Adjunctive Diagnosis of Mycobacterium gordonae Pneumonia by Metagenomic Next-Generation Sequencing in an Immunocompetent Patient: A Case Report and Literature Review

Abstract

Introduction: Mycobacterium gordonae is a nonpathogenic pathogen commonly found in nature and is generally considered a contaminant in clinical practice. Although there have been few reported cases of infection, most of them are secondary to immunosuppression. This paper described a rare case of globular shadow in the chest of an immunocompetent male who was diagnosed with M. gordonae pulmonary disease. He went to the hospital with chest pains that had lasted for more than two weeks. The routine clinical pathogen detection failed to discover the cause of the infection. Although metagenomic next-generation sequencing (mNGS) of the lung tissue was negative, M. gordonae was detected in the background microorganism with only one read. Based on the pathological results, it was considered to be the causative pathogen. Two months of treatment with rifampicin, ethambutol, clarithromycin, and levofloxacin resulted in significant reduction and absorption of lung lesions. No abnormalities were detected in either lung one year later. The lack of positive culture and other conventional microbiological test results make this case is not a strictly confirmed case. This study also explored the clinical features and treatment options of 32 cases of M. gordonae pulmonary disease through a systematic review of the literature. Although there is no standard recommended treatment regimen for M. gordonae infection, but combination therapy with macrolides, rifampicin, and ethambutol has been proven effective.

Conclusion: This case highlights that when the clinical highly suspected of infection, mNGS can contribute to the early identification of non-tuberculous Mycobacterium (NTM) even with low reads, when clinical suspicion is high. Analyzing background microorganisms in sterile samples may help diagnose rare pathogens.

Keywords: Mycobacterium gordonae; globular shadow; mNGS; nontuberculous mycobacterium; pulmonary disease.

Figure 1

CT findings of the patient’s lungs at different times. (A) On April 27, CT images of lung window showed a lumpy high-density shadow in the upper right lung (red arrow), limited bronchial stenosis in the apical segment of the right upper lobe of the lung (green arrow). (B) On April 27, CT images of mediastinal window showed multiple enlarged lymph nodes in the right hilum (blue arrow) and mediastinum (yellow arrow). Red arrow presents the lumpy high-density shadow in the upper right lung. (C) On August 10, a mass-like lesion (red arrow) in the upper lobe of the right lung was enlarged. (D) On October 27, the mass-like lesion (red arrow) in the upper lobe of the right lung was significantly absorbed and reduced in size. (E) On March 24, 2023, the follow-up CT results suggested the mass-like lesion in the upper lobe of the right lung was completely absorbed.

Figure 2

Bronchoscopy findings on 10 June. (A and B) a bronchial neoplasm (black arrow) in the apical segment of the upper lobe of the right lung. (C and D) enlarged lymph nodes (red arrow) in group 10R.

Figure 3

Histopathological findings of a percutaneous lung aspiration biopsy performed. (A) Coagulative necrosis (red box) and granulomatous tissue hyperplasia (black box). Scale bars, 200 μm. (B) Massive lymphocytic plasma cell infiltration with foci of hyperplastic granuloma. Multinucleated giant cells: blue circle; plasma cells: green circle. Scale bars, 50 μm.