INHIBITION OF LISTERIA IN BUFFER, BROTH, AND MILK BY ENTEROCIN-1146, A BACTERIOCIN PRODUCED BY ENTEROCOCCUS-FAECIUM

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 10(3) or 10(5) CFU/ml of Listeria monocytogenes Scott A, populations reached only 5-14% of the control after 24 h at 30-degrees-C, with numbers exceeding 10(7). while at 6-degrees-C a slow decrease in population was found.