Pearls & Oy-sters: Diagnosis and Subtyping of Listeria Ventriculitis in an Immunocompetent Host.

Listeria monocytogenes is a Gram-positive food-borne pathogen that causes gastrointestinal symptoms and CNS infection in susceptible hosts. Two lineages of Listeria cause the majority of neurolisteriosis in humans. In this report, we discuss a case of a 23-year-old previously healthy woman who presented with acute-onset rapidly progressive altered mental status after eating undercooked meats at a local restaurant. Given her age and lack of comorbidities, bacterial meningitis was suspected, and she was treated with ceftriaxone, vancomycin, and steroids. MRI of the brain was consistent with meningitis and ventriculitis; CSF analysis also suggested bacterial meningitis. Despite mechanical ventilation, pressors, and ventricular drain placement, she quickly decompensated and died 12 hours after arrival. CSF culture later returned positive for Listeria monocytogenes We used whole-genome sequencing and near-source comparison to identify the Listeria subtype that led to her unexpected presentation. The results suggest that her CSF isolate was consistent with a lineage II Listeria serotype, which is known to exhibit greater genetic variation than the more commonly isolated lineage I serotypes. We conclude the discussion with diagnostic and treatment approaches to neurolisteriosis. In susceptible hosts, namely immunocompromised, pregnant, neonatal, or elderly patients, Listeria infection may result in CNS invasion, causing meningoencephalitis and, rarely, ventriculitis and rhombencephalitis. Although neurolisteriosis most commonly affects individuals with known risk factors, CNS infection is nevertheless possible in otherwise healthy young patients. Suspicion should be raised in patients with an exposure history who do not improve with empiric antibiotics.