Brain Abscess Caused by Nocardia farcinica in a Young Immunocompetent Patient

Cerebral nocardiosis is a rare opportunistic infectious disease that occurs mainly in immunocompromised hosts; however, immunocompetent patients may be affected too. It often results in the formation of intraparenchymal brain abscess, which represents only 2% of all cerebral abscesses. The overall mortality rate exceeds 20% in immunocompetent patients and 55% in immunocompromised patients. Bacteriological diagnosis is often confirmed only after the surgical excision of the abscess. Thus, the initiation of effective therapy is frequently delayed. Our goal is to highlight a diagnostic approach to cerebral nocardiosis in an immunocompetent patient with the purpose of accelerating the initiation of the appropriate therapy. We report a rare case of brain abscess caused by Nocardia farcinica in a 39-year-old male, a resident of New York City, USA, with a past medical history of intravenous (IV) drug use, who was admitted for altered mental status. The patient was cachectic and ill-appearing. Initial laboratory tests showed neutrophilic leukocytosis. Computed tomography (CT) of the head revealed a large ill-defined multilobulated mass of size 6 × 5 × 4.5 cm in the right cerebral hemisphere, which was confirmed with magnetic resonance imaging (MRI). The hospital course was complicated by the deterioration of mental status requiring endotracheal intubation. The patient underwent a right-sided hemicraniectomy; a wound culture identified Nocardia farcinica. The patient was started on intravenous (IV) Bactrim, which caused an allergic reaction. Thus, he was switched to IV imipenem-cilastatin. After E-test was performed, the patient was switched to oral linezolid. The initiation of targeted antibiotic therapy was crucial for the management of this patient and resulted in a good clinical outcome. In conclusion, cerebral nocardiosis, being an unusual and a potentially fatal infection, should be considered in the differential diagnosis of brain abscess even in immunocompetent hosts. Prompt bacteriological diagnosis helps to initiate a specific antimicrobial therapy. Long-term antimicrobial therapy and long-term follow-up are necessary to prevent relapse.