Nocardiosis in Japan: a multicentric retrospective cohort study

Background Nocardia species cause a broad spectrum of infections, especially in immunocompromised patients. Given its relative rarity, data on the prognosis and distribution of nocardiosis from a large cohort are scarce. The present study aimed to scrutinize the clinical features and outcomes of nocardiosis in Japan, including one-year mortality and microbiological data. Methods The present, multicentric, retrospective cohort study enrolled patients aged ≥ 18 years with nocardiosis diagnosed between January 2010 and December 2017 and recorded their clinical and microbiological characteristics. Factors associated with one-year mortality were also determined using Cox proportional hazard analysis. Results In total, 317 patients were identified at 89 hospitals. Almost half (155/317, 48.9%) were receiving immunosuppressive agents, and 51 had disseminated nocardiosis (51/317, 16.1%). The one-year, all-cause mortality rate was 29.4% (80/272; lost to follow-up, n = 45). The most frequently isolated species was Nocardia farcinica (79/317, 24.9%) followed by the N. nova complex (61/317, 19.2%). Selected antimicrobial agents were generally effective, with linezolid (100% susceptibility [S]) and amikacin (94% S) having the most activity against Nocardia species. In Cox proportional hazard analysis, factors independently associated with one-year mortality were a Charlson Comorbidity Index score ≥ 5 (adjusted hazard ratio [aHR], 3.61; 95% confidence interval [CI], 1.95-6.71, P < 0.001) and disseminated nocardiosis (aHR, 1.79; 95%CI, 1.01-3.18, P = 0.047). Conclusions The presence of advanced comorbidities and disseminated infection, rather than variations in antimicrobial therapy or Nocardia species, were independently associated with one-year mortality.

A case report of Nocardia spp. infective endocarditis in an injection drug user

Background Nocardia-related endocarditis is rare. Intravenous drug use with nonsterile injection practices is a potential risk factor for nocardia infection. Disseminated nocardiosis with endovascular involvement is rarely reported in immunocompetent individuals. Case presentation A 54-year-old male was diagnosed with infective endocarditis due to Nocardia asteroides with septic emboli in the brain and spleen. The use of a matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) rapid diagnostic system was beneficial in identifying the causative organism. He was empirically treated with combination therapy consisting of three antibiotics. Antimicrobial susceptibility testing indicated that all three antibiotics had favorable minimum inhibitory concentrations (MICs). Due to his clinical status, he was not a surgical candidate. Patient passed away after discharge to hospice. Conclusions This case demonstrates unique challenges in the identification, diagnosis, and management of Nocardia-related infective endocarditis. A detailed history of injection practices should guide clinicians in assessing the risk for environmental pathogens. Valvular surgery and combination antibiotic therapy should be recommended for all eligible patients to improve the chances of survival.