ANTIBACTERIAL ACTIVITY OF THE LACTOPEROXIDASE SYSTEM AGAINST SALMONELLA-TYPHIMURIUM IN TRYPTICASE SOY BROTH IN THE PRESENCE AND ABSENCE OF A HEAT-TREATMENT

The antibacterial activity of the lactoperoxidase system (LP system) o n the growth and survival of Salmonella typhimurium in tryptic soy bro th (TSB) was determined. The LP system, consisting of lactoperoxidase (1 mug/ml), potassium thiocynante (KSCN) (5.9 mM) and H2O2 (2.5 mM), w as found to have both bacteriostatic and bactericidal activities again st strains of S. typhimurium. The bactericidal activity was clearly de pendent on the initial inoculum level. Levels of 10(2)-10(5) CFU/ml we re killed at 37-degrees-C as opposed to the bacteriostatic activity wi th inoculum levels of 10(6) 10(7) CFU/ml, which exhibited a 25-h lag. The LP system also enhanced thermal inactivation of S. typhimurium. D5 0-degrees-C values were > 60 min (untreated broth) and 12 min (LP syst em activated); corresponding D52-degrees-C-values were 20 min and 7.5 min; corresponding D55-degrees-C-values were 14 min and 4 min; corresp onding D58-C-values were 5 min and 2.5 min and corresponding D60-degre es-C-values were .31 min and .20 min.