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

Introduction: 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 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, 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 pulmonary disease through a systematic review of the literature. Although there is no standard recommended treatment regimen for 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.