Inhibition of listeria in buffer, broth, and milk by enterocin 1146, a bacteriocin produced by Enterococcus faecium

Abstract

Enterocin 1146, a bacteriocin produced by Enterococcus faecium. DPC1146, has a rapid bactericidal effect on Listeria in buffer systems, broth, and milk. In trypticase soy broth, increasing the bacteriocin dose and/or decreasing the pH extended the lag phase of Listeria innocua. A logarithmic relationship was found between response (as proportion of survivors or growth compared to a control) and dose. Increasing the inoculum level of the indicator reduced the effectiveness of enterocin 1146. Log-phase cells of L. innocua were more resistant than stationary-phase cells in both broth and buffer systems. In milk treated with 250 arbitrary units of enterocin 1146/ml and inoculated with 103 or 105 CFU/ml of Listeria monocytogenes Scott A, populations reached only 5-14% of the control after 24 h at 30°C, with numbers exceeding 107, while at 6°C a slow decrease in population was found.