Identification of Genetic Determinants Associated with Biofilm Formation Capacity of Listeria Monocytogenes

Abstract

Persistence of Listeria monocytogenes in food processing plants is a huge health and economic burden. Biofilms are considered to be one of the major mechanisms by which this pathogen persists within these environments. Studies so far have mostly used optimal growth conditions in their investigations which may not provide a realistic understanding of the biofilm forming abilities of L. monocytogenes in food processing plants. Therefore the aim of this study was to 1) establish a model (12 ºC, Beef Broth) that closely relates to the food processing environment 2) screen 66 isolates of L. monocytogenes from food and clinical sources and determine their biofilm forming phenotypes (non-, weak, moderate and strong formers) and 3) analyze the correlation between biofilm formation phenotypes and biofilm associated genes detected using polymerase chain reaction (PCR) and Basic Local Alignment Search Tool (BLAST) for whole genome sequences. Biofilm formation established at 12 ºC in Beef Broth was the most consistent and quantifiable at day 9 of incubation. Subsequently, 66 isolates were screened using this model, resulting in 60 isolates being identified as strong biofilm formers, 5 isolates as moderate biofilm formers and 1 isolate as a weak biofilm former. Twenty biofilm associated genes were analyzed using PCR in 27 representative isolates. Out of the 20 genes, at least 17 of them were detected in all the tested isolates. Out of the 106 biofilm associated genes analyzed using BLAST, all the isolates were found to show the presence of at least 92 genes. In conclusion, there was no obvious correlation between the presence/absence of the genes selected for analysis and the ability to form biofilms using approaches performed in this study. However, the model established in the study will be useful in further analysis (transcription and translation studies) of genetic markers responsible for biofilm formation of L. monocytogenes under food processing conditions.