Nocardia abscessus brain abscess in an immunocompetent host

Abstract

Background: Nocardia brain abscesses are a rare central nervous system infection with high morbidity and mortality. They typically occur in immunocompromised patients. The most frequent agents involved are Nocardia asteroids complex and Nocardia brasiliensis. Case description: We present the case of a 42-year-old man who was admitted with a 1-week history of headache and incoherent speech, gradually worsened during this period. The patient did not report either fever, chills, weakness or numbness in the limbs. He was a construction worker and lived in a rural environment. He had been recently hospitalized and diagnosed with a solitary pulmonary nodule, still under study in another hospital. The initial finding in CT was an intra-axial, left temporal posterior space-occupying lesion with extensive surrounding oedema, which was presumed to be a metastasis from a possible lung cancer. The patient had a normal neutrophil function test, lymphocyte count and normal immunoglobulin levels. He was negative for human immunodeficiency virus. After admission, the patient underwent a craniotomy with stereotactic biopsy of the lesion. During the surgery, turbid pus was drained and a cerebral abscess was diagnosed. Empiric parenteral antibiotics were started with Ceftriaxone 2 g bid and Metronidazole 500 mg tid. After identifying Nocardia abscessus in the pus culture, the antibiotic regimen was changed to SMX-TMP (15 mg/kg/day of the TMP component) and Meropenem 2 g tid. In the absence of clinical and radiologic improvement, amikacin was added to the treatment, but no surgical re-intervention was performed. During hospitalisation, he also developed a pulmonary invasive aspergillosis, treated with parenteral Voriconazole 4 mg/kg bid. The patient's response to treatment was slow but effective. He was discharged with oral SMX-TMP and Voriconazole therapy. Discussion: Despite several difficulties in diagnosis of a Nocardia infection, there are some characteristics that can suggest the presence of this bacteria. Treatment should be instituted as soon as possible, regarding both surgical and medical approaches. Conclusion: Nocardial brain abscesses are a rare condition that needs to be considered as a differential diagnosis in patients with brain lesions, even in immunocompetent hosts.