Case Presentation: A 31-year-old male with no past medical history presented with fevers and headaches for two days. Patient also complained of malaise, neck stiffness and photophobia. Physical exam notable for positive Kernig’s sign. Labs revealed a leukocytosis with neutrophillic predominance. A lumbar puncture was performed to assess for meningitis. The results were initially consistent with aseptic meningitis and patient was monitored off antibiotics.  On day 3 of admission the patient’s CSF culture grew Listeria monocytogenes  (L. monocytogenes). Ampicillin was initiated. An assessment of the immunological status of the patient was performed. Patient was found to be negative for HIV and Mononucleosis. A Respiratory Viral Panel, Hepatitis Panel, urinalysis, urine culture, liver function, kidney function and blood culture tests were all normal. CT head, CT sinuses, and CT chest were all negative. A repeat lumbar puncture 5 days after initiation of antibiotics showed a decrease in total nucleated cells. A PICC line was placed and the patient was discharged on IV penicillin G for 3 weeks duration with infectious disease follow up.

Discussion: In young patients without comorbidities who present with signs concerning for bacterial meningitis, the standard empiric treatment consists of a broad-spectrum cephalosporin and vancomycin to cover typical causative agents: S. pneumoniae and N. meningitdis. L. monocytogenes coverage with ampicillin, penicillin G or Trimethoprim-Sulfamethoxazole (TMP-SMX) is considered when patients between 18-50 years old present with predisposing conditions including alcoholism, malignancy, diabetes, immunosuppression, liver disease, chronic kidney disease, collagen-vascular diseases, and conditions associated with iron overload. Two studies to date have explored cases of L. monocytogenes meningitis in patients between the ages of 18 to 50 with no comorbidities. In the first, a small prospective case series, no previously healthy patients in this age group had L. monocytogenes meningitis. In the second study, a large review, it was reported that only 6% of young and previously healthy patients had L. monocytogenes CNS disease, however it did not differentiate between meningitis and brainstem encephalitis. Of note, brainstem encephalitis caused by L. monocytogenes is known to occur in young healthy patients. Treatment that covers L. monocytogenes is important given it has the highest fatality rate of all bacterial meningitis (18.1%) even with treatment.

Conclusions: Studies show that of the 2% of acute bacterial meningitis adult patients infected with L. monocytogenes, 94-100% have a predisposing condition or are over the age of 50 years old. We report an uncommon case of L. monocytogenes meningitis in a young male without any predisposing condition. It is important that in the practice of hospital medicine, L. monocytogenes coverage should be considered in patients younger than 50 years old without comorbidities especially given the high reported fatality rate.