American Board of Internal Medicine (ABIM) Certification Practice Exam

To reduce the risk of Clostridium difficile infection in hospitalized patients, when should probiotics be administered relative to the first dose of antibiotics?

1. 24 hours

2. 48 hours

3. 72 hours

4. 1 week

The correct answer is: 48 hours

Administering probiotics within 48 hours of starting the first dose of antibiotics is considered beneficial for reducing the risk of Clostridium difficile infection in hospitalized patients. This timing is crucial because the establishment of the gut microbiota can be significantly disrupted by antibiotic treatments, leading to an increased risk of C. difficile overgrowth. Probiotics, which are live microorganisms, aim to maintain or restore the balance of gut microbiota that antibiotics may disrupt. Research indicates that starting probiotics within the first 48 hours allows for a more effective intervention against the potential negative impacts of antibiotics on the intestinal flora while the patient is still receiving antibiotic treatment. If probiotics are administered too late (like 72 hours or more), the gut might already be compromised, diminishing the potential protective effect. Administering them sooner lets the beneficial bacteria start to colonize the gastrointestinal tract before significant disruption occurs, thus helping to prevent the colonization of harmful bacteria like C. difficile. In contrast, administering probiotics at one week after starting antibiotics would likely be too late to have an effect on preventing infection, as the gut flora could already be significantly altered at that point.