A Challenging Case of Mycobacterium Chimaera Pulmonary Infection in an Elderly Patient With Recurrent Pneumonia

Abstract Introduction: M. chimaera, a non-tuberculous mycobacterium, is an emerging pathogen that poses diagnostic and therapeutic challenges, particularly in patients with chronic health conditions. Case presentation: An 80-year-old male with a history of diabetes, hypertension, atrial fibrillation on Eliquis, and OSA on CPAP experienced multiple hospitalizations due to persistent cough and progressively worsening shortness of breath. Initial imaging showed a right lower lobe consolidation, for which he was treated as having community-acquired pneumonia. Due to persistent lung opacity, he was referred to Pulmonology, underwent bronchoscopy, and was diagnosed with Mycobacterium chimaera infection. Before he could follow up with Infectious Diseases for his non-tuberculous M. chimaera infection, he was re-hospitalized for severe shortness of breath and hypoxia. This time, he was found to have post-obstructive pneumonia with a lung abscess and empyema secondary to chronic food impaction. He underwent bronchoscopy, right VATS with decortication, pleural biopsy, chest tube and Blake drain placement, and removal of the food bolus from his right lower lobe bronchus. His symptoms improved significantly post-procedure, with BAL cultures growing Stenotrophomonas and Pseudomonas. He was treated with IV piperacillin-tazobactam and doxycycline and discharged on these antibiotics. A follow-up with Infectious Diseases was recommended for ongoing management of his chronic M. chimaera infection pending sensitivities. Discussion: Mycobacterium chimaera is a non-tuberculous mycobacterium (NTM) associated with healthcare-associated infections, particularly in post-surgical patients who undergo cardiac procedures involving extracorporeal circuits. This pathogen, part of the Mycobacterium avium complex (MAC), has gained attention due to outbreaks linked to contaminated heater-cooler units (HCUs) used in operating rooms. The slow-growing nature of M. chimaera and its preference for biofilm formation make it difficult to detect and treat, as symptoms may not emerge until years after exposure. Clinical manifestations of M. chimaera infections are diverse, ranging from low-grade fever, fatigue, and weight loss to severe presentations such as endocarditis, disseminated disease, and even prosthetic valve infections. Diagnosis of M. chimaera is challenging due to its slow growth rate and similarity to other MAC organisms, often necessitating specialized molecular methods for accurate identification. Treatment requires prolonged multidrug regimens including macrolides, rifamycin, and ethambutol. However, therapeutic outcomes are frequently complicated by antimicrobial resistance and the immunocompromised status of affected patients. Conclusion: This case emphasizes the importance of considering M. chimaera in patients with persistent pulmonary infections that do not respond to standard antibiotics. Effective management requires a multidisciplinary approach to address the complexities and improve patient outcomes.