A 54-year-old male, a ceramic worker with no previous history of immune dysfunction, was admitted to the hospital with persistent fever for 19 days. The patient had a cough occasionally and joint soreness but denied any other symptoms. On initial clinical evaluation, the patient's body temperature was 38.4  C, and other signs were within normal limits. Pulmonary, abdominal, cardiac, and neurologic examinations showed unremarkable findings. Laboratory tests revealed that the patient had leukocytosis (20.72 x 109/ml) with 87.4% neutrophils. His C-reactive protein level was high (90.61 mg/L), and a procalcitonin level was slightly increased (0.173 ng/ml). Contrast-enhanced chest CT revealed a large mediastinal mass measuring approximately 7.76 x 4.55 cm (Figure 1A). The rest of the examination was regular.
At initial admission, the patient was treated with empiric antibiotic therapy, including piperacillin and sulbactam. However, he still had a recurrent fever, and there was no significant improvement in inflammatory indicators and blood routine examination. To determine the etiology, the patient underwent Endobronchial ultrasound-guided transbronchial needle aspiration (EBUS-TBNA) on the fifth day of admission. The Virtual bronchoscopic navigation (VBN) system is a method to guide the bronchoscope to the lesion by making a bronchial path on a virtual image. The digitized information from the patient's CT scan was imported into the Archimedes VBN system, in which multislice views of the chest and virtual bronchoscopy images were reconstructed. The VBN system shows the bronchial tree, the anatomical structure of the mediastinal mass and visualizes the best path to reach the mediastinal mass (Figures 2A-E). With the guidance of the VBN system, the bronchoscope was navigated to the target bronchus and advanced to the lesion, and then EBUS-TBNA was performed to obtain purulent exudate (Figures 3A-D). Biopsy showed more purulent secretions and a few lymphocytes and macrophages (Figure 4A). Microscopic analysis revealed numerous weakly acid-fast and branching filamentous rod bacteria were identified from the samples on the aspirate smear, and a presumptive microbiological diagnosis (Nocardia) was made (Figure 4B). Metagenomic next-generation sequencing (mNGS) subsequently identified the pathogens as Nocardia species (Nocardia arizonensis and Nocardia cyriacigeorgica). And after seven days of culture, the cultures of purulent exudates ultimately grew the Nocardia species (Figure 4C).
After microscopic examination and mNGS confirmed Nocardia, intravenous imipenem/amikacin was given. The clinical symptoms of the patient were significantly improved after 6 days of treatment. Then he was switched to intravenous imipenem with oral trimethoprim/sulfamethoxazole (TMP/SMX, 80 mg of TMP, and 400 mg of SMZ/tablet) 3 tablets q6h. One month after treatment, the patient improved, and their Chest CT showed a decrease in the size of the mediastinal mass (Figure 1B). He was discharged and continued to be treated with oral TMP/SMX 3 tablets q8h and sodium bicarbonate for 3 months. Over the next 3 months, he continued on oral TMP/SMX 2 tablets q8h and sodium bicarbonate. After six months of treatment, the patient was asymptomatic. His CT showed significant improvement in the mediastinal mass size (Figure 1C). At one and a half years of follow-up, the patient recovered well, and no complications were noted (Figure 1D).