ABIM Infectious Disease — Questions and Answers
Question 1: A healthy 28-year-old non-pregnant woman has dysuria and urinary frequency with no fever or flank pain. Which is an appropriate first-line treatment for her uncomplicated cystitis?
- Ciprofloxacin for 14 days
- Nitrofurantoin for 5 days (Correct answer)
- IV ceftriaxone for 7 days
- Amoxicillin for 3 days
Correct answer: Nitrofurantoin for 5 days
IDSA guidelines list nitrofurantoin for 5 days as a first-line choice for acute uncomplicated cystitis. Fluoroquinolones are saved for other uses because of resistance and adverse effects. Amoxicillin alone works poorly because of high resistance rates, and IV therapy is not needed.
Question 2: A 40-year-old man with no comorbidities and no recent antibiotic use has outpatient community-acquired pneumonia. Per the 2019 ATS/IDSA guideline, which is a recommended empiric regimen?
- Amoxicillin (Correct answer)
- Levofloxacin plus azithromycin
- Vancomycin plus piperacillin-tazobactam
- Ceftriaxone IV
Correct answer: Amoxicillin
For healthy outpatients without comorbidities, the 2019 ATS/IDSA guideline recommends high-dose amoxicillin, with doxycycline or a macrolide as alternatives where local resistance allows. Broad-spectrum or IV regimens are for patients with comorbidities or those who are hospitalized.
Question 3: Which of the following is a CDC-recommended treatment regimen for latent tuberculosis infection?
- Ethambutol daily for 9 months
- Rifampin plus pyrazinamide for 2 months
- Rifampin daily for 4 months (Correct answer)
- Moxifloxacin daily for 6 months
Correct answer: Rifampin daily for 4 months
The CDC's preferred short-course options for latent TB are 4 months of daily rifampin, 3 months of weekly isoniazid plus rifapentine, and 3 months of daily isoniazid plus rifampin. Rifampin plus pyrazinamide is not recommended because of severe hepatotoxicity.
Question 4: A 55-year-old has a first episode of non-severe Clostridioides difficile infection. According to the 2021 IDSA/SHEA update, which treatment is preferred?
- IV vancomycin
- Oral clindamycin
- Oral metronidazole as preferred therapy
- Oral fidaxomicin (Correct answer)
Correct answer: Oral fidaxomicin
The 2021 IDSA/SHEA update prefers fidaxomicin for an initial episode because it lowers the recurrence rate. Oral vancomycin is an acceptable alternative. IV vancomycin does not reach the colon, and metronidazole is reserved for when the other options are unavailable.
Question 5: A 67-year-old presents with fever, neck stiffness, and confusion. Besides dexamethasone, which is the most appropriate empiric antibiotic regimen for suspected bacterial meningitis?
- Ceftriaxone alone
- Vancomycin plus ceftriaxone plus ampicillin (Correct answer)
- Vancomycin plus ceftriaxone
- Ampicillin plus gentamicin alone
Correct answer: Vancomycin plus ceftriaxone plus ampicillin
Adults over 50 need ampicillin added to vancomycin and ceftriaxone to cover Listeria monocytogenes, in addition to resistant pneumococcus and meningococcus.
Question 6: A patient has an expanding erythematous annular rash 8 days after a tick bite in Connecticut and no other symptoms. What is the most appropriate management?
- Doxycycline for 10 days (Correct answer)
- Serologic testing before any treatment
- IV ceftriaxone for 28 days
- Observation only
Correct answer: Doxycycline for 10 days
Erythema migrans in an endemic area is diagnosed clinically. Serology is often negative this early, so you treat without it. Oral doxycycline for 10 days is first-line for early localized Lyme disease. IV ceftriaxone is for certain disseminated forms, such as meningitis or high-degree heart block.
