To retrospectively analyze the clinical and prognostic features, and diagnosis and treatment strategies of nocardiosis in patients undergoing long-term glucocorticoid and/or immunosuppressive agent therapy.

Seven cases with confirmed diagnosis of nocardiosis who received long-term glucocorticoid and/or immunosuppressive agent therapy during the past 5 years in our hospital were reviewed. Nocardiosis diagnostic criteria: Nocardia presented in bacteria culture of various body fluids (sputum, blood, hydrothorax, pus) and/or biopsy specimens (skin biopsy, lung biopsy). Disseminated nocardiosis diagnostic criteria: Nocardia culture was positive with nocardiosis involving two or more organs.

Five patients were male (71%) and 2 were female (29%) with a mean age of 56.1±11.6 years. All the patients received long-term immunosuppressive therapy for nephrotic syndrome (3 cases) and autoimmune diseases (4 cases). Pre-admission anti-infective treatment was given in 5 cases, but the effect was poor. The median duration of immunosuppressive therapy at diagnosis of nocardiosis was 6 months (IQR 5 to 9). The average dose of glucocorticoids on admission was 21.0±8.8 mg. All 7 cases had pulmonary nocardiosis, among which 5 cases (71%) had disseminated nocardiosis. The median disseminating time was 2 months. Six cases presented high fever in the disease course with an average highest temperature of 39.5±0.7℃. All of the patients had cough and sputum, with dyspnea in 3 cases, chest pain in 2 cases, and hemoptysis in 1 case. Five cases had skin nocardiosis of subcutaneous abscess, of which 1 case also had joint abscess. Two patients with intracranial infections had blurred vision, of which 1 case had epilepsy. CRP was elevated in 7 patients (100%), with an average of 11.4 ± 14.0 mg/dl. The procalcitonin had an average level of 0.4 ng/ml (IQR 0.14 to 0.64), and increased in only 1 case (1/6, 17%). Lymphocytes decreased in 6 cases (6/7, 86%), and were less than 10% in 5 of them. In 2 patients (2/2, 100%), CD4⁺ count was less than 200/ul, and the ratio of CD4⁺ /CD8⁺ decreased significantly. The average IgG level was 765.0±226.9 mg/dl, and the average albumin level was 30.6±6.6 g/L. Lung CT scan showed pulmonary cavity in 5 cases (71%), nodules in 5 cases (71%), patchy shadow in 5 cases (71%), and ground glass opacities in cases (71%). The positive rates of bacterial culture from various body fluids and tissues were as follows: lung biopsy (1/1, 100%), pus (3/3, 100%), hydrothorax (43%), and blood culture (2/6, 33%). Sulfanilamide/linezolid-based treatment regimens were effective (71%), while 2 (29%) died and 2 (29%) relapsed after treatment discontinuation.

Nocardiosis is an opportunistic infection with a high rate of misdiagnosis, and is subject to dissemination and relapse. Tissue biopsy specimens and sterile humoral fluids culture had higher positive rates. Early diagnosis and rational treatment are key for improving its prognosis and reducing its spread and recurrence.