Internal Medicine Shelf Exam Sample Questions

The correct answer is A. Age >50 and consumption of soft cheese

Explanation: The Gram stain of CSF shows Gram-positive bacilli consistent with Listeria monocytogenes meningitis. Streptococcus pneumonia is a Gram-positive diplococcus, and H. influenzae is a small pleomorphic Gram-negative rod; Neisseria meningitidis is a Gram-negative diplococcus. Strep. pneumoniae, N. meningitidis, and H. influenzae type b are respiratory pathogens and can be transmitted from person to person via airborne droplets. Listeria monocytogenes is acquired through ingestion of contaminated foods (meats, vegetables, cheeses were implicated in the past) as well as trans-placentally to fetuses. The CDC website has an updated list of contaminated products and their manufacturers. Risk factors for Listeria monocytogenes include extremes of age (adults >50 years of age and children <1 month), pregnancy, immunosuppressed state, alcoholism, CKD, chronic liver disease, and diabetes mellitus, among few others. This patient's advanced age and consumption of contaminated food would place her at risk for developing Listeria meningitis. (B) This patient does not meet the criteria for requiring meningococcal vaccination (no history of asplenia, no travel to endemic areas, no complement deficiency), and this will not be protective against Listeria monocytogenes. (C) This patient is 69 and should have been routinely immunized against Strep. pneumoniae starting at age 65. Currently, ACIP guidelines recommend conjugated Prevnar 13 followed by Pneumovax23 6-12 months later, but this will not provide defense against Listeria monocytogenes. (D) After initiation of routine vaccination of all infants against Haemophilus influenza type b in 1990, the incidence of HIB meningitis went drastically down among children and (through herd immunity) among adults as well. Currently, H. influenzae type b meningitis occurs mainly in unimmunized children and rarely in adults. Exposure to an unvaccinated child would potentially place this patient at risk for developing H. influenzae meningitis but not Listeria monocytogenes meningitis.