Chemical composition and anti-biofilm activity of essential oil from Citrus medica L. var. sarcodactylis Swingle against Listeria monocytogenes

Listeria monocytogenes is an important foodborne pathogen that could cause listeriosis and poses potential threats to human health. Citrus medica L. var. sarcodactylis Swingle, also known as Fingered Citron, is a citrus species widely cultivated in South China. The aim of this work was to investigate the anti-biofilm efficacy of essential oil from Fingered Citron (FCEO) against L. monocytogenes. The crystal violet assay showed that FCEO exhibited strong anti-biofilm activity on both inhibiting biofilm formation and eradicating preformed biofilm. XTT assay indicated that FCEO significantly increased the metabolic active cells in the biofilm. Confocal scanning laser microscopy images and COMSTAT assay revealed that FCEO destroyed the intact architecture of biofilm, reduced biofilm biomass, thickness and substratum coverage. The morphological changes of cells in the biofilm were observed by scanning electron microscopy, which showed that FCEO could cause the wrinkle, collapse, lysis and cytoplasmic content leakage of cells. Our results also indicated that FCEO displayed its anti-biofilm activity through both biofilm dispersal and cell killing. Our findings provide evidence that FCEO exhibits strong anti-biofilm activity and might be used as a potential agent to control L. monocytogenes biofilm.