ATC Vet Code: QJ01CR02

The mechanism by which ß-lactam antibiotics bind with proteins associated with developing the bacterial cell wall, resulting in the ultimate lysis of the cell, is well established. In the case of Gram-positive bacteria the ß-lactam can freely pass across the peptidoglycan layer in the aqueous phase to the site of activity at the cytoplasmic membrane. In the case of Gram-negative bacteria there is a hydrophobic barrier outside the peptidoglycan layer. Broad-spectrum ß-lactam antibiotics have the ability to cross this barrier by way of small pores in its structure.

There are three major mechanisms of resistance available to bacteria: the production of ß-lactamase enzymes, impermeability of the cell wall by modification of the small pores and by modifications of the amino acid sequences at the cytoplasmic membrane interface where the cell wall is constructed.

In the absence of specific inhibitor enzymes with ß-lactamase activity, ß-lactamases either form complexes with the antibiotic or cause a breakdown of the ß-lactam ring. In either case the antibacterial activity is lost.

Clavulanic acid has a ß-lactam ring in its structure which is recognised by ß-lactamases as a type of “penicillin”. The enzyme/clavulanate interaction is irreversible and results in the depletion of enzymes molecules.