Biological Activity
ampicillin sodium is a competitive inhibitor of the enzyme transpeptidase with ic50 value of 1.8 μg/ml [1].ampicillin is a β-lactam antibiotic that kills bacteria by inhibiting transpeptidase reactions. transpeptidase is involved in the final stages of cell wall biosynthesis and inhibition of it ultimately leads to cell lysis [1].in e. coli 146 cells treated with ether, ampicillin showed no significant inhibition on the transpeptidase reaction at concentrations below 0.5 μg/ml, but exhibited 50% inhibition at the concentration of 1.8 μg/ml. in e. coli 146 cells, the minimal inhibitory concentration (mic) of ampicillin was 3.1 μg/ml [1]. in e. coli and s. typhi, ampicillin and epicillin at concentrations close to mic values killed bacteria at slower rates than amoxycillin [2].in experimental mouse infections, oral or subcutaneous treatment of ampicillin at the dose of 0.2 ml/20 g was significantly more effective than epicillin and amoxycillin against the majority of infections [2].[1]. moore b a, jevons s, brammer k w. inhibition of transpeptidase activity in escherichia coli by thienamycin. antimicrobial agents and chemotherapy, 1979, 15(6): 831-833.[2]. basker m j, gwynn m n, white a r. comparative activities of ampicillin, epicillin and amoxycillin in vitro and in vivo. chemotherapy, 1979, 25(3): 170-180.
Biochem/physiol Actions
Mode of Action: This is a ?-lactam antibiotic that inhibits bacterial cell-wall synthesis by inactivating transpeptidases on the inner surface of the bacterial cell membrane. Mode of Resistance: Administration with ?-lactamase cleaves the ?-lactam ring of Ampicillin and inactivates it. Antimicrobial Spectrum: Includes both gram-positive (similar to benzylpenicillin) and gram-negative bacteria (similar to tetracyclines and chloramphenicol.
