<n0:ComplexDefinition xmlns:n0="http://ncicb.nci.nih.gov/xml/owl/EVS/ComplexProperties.xsd#"><n0:def-definition>A broad-spectrum, semi-synthetic, beta-lactam penicillin antibiotic with bactericidal activity. Ampicillin binds to and inactivates penicillin-binding proteins (PBP) located on the inner membrane of the bacterial cell wall. Inactivation of PBPs interferes with the cross-linkage of peptidoglycan chains necessary for bacterial cell wall strength and rigidity. This interrupts bacterial cell wall synthesis and results in the weakening of the bacterial cell wall and causes cell lysis. Ampicillin is stable against hydrolysis by a variety of beta-lactamases, therefore, can be used in wide range of gram-positive and -negative infections.</n0:def-definition><n0:def-source>NCI</n0:def-source></n0:ComplexDefinition>