Nocardiosis following hematopoietic stem cell transplantation

Background: Nocardia species are ubiquitous environmental organisms that can cause a diverse spectrum of disease. Clinical manifestations range from localized skin and soft tissue infections to life-threatening pulmonary, central nervous system, and/or disseminated infections. Patients with hematologic malignancies undergoing hematopoietic stem cell transplantation (HSCT) are at risk for nocardiosis, and further data in regard to characteristics of disease in this population are warranted.

Methods: We performed retrospective chart review of patients post allogeneic HSCT at Moffitt Cancer Center in Florida diagnosed with nocardiosis from 2003 to 2013.

Results: In a decade, 15 cases of nocardiosis were identified. The majority of patients were men (11/15). The median age was 55 years (range 25-65). The most common type of transplant was matched-related donor (n = 8), followed by matched-unrelated donor (n = 3), mismatched-unrelated donor (n = 3), and double umbilical cord (n = 1). Ten received myeloablative conditioning (MAC) regimens. Twelve of 15 patients were on prednisone, 10 of which were on a total daily dose ≥20 mg. The median time from transplant to first positive culture was 10 months (range 1.5-93). Pulmonary nocardiosis was the most prevalent manifestation at 87%. Disseminated disease (2 or more sites of infection) was seen in 47%, whereas blood cultures were positive in 27% of the total cohort. The most common species was Nocardia nova (n = 4). At the time of diagnosis, 20% of the patients were receiving prophylaxis for Pneumocystis jirovecii pneumonia (PJP) with trimethoprim-sulfamethoxazole (TMP-SMX). Susceptibility data were available for 8 patients: all 8 samples were susceptible to TMP-SMX. Nocardiosis was treated with 2 or more active drugs in 93% of the patients. Overall mortality was 53%, with nocardiosis attributed as the cause in 62.5% (5/8). The absolute lymphocyte count at time of diagnoses was significantly lower in patients who ultimately experienced treatment failure.

Conclusion: Infection with Nocardia species in allogeneic HSCT recipients appears to be a late complication of transplantation and most commonly involves the lung. Two-thirds of the cohort received a MAC regimen and the majority of the patients were receiving steroids at the time of diagnosis. Most patients were not receiving TMP-SMX for PJP prophylaxis at the time of nocardiosis diagnosis, and TMP-SMX may therefore have a protective effect.