Abstract Non-tuberculous mycobacteria (NTM), particularly those within the Mycobacterium avium complex (MAC) family, are increasing causes of pulmonary disease, especially in patients with underlying lung disease. Mycobacterium intracellulare subspecies chimaera (M. chimaera) is an emerging MAC pathogen, less frequently identified than M. avium or M. intracellulare, but associated with distinct antimicrobial resistance patterns. We report a case of pulmonary M. chimaera presenting with a rare complication and co-infection in an immunocompetent host. A 61-year-old male with a 46 pack-year smoking history and past polysubstance abuse presented to our institution following a ground-level fall, resulting in a left intertrochanteric fracture. Initial trauma imaging was diagnostic for the primary injury, but provided incidental findings of extrapleural air in the left lung apex with surrounding soft tissue thickening, highly suggestive of an apical cavitary lesion on computed tomography (CT) of C-spine. Subsequent CT chest confirmed diffuse airspace opacities, asymmetric apical pleural thickening, and centrilobular emphysema Figure 1. Two separate sputum samples were positive for numerous acid-fast bacilli. Tests for M. tuberculosis (QuantiFERON) and HIV were negative. Bronchoscopy with transbronchial biopsy showed extensive necro-inflammatory debris and foreign body giant cells, consistent with granulomatous infection. Bronchoalveolar lavage (BAL) was acid-fast stain positive and grew M. intracellulare subspecies chimaera, which demonstrated resistance to linezolid and moxifloxacin. Additionally, the BAL grew methicillin-resistant Staphylococcus aureus (MRSA). The patient was started on a multi-drug regimen of Azithromycin, Ethambutol, and Rifampin for a planned 12 months, supplemented by an eight-week induction course of Amikacin via a PICC line. He was medically stabilized and discharged for complex antibiotic completion and close pulmonology follow-up.This case highlights an incidentally discovered, rare presentation of M. chimaera pulmonary disease in an immunocompetent host. While apical cavitary disease and emphysema are classic MAC findings in heavy smokers, the presence of pleural involvement and extrapleural air is uncommon and indicates a more severe, complicated course. The identification of M. chimaera is notable as an emerging pathogen that accounts for a significant minority of MAC lung disease cases and is frequently associated with resistance to drugs like moxifloxacin and linezolid, as observed in this patient. Furthermore, the co-infection with MRSA underscores the risk of secondary bacterial infection in patients with structural lung damage and cavitary lesions. This abstract is funded by: None
Kosnik et al. (Fri,) studied this question.