In vitro antibacterial activity of the lactoperoxidase system towards enterotoxigenic strains of Escherichia coli.

The lactoperoxidase-thiocyanate-hydrogen peroxide (LP) system inhibited the growth of enterotoxigenic Escherichia coli strains responsible for scouring in neonatal and post-weaning piglets. An enzymatic system for hydrogen peroxide generation (glucose oxidase, GO; 0.1 U/ml) and a chemical source (sodium carbonate peroxyhydrate, SCP; 90 mg/l) were used in the LP system to test 19 strains in a 6-h growth assay at 37 degrees C. Only three strains were highly sensitive to the LP/GO system, while all exhibited significant growth inhibition with the LP/SCP system. Hydrogen peroxide alone had less effect than the complete system. The bactericidal activity of the LP/GO system towards a previously resistant strain was greatly increased by increasing the level of glucose oxidase in the system by three- or five-fold.