Ampicillin and amoxicillin differ from penicillin primarily by their what?

Ampicillin and amoxicillin are both classified as aminopenicillins and are broader-spectrum antibiotics compared to penicillin. This broader spectrum comes from their ability to target a wider range of gram-negative bacteria. However, they are still susceptible to penicillinase, which is an enzyme produced by certain bacteria that can inactivate penicillins.

The broader spectrum allows them to be effective against organisms such as Haemophilus influenzae and Escherichia coli, which are not well-targeted by penicillin. This characteristic is what primarily distinguishes ampicillin and amoxicillin from traditional penicillin, making the answer about them being broad-spectrum yet still susceptible to penicillinase the most accurate reflection of their pharmacological properties.