Listeria monocytogenes brain abscess: two cases and review of the literature.

Listeria monocytogenes is a gram-positive bacillus that exhibits predilection to infect the central nervous system in immunocompromised individuals; the most common manifestations are meningitis and rhombencephalitis. Listerial brain abscesses are rare. We report here two brain abscess cases caused by L. monocytogenes in patients receiving immunosuppressive agents. The first patient presented with left hemiparesis mimicking stroke and the second patient presented with neurological symptoms without fever, which was indistinguishable from brain tumor. In both cases, magnetic resonance spectroscopy (MRS) was performed to differentiate infectious processes from other causes. Diagnosis was made with a positive blood culture in both cases. Listerial DNA was detected in the pus aspirated from the abscess in the first case. Both patients were successfully treated with intravenous ampicillin followed by oral amoxicillin. MRS was useful in differentiating infectious processes from non-infectious causes.