In microbiology, what does it mean when an antibiotic is described as broad-spectrum?

• A. It is effective against a wide range of bacteria, typically including many Gram-positive and Gram-negative species.
• B. It kills bacteria only by inhibiting cell membrane synthesis and cannot target other cellular processes.
• C. It works only against viruses and has no activity against bacteria.
• D. It is effective only against a single bacterial species or a very limited group of closely related bacteria.

Answer: (A)

Verified step by step guidance

1. Step 1: Understand the term 'broad-spectrum' in the context of antibiotics. It refers to the range of bacterial types an antibiotic can act against.
2. Step 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. Step 3: Recognize that a broad-spectrum antibiotic is effective against a wide variety of bacteria, including both Gram-positive and Gram-negative species, rather than targeting a narrow group.
4. Step 4: Contrast this with narrow-spectrum antibiotics, which are effective against only a specific type or limited group of bacteria.
5. Step 5: Note that broad-spectrum antibiotics do not specifically target viruses, nor are they limited to killing bacteria by only one mechanism such as inhibiting cell membrane synthesis.