1. A 65-year-old male patient with a history of diabetes mellitus and chronic kidney

disease is admitted to the hospital with fever, abdominal pain and diarrhea. He is

diagnosed with Clostridioides difficile infection (CDI) and started on oral

vancomycin. Which of the following factors increases his risk of developing CDI?

a) Age

b) Diabetes mellitus

c) Chronic kidney disease

d) All of the above*

Rationale: All of the above factors are associated with increased risk of CDI, as

they impair the immune system, alter the gut microbiota or increase exposure to

antibiotics.

2. A 45-year-old female patient with ulcerative colitis is treated with infliximab, a

monoclonal antibody that blocks tumor necrosis factor alpha (TNF-alpha). She

develops CDI after two weeks of therapy. What is the most likely mechanism of

CDI in this patient?

a) Infliximab reduces the production of protective antibodies against C. difficile

toxins

b) Infliximab disrupts the intestinal epithelial barrier and allows C. difficile to invade

the mucosa

c) Infliximab inhibits the inflammatory response and prevents the clearance of C.

difficile

d) All of the above*

Rationale: All of the above mechanisms are possible ways that infliximab can

predispose to CDI, as TNF-alpha is involved in mucosal immunity, epithelial

integrity and inflammation.

3. A 70-year-old female patient with rheumatoid arthritis is treated with

methotrexate, a folate antagonist that inhibits DNA synthesis. She develops CDI

after three months of therapy. What is the most appropriate treatment for her CDI?

a) Oral metronidazole

b) Oral vancomycin

c) Oral fidaxomicin*

d) Intravenous immunoglobulin

Rationale: Oral fidaxomicin is a narrow-spectrum antibiotic that targets C. difficile

and spares the normal flora. It is recommended for patients with moderate to

severe CDI who have risk factors for recurrence, such as advanced age,

immunosuppression or prior CDI episodes.

4. A 55-year-old male patient with HIV infection and a CD4 count of 200 cells/mm3

is admitted to the hospital with pneumonia. He is treated with intravenous

ceftriaxone and azithromycin. He develops CDI after five days of therapy. What is

the most effective way to prevent CDI in this patient?

a) Prophylactic oral vancomycin