THE INHIBITION OF LISTERIA-MONOCYTOGENES IN MILK BY PEDIOCOCCI

Each of five strains of pediococci was tested in milk for its ability to control each one of four strains of Listeria monocytogenes. Four out of the five strains of pediococci were either bacteriostatic or bactericidal toward the pathogen. One of the strains of the pediococci did not control the growth of L. monocytogenes in milk. Pure cultures of the strains of L. monocytogenes in milk at 4·5 and 32°C attained populations of about log10 9·0 cfu ml-1 after 6 and 4 days, respectively. Some of the pediococci not only prevented L. monocytogenes strains from attaining populations it would have in pure culture (P < 0·01), but brought about reduction in populations of >4·0 log10 cfu ml-1. The Pediococcus strain PAC was the least antagonistic toward the strains of Listeria; while L. monocytogenes strain SA was the most resistant to the pediococcal action. The pH of the milk never dropped below 5·3, an indication that acid may have played a role in concert with other factors in the observed inhibition of Listeria. © 1993 by Academic Press, Inc.