Which statement best defines a broad-spectrum antibiotic?

• A. An antibiotic that targets a single, specific bacterial species with minimal effect on others
• B. An antibiotic effective only against Gram-negative bacteria
• C. An antibiotic effective only against Gram-positive bacteria
• D. An antibiotic effective against a wide range of bacteria, including both Gram-positive and Gram-negative organisms

Answer: (D)

Verified step by step guidance

1. Understand the term 'broad-spectrum antibiotic' by breaking down the phrase: 'broad-spectrum' implies activity against a wide variety of targets, not just one specific type.
2. Recall that bacteria are broadly classified into Gram-positive and Gram-negative groups based on their cell wall structure, which affects antibiotic susceptibility.
3. Recognize that a broad-spectrum antibiotic is effective against multiple types of bacteria, including both Gram-positive and Gram-negative species, rather than targeting only one group.
4. Compare the options given: those specifying activity against only Gram-positive or only Gram-negative bacteria describe narrow-spectrum antibiotics, not broad-spectrum.
5. Conclude that the best definition of a broad-spectrum antibiotic is one that is effective against a wide range of bacteria, encompassing both Gram-positive and Gram-negative organisms.