ANTAGONISTIC EFFECTS OF STRAINS OF BREVIB ACTERIUM LINENS AGAINST LISTERIA

Three isolates of Brevibacterium (B.) linens from the brine of a red s mear cheese manufacturer produced Listeria inhibiting principles which could be demonstrated by deferred stab inoculation, spot on the lawn technique, well assay, associate growth and in cellfree fluid culture. The antimicrobial agent was dialyzable through tubing MWCO 1 kDa, sta ble at pH 4,0-9,0 and after heating (80 degrees C, 30 min) at acid pH, but not at alkaline pH, remained active after treatment with protease s, catalase and lipase, was soluble in water and ethanol and insoluble in acetone. Its mode of action was dependent on the strain of L. mono cytogenes and the activity was more efficient at pH 7,6 than at pH 5,7 . The spectrum of activity comprised 96 % of strains of L. monocytogen es (n = 48) and all strains of L. innocua (n = 20), L. seeligeri (n = 3), L. ivanovii (n = 2) and L. welshimeri (n = 2). L. monocytogenes co uld not be detected after associate growth with B. linens on agar for at least five days at 16 degrees C, if the inocula of L. monocytogenes was was very low and that of B. linens very high. L. monocytogenes wa s, however, detectable inoculated in enrichments of agar culture of B. linens. Hence microbiological control of growth of Listeria by antago nistic active strains of B. linens cannot replace hygiene concepts for controlling L. monocytogenes.