review of our total joint registry compared 249 primary TKAs requiring an aseptic reoperation within 1 year following index arthroplasty to a control group of 17,867 TKAs not requiring reoperation within 1 year. Patients were divided into groups based on time from index TKA: (1) 90 days or less (114 TKAs) and (2) 91 to 365 days (135 TKAs). Mean age was 68 years with 57% female. Mean follow-up was 7 years. RESULTS: At 2 years postoperatively, patients undergoing an aseptic reoperation within 90 days subsequently had a 9% PJI rate, while patients undergoing an aseptic reoperation between 91 and 365 days subsequently had a 3% PJI rate. The control group had a 0.4% PJI rate. Compared to the control group, patients undergoing an aseptic reoperation within 90 days had an elevated risk of PJI (hazard ratio, 9; P < .0001), as did patients who had a reoperation between 91 and 365 days (hazard ratio, 4; P < .0001). CONCLUSION: Aseptic reoperation within 1 year of primary TKA was associated with a notably increased risk of subsequent PJI.

Destination Joint Spacers, Reinfection, and Antimicrobial Suppression.

In this cohort of 51 patients managed with retained "destination spacers" after the resection of infected joint prostheses, the presence of preoperative sinus drainage was significantly associated with reinfection. Chronic antimicrobial suppression after destination-spacer retention did not significantly prevent reinfections.

In Vitro Activity of Rifampin, Rifabutin, Rifapentine, and Rifaximin against Planktonic and Biofilm States of Staphylococci Isolated from Periprosthetic Joint Infection.

The in vitro activities of rifampin, rifabutin, rifapentine, and rifaximin were tested against 200 periprosthetic joint infection (PJI)-associated staphylococci. Seven rifampin-resistant isolates had MICs of ≥4 µg/ml. Three isolates had rifampin MICs of 0.25 to 1 µg/ml and harbored an Asp471Gly RpoB variant, suggesting that the CLSI rifampin-susceptible staphylococcal breakpoint of ≤1 µg/ml may be too high. The remaining isolates had rifampin MICs of ≤0.016 µg/ml, and the rifampin, rifabutin, rifapentine, and rifaximin minimum biofilm bactericidal concentrations (MBBC) for ≥50% of isolates were 8, 1, 2, and 4 µg/ml (for S. aureus) and 2, 0.06, 0.25, and 0.5 µg/ml (for S. epidermidis), respectively, for rifampin-susceptible isolates. Nonrifampin rifamycins have promising staphylococcal activity, including antibiofilm activity.

Comparison of Diagnostic Accuracy of Periprosthetic Tissue Culture in Blood Culture Bottles to That of Prosthesis Sonication Fluid Culture for Diagnosis of Prosthetic Joint Infection (PJI) by Use of Bayesian Latent Class Modeling and IDSA PJI Criteria for Classification.

We have previously demonstrated that culturing periprosthetic tissue in blood culture bottles (BCBs) improves sensitivity compared to conventional agar and broth culture methods for diagnosis of prosthetic joint infection (PJI). We have also shown that prosthesis sonication culture improves sensitivity compared to periprosthetic tissue culture using conventional agar and broth methods. The purpose of this study was to compare the diagnostic accuracy of tissue culture in BCBs (subsequently referred to as tissue culture) to prosthesis sonication culture (subsequently referred to as sonicate fluid culture). We studied 229 subjects who underwent arthroplasty revision or resection surgery between March 2016 and October 2017 at Mayo Clinic in Rochester, Minnesota. Using the Infectious Diseases Society of America (IDSA) PJI diagnostic criteria (omitting culture criteria) as the gold standard, the sensitivity of tissue culture was similar to that of the sonicate fluid culture (66.4% versus 73.1%, P = 0.07) but was significantly lower than that of the two tests combined (66.4% versus 76.9%, P < 0.001). Using Bayesian latent class modeling, which assumes no gold standard for PJI diagnosis, the sensitivity of tissue culture was slightly lower than that of sonicate fluid culture (86.3% versus 88.7%) and much lower than that of the two tests combined (86.3% versus 99.1%). In conclusion, tissue culture in BCBs reached sensitivity similar to that of prosthesis sonicate fluid culture for diagnosis of PJI, but the two tests combined had the highest sensitivity without compromising specificity. The combination of tissue culture in BCBs and sonicate fluid culture is recommended to achieve the highest level of microbiological diagnosis of PJI.

Periprosthetic Joint Infection With Fungal Pathogens.

BACKGROUND: Although there is abundant information about bacterial periprosthetic joint infections (PJIs), there is a notable paucity of information about fungal PJIs. The goals of this study are to describe the patient demographics, diagnostic findings, and treatment results of fungal PJIs after total joint arthroplasty. METHODS: We identified 31 fungal PJIs (13 total hip arthroplasties and 18 total knee arthroplasties) in 31 patients treated between 1996 and 2014. This represented 0.9% of the 3525 PJIs treated at our institution during this time period. Candida species accounted for 81% of infections. The mean patient age at diagnosis of fungal PJI was 68 years. Mean follow-up after initiation of treatment was 4 years. RESULTS: In the total hip arthroplasty cohort, survivorship free from all-cause revision or implant removal was 44% at 2 years. Survivorship free from reinfection was 38% at 2 years. Mean Harris hip score was 27 at final follow-up.In the total knee arthroplasty cohort, survivorship free from all-cause revision was 70% at 2 years. Survivorship free from reinfection was 76% at 2 years. Mean Knee Society scores were 36 at final follow-up. CONCLUSION: Fungal PJIs are rare (0.9% of diagnosed PJIs). Survivorship free of all-cause revision or implant removal was very low in the hip group (44% at 2 years), but slightly better in the knee group (70% at 2 years). Moreover, clinical outcomes were poor with high perioperative complication rates. Improved treatment regimens are needed for this unsolved clinical problem.

A Novel Prosthetic Joint Infection Pathogen, Mycoplasma salivarium, Identified by Metagenomic Shotgun Sequencing.

Defining the microbial etiology of culture-negative prosthetic joint infection (PJI) can be challenging. Metagenomic shotgun sequencing is a new tool to identify organisms undetected by conventional methods. We present a case where metagenomics was used to identify Mycoplasma salivarium as a novel PJI pathogen in a patient with hypogammaglobulinemia.

Coadministration of Liposomal Amphotericin B and Contrast Medium Does Not Increase Risk of Kidney Injury.

Intravenous radiographic contrast medium and amphotericin B are commonly required in the care of patients with fungal infections. Both interventions have proposed nephrotoxicity through similar mechanisms. We systematically examined patients who received coadministration of liposomal amphotericin B (AmBisome; GE Healthcare) and intravenous contrast medium within a 24-h period and compared the results for those patients with the results for patients who underwent non-contrast medium studies. We found 114 cases and 85 controls during our study period. Overall, no increased risk of renal injury was seen with coadministration of these 2 agents. Adjustment for age, baseline kidney function, and other clinical factors through propensity score adjustment did not change this result. Our observations suggest that, when clinically indicated, coadministration of contrast medium and liposomal amphotericin B does not present excess risk compared with that from the administration of liposomal amphotericin B alone.

Evaluation of a Genus- and Group-Specific Rapid PCR Assay Panel on Synovial Fluid for Diagnosis of Prosthetic Knee Infection.

We evaluated a genus- and group-specific PCR assay panel using 284 prosthetic knee synovial fluid samples collected from patients presenting to our institution with implant failure. Using the Musculoskeletal Infection Society diagnostic criteria, 88 and 196 samples were classified as showing prosthetic joint infection (PJI) and aseptic failure (AF), respectively. Sensitivities of the synovial fluid PCR panel and culture were 55.6% and 76.1% (P ≤ 0.001), respectively, and specificities were 91.8% and 97.4% (P = 0.016), respectively. Among the 70 subjects who had received antibiotics within the month preceding synovial fluid aspiration (48 of whom had PJI), PCR panel and synovial fluid culture sensitivities were 64.5% and 85.4%, respectively (P < 0.0001). In this group, the PCR panel detected Staphylococcus aureus in two culture-negative PJI cases. Overall, the evaluated molecular diagnostic tool had low sensitivity when applied to synovial fluid.

Low incidence of pneumocystis pneumonia utilizing PCR-based diagnosis in patients with B-cell lymphoma receiving rituximab-containing combination chemotherapy.

Recent literature has demonstrated concern over the risk of Pneumocystis jirovecii pneumonia (PJP) when administering rituximab with combination chemotherapy such as in R-CHOP; however, the exact risk and potential need for prophylaxis is unknown. We sought to determine the incidence of PJP infection following R-CHOP administration in patients with B-cell lymphoma. Consecutive patients diagnosed with B-cell lymphoma receiving R-CHOP were evaluated from chemotherapy initiation until 180 days after the last administration. The primary outcome was cumulative incidence of PJP infection. Secondary endpoints included the association of rituximab, prednisone and subsequent chemotherapy with PJP infection risk. A total of 689 patients (53% male, median age 66 years) were included. Seventy-three percent of patients completed at least 6 cycles of R-CHOP treatment. Median rituximab and prednisone cumulative doses were 3950 mg and 5325 mg, respectively. Median daily prednisone dose through end of treatment was 45 mg (range 7.6 mg to 119 mg). The cumulative incidence of PJP was 1.51% (95% CI 0.57-2.43, at maximum follow-up of 330 days), below 3.5%, the conventional threshold for prophylaxis. Univariate analysis did not detect a statistically significant association between PJP and rituximab, steroids, or receipt of additional chemotherapy in this patient population. Our results demonstrate a low occurrence of Pneumocystis pneumonia during R-CHOP treatment of B-cell lymphoma and argue against universal anti-Pneumocystis prophylaxis in this setting. Further investigations should focus on targeted anti-Pneumocystis prophylaxis for patients presenting with high-risk baseline characteristics or when receiving rituximab-inclusive intensive combination chemotherapy regimens as treatment for other aggressive lymphoma subtypes. Am. J. Hematol. 91:1113-1117, 2016. © 2016 Wiley Periodicals, Inc.