N. paucivorans infection presenting as a brain abscess.

We report an intracerebral abscess caused by a recently identified nocardial species, in an immunocompetent individual without extraneural involvement. A 63-year-old non-smoking Caucasian male with an unremarkable history of hypertension, presented with a 2-week history of personality changes including apathy, some difficulty walking, a tendency to veer to the left and a possible seizure. Preliminary assessment, including laboratory investigations were unremarkable. Computed tomography (CT) of his brain revealed a right frontal lobe multi-loculated, ring-enhancing lesion with vasogenic edema and associated mass effect (Figure 1). He was then referred to our institution. We found the patient afebrile, with no other focal neurological deficits. Repeat investigations including white blood cell count and chest x-ray, were normal. With a presumptive diagnosis of brain tumor, the patient was started on oral steroids and anti-seizure medication. A right frontal craniotomy was performed. Using bipolar cautery, a small corticectomy was made in the abnormal hyperemic brain surface overlying the lesion. An odorless, yellowish, creamy, pus-like discharge emanated from just underneath the cortex. Further dissection revealed a thick walled and multi-loculated cavity. Specimens were collected and the site was copiously irrigated to remove the pus-like material. The lateral ventricle was carefully avoided. Broad-spectrum coverage with ceftriaxone and metronidazole was commenced. Tissue histopathology returned consistent with Nocardia. Therefore, the antibiotics were changed to intravenous (i.v.) trimethoprim/sulfamethoxazole (TMP/SMX) and metronidazole. Metronidazole was discontinued when the anaerobic cultures returned negative. Tissue and fluid specimens were cultured on blood and chocolate agars. Gram-positive, non-hemolytic, catalase positive, weakly acid-fast, filamentous, branching bacilli were observed within 72 hours. The organism was presumptively identified as a Nocardia species. The Canadian Science Centre for Human and Animal Health confirmed it as N. paucivorans, based on 16S rDNA gene sequencing and conventional biochemical tests. Post-operatively, the patient made a rapid recovery and remained without focal deficits. The CT scan demonstrated a residual cavity behind the area of resection. Further investigations did not reveal any evidence of immunocompromise, or of nocardiosis elsewhere in the body. After a week in hospital, the patient was discharged home on i.v. TMP/SMX. Trimethoprim/sulfamethoxazole was changed to oral route when a CT, done three weeks postoperatively, showed marked attenuation of the residual abscess. Complete resolution was N. Paucivorans Infection Presenting as a Brain Abscess