Solitary Supratentorial Listeria Monocytogenes Brain Abscess in an Immunocompromised Patient

Abstract

We describe an 81-year-old man receiving azacitidine monotherapy for myelodysplastic syndrome who was improving from Listeria monocy-togenes bacteremia after receiving antibiotic therapy during an earlier hospital admission. Shortly after discharge he developed new-onset seizure activity, with brain imaging on subsequent admissions demonstrating a posterior right frontal lobe mass. Specimen cultures after resection of the mass revealed this to be a cerebral abscess related to L. monocytogenes. Brain abscesses related to this organism are rare. L isteria monocytogenes is a ubiquitous, opportunistic pathogen that rarely causes illness in healthy individuals. Th e immunocompromised and those with underlying illness are at greater risk for serious and potentially fatal infection. Approximately 20% of all listeriosis patients succumb to infection despite early aggressive treatment, with particularly elevated case fatality rates in those with comorbid illnesses and in immunocompromised states (1-4). While L. monocytogenes is a well-known cause of meningitis and encephalitis, brain abscesses related to this organism are rare and reported to occur in only 10% of all Listeria central nervous system (CNS) infections (4). Here we present the case of an immunocompromised man who developed L. monocytogenes bacteremia and a subsequent single supratentorial brain abscess. CASE DESCRIPTION An 81-year-old man with myelodysplastic syndrome was being treated with azacitidine monotherapy. He also had a remote history of acute myelogenous leukemia in remission, medically controlled atrial fi brillation, basal cell skin carcinoma resection, and treated prostate cancer. For 1 week, the patient complained only of intermittent fevers, reaching a maximum temperature of 102.4°F, and mild fatigue. Four days after the onset of fevers, blood cultures were drawn and he was started on levofl oxacin and later on amoxicillin clavulanate once Gram-positive rods were isolated. Blood cultures grew L. monocytogenes, and the patient was hospitalized. He received intravenous piperacillin-tazobactam for 2 days. When sensitivity tests revealed susceptibility to ampicillin, penicillin G, and trimethoprim sulfamethoxazole, the treatment was changed to intravenous ampicillin, which continued for his remaining 2 days in the hospital. Repeat blood cultures were negative at the time of discharge and he was afebrile. Th e patient was discharged home on continuous intravenous penicillin infusion. During the hospital admission there were no specifi c neurologic complaints, headaches, or altered sensorium. Th e morning after discharge, the patient had generalized jerking movements and left facial droop that lasted approximately 10 minutes while he remained lucid. Two additional seizure-like episodes occurred during transport to the emergency department. Noncontrast head computed tomography (CT) demonstrated a mass in the right frontoparietal region. Treatment with lorazepam and dexamethasone was initiated. Subsequent contrast-enhanced magnetic resonance imaging (MRI) of the brain showed a 2.2 cm rim-enhancing mass within the posterior right frontal lobe with mild surrounding edema (Figure 1). Intravenous ampicillin was restarted and levetirace-tam treatment initiated. A 2-day posttreatment contrast-enhanced brain MRI demonstrated a slightly decreased volume of the mass, a similar degree of edema, and imaging characteristics most suggestive of an isolated cerebral abscess. A right frontal craniotomy was performed and a purulent cavity in the posterior right frontal lobe was resected. Specimens revealed acute infl ammation consistent with cerebritis/abscess, although no organisms were identifi ed by microscopy. Cultures of the abscess fl uid were positive for L. monocytogenes susceptible to ampicillin, penicillin G, and trimethoprim sulfamethoxazole. No additional seizures occurred, and the patient was discharged on long-term intravenous ampicillin therapy, with surveillance imaging 7 days after the abscess was resected. DISCUSSION L. monocytogenes is a ubiquitous, Gram-positive, facultative intracellular bacterium that is typically acquired via food contamination (4). Th e groups considered at risk for listeriosis are pregnant women and neonates, the elderly, and immunocompromised or