UCLA

Nocardial infections have been rare after allogeneic hematopoietic stem cell transplantation (HSCT). We report 10 recent cases of late-onset nocardiosis (median time of onset of 508 days after transplantation) primarily in patients on high doses of corticosteroids for graft-versus-host disease. All 10 patients had pulmonary infection caused by Nocardia species susceptible to trimethoprim-sulfamethoxazole (TMP-SMX). At time of diagnosis 8 of 10 patients were not receiving TMP-SMX for prophylaxis of Pneumocystis jiroveci pneumonia (PJP; 7 on atovaquone, 1 on i.v. pentamidine). After the initiation of atovaquone prophylaxis for PJP in place of TMP-SMX for many UCLA allogeneic HSCT patients in 2012, 9 cases of nocardiosis occurred in 411 patients (2.2%) over the next 6 years (2012 to 2017) compared with only 1 case in 575 patients (0.17%) during the previous 12 years (2000 to 2011). Although there were no deaths directly related to nocardial infection treated primarily with TMP-SMX, overall mortality in this group of patients was 40%. Based on this experience, the use of atovaquone for PJP prophylaxis in place of TMP-SMX may be associated with an increased risk for previously rare nocardial infections after allogeneic HSCT.