FREE Internal Medicine Common Infectious Diseases Questions and Answers

Question 1

A 72-year-old male recently treated with clindamycin presents with 5-6 watery, non-bloody stools per day for three days. He has lower abdominal cramping but no fever. His WBC count is 10,500/μL and serum creatinine is 1.0 mg/dL. A stool test is positive for Clostridioides difficile toxin. According to the most recent IDSA guidelines, which of the following is the most appropriate initial treatment for this patient's non-severe C. difficile infection?

Accepted Answer

Oral Fidaxomicin 200 mg twice daily for 10 days

Answer

The 2021 IDSA guidelines recommend fidaxomicin as the preferred therapy for an initial episode of non-severe C. difficile infection based on superior sustained response rates. Oral vancomycin is an acceptable alternative. Metronidazole is no longer recommended for initial treatment of even mild-to-moderate CDI due to inferior efficacy compared to vancomycin and fidaxomicin.

Question 2

A 28-year-old healthy, non-pregnant female presents with a 3-day history of dysuria, urinary frequency, and urgency. She has no fever or flank pain. A urine dipstick is positive for nitrites and leukocyte esterase. Assuming no drug allergies and local E. coli resistance rates to trimethoprim-sulfamethoxazole are known to be >20%, which of the following is the most appropriate first-line oral antibiotic?

Accepted Answer

Nitrofurantoin

Answer

For uncomplicated cystitis in regions where E. coli resistance to trimethoprim-sulfamethoxazole is high (>20%), nitrofurantoin is a recommended first-line agent according to IDSA guidelines. Fluoroquinolones like ciprofloxacin should be reserved for more serious infections to avoid promoting resistance and due to potential side effects. Beta-lactams like amoxicillin-clavulanate and cephalexin are considered alternative agents but generally have lower efficacy for cystitis.

Question 3

A 55-year-old male with type 2 diabetes presents with a 2-day history of a warm, tender, erythematous rash on his left lower leg. The area is non-fluctuant and there is no purulent drainage or abscess. He is afebrile and hemodynamically stable. What is the most appropriate initial oral antibiotic therapy for this patient's non-purulent cellulitis?

Accepted Answer

Cephalexin

Answer

This patient presents with non-purulent cellulitis, which is most commonly caused by beta-hemolytic streptococci. Therefore, empiric treatment should primarily target this organism. Cephalexin is a first-generation cephalosporin with excellent activity against both streptococci and methicillin-susceptible Staphylococcus aureus (MSSA). Trimethoprim-sulfamethoxazole and doxycycline have poor activity against streptococci and are typically reserved for purulent infections where MRSA is a concern.

Question 4

A 45-year-old man presents with a 36-hour history of fever, myalgias, headache, and a non-productive cough during peak influenza season. A rapid influenza antigen test is positive. For an otherwise healthy outpatient, antiviral treatment with a neuraminidase inhibitor is most effective when initiated within what timeframe from symptom onset?

Accepted Answer

Within 48 hours

Answer

Clinical trials have demonstrated that neuraminidase inhibitors, such as oseltamivir, provide the greatest clinical benefit by reducing the duration and severity of symptoms when they are initiated within 48 hours of illness onset in outpatients with uncomplicated influenza. Benefit may be seen when started later in hospitalized patients or those with severe disease, but the 48-hour window is key for maximal efficacy in the typical outpatient setting.

Question 5

A 35-year-old healthcare worker has a newly positive tuberculin skin test (12 mm induration) as part of an annual screening. A chest X-ray is normal, and she denies any symptoms such as cough, fever, or weight loss. Which of the following is a preferred short-course regimen for the treatment of latent tuberculosis infection (LTBI) in this patient?

Accepted Answer

Isoniazid and rifapentine weekly for 3 months

Answer

The CDC and ATS currently recommend several rifamycin-based, short-course regimens for the treatment of LTBI due to their efficacy and higher rates of treatment completion. The 3-month regimen of once-weekly isoniazid plus rifapentine (3HP) is a preferred option. Other preferred short-course options include 4 months of daily rifampin (4R) or 3 months of daily isoniazid and rifampin (3HR). While 9 months of isoniazid is still an acceptable alternative, shorter courses are now favored. Ethambutol and pyrazinamide are used for active TB, not latent infection.

Internal Medicine Exam Practice Test

Internal Medicine Exam Practice Test

FREE Internal Medicine Common Infectious Diseases Questions and Answers