Abstract
Cronobacter sakazakii is an opportunistic food-borne pathogen that endangers the health of neonates and infants. This study aims to elucidate the antibacterial activity and mechanism of Chrysanthemum buds crude extract (CBCE) against C. sakazakii and its application as a natural disinfectant. The antibacterial activity was evaluated by the determination of the diameter of inhibition zone (DIZ), minimum inhibitory concentration (MIC), and minimum bactericide concentration (MBC). The antibacterial mechanism was explored based on the changes of growth curve assay, intracellular ATP concentration, membrane potential, intracellular pH (pHin), content of soluble protein and nucleic acid, and cell morphology. Finally, the inactivation effects of CBCE against C. sakazakii in biofilm on stainless steel tube, tinplate, glass, and polystyrene were evaluated. The results showed that the DIZ, MIC, and MBC of CBCE against C. sakazakii were 14.55 ± 0.44–14.84 ± 0.38 mm, 10 mg/mL, and 20 mg/mL, respectively. In the process of CBCE acting on C. sakazakii, the logarithmic growth phase of the tested bacteria disappeared, and the concentrations of intracellular ATP, pHin, bacterial protein, and nucleic acid were reduced. Meanwhile, CBCE caused the cell membrane depolarization and leakage of cytoplasm of C. sakazakii. In addition, about 6.5 log CFU/mL of viable C. sakazakii in biofilm on stainless steel tube, tinplate, glass, and polystyrene could be inactivated after treatment with 1 MIC of CBCE for 30 min at 25°C. These findings reveal the antibacterial activity and mechanism of CBCE against C. sakazakii and provide a possibility of using a natural disinfectant to kill C. sakazakii in the production environment, packaging materials, and utensils.
Highlights
Cronobacter sakazakii, a gram-negative, facultatively anaerobic, motile emerging food-borne pathogen, can adhere tightly to the surface of equipment, packaging materials, and utensils due to its strong ability for biofilm formation, which is believed to be one of the important reasons for the contamination of food by this pathogen (Friedemann, 2007; Amalaradjou and Venkitanarayanan, 2011)
The results showed that the diameter of inhibition zone (DIZ) ranged from 14.55 ± 0.44 to 14.84 ± 0.38 mm, and no significant difference (P > 0.05) was found between these strains
When C. sakazakii was treated by 1 minimum inhibitory concentration (MIC) of Chrysanthemum buds crude extract (CBCE), the logarithmic phase of C. sakazakii disappeared
Summary
Cronobacter sakazakii, a gram-negative, facultatively anaerobic, motile emerging food-borne pathogen, can adhere tightly to the surface of equipment, packaging materials, and utensils due to its strong ability for biofilm formation, which is believed to be one of the important reasons for the contamination of food by this pathogen (Friedemann, 2007; Amalaradjou and Venkitanarayanan, 2011). Previous studies have shown that C. sakazakii mainly leads to food safety risks by contaminating processing equipment, packaging materials, and utensils (Kusumaningrum et al, 2003; Brandl et al, 2014). The most common way to eliminate C. sakazakii from the environment in which food is exposed is still the use of chemical disinfectants (Meireles et al, 2016). C. sakazakii strains have strong efficient biofilm formation ability, which helps weaken the bactericidal effect of chemical disinfectants (Lehner et al, 2005; Kim et al, 2006). A natural disinfectant with good antibacterial effect is urgently needed
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