Nodular-bronchiectatic Pattern in Pulmonary Nocardiosis: Immune Status and Treatment Outcomes in a Multicenter Retrospective Study.

Background: Pulmonary nocardiosis is a rare opportunistic infection, with approximately 15% of patients being immunocompetent. The isolation rate of Nocardia spp. has recently increased, indicating rising clinical concern. This study aimed to summarize computed tomography (CT) findings, evaluate treatment outcomes, and improve disease recognition.

Methods: We retrospectively analyzed 12 pulmonary nocardiosis cases recorded over 10 years in three hospitals, excluding two unclear cases. All pathogens were detected on smears and isolated from respiratory specimens.

Results: The mean age was 73.0 ± 12.9 years, with 9 men and 6 smokers. Among the included patients, 8 had underlying pulmonary diseases, 4 had non-pulmonary diseases, and 3 were on steroids. The most common species were N. cyriacigeorgica and N. nova. CT findings included cavitary, consolidation/infiltrative, and nodular-bronchiectatic (NB) patterns. The NB pattern, particularly common in immunocompetent patients, was associated with significantly better treatment outcomes than non-NB patterns (Fisher's exact test, p=0.0476). All isolates were susceptible to trimethoprim/sulfamethoxazole. Eight patients recovered with appropriate antimicrobial therapy, while two patients died.

Conclusions: Pulmonary nocardiosis presented three CT patterns, with the NB pattern being the most frequent and showing favorable treatment outcomes, especially in immunocompetent patients. While Nocardia spp. can develop in patients with preexisting bronchiectasis, it may also independently cause bronchiectasis. Nocardia infection should be considered as a differential diagnosis in patients exhibiting the NB pattern, resembling that of nontuberculous mycobacterial pulmonary diseases.