Abstract Nocardia is an aerobic, gram-positive, partially acid-fast bacillus widely distributed in soil and water. It primarily causes opportunistic infections but can also affect immunocompetent individuals, particularly those with structural lung diseases. Disseminated nocardiosis can involve various organs, with the central nervous system and skin being the most frequently affected sites. Nocardia Mexicana, a strain identified in 2014, has limited documentation in the literature. There has been no known report of intraabdominal nocardiosis associated with Nocardia Mexicana pneumonia. We are presenting the first known case of Nocardia Mexicana pneumonia complicated by omental dissemination that was successfully treated with intrapleural fibrinolysis therapy and antibiotics therapy with Trimethoprim/Sulfamethoxazole and Moxifloxacin. 33-year-old male construction worker with a history of 7 pack-years of smoking and multifocal pneumonia three years prior presented with a three-week history of worsening productive cough and intermittent fever, along with a one-week history of abdominal pain. Chest computed tomography (CT) revealed a left upper lobe opacity with possible cavitation and a 3 cm x 2 cm abdominal mass. An omental biopsy demonstrated necrotizing and non-necrotizing granulomatous inflammation, which tested positive for Nocardia Mexicana. The patient was initially started on antibiotics but showed resistance to therapy, necessitating intrapleural fibrinolysis for empyema. Subsequently, the patient responded to treatment with Trimethoprim/Sulfamethoxazole and Moxifloxacin. Nocardia infections are rare, often challenging to treat, and can be life-threatening. Nocardiosis typically involves the lungs and frequently disseminates to other sites, most commonly the skin and brain. The precise acquisition route of intra-abdominal nocardiosis remains unclear, although hematologic dissemination following initial pulmonary or percutaneous infection has been proposed. Malignancy is a common differential diagnosis for an abdominal mass, making biopsy a reasonable diagnostic approach for patients presenting with lung lesion and an omental lesion. Structural lung diseases are recognized risk factors for pulmonary nocardiosis. In our case, the patient was a smoker and worked in construction, raising concern for silicosis; these factors may have contributed to the development of nocardiosis. Currently, there are no established therapeutic guidelines for abdominal nocardiosis. In our case, successful treatment was achieved with intrapleural fibrinolysis and antibiotic therapy using Trimethoprim/Sulfamethoxazole and Moxifloxacin. We present the first reported case of Nocardia mexicana pneumonia complicated by omental dissemination, successfully treated with intrapleural fibrinolysis and antibiotic therapy using Trimethoprim/Sulfamethoxazole and Moxifloxacin. Given the lack of established guidelines for managing disseminated nocardiosis involving the lungs and abdomen, it is important to raise awareness of abdominal nocardiosis. This abstract is funded by: None
Shiraishi et al. (2026) studied this question.