USMLE Step 1 Meningitis practice questions
Meningitis is inflammation of the leptomeninges and subarachnoid CSF, most often due to bacterial, viral, or fungal pathogens whose relative likelihood shifts predictably with patient age and immune status. For USMLE Step 1, the emphasis is less on memorizing empiric antibiotics and more on linking each pathogen to its virulence mechanism, the resulting CSF profile, and downstream pathophysiologic complications (e.g., DIC, adrenal hemorrhage, immune evasion). Expect integration across microbiology, immunology, and pathology rather than isolated organism recall.
A 5-day-old male infant born at 39 weeks' gestation to a mother with no prenatal care is brought to the emergency department because of poor feeding, lethargy, and temperature instability over the past 12 hours. He was delivered vaginally after prolonged rupture of membranes. Temperature is 38.9°C (102°F). Physical examination shows a bulging anterior fontanelle and diffuse hypotonia. Lumbar puncture shows cloudy cerebrospinal fluid with a leukocyte count of 5000/mm3 (90% neutrophils), glucose of 25 mg/dL, and protein of 150 mg/dL. Which of the following organisms is the most likely cause of this infant's condition?
An 8-year-old boy is brought to clinic in August with a 2-day history of fever, headache, and photophobia. He is alert, oriented, and cooperative with the examination. Temperature is 38.3°C (101°F). Neck stiffness is present, but there are no focal neurologic deficits and no petechial rash. Lumbar puncture shows an opening pressure within normal limits, a leukocyte count of 150/mm3 with 85% lymphocytes, a glucose concentration of 65 mg/dL, and a protein concentration of 50 mg/dL. Which of the following is the most likely causative organism?
A 16-year-old boy living in a college dormitory is brought to the emergency department after 8 hours of high fever, severe headache, and a rapidly spreading purpuric rash over his trunk and extremities. Within hours he develops hypotension that does not respond adequately to intravenous fluids. Laboratory studies show thrombocytopenia, prolonged prothrombin and partial thromboplastin times, and a low fibrinogen level. He dies despite aggressive resuscitation, and autopsy reveals bilateral hemorrhagic necrosis of the adrenal glands. Which of the following is the most likely mechanism underlying this patient's adrenal findings?
A 38-year-old man with HIV infection, last CD4+ T-lymphocyte count 45 cells/mm3, and not currently on antiretroviral therapy comes to the clinic because of a headache that has gradually worsened over 3 weeks, accompanied by mild confusion. He has no fever, photophobia, or neck stiffness. Lumbar puncture shows an opening pressure of 350 mmH2O, a leukocyte count of 20/mm3 with lymphocytic predominance, a glucose concentration of 45 mg/dL, and a protein concentration of 60 mg/dL. Which of the following properties of the most likely causative organism best explains its virulence in this patient?
A 15-month-old girl receives a scheduled vaccination against Haemophilus influenzae type b as part of the routine childhood immunization schedule. The vaccine consists of the type b capsular polysaccharide covalently linked to a carrier protein. Which of the following best explains why this conjugate formulation produces a more effective and durable immune response in a young child than the polysaccharide antigen alone would?
Meningitis, answered
Do I need to memorize specific antibiotic regimens for meningitis for Step 1?
No. Step 1 tests mechanisms, not management — focus on which organism is most likely given age/host factors, the underlying virulence factor or pathophysiology, and the expected CSF profile, rather than empiric drug choice or dosing.
What's the fastest way to remember CSF findings across bacterial, viral, TB, and fungal meningitis?
Think in terms of opening pressure, cell type, and glucose: bacterial = high pressure, neutrophil-predominant, low glucose; viral = normal/mildly elevated pressure, lymphocyte-predominant, normal glucose; TB and fungal = high pressure, lymphocyte-predominant, low glucose, with TB often showing markedly elevated protein.
How much should I know about age-specific bacterial pathogens?
This is high yield. Know the general pattern: neonates — Group B Streptococcus, E. coli, Listeria; infants/children — Streptococcus pneumoniae, Neisseria meningitidis, (historically) Haemophilus influenzae type b; adolescents/young adults — Neisseria meningitidis; older/immunocompromised adults — Streptococcus pneumoniae and Listeria.
Is Waterhouse-Friderichsen syndrome actually tested, or is it too rare to prioritize?
It shows up periodically because it links a classic organism (N. meningitidis) to a testable mechanism (endotoxin-driven DIC causing adrenal hemorrhage), which is exactly the kind of basic-science-to-clinical-finding link Step 1 favors — worth knowing the mechanism even if the syndrome itself is uncommon in practice.
Want unlimited Meningitis questions from your own notes?
Upload your lecture notes and QuizMed writes USMLE Step 1-style MCQs tuned to your material, free for your first five quizzes.
No credit card required.