GWAS Study Applied To Phenotypically Slow Growth Strains of Listeria monocytogenes. Workflow and Out-come

Listeria monocytogenes (Lm) is a serious public health foodborne pathogen cause of lis-teriosis, usually in elderly, pregnant and immunocompromised people, linked to con-sumption of contaminated food, especially ready-to-eat (RTE) products. Different pro-tocols can be used to detect Lm, and ISO11290-1:2017 is the reference method in Eu-rope. Through molecular techniques such as whole genome sequencing (WGS) it is possible to discriminate between Lm strains, which are unequally distributed between clinical cases, food or food related environments, probably also due to enrichment step bias towards some Lm serogroup (IIa) compared to IVb. In the present work a set of Lm strains, detected in clinical cases and food, was investigated to define Lm strains growth ability after incubation in Half Fraser broth, and Genome Wide Association Studies (GWAS) applied to correlate the growth phenotype traits to presence of rele-vant genes. GWAS enabled the identification of a more relevant cassette of genes asso-ciated to a holin region of bacteriophage A118 and the determination of the distribution of relevant genes, highlighted from GWAS analysis within a population of Lm IVb and IIa.