Risk factors, clinical characteristics, and outcome of Nocardia infection in organ transplant recipients: a matched case-control study.

Background: Risk factors for Nocardia infection in organ transplant recipients have not been formally assessed in the current era of transplantation.
Methods: We performed a matched case-control study (1:2 ratio) between January 1995 and December 2005. Control subjects were matched for transplant type and timing. Univariate matched odds ratios were determined and conditional logistic regression was performed to identify independent risk factors. Clinical and microbiological characteristics of all case patients were reviewed.
Results: Among 5126 organ transplant recipients, 35 (0.6%) were identified as having cases of Nocardia infection. The highest frequency was among recipients of lung transplants (18 [3.5%] of 521 patients), followed by recipients of heart (10 [2.5%] of 392), intestinal (2 [1.3%] of 155), kidney (3 [0.2%] of 1717), and liver (2 [0.1%] of 1840) transplants. In a comparison of case patients with 70 matched control subjects, receipt of high-dose steroids (odds ratio, 27; 95% confidence interval, 3.2-235; P=.003) and cytomegalovirus disease (odds ratio, 6.9; 95% confidence interval, 1.02-46; P=.047) in the preceding 6 months and a high median calcineurin inhibitor level in the preceding 30 days (odds ratio, 5.8; 95% confidence interval, 1.5-22; P=.012) were found to be independent risk factors for Nocardia infection. The majority of case patients (27 [77%] of 35) had pulmonary disease only. Seven transplant recipients (20%) had disseminated disease. Nocardia nova was the most common species (found in 17 [49%] of the patients), followed by Nocardia farcinica (9 [28%]), Nocardia asteroides (8 [23%]), and Nocardia brasiliensis (1 [3%]). Of the 35 case patients, 24 (69%) were receiving trimethoprim-sulfamethoxazole for Pneumocystis jirovecii pneumonia prophylaxis. Thirty-one case patients (89%) experienced cure of their Nocardia infection.
Conclusions: Receipt of high-dose steroids, history of cytomegalovirus disease, and high levels of calcineurin inhibitors are independent risk factors for Nocardia infection in organ transplant recipients. Our study provides insights into the epidemiology of Nocardia infection in the current era, a period in which immunosuppressive and prophylactic regimens have greatly evolved.