Pyrrole-2-carboxylic acid inhibits biofilm formation and suppresses the virulence of Listeria monocytogenes.

Bacterial adhesion and biofilm formation of Listeria monocytogenes on food-contact surfaces result in serious safety concerns. This study aimed to explore the antibiofilm efficacy of pyrrole-2-carboxylic acid (PCA) against L. monocytogenes. Crystal violet staining assay demonstrated that PCA reduced the biofilm biomass of L. monocytogenes. The 2,3-bis-(2-methoxy-4-nitro-5-sulfophenyl)-2H-tetrazolium-5-carboxanilide reduction and flow cytometric assays indicated that PCA attenuated the metabolic activity of L. monocytogenes biofilm together with a decrease in viability. Morphologic observations revealed that PCA exposure collapsed the biofilm architecture. PCA administration of 0.75 mg ml^-1 decreased the excretion of extracellular DNA, protein and polysaccharide by 48.58%, 61.60% and 75.63%, respectively. PCA failed to disperse the mature biofilm, even at 1.5 mg ml^-1. However, PCA suppressed L. monocytogenes adhesion on common food-contact surfaces. Additionally, PCA exposure suppressed the hemolytic activity of L. monocytogenes. These findings suggested that PCA might serve as an alternative antibiofilm agent to control L. monocytogenes contamination.