Risk Factors and Outcomes of Nocardiosis in Hematopoietic Stem Cell Transplantation Recipients

Nocardiosis occurs in up to 1.7% of hematopoietic stem cell transplantation (HSCT) recipients. Risk factors for its development and subsequent outcomes have been incompletely studied. The present study evaluated risk factors for nocardiosis in HSCT recipients and an association with 12-month mortality following Nocardia infection. We performed a nested case-control study of HSCT recipients at 3 transplantation centers between 2011 and 2021. Allogeneic HSCT recipients were matched 1:4 to controls based on age, sex, date of transplantation, and transplantation site. Because of theorized differences in the risk for nocardiosis between allogeneic HSCT recipients and autologous HSCT recipients and a low number of infected autologous HSCT recipients, only allogeneic HSCT recipients were matched to controls. Associations with nocardiosis in the allogeneic group were assessed by multivariable conditional logistic regression. Outcomes of all HSCT recipients with nocardiosis included 12-month mortality and post-treatment recurrence. Twenty-seven HSCT recipients were diagnosed with nocardiosis, including 20 allogeneic HSCT recipients and 7 autologous HSCT recipients. Twenty (74.1%) had localized pulmonary infection, 4 (14.8%) had disseminated infection, and 3 (11.1%) had localized skin infection. The allogeneic recipients were diagnosed at a median of 12.2 months after transplantation, compared with 41 months for the autologous recipients. All autologous HSCT recipients had alternative reasons for ongoing immunosuppression at diagnosis, most frequently therapy for relapsed hematologic disease. No infected patients were receiving trimethoprim-sulfamethoxazole (TMP-SMX) prophylaxis. In multivariable analysis of 20 allogeneic patients and 80 matched controls, graft-versus-host disease (GVHD) requiring current immunosuppression and lack of prophylaxis were associated with nocardiosis. Nocardiosis was significantly associated with subsequent mortality, with a 12-month mortality rate of 29.6%; however, no patients who completed treatment experienced Nocardia recurrence. Our data indicate that: intensified immunosuppression following allogeneic HSCT, such as treatment for GVHD, is associated with the development of nocardiosis. Nocardiosis occurs more distantly from transplantation in autolo-gous recipients, possibly driven by therapy for relapsed hematologic disease. No patients receiving TMP-SMX pro-phylaxis developed nocardiosis. Nocardia infection is associated with high mortality, and further strategies for prevention and treatment are needed.