Houttuynia cordata Thunb. crude extract inactivates Cronobacter sakazakii: Antibacterial components, antibacterial mechanism, and application as a natural disinfectant

Abstract

The purpose of this study was to reveal the antibacterial components of Houttuynia cordata Thunb. crude extract (HCCE), analyze the antibacterial activity and mechanism of HCCE against Cronobacter sakazakii, and evaluate the bactericidal effect of HCCE as a natural disinfectant. Using an ultra high performance liquid chromatography-tandem mass spectrometry (UHPLC-QE-MS) non-target metabolomics technology, 15 kinds oforganic acids (18.65%), 14 kinds of phenols (16.17%), 10 kinds of flavonoids (12.32%), 5 kinds of terpenoids (5.87%), 3 kinds of alkaloids (1.62%), and 3 kinds of aldehydes (1.28%) were detected from HCCE. The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of HCCE against C. sakazakii were 7.5 mg/mL and 15 mg/mL, respectively, and when the concentration was 2 MIC, C. sakazakii stagnated in sluggish phase. C. sakazakii exposed to HCCE showed hyperpolarization of cell membrane, increased intracellular ROS content, decreased protein and DNA content, impaired cell membrane integrity, improved cell membrane permeability, cell fluid leakage, and partial cell fragmentation. After treatments with 1 MIC and 2 MIC of HCCE for 5 min, C. sakazakii strains on 8 contact surfaces including stainless steel, tinplate, glass, polystyrene, bamboo, plank, ceramic, and tin foil paper were significantly inhibited (P < 0.05), and the reduction amounts ranged from 3.00 to 3.68 log CFU/100 cm2 and 3.97 to 4.53 log CFU/100 cm2, respectively. These findings demonstrate the potential of HCCE as a natural disinfectant and provide a new idea to reduce the C. sakazakii contamination caused by surface contact.