Aminopenicillins are typically described as having which spectrum?

• A. Broad spectrum
• B. Narrow spectrum
• C. Unknown spectrum
• D. Selective Gram-negative only

Answer: (B)

Spectrum describes the range of bacteria an antibiotic can effectively inhibit. Aminopenicillins, such as amoxicillin and ampicillin, are designed to extend penicillin’s activity beyond just Gram-positive cocci to include many common Gram-negative bacteria (for example, Haemophilus influenzae, E. coli, and Proteus species) while still retaining good activity against many Gram-positive organisms. This broader activity within the penicillin family is why they’re described as broad-spectrum penicillins. They’re not limited to Gram-negative bacteria only, and they don’t cover all bacteria (notably, they’re not effective against many resistant organisms and against Pseudomonas without specific combinations or other agents). The other descriptors don’t fit because one suggests activity only against Gram-negative bacteria, another suggests no defined range, and another would imply they’re restricted to a narrow subset of bacteria.