Which of the following best explains why broad-spectrum antimicrobials are more likely to lead to superinfections?

• A. Bacteria that are resistant to broad-spectrum drugs tend to be able to replicate & spread faster.
• B. Broad-spectrum drugs are more likely to disrupt a larger portion of the normal flora, which provides an opportunity for resistant microbes to colonize.
• C. Broad-spectrum drugs are more likely to cause mutations that lead to antibiotic resistance.
• D. Broad-spectrum drugs tend to be less potent than narrow-spectrum drugs, which allows resistant bacteria to thrive and cause a superinfection.

Answer: (B)

Verified step by step guidance

1. Understand the concept of broad-spectrum antimicrobials: these drugs target a wide range of bacteria, including many types of normal flora (the beneficial bacteria normally present in the body).
2. Recognize that normal flora plays a protective role by competing with potentially harmful microbes, preventing their overgrowth.
3. Consider what happens when broad-spectrum antimicrobials disrupt this normal flora: many beneficial bacteria are killed or suppressed, reducing competition.
4. With reduced competition, resistant microbes that are not affected by the drug have an opportunity to grow unchecked, potentially leading to a superinfection.
5. Therefore, the key reason broad-spectrum antimicrobials are more likely to cause superinfections is because they disrupt a larger portion of the normal flora, allowing resistant microbes to colonize and multiply.