Ampicillin

Ampicillin is a amoxicillin in terms of spectrum and level of activity.^[1] It can sometimes result in allergic reactions that range in severity from a rash (e.g. patients with mononucleosis) to potentially lethal anaphylaxis.

Mechanism of action

Belonging to the amino group. The amino group helps the drug penetrate the outer membrane of gram-negative bacteria. Ampicillin acts as a competitive inhibitor of the enzyme transpeptidase. Transpeptidase is needed by bacteria to make their cell walls.^[1] It inhibits the third and final stage of bacterial cell wall synthesis, which ultimately leads to cell lysis.

Indications

Ampicillin is closely related to antibiotics.

All Pseudomonas and most strains of Klebsiella and Aerobacter are considered resistant.^[2]

Use in research

Ampicillin is often used as a selective agent in molecular biology to confirm the uptake of genes (e.g., of plasmids) by bacteria (e.g., E. coli). A gene that is to be inserted into a bacterium is coupled to a gene coding for an ampicillin resistance (in E. coli, usually the bla (TEM-1) gene, coding for β-lactamase). The treated bacteria are then grown on a medium containing ampicillin. Only the bacteria that successfully take up the desired genes become ampicillin resistant, and therefore contain the other desired gene as well.