Ampicillin is a semi-synthetic derivative of penicillin, active as a broad-spectrum antibiotic. It is inactivated by beta-lactamases and for this reason a beta-lactamase inhibitor should be considered when using ampicillin. Against gram-positive bacteria, ampicillin has a similar mode of action as benzylpenicillin; against gram-negative bacteria, it has a similar mode of action as chloramphenicol and tetracyclines. In E. coli it inhibits cell wall synthesis.
Used to select for ampicillin resistance in mutated and transformed cells.
A β-lactam antibiotic with an amino group side chain attached to the penicillin structure. Penicillin derivative that inhibits bacterial cell-wall synthesis (peptidoglycan cross-linking) by inactivating transpeptidases on the inner surface of the bacterial cell membrane. Bactericidal only to growing Escherichia coli. Mode of resistance: Cleavage of β-lactam ring of ampicillin by β-lactamase. Antimicrobial spectrum: Gram-negative and Gram-positive bacteria.