[Clinical analysis of thirteen cases of pulmonary infection caused by <i>Nocardia otitidiscaviarum</i>].

<b>Objective:</b> To explore the clinical characteristics of patients with pulmonary nocardiosis caused by <i>Nocardia otitidiscaviarum</i> and to enhance understanding of this disease. <b>Methods:</b> A retrospective analysis was conducted on the clinical, imaging, and pathogenic data of 13 patients diagnosed with pulmonary infections caused by <i>Nocardia otitidiscaviarum</i> at Binzhou People's Hospital between January 2022 and December 2024. <b>Results:</b> The patients' age ranged from 42 to 89 (69±13) years. There were 8 females (4 with smoking history) and 5 males (3 with smoking history). The clinical symptoms included cough and sputum production in 8 patients (including 1 with a dry cough), fever in 8 patients, wheezing and chest tightness in 6 patients, and hemoptysis in 3 patients. Computed tomography (CT) scans of the chest showed that 11 patients had involvement of the lower lobe of the left lung, 6 had bilateral lung involvement, 5 presented with involvement of the upper lobe of the right lung, 4 showed changes in both the middle and lower lobes of the right lung, and only 2 had involvement of the upper lobe of the left lung. Of the imaging findings, 8 patients exhibited consolidation shadows, 5 displayed nodule shadows, and 4 had necrotic cavities (with 3 of these located in the lower lobe of the left lung). Additionally, 3 patients were diagnosed with bronchiectasis, 1 with a necrotic lymph node, and 5 with pleural effusion. Microbial study results showed concomitant Aspergillus in 3 cases, <i>Klebsiella pneumoniae</i> in 1, COVID-19 infection in 3, influenza A in 1, and influenza B in 1. All 13 patients demonstrated improvement following treatment with trimethoprim/sulfamethoxazole tablets. <b>Conclusions:</b> <i>Nocardia otitidiscaviarum</i> is a rare form of pulmonary nocardiosis that can occur in individuals with a preserved immune system. This pathogen is associated with more severe clinical manifestations. Furthermore, the risk of <i>Nocardia otitidiscaviarum</i> infections may be exacerbated by the presence of the COVID-19 virus and influenza viruses A and B. Monitoring patients with Aspergillus infection is particularly crucial, as their condition can deteriorate rapidly, posing a considerable danger. Consequently, when patients present with aforementioned risk factors or exhibit specific imaging features, prompt screening and diagnosis using metagenomic next-generation sequencing (mNGS) is essential.