Nocardia species is an aerobic soil-saprophyte bacterium, responsible for rare opportunistic infections, mainly reported in immunocompromised patients. Nocardia brain abscess accounts for 1 to 2% of cerebral abscesses. Prognosis is poor.
We describe clinical, radiological and bacteriological findings along with therapeutic aspects for five patients and review the literature on Nocardia cerebral abscess.
The clinical features of Nocardia brain abscess are insidious and nonspecific, occurring frequently with a medical background of obvious or latent immunodeficiency; fever, if any, is observed subordinate to extracerebral nocardiosis. Computerized tomography scan and conventional magnetic resonance (MR) scan show lesions with a necrotic core and multilobed thick walls enhancing after injection of gadolinium or iodine. Abscesses are mainly located in the brain stem, basal ganglia and cerebral cortex of the frontal, parietal and occipital lobes; cerebellar and spinal locations are uncommon. MR diffusion-weighted imaging with calculation of apparent diffusion coefficient and proton MR spectroscopy can provide additional data for accurate differential diagnosis between abscess and other necrotic lesions, such as tumor and cyst formations. Bacteriological identification has progressed with advances in molecular microbiology: 16S rRNA sequencing, allowing a more rapid routine identification of Nocardia strains from clinical samples. Clinical management of patients with a Nocardia brain abscess relies upon early use of intravenous antibiotics adapted to the strains identified and their susceptibility. Most Nocardia strains display susceptibility to cotrimoxazol, amikacin and linezolid, but develop beta-lactamase activity.
Early pus samples, obtained by biopsy or surgical resection, are needed to establish a certain bacteriological diagnosis and initiate appropriate intravenous antibiotics.