Clinical Features of Pulmonary Nocardiosis and Diagnostic Value of Metagenomic Next-Generation Sequencing: A Retrospective Study

Abstract

Pulmonary nocardiosis (PN) is a rare, opportunistic, and potentially life-threatening infection, especially in disseminated cases. This retrospective study aimed to characterize the clinical features of PN and assess the diagnostic utility of metagenomic next-generation sequencing (mNGS). We reviewed data from 19 patients diagnosed with PN between September 2019 and August 2022, including 3 with disseminated disease. Common symptoms included fever, cough, and sputum production, while chest imaging frequently revealed nodules, consolidations, exudates, cavities, and pleural effusions. The sensitivity of mNGS for detecting Nocardia was significantly higher than that of culture (100% vs. 36.84%, p < 0.001). mNGS successfully identified Nocardia species and co-infected pathogens. The most common species was Nocardia farcinica. Four PN cases were co-infected with Rhizomucor pusillus, Cryptococcus neoformans, Lichtheimia ramosa, and Aspergillus spp. Eighteen patients (94.7%) received trimethoprim-sulfamethoxazole (TMP-SMZ). Sixteen cases (84.2%) were improved or cured. Misdiagnosis is common due to the nonspecificity of clinical and imaging presentations of pulmonary nocardiosis. The timely combination of mNGS represents a promising approach to enhance the diagnosis of pulmonary nocardiosis and inform targeted antimicrobial therapy. TMP-SMZ is the first line of treatment.

Keywords: Nocardia infection; clinical characteristics; detection performance; treatment.

Figure 1

Diagnostic findings in nocardiosis. (A) Representative imaging of lung (P1 and P2) and brain (P14). Red arrows indicate lesion sites. (B) The frequency of the Nocardia species found in patients by metagenomic next-generation sequencing. The number of circles denotes the case count for each detected Nocardia species.

Figure 2

Other microorganisms detected by metagenomic next-generation sequencing (mNGS) are shown in three categories: bacteria, fungi, and viruses.

Figure 3

Treatment strategies for all patients by Sankey diagram. B: blood, Br: brain, E: eye, L: lung, P: pleural, S: skin, Fungi-R: Rhizomucor pusillus, Fungi-C: Cryptococcus neoformans, Fungi-A: Aspergillus spp., Fungi-L: Lichtheimia ramosa, OT: other drugs for Nocardia, A: amphotericin B, V: voriconazole.