(347a) Listeria Biofilm Control Via Leuconostoc Mesenteroides Probiotic Isolates

A food-borne pathogen Listeria monocytogenes causes listeriosis, which is considered as lethal illness among immunocompromised patients. Biofilm formation of L. monocytogenes poses resistance and toughness toward sanitation methods such as traditional antibiotics. This study investigated the efficacy of six probiotic strains in controlling L. monocytogenes biofilms. Three probiotic strains of Leuconostoc mesenteroides showed the inhibitory effects toward Listeria biofilms assessed by 96-well based crystal violet assay, colony counting method, and confocal microscopy observation. Biofilm populations of two Listeria strains (serotype 1/2a ATCC15313 and serotype 4b ATCC19115) in dual culture with each probiotic strain were decreased by 4 to 44-fold compared with single species Listeria biofilms in BHI medium. Among the three probiotics, W51 strain resulted in the highest Listeria biofilm inhibition without affecting the growth of L. monocytogenes. Further Listeria biofilm study in the cell-free supernatant of W51 culture with different molecular weight revealed that large protein molecules (> 30 kDa) secreted by the W51 probiotic may be responsible for inhibiting Listeria biofilms. Therefore, our investigation suggests that the probiotics can be used to repress the biofilm development of L. monocytogenes.