Pulmonary nocardiosis with bloodstream infection diagnosed by metagenomic next-generation sequencing in a kidney transplant recipient: A case report

BACKGROUND: Pulmonary nocardiosis is difficult to diagnose by culture and other conventional testing, and is often associated with lethal disseminated infections. This difficulty poses a great challenge to the timeliness and accuracy of clinical detection, especially in susceptible immunosuppressed individuals. Metagenomic next-generation sequencing (mNGS) has transformed the conventional diagnosis pattern by providing a rapid and precise method to assess all microorganisms in a sample. CASE SUMMARY: A 45-year-old male was hospitalized for cough, chest tightness and fatigue for 3 consecutive days. He had received a kidney transplant 42 d prior to admission. No pathogens were detected at admission. Chest computed tomography showed nodules, streak shadows and fiber lesions in both lung lobes as well as right pleural effusion. Pulmonary tuberculosis with pleural effusion was highly suspected based on the symptoms, imaging and residence in a high tuberculosis-burden area. However, anti-tuberculosis treatment was ineffective, showing no improvement in computed tomography imaging. Pleural effusion and blood samples were subsequently sent for mNGS. The results indicated Nocardia farcinica as the major pathogen. After switching to sulphamethoxazole combined with minocycline for anti-nocardiosis treatment, the patient gradually improved and was finally discharged. CONCLUSION: A case of pulmonary nocardiosis with an accompanying bloodstream infection was diagnosed and promptly treated before the dissemination of the infection. This report emphasizes the value of mNGS in the diagnosis of nocardiosis. mNGS may be an effective method for facilitating early diagnosis and prompt treatment in infectious diseases, which overcomes the shortcomings of conventional testing.