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Background : Nocardia is an uncommon pathogen that has been reported to infect musculoskeletal structures. However, studies are largely limited to case reports, and little is known regarding management and outcomes of these infections. Methods : We performed a multicenter retrospective cohort study of adults with culture-confirmed musculoskeletal Nocardia infections at three Mayo Clinic centers in Arizona, Florida, and Minnesota from November 2011 through April 2022. Results : Nine cases of Nocardia musculoskeletal infection were identified. Seven (78 %) occurred in men, and the median age was 57.3 years (range 32.6-79.0). Specific infections included native joint septic arthritis with or without associated osteomyelitis ( N = 3 ), hardware-associated infection ( N = 1 ), sternal osteomyelitis ( N = 1 ), pyomyositis ( N = 2 ), bursitis ( N = 1 ), and tenosynovitis ( N = 1 ). Three cases (33 %) were associated with disseminated disease, all three occurring in solid organ transplant recipients. Surgical intervention was performed in all but the bursitis case. Length of treatment varied from 21 d for tenosynovitis to 467 d for osteomyelitis. The 1-year mortality was 22 %, and all fatal cases involved disseminated disease. Conclusion : Patients with localized nocardiosis affecting musculoskeletal structures generally have good outcomes, as opposed to those with disseminated infection. Management often required operative intervention, with one patient experiencing recurrence within 1 year., Competing Interests: The contact author has declared that none of the authors has any competing interests., (Copyright: © 2024 Ryan B. Khodadadi et al.)

Objective : confluent T1 hypointense marrow signal is widely accepted to represent osteomyelitis on MRI. Some authors have suggested that non-confluent bone marrow signal abnormality should be considered early osteomyelitis. The purpose of this study was to address this issue by comparing the rate of osteomyelitis and amputation based on T1 marrow signal characteristics. Materials and methods : a total of 112 patients who underwent MRI of the foot for the evaluation of possible osteomyelitis were included. Patients were assigned to confluent T1 hypointense, reticulated T1 hypointense, and normal bone marrow signal groups. Results : patients with confluent T1 hypointense signal on MRI had significantly higher rates of osteomyelitis and amputation at 2 and 14 months post-MRI than the reticulated T1 hypointense group ( p < 0.001 ). Six patients had normal T1 signal, 16.7 % of whom had osteomyelitis and underwent amputation by 2 months post-MRI. Of 61 patients with reticulated T1 hypointense signal, 19.7 % had a diagnosis of osteomyelitis at 2 months post-MRI and 30.8 % had a diagnosis of osteomyelitis at 14 months post-MRI; moreover, 14.8 % and 31.5 % underwent amputation by 2 and 14 months post-MRI, respectively. Of 45 patients with confluent T1 hypointense signal, 73.3 % of patients had osteomyelitis at 2 months post-MRI and 82.5 % had osteomyelitis at 14 months post-MRI. In this group, 66.7 % underwent amputation by 2 months post-MRI and 77.8 % underwent amputation by 14 months post-MRI. Conclusions : over half of the patients with suspected pedal osteomyelitis who had reticulated or normal T1 bone marrow signal on MRI healed with conservative measures. Therefore, we recommend terminology such as "osteitis", "reactive osteitis", or "nonspecific reactive change" to describe bone marrow edema-like signal and reticulated hazy T1 hypointense signal without associated confluent T1 hypointensity. Moreover, we recommend that the MRI diagnosis of osteomyelitis is reserved for confluent T1 hypointense bone signal in the area of concern., Competing Interests: The contact author has declared that none of the authors has any competing interests., (Copyright: © 2023 Christin A. Tiegs-Heiden et al.)

High-dose liquid antibiotics are uncommon in bone cement. We present a case series of patients in which up to 16 mL of liquid amikacin (250 mg mL - 1 ) was successfully incorporated into bone cement to treat periprosthetic joint infections. We did not observe adverse drug reactions definitively attributed to its use., Competing Interests: Don Bambino Geno Tai, Nathan J. Brinkman, Omar Abu Saleh, Christina G. Rivera, Douglas R. Osmon declare that they have no conflict of interest. Matthew P. Abdel receives royalties from Stryker and Springer. He is a member of the American Academy of Orthopedic Surgeons' board of directors., (Copyright: © 2021 Don Bambino Geno Tai et al.)

Background : Fungal prosthetic joint infections (PJIs) are rare and often associated with poor outcome; however, risk factors are not well described. Methods : This was a retrospective case control study among all patients with PJIs from 2006-2016 at two major academic centers. Each fungal PJI case was matched 1:1 with a bacterial PJI control by joint (hip, knee, shoulder) and year of diagnosis. We compared demographics, comorbidities, and clinical characteristics between cases and controls using chi square/Fisher's exact or Wilcoxon rank sum test. Independent risk factors were identified with multivariable logistic regression. Results : Forty-one fungal PJIs occurred over the study and 61% were due to Candida albicans . The hip was involved in 51.2% of cases, followed by the knee (46.3%). Compared to bacterial PJI, fungal PJI cases were more likely to have received antibiotics within the previous 3 months (70.7% vs 34%, P =.001), wound drainage lasting >5 days (48% vs 9%, P =.0002), had a lower median CRP (2.95 mg/dl vs 5.99, P =.013) and synovial fluid white blood cell count (13,953 cells/mm 3 vs 33,198, P =.007), and a higher proportion of prior two-stage exchanges (82.9% vs 53.6%, P =.008). After controlling for center, prolonged wound drainage (OR, 7.3; 95% CI, 2.02-26.95) and recent antibiotics (OR, 3.4; 95% CI, 1.2-9.3) were significantly associated with fungal PJI. Conclusion : In our study, Candida albicans was the most common species in fungal PJIs and prolonged wound drainage and recent antibiotics were independent risk factors. These clinical characteristics may help providers anticipate fungal PJI and adjust management strategies., Competing Interests: Competing Interests: The authors have declared that no competing interest exists., (© The author(s).)

Introduction: Prosthetic joint infection (PJI) due to Streptococcus bovis group (SBG), specifically S. bovis biotype I ( S. gallolyticus ), is rare and associated with colorectal carcinoma. Little has been published regarding SBG PJI. We analyzed nine cases of SBG PJI at our institution, the largest series to date. Methods : The medical records of patients diagnosed with SBG PJI between 2000-2017 were reviewed. Patients were followed until death, failure, or loss to follow-up. Mean follow-up was 37 months (range 0.5-74 months). Results: Nine PJI in 8 patients with mean prosthesis age at diagnosis of 8 years (range 4 weeks-17 years) were identified. The median duration between symptom onset and treatment was 38 weeks (range 0.3 weeks-175 weeks). 8/9 had their PJI eradicated with treatment based on acuity of symptoms. Acute PJI (2) was treated with DAIR, and chronic PJI (7) was treated with 2-stage revision arthroplasty. 1 PJI with chronic PJI developed recurrent infection after initial treatment. All patients received post-operative IV antibiotics. 7/8 patients received Ceftriaxone. Three patients received lifelong oral antibiotics. 7/8 patients underwent colonoscopy. 5/7 patients were found to have polyps following PJI diagnosis with one carcinoma and two dysplastic polyps. The two patients without polyps had identifiable gastrointestinal (GI) mucosal abnormality: tooth extraction prior to symptom onset and diverticulosis on chronic anticoagulation. Conclusion: SBG PJI is typically due to hematologic seeding. Colonoscopy should be pursued for patients with SBG PJI. Surgical treatment dictated by infection acuity and 6-week course of Ceftriaxone seems sufficient to control infection., Competing Interests: Competing Interests: The authors have declared that no competing interest exists., (© The author(s).)

Background: Hematopoietic stem cell transplantation (HSCT) recipients are at increased risk for infection. This study describes bone and joint infections (BJI) among HSCT recipients. Methods: We reviewed 5861 patients who underwent HSCT at Mayo Clinic, Rochester, MN from January 1, 2005 through January 1, 2015 for study inclusion. BJI was defined as native septic arthritis, prosthetic joint infection, osteomyelitis, and orthopedic implant infection. All adults with BJI after HSCT were included in the analysis. Results: Of 5861 patients, 33 (0.6%) developed BJI. Native joint septic arthritis was the most common BJI occurring in 15/33 (45.4%) patients. Patients were predominantly male (24/33, 72.7%), with median age of 58 (range 20-72) years. BJI was diagnosed a median of 39 (range 1-114) months after allogeneic (14/33, 42.4%) or autologous (19/33, 57.6%) HSCT. Organisms were recovered via tissue (24/27, 88.9%), synovial fluid (13/17, 76.5%), and/or blood cultures (16/25, 64%). Most underwent surgical debridement (23/33, 69.7%). Patients were followed a median of 78.3 months (range 74-119). Therapy was unsuccessful in 4/33 (12.1%), with death related to the underlying BJI in two (50%). Failure occurred a median of 3.4 (0.1-48.5) months from diagnosis. At last follow up, 7/33 (21.2%) patients were alive. Median overall survival was 13 months (0.07-70.6). Conclusion: BJI among HSCT recipients is infrequent. The most common infection is native joint septic arthritis. Pathogens appear similar to patients without HSCT. Treatment involving surgical-medical modalities is successful, with most patients surviving >1 year after BJI., Competing Interests: Competing Interests: One author (PK) has received funding from Amgen, Takeda and Sanofi., (© The author(s).)

Background: Actinomyces prosthetic joint infections (APJIs) are rare and optimal medical and surgical treatment strategies are unknown. The purpose of our study was to characterize the demographics, risk factors, management and outcomes of patients with PJIs due to Actinomyces spp. Methods: Using a retrospective cohort study design, the medical records of all patients with Actinomyces spp. total hip or knee arthroplasty infection (APJI) seen at a single institution between January 1, 1969 and December 31, 2016 were reviewed. We abstracted information including patient demographics, co-morbidities, joint age, surgical history, microbiology, management and outcomes. A simultaneous literature search via PubMed was performed to identify cases of APJI published in literature and a descriptive analysis was performed. Results: Eleven cases were identified over a 47 year study period at our institution. Seven patients (64%) were female. The median age at the time of diagnosis of infection was 71 years (range, 57-89). The knee was involved in six cases (55%) followed by the hip in 5 (45 %) cases. Three cases had dentures, broken teeth, or poor dentition. Actinomyces odonotlyticus was the most commonly found subspecies at our institution. Median ESR and CRP values were 61mm/hr and 64 mg/L respectively. Eight (72%) patients were managed with 2 stage exchange. Most patients received a course of beta-lactam therapy for 6 weeks. Ten cases (91%) were free of failure after a median duration of follow-up of 2 years (range, 0.67 - 5 years). The median duration from joint arthroplasty to the onset of symptoms was 162 days, range (20-3318). Six (54%) had a history of prior PJI with a different microorganism at the same joint site and 4 patients had history of prior 2 stage exchange (36%). In the literature group, we identified 12 cases and the most common subspecies was Actinomyces israelii ; most patients underwent two stage exchange and were treated with 6 weeks of beta lactam antibiotics. Conclusions: Based on our observational study, Actinomyces PJI presents as a late complication of TJR, may be associated with prior PJI at the index joint and antecedent dental manipulation may portend as an additional risk factor. Treatment includes two stage exchange and beta- lactam therapy for 6weeks. These results will help clinicians in improved understanding and management of APJIs which although are rare but warrant special attention as population with implanted joint arthroplasties continues to rise., Competing Interests: Competing Interests: The authors have declared that no competing interest exists.

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., Competing Interests: Competing Interests: No conflicts of interest are present between this work and any of the authors. This work was supported by Grant Number UL1 TR000135 from the National Center for Advancing Translational Sciences (NCATS). Its contents are solely the responsibility of the authors and do not necessarily represent the official views of the NIH.