Snapshot A 73-year-old woman is brought to the emergency room by family members due to intense headache, subjective fever, and altered mental status. She currently lives in an independent living facility and enjoys eating charcuterie and cheese plates. On physical exam, she is oriented to person and place, but not time, a change from her mental baseline, and found to have nuchal rigidity. A lumbar puncture is done and the cerebral spinal fluid is sent for studies. In the meantime, she is started empirically on ceftriaxone, vancomycin, and ampicillin. Introduction Classification Listeria monocytogenes a facultative intracellular, aerobic, catalase-positive gram-positive bacillus transmission ingestion of unpasteurized dairy products or cold deli meats transplacental vertical transmission vaginal transmission during birth to neonate clinical syndromes amnionitis septicemia spontaneous abortion granulomatosis infantiseptica meningitis neonates immunocompromised patients gastroenteritis immunocompetent patients Epidemiology incidence rare demographics neonates elderly pregnant women risk factors eating unpasteurized products and deli meat immunocompromised status older age Pathogenesis the bacteria move from cell-to-cell across cell membranes via actin polymerization avoids antibody attack toxin listeriolysin O forms pores in host phagosomes to promote intracellular replication 3rd trimester pregnant women are most susceptible due to T-cell immunity impairment Prevention avoidance of unpasteurized products and deli meats in pregnant women Prognosis mortality is 20-50% in central nervous system infections Presentation Gastroenteritis nausea vomiting fever headache Meningitis fever headache altered mental status Infection in a pregnant woman flu-like syndrome or gastroenteritis premature labor spontaneous abortion meningitis or sepsis in the neonate Imaging Brain computed tomography (CT) indication all patients evaluate for abscesses findings often normal may have hydrocephalus Studies Labs cerebrospinal fluid (CSF) studies neutrophil-dominant pleocytosis elevated protein low or normal glucose gram-positive or gram-variable rods positive culture blood culture tumbling motility in broth at 22°C Making the diagnosis based on clinical presentation and laboratory studies Differential Neisseria meningitis distinguishing factors CSF Gram stain would show gram-negative diplococci patients often present with a petechial rash however, treatment regimen should include ampicillin empirically if Listeria is suspected in a patient with meningitis Treatment Medical ampicillin indication first-line trimethoprim-sulfamethoxazole indication second-line Complications Seizures Fetal loss