Fig. 1: Quantification of L. monocytogenes biofilm formation and morphological analysis.

a The biofilm-forming capabilities of over 100 food-(top panel) or clinical-isolated (bottom panel) L. monocytogenes (Lm) strains were tested using crystal violet staining assay. Arrows indicate the strains selected for further characterization. b Assemblage (strong, moderate, and weak) of isolates based on their ability to form biofilms. c Comparison of biofilm formation by food and clinical isolates and isolates of lineage I and II. Food isolates have significantly higher biofilm-forming capability than the clinical isolates, and isolates of lineage II also have a significantly higher capacity than isolates of lineage I. Mann–Whitney test was used for statistical analysis. **P < 0.005; *P < 0.05.