title: Beta-lactamase evaluation of the amoxycillin-clavulanate association.
abstract: The capability of potassium clavulanate to protect amoxycillin from destruction by three partially purified beta-lactamases (from E. cloacae, B. cereus 569/H9 and E. coli R-TEM) was evaluated. The enzymatic inhibition was determined spectrophotometrically by assessing the ability of either amoxycillin or potassium clavulanate or their combination (at a 7:1 ratio by weight) to prevent the hydrolysis of a chromogenic substrate (nitrocefin) after different pre-incubation times, thus determining the IC50 and Ki values. Potassium clavulanate significantly reduced the IC50 values of amoxycillin for B. cereus and TEM enzymes by a factor ranging from 500 to 1200, by inhibiting these beta-lactamases at concentrations ranging from 4 to 0.008 microM. However, clavulanic acid was quite ineffective against type I enzymes (from E. cloacae), while amoxycillin was found to be sufficiently stable (IC50 of 0.8-1.4 microM).
authors.affiliation: Department of Preclinical and Clinical Pharmacology, University of Florence, Italy.
authors.forename: A
authors.initials: A
authors.lastname: Novelli
authors.forename: E F
authors.initials: EF
authors.lastname: Reali
authors.forename: S
authors.initials: S
authors.lastname: Fallani
authors.forename: P
authors.initials: P
authors.lastname: Periti
mesh_terms: D000658:Amoxicillin / Q000378:metabolism / Q000494:pharmacology*; D001409:Bacillus cereus / Q000201:enzymology; D002969:Clavulanic Acids / Q000378:metabolism / Q000494:pharmacology*; D004754:Enterobacter / Q000201:enzymology; D004926:Escherichia coli / Q000201:enzymology; D065093:beta-Lactamase Inhibitors; D001618:beta-Lactamases / Q000378:metabolism*
chemical_list: D002969:Clavulanic Acids; D065093:beta-Lactamase Inhibitors; D000658:Amoxicillin; D001618:beta-Lactamases