Technical Advantage:  Effect against Gram-positive and -negative bacteria Ampicillin is a Penicillin derivative that inhibits bacterial cell-wall synthesis by inactivating transpeptidases on the inner surface of the bacterial cell membrane.  A ß-lactam antibiotic with an amino group side chain attached to the penicillin structure, its mode of resistance is through the cleavage of ß-lactam ring of ampicillin by ß-lactamase.  Ampicillin is effective against Gram-positive and some Gram-negative bacteria. Technical Advantage:  Effect against Gram-positive and -negative bacteria Ampicillin is a Penicillin derivative that inhibits bacterial cell-wall synthesis by inactivating transpeptidases on the inner surface of the bacterial cell membrane.  A ß-lactam antibiotic with an amino group side chain attached to the penicillin structure, its mode of resistance is through the cleavage of ß-lactam ring of ampicillin by ß-lactamase.  Ampicillin is effective against Gram-positive and some Gram-negative bacteria.