Outcomes of Nocardiosis and Treatment of Disseminated Infection in Solid Organ Transplant Recipients

Abstract

Background: Nocardia is an environmental pathogen with a predilection for causing opportunistic infections in immunocompromised patients, including solid organ transplant (SOT) recipients. Although risk factors have been identified for developing nocardiosis in this population, little is known regarding clinical factors resulting in poor outcomes. We evaluated a cohort of SOT recipients with nocardiosis for associations with 12-month mortality.

Methods: We performed a multicenter retrospective cohort study of adult SOT recipients diagnosed with culture-confirmed nocardiosis from 2000 to 2020. Patients were followed for 12 months after diagnosis, unless abbreviated by mortality. Multivariable Cox regression was performed to analyze associations with 12-month mortality. A subgroup analysis of patients with disseminated nocardiosis was performed to analyze treatment variables.

Results: A total of 125 SOT recipients met inclusion criteria; 12-month mortality was 16.8%. Liver transplantation (hazard ratio [HR] 3.52; 95% confidence interval [CI] 1.27-9.76) and time from symptom onset to presentation (HR 0.92/d; 95% CI 0.86-0.99) were independently associated with 12-month mortality, whereas disseminated infection was not (HR 1.23; 95% CI 0.49-3.13). No treatment-specific factors were significantly associated with mortality in 33 patients with disseminated nocardiosis, although survivors had a higher rate of linezolid use.

Conclusions: This study identified 2 independent associations with 12-month mortality, representing demographics and infection severity. Disseminated infection was not independently associated with poor outcomes, and specific sites of infection may be more important than dissemination itself. No treatment-specific factors were associated with mortality, though this analysis was likely underpowered. Further study of treatment strategies based on specific Nocardia syndromes is warranted.

Figure 1:

Bar chart of the number of each identified Nocardia species.

Figure 2:

Kaplan-Meier curves comparing 12-month survival after diagnosis of nocardiosis in solid organ transplant recipients, stratified by variables of interest. The numbers near the bottom of the graph indicate number of patients alive at the respective time-point by group. The p-values are calculated through log-rank tests. A, stratified by transplanted organ type. B, stratified by presence of disseminated infection at presentation. C, stratified by chronic dialysis dependency at time of Nocardia infection diagnosis. D, stratified by presence of Nocardia bloodstream infection at presentation.