Nocardia Infections

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.A retrospective review of patients' medical records and UCLA Clinical Microbiology Laboratory culture results was performed to identify allogeneic HSCT recipients with a diagnosis of nocardiosis between January 1, 2000 and August 30, 2017. Baseline patient characteristics, underlying disease, allograft type, conditioning regimen, pretransplant and donor cytomegalovirus serology, immunosuppressive agents, and graft-versus-host disease (GVHD) status were collected. The clinical features of Nocardia infection and PJP prophylaxis at the time of diagnosis were also included in this review. The diagnosis of nocardiosis was made based on at least 1 culture of respiratory secretions or blood positive for Nocardia from a patient with clinical features of Nocardia infection not explainable by other causes. All Nocardia isolates were identified in the UCLA Clinical Microbiology Laboratory. Before 2013 a 7H11 solid media was used to recover Nocardia from clinical specimens. From 2013 to the present a buffered-charcoal yeast extract media was used to enhance recovery of Nocardia from cultures. All cultures were held for at least 3 weeks and examined daily for growth. Before 2013 Nocardia susceptibility testing was performed by an outside reference laboratory (Quest Diagnostics Infectious Disease, Inc., San Juan Capistrano, CA). After 2013 Nocardia susceptibility testing was performed at the UCLA Clinical Microbiology Laboratory. Nocardia susceptibility testing was performed at both Quest Diagnostics Infectious Disease and at UCLA, using broth microdilution trays. After inoculation of organisms, these trays are incubated for 72 hours and then read per standard antimicrobial susceptibility testing protocols to determine minimum inhibitory concentrations. CLSI M24-A2 susceptibility breakpoints are used