Evaluation of the Incidence of Nocardia Infection in Solid Organ Transplant Recipients on Trimethoprim-Sulfamethoxazole for Opportunistic Infection Prophylaxis

Background: Trimethoprim-sulfamethoxazole (TMP-SMX) is the preferred prophylactic agent for Pneumocystis jiroveci pneumonia (PJP) and toxoplasmosis after solid organ transplant (SOT). Compared with other agents, it has additional activity against Nocardia species.

Objective: The purpose of this study was to evaluate the incidence of Nocardia infection in SOT patients receiving TMP-SMX or an alternative agent for opportunistic infection (OI) prophylaxis.

Methods: This retrospective analysis included transplant recipients at a large urban medical center over a period of 4 years. All patients received either TMP-SMX or an alternative agent for PJP prophylaxis. The primary outcome was the incidence of Nocardia infection within 24 months posttransplant. Secondary outcomes included resistance rates of Nocardia isolates, usage rates of alternative prophylactic agents, reasons for using alternative agents, and rate of conversion from an alternative agent back to TMP-SMX.

Results: A total of 791 adult SOT recipients who received PJP or toxoplasmosis prophylaxis were included. Mean age at transplantation was 60.9 years with the majority of patients being male (67.3%) lung transplant recipients (63.6%). TMP-SMX was the most commonly used initial prophylactic agent (84.6%), followed by atovaquone (15.4%). Of the 791 SOT recipients, 16 (2.0%) were diagnosed with nocardiosis within 24 months posttransplant. Patients receiving alternative agents had a higher incidence of infection compared with those receiving TMP-SMX prophylaxis (P < 0.001).

Conclusion and relevance: Our findings suggest that OI prophylaxis with TMP-SMX may be protective against nocardiosis in SOT recipients. If possible, patients who are switched to an alternative agent due to TMP-SMX intolerance should be re-challenged when the adverse effect resolves. Most patients in our study were able to tolerate re-initiation, suggesting that the adverse effects associated with TMP-SMX may be temporary and may not warrant discontinuation.