Abstract

Listeria monocytogenes is a foodborne pathogen, with relatively low incidence but high case-fatality. Phytochemicals have been recognized as a promising antimicrobial agent as an alternative to synthetic chemicals due to their safety and high efficacy with multi-target sites. This study identified and characterized a novel antibacterial agent, dehydrocorydaline, in the Corydalis turschaninovii rhizome using HPLC-LTQ-Orbitrap-HRMS, and its antibacterial effect with lowest MIC (1 mg/mL) and MBC (2 mg/mL) values. In addition, an in vitro growth kinetic assay, cytoplasmic nucleic acid and protein leakage assay, and observation of morphological changes in bacterial cells supported the strong antibacterial activity. Dehydrocorydaline also displayed effective inhibitory effects on biofilm formation and bacterial motility. In order to investigate the potential antibacterial mechanism of action of dehydrocorydaline against L. monocytogenes, label-free quantitative proteomics was used, demonstrating that dehydrocorydaline has multiple targets for combating L. monocytogenes including dysregulation of carbohydrate metabolism, suppression of cell wall synthesis, and inhibition of bacterial motility. Overall, this study demonstrated that dehydrocorydaline has potential as a natural and effective antibacterial agent with multi-target sites in pathogenic bacteria, and provides the basis for development of a new class of antibacterial agent.

Highlights

  • Listeria monocytogenes is the causative agent of listeriosis, which is of relatively low incidence but presents a high case-fatality rate (20–30%) and causes serious disease such as gastroenteritis, meningitis, sepsis, and encephalitis (Radoshevich and Cossart, 2018)

  • Listeria monocytogenes biofilm, which is a microbial aggregate embedded in a self-produced matrix containing extracellular polymeric substances, is highly resistant to antibiotics compared to planktonic cells (Oloketuyi and Khan, 2017)

  • We aimed to identify major compounds in crude extract of the C. turtschaninovii rhizome using liquid chromatography coupled with hybrid linear ion trap quadrupoleorbitrap mass spectrometry (HPLC-LTQ-Orbitrap-MS/MS) and to evaluate antibacterial activity of identified compounds against L. monocytogenes

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Summary

Introduction

Listeria monocytogenes is the causative agent of listeriosis, which is of relatively low incidence but presents a high case-fatality rate (20–30%) and causes serious disease such as gastroenteritis, meningitis, sepsis, and encephalitis (Radoshevich and Cossart, 2018). Listeria monocytogenes biofilm, which is a microbial aggregate embedded in a self-produced matrix containing extracellular polymeric substances (proteins, nucleic acids, and polysaccharides), is highly resistant to antibiotics compared to planktonic cells (Oloketuyi and Khan, 2017). This resistance is attributed to poor penetration, inactivation of antimicrobials in the biofilm matrix, and a change of bacterial metabolic state to dormancy (de la Fuente-Núñez et al, 2012). Developing effective methods for the control of resistant strains and biofilms is crucial

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