Nocardiosis in Japan: A Multicentric Retrospective Cohort Study

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 1-year mortality and microbiological data. 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 1- year mortality were also determined using Cox proportional hazard analysis. 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 1- 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 Nocardia 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 1-year mortality were a Charlson comorbidity index score of $5 (adjusted hazard ratio [aHR], 3.61; 95% confidence interval [CI], 1.95 to 6.71, P , 0.001) and disseminated nocardiosis (aHR, 1.79; 95%CI, 1.01 to 3.18, P = 0.047). The presence of advanced comorbidities and disseminated infection, rather than variations in antimicrobial therapy or Nocardia species, was independently associated with 1-year mortality.