title: Antagonistic Effect ofPseudomonassp. CMI-1 on Foodborne PathogenicListeria monocytogenes.
abstract: Bacterial isolates derived from food or raw food materials of animal origin were screened for potential antagonistic activity against foodborne pathogenicListeria monocytogenes. Using the agar spot method, ten out of the 94 tested bacteria showed antilisterial activity. All of the antagonistic isolates identified by sequence analysis as strains of the genusPseudomonaswere able to inhibit the growth of all the examinedListeriaspecies including the ruminal pathogenicL. ivanoviiand the opportunistic human pathogenicL. innocua. Pseudomonassp. CMI-1 had the highest inhibitory effect on the growth of differentListeriastrains. Co-culturing studies revealed that the inhibition ofL. monocytogenescould not be achieved efficiently. Although the population of thePseudomonassp. CMI-1 strain increased by up to 10 orders of magnitude during 2 days of culturing period at 20 °C in the presence ofL. monocytogenes, the cell count of the pathogen also increased by approx. 6 orders of magnitude. At the same time, appropriate inhibition of cell-free supernatants generated from 6-day-old cultures ofPseudomonassp. CMI-1 was observed. The inhibitory compound of this antagonistic strain is presumably a chromopeptide siderophore, whose activity and production can be affected by iron supplementation, and which had an absorption maximum typical of siderophores of fluorescentPseudomonasspecies. Production of the antilisterial substance was influenced by the oxygen concentration, as in static cultures the concentration of the siderophore was higher than in shake flask cultures.
authors.affiliation: Department of Microbiology and Biotechnology, Faculty of Food Science, Corvinus University of Budapest, Somlói út 14-16, HU-1118 Budapest, Hungary.
authors.forename: Ágnes
authors.initials: Á
authors.lastname: Belák
authors.affiliation: Department of Microbiology and Biotechnology, Faculty of Food Science, Corvinus University of Budapest, Somlói út 14-16, HU-1118 Budapest, Hungary.
authors.forename: Anna
authors.initials: A
authors.lastname: Maráz
keywords: Listeria monocytogenes; antagonistic bacteria; fluorescent Pseudomonas sp; siderophore