An 82-year-old man presented to the emergency department with a severe headache, nausea, and vomiting for two days. On examination, he was lethargic with neck stiffness and a fever. A lumbar puncture found signs of bacterial meningitis. Gram staining of the cerebrospinal fluid revealed small gram-positive rods. The patient was initially treated with ceftriaxone and vancomycin empirically. Based on the presentation and lab results, ampicillin plus gentamicin is the recommended treatment for Listeria monocytogenes meningitis.

1. Question of the week
December 27, 2016

2. History
• An 82-year-old man is brought to the
emergency department by his daughter.
• He has had an increasingly severe headache,
plus nausea and vomiting, for the past 2 days.

3. History
• The daughter reports that this morning he
was difficult to rouse and that he has not
seen a doctor in "years" because he has been
very healthy.
• He has no drug allergies. .

4. On examination
• he is lethargic, with neck stiffness and a
temperature of 38.9°C.

5. In the ER
• After receiving empiric ceftriaxone and
vancomycin, he undergoes an urgent lumbar
puncture.

6. The cerebrospinal fluid
• leukocyte count of 1300 per mm3 (75%
neutrophils and 25% lymphocytes)
• protein level of 110 mg/dL (reference range,
15–45)
• glucose level of 50 mg/dL (40–70).
• Serum glucose is within normal limits.
• Gram's stain of CSF : small gram-positive rods.

7. Which one of the following antimicrobial
treatments should be added to this patient's
treatment?
A. Rifampin
B. Ampicillin plus gentamicin
C. Acyclovir
D. Chloramphenicol
E. Trimethoprim–sulfamethoxazole

8. Your answer is correct.
• Ampicillin plus gentamicin

9. Key Learning Point
• The antimicrobial treatment of choice for
bacterial meningitis that is due to Listeria
monocytogenes is ampicillin plus gentamicin.
-

10. Listeria monocytogenes
• Ggram-positive rod, is a foodborne pathogen
with a tropism for the central nervous
system.
• L. monocytogenes outbreaks have been
associated with unpasteurized milk, soft
cheeses, and deli-style meats .

11. Risk factors
• newborns, pregnant women, the elderly, and
people with impaired, cell-mediated
immunity, such as transplant recipients and
patients with AIDS.
• In 1995, the Centers for Disease Control and
Prevention reported that L.
monocytogenes accounted for 20% of
bacterial meningitis cases among people >60
years of age.

12. Pregnant women
• Pregnant women are also at increased risk
for listeria infection. In this population, it
causes chorioamnionitis in the woman (not
meningitis), which at the time of delivery can
lead to neonatal meningitis. Because of this
risk, pregnant women are advised to avoid
foods that may be sources of listeria
infection, such as soft cheeses and deli
meats.

13. Presentation
• may be more subacute (>24 hours) than it is
with other forms of bacterial meningitis.
• CSF Gram’s stain may be positive in only 30%
to 40% of cases.

14. Treatment
• In adults with suspected bacterial meningitis, empiric
ceftriaxone and vancomycin should be administered
immediately to cover the most common etiologic agents.
• Empiric addition of ampicillin is recommended for
treatment of bacterial meningitis in people >50 years of
age.
• Ampicillin or penicillin is the preferred agent for
treating L. monocytogenes infections.
• Synergy with aminoglycosides, such as gentamicin, has
been demonstrated in vitro, and these agents are often
used in conjunction with penicillins in
treating Listeria meningitis.

15. Trimethoprim–sulfamethoxazole
• is the treatment of choice for a patient with a
penicillin allergy.

16. Cephalosporins
• have limited activity
against L. monocytogenes, and high reported
rates of failure have been associated with
chloramphenicol and rifampin.

17. Acyclovir
• is an antiviral agent with no activity against
bacteria.

18. Reference
• NEJM December 27, 2106