Clinical Characteristics of Nocardiosis: a Multicenter Retrospective Study in Korea.

Background: Nocardiosis is a rare, but potentially life-threatening condition. It is difficult to diagnose, and bacterial culture identification can be time consuming. We investigated the characteristics of nocardiosis and the suitability of the treatment approach in Korea.

Materials and methods: This retrospective study was conducted at 5 medical institutions between 2011 and 2021. We reviewed the medical records of patients with microbiologically confirmed nocardiosis. Appropriate antibiotic selection was defined as follows: (1) selecting antibiotics according to the species, (2) if the species of Nocardia was unknown, trimethoprim-sulfamethoxazole-based therapy or linezolid-based therapy was administered, and (3) selection of antibiotics using the antibiotic susceptibility test. The appropriate treatment periods for antibiotics were defined as treatment maintained from 3 to 12 months, depending on involvement of the organs. Descriptive analysis and Fisher exact test were used. Statistical significance was set at P-values of <0.05.

Results: Thirty patients were enrolled. Of these patients, 18 (60.0%) were male. The median age was 70.5 years. Among the diagnosed patients, 12 (40.0%) had an immunocompromised status. Eight (30.0%) patients received optimal treatment for the appropriate treatment period. Appropriate dosing duration was observed in 3 of the 12 (25.0%) immunocompromised patients. There was no significant difference between the presence or absence of immunosuppression and the adequacy of treatment for nocardiosis (P = 1.000). Skin and soft tissue (14 patients) were most frequently involved in this study. Nocardia species (spp.) were isolated from culture at a median of 6.0 days. There were 7 cases with N. farcinica (23.3%).

Conclusion: We found that 60.0% of the patients with nocardiosis did not have an immunocompromised status. Further, 26.7% of the total patients received adequate treatment for nocardiosis. The reasons for suboptimal management of nocardiosis in Korea are presumed to be diagnostic difficulties, lack of awareness about nocardiosis, and difficulties in selecting antibiotics for Nocardia spp. among clinicians. The lack of antibiotic susceptibility tests for Nocardia spp. could be the source of these problems. Nocardiosis should be suspected in cases of recurrent infections with skin and soft tissue, musculoskeletal, or respiratory system involvement with or without an immunocompromised status. Clinical microbiological support is required for the diagnosis and selection of antibiotics in Korea. High clinical index of suspicion and clinical microbiological support are required for the accurate diagnosis of nocardiosis in Korea.