Nocardia bacteria primarily enter the human body through the respiratory tract or open wounds, leading to suppurative infections. These infections are more prevalent in individuals with compromised immune systems and can affect the lungs, resulting in pulmonary nocardiosis. The bacteria may also disseminate via the bloodstream to adjacent tissues or infect various organs. Clinical manifestations, physical signs, and imaging findings of nocardial pneumonia lack specificity. Additionally, Nocardia grows slowly and is often overgrown by faster-growing bacteria in sputum cultures, making it difficult to isolate. As a result, clinical misdiagnosis and missed diagnosis are common. With the growing number of immunocompromised individuals, the incidence of nocardial infections has been increasing. Improving laboratory personnel's awareness of this pathogen and enhancing their technical capabilities are crucial for accurate and timely clinical diagnosis. A 34-year-old female patient was reported to have contracted pneumonia caused by Nocardia cyriacigeorgica. The patient experienced a cough and sputum production without a clear cause 20 days prior. Despite clinical empirical treatment, the cough and sputum persisted, and there was also a high fever accompanied by chills and shivering. Metagenomic next-generation sequencing (mNGS) results of the bronchoalveolar lavage fluid showed that it was caused by Nocardia cyriacigeorgica. After four days of sputum culture, bacterial colonies were observed and subsequently identified by matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF-MS) as Nocardia cyriacigeorgica. This patient received a combined treatment of compound sulfamethoxazole/trimethoprim and linezolid. Soon, his condition improved, and he was discharged from the hospital. During the two-month follow-up examination, it was observed that the lesion had been largely absorbed and the affected area had significantly reduced in size. The patient no longer experienced coughing or phlegm production. Following a comprehensive review of the clinical data of this case and relevant literature, we aim to improve the capacity of laboratory personnel in cultivating and identifying this rare bacterial pathogen. Furthermore, this study seeks to emphasize to clinical practitioners that bronchoalveolar lavage fluid should be collected for mNGS when pulmonary Nocardia infection is suspected, which can enhance diagnostic accuracy, facilitate early detection and timely intervention, and ultimately alleviate the burden on patients.
Keywords: cough; hiv; mycobacterium; nocardia cyriacigeorgica; nocardia species.
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