Drain biofilm microbiota inside a cheese processing facility: Comparison of Listeria positive and Listeria negative drains

Abstract

Listeria monocytogenes was identified as one of the most dangerous food-borne pathogens of the 21st century, not only due to its high mortality rate but also because of its ability to establish itself as a part of drain biofilms and persist there over long periods of time. The insides of twelve drains in a cheese processing facility were swabbed over a period of five months. Bacterial DNA was isolated and quantified to ascertain the presence and abundance of the biofilm. Presence of Listeria spp. prs gene was found in four of the twelve drains, with one drain testing positive for the prs gene presence on three different occasions. 16S rRNA amplicon sequencing was conducted on the isolated DNA from two Listeria positive and two Listeria negative drains. The microbial community composition was evaluated. Most notably genera Streptococci and unclassified Lactobacillales were significantly different in abundance in the Listeria negative drains. Genera Flavobacterium and unclassified Xanthomonadaceae were found to be significantly more different in abundance in the LisTeria positive drains. The latter two genera were not previously associated with Listeria spp. or reported to be widespread in food processing environments (FPE), however, they help to illustrate the higher diversity that was seen in Listeria positive drains. This study suggests that even though the alpha diversity is not sigN ificantly different, there are differences between the drain biofilm composition between Listeria positive and Listeria negative drains, which can be further researched to ascertain how these organisms affect the presence of Listeria spp. inside drain biofilms.