Ampicillin is a type of antibiotic similar to penicillin, which is used in the treatment of bacterial infections caused by susceptible, usually gram-positive, organisms. Ampicillin has in vitro activity against gram-positive and gram-negative aerobic and anaerobic bacteria. The bactericidal activity of Ampicillin results from the inhibition of cell wall synthesis and is mediated through Ampicillin binding to penicillin binding proteins (PBPs). It is indicated for use mainly against infections caused by Escherichia coli, Shigella, Listeria monocytogenes, Salmonella, enterococci, and staphylococci..
Ampicillin has a short half life (2-3 times daily), orally low resorption, and low toxicity.