Ampicillin (C16H18N3O4S ; CAS No.: 69-53-4) is an aminopenicillin and, as such, is a broad-spectrum antibiotic and has been used extensively to treat bacterial infections since 1961. It is suspected to cause certain types of cancer in animals, including humans. Belonging to the group of beta-lactam antibiotics, ampicillin is able to penetrate Gram-negative bacteria. It inhibits the third and final stage of bacterial cell wall synthesis, which ultimately leads to cell lysis.