N. Paucivorans Infection Presenting as a Brain Abscess

Abstract

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.

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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.
T
issue 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 immuno-
compromise, or of nocardiosis elsewhere in the body. After a
week in hospital, the patient was discharged home on i.v.
TMP/SMX.
T
rimethoprim/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
Shah-Naz Hayat Khan, Stephen E. Sanche, Christopher A. Robinson, Farhad Pirouzmand
Can. J. Neurol. Sci. 2006; 33: 426-427
P
EER REVIEWED LETTER
documented on the CT performed three months postoperatively
(Figure 2).
Antibiotics were discontinued.
When last evaluated
nine months after discharge, the patient continued to remain
well, with no recurrent abscess on CT.
Nocardiosis is primarily a pulmonary disease. It causes up
to 2% of cerebral abscesses, mostly in the immuno-
2904
Figure 1: Computed tomography scan with contrast. The
pr
eoperative scan shows an enhancing, multi-loculated lesion
in the right fr
ontal lobe.
From the Division of Neurosurgery, Department of Surgery (SHK), Division of
Infectious Diseases, Department of Medicine (SES), Department of Pathology (SES,
CAR); Saskatoon Health Region (SES, CAR), Saskatoon, SK, Canada; Division of
Neurosurgery (FP), Sunnybrook and Women’s College Health Science Centre,
University of Toronto, Toronto, ON, Canada.
R
ECEIVED AUGUST 12, 2005. ACCEPTED IN FINAL FORM JUNE 27, 2006.
Reprint r
equests to:
S.H. Khan, Department of Neurosur
gery
,University of Cincinnati
Medical Center
, PO Box 670515, Cincinnati, Ohio, 45267-0515, U.S.A.

compromised.
1,2,3
Increasingly, it is being recognized in
immunocompetent individuals with cerebral abscesses.
4,5,7
Primary cerebral abscesses without evidence of pulmonary
infection are unusual.
3
The immune status and the timeliness of
treatment influence outcome, so that the immunocompetent
patient receiving early treatment intervention will do better.
2,3,5,6
To date, 73 Nocardia species have been identified, including
42 additions since 2000.
9
Only a few species are neuroinvasive,
with
N. asteroides being the most frequent.
2,5,6
There are three
previous reports of
N. paucivorans infection.
10,12
Two patients
were immunocompromised and had intracranial abscesses. The
third had chronic pulmonary disease and N. paucivorans was
isolated from sputum. In our case, the patient was
immunocompetent and without any chronic debilitating
disorders.
Based on history and radiological findings, we made a
presumptive diagnosis of a neoplastic process, with abscess
considered less likely. A slow, afebrile presentation with
radiological imaging consistent with brain tumor, has been
reported in cerebral nocardiosis.
5,7
In previous reports, diagnosis
of a neoplastic process was revised following operative findings
and pathology results.
2-5,13
Preoperative magnetic resonance
imaging or MR spectroscopy most probably would have made
the distinction between an abscess and a tumor. However, that
information would not have altered the intent of early sur
gical
intervention.
Compared with poor outcomes in other cases,
3,7
our plan of
early surgery and prolonged antibiotics administration, led to a
c
omplete recovery. Unlike previous reports,
7
,14
w
e were able to
administer steroids for a week post-operatively without any
adverse effects. The duration of antibiotic therapy remains
empirical.
2,3,5,13
We used clinical, laboratory and radiological
evidence to determine the duration. Antibiotics were
administered i.v. for a month and orally for 3 months (total=4
months), effecting a cure. In vitro data supports the efficacy of
TMP/SMX in
N. paucivorans infections.
10,11
This case highlights nocardial cerebral abscesses in
immunocompetent patients, where the residual nocardial
abscess can be successfully treated with antibiotics. Further
studies are needed to better understand the pathogenesis,
improve management and establish preventive measures.
AC
KNOWLEDGEMENTS
The authors thank Dr. Katherine Bernard and her associates at
the Canadian Science Centre for Human and Animal Health for
their kind assistance.
Dr S.H. Khan was a resident sponsored by Saskatoon Health
Region.
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Figure 2: Computed tomography scan with contrast.
Complete resolution of the abscess following 3 months of
tr
eatment.
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Volume 33, No. 4 – November 2006 427