Context matters: environmental microbiota of ice cream processing facilities affects the inhibitory performance of two lactic acid bacteria against Listeria monocytogenes

Pathogenic L. monocytogenes may inhabit dairy processing environments, increasing the risk for cross-contamination of foods. Using biocontrol microorganisms that inhibit or outcompete L. monocytogenes to complement sanitation of dairy processing facilities may enhance the control of L. monocytogenes. However, it remains unknown whether the resident microbiota of dairy processing facilities affects the antilisterial activity of biocontrol strains. Here, two lactic acid bacteria (LAB) strains (Enterococcus PS01155 and PS01156) were tested for their biocontrol potential in the context of microbiomes collected from three ice cream processing facilities (A, B, and C). Antilisterial ability was assessed by co-culturing LABs with 8-L. monocytogenes strains in the presence of microbiota for 3 days at 15{degrees}C, followed by quantification of the most probable number of attached L. monocytogenes. L. monocytogenes concentration increased by 0.38{+/-}0.77 log10 MPN/sample in treatments containing microbiota from facility A, while it decreased by 0.99{+/-}1.13 and 2.54{+/-}0.84 log10 MPN/sample in treatments with microbiota from facilities B and C, respectively. The attachment of LAB to an abiotic surface was assessed by co-culturing LABs in with the microbiomes at 15{degrees}C for 3 days, followed by characterization of attached microbiota composition using amplicon sequencing. All samples containing microbiomes from facilities A and B had high relative abundance of Pseudomonas, while samples with facility C microbiome had high relative abundance of Enterococcus. Overall, we show that microbiota composition of ice cream processing facilities affected the antilisterial ability of LABs. IMPORTANCEAntilisterial lactic acid bacteria strains had been proposed as biological pathogen control agents for application in food processing environments. However, the effect of resident food processing environment microbiota on the performance on antilisterial lactic acid bacteria strains is poorly understood. Our study shows that the composition of the microbiota collected from ice cream processing facilities environmental surfaces can affect the attachment and inhibitory effect of lactic acid bacteria strains against L. monocytogenes. Further studies are therefore needed to evaluate whether individual microbial taxa affect antilisterial properties of lactic acid bacteria strains and to characterize the underlying mechanisms.