National Dental Examining Board of Canada (NDEB) Practice Exam

Whereas Penicillin G, Penicillin V, and Amoxicillin are most effective against gram-positive bacteria, Ampicillin is unique in its effectiveness against both gram-positive and gram-negative bacteria. This is due to its ability to bind to and inhibit the growth of the cell walls in both types of bacteria. Thus, Ampicillin is the best option when targeting gram-negative bacteria.