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Ch. 15 - Antimicrobial Drugs
Norman-McKay- Microbiology: Basic and Clinical Principles 2nd Edition
Norman-McKay2nd EditionMicrobiology: Basic and Clinical PrinciplesISBN: 9780137661619Not the one you use?Change textbook
Chapter 15, Problem 2

A patient who is not a healthcare worker is diagnosed with C. difficile pseudomembranous colitis. What most likely led to this infection?
a. The patient was recently treated with a bacteriostatic drug.
b. The patient was recently treated with a broad-spectrum drug.
c. The patient was treated with a bactericidal drug.
d. The patient recently became immune compromised and therefore had an increased risk for infection.
e. The patient was recently exposed to someone with an active C. difficile infection.

Verified step by step guidance
1
Understand that Clostridioides difficile (C. difficile) pseudomembranous colitis typically occurs when the normal gut flora is disrupted, allowing C. difficile to overgrow and produce toxins that damage the colon.
Recognize that broad-spectrum antibiotics can disrupt the normal intestinal microbiota by killing a wide range of bacteria, including beneficial ones, which creates an environment where C. difficile can thrive.
Consider that bacteriostatic and bactericidal drugs differ in their mechanisms, but the key factor in C. difficile infection is the disruption of normal flora rather than the killing mechanism alone.
Evaluate the options: immunocompromised status or direct exposure to an infected person can increase risk but are less common causes compared to antibiotic use in community-acquired cases.
Conclude that the most likely cause in a non-healthcare worker patient is recent treatment with a broad-spectrum antibiotic, which disrupts gut flora and predisposes to C. difficile infection.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Clostridioides difficile Infection and Pseudomembranous Colitis

C. difficile is a spore-forming bacterium that causes pseudomembranous colitis, an inflammation of the colon characterized by toxin-mediated damage. It often occurs after disruption of normal gut flora, leading to overgrowth of C. difficile and toxin production, which damages the intestinal lining.
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Impact of Broad-Spectrum Antibiotics on Gut Microbiota

Broad-spectrum antibiotics kill a wide range of bacteria, including beneficial gut flora. This disruption reduces microbial competition, allowing resistant organisms like C. difficile to proliferate and cause infection, especially after antibiotic treatment.
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Difference Between Bacteriostatic and Bactericidal Drugs

Bacteriostatic drugs inhibit bacterial growth without killing bacteria, while bactericidal drugs kill bacteria directly. Both can affect gut flora, but the key factor in C. difficile infection is the broad-spectrum activity that disrupts normal flora, not whether the drug is bacteriostatic or bactericidal.
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