Abstract
Foodborne Staphylococcus aureus (S. aureus) has attracted widespread attention due to its foodborne infection and food poisoning in human. Shikonin exhibits antibacterial activity against a variety of microorganisms, but there are few studies on its antibacterial activity against S. aureus. This study aims to explore the antibacterial activity and mechanism of shikonin against foodborne S. aureus. The results show that the minimum inhibitory concentrations (MICs) and the minimum bactericidal concentrations (MBCs) of shikonin were equal for all tested strains ranging from 35 μg/mL to 70 μg/mL. Shikonin inhibited the growth of S. aureus by reducing intracellular ATP concentrations, hyperpolarizing cell membrane, destroying the integrity of cell membrane, and changing cell morphology. At the non-inhibitory concentrations (NICs), shikonin significantly inhibited biofilm formation of S. aureus, which was attributed to inhibiting the expression of cidA and sarA genes. Moreover, shikonin also markedly inhibited the transcription and expression of virulence genes (sea and hla) in S. aureus. In addition, shikonin has exhibited antibacterial ability against both planktonic and biofilm forms of S. aureus. Importantly, in vivo results show that shikonin has excellent biocompatibility. Moreover, both the heat stability of shikonin and the antimicrobial activity of shikonin against S. aureus were excellent in food. Our findings suggest that shikonin are promising for use as a natural food additive, and it also has great potential in effectively controlling the contamination of S. aureus in food and reducing the number of illnesses associated with S. aureus.
Highlights
Staphylococcus aureus is an important foodborne pathogen, causing human food poisoning and infections worldwide [1]
In this study the morphology of S. aureus was observed by scanning electron microscopy, and the results showed that shikonin did not cause significant cell disintegration, which indicated that shikonin exert antibacterial activity might by binding to target molecules on the cell membrane of the bacteria [46]
Liu et al (2020) confirmed that fusidic acid at non-inhibitory concentrations inhibits the biofilm biomass of S. aureus by inhibiting the transcription of icaA and sarA [49]. In this experiment, we found that shikonin inhibits the formation of biofilms by inhibiting the transcription of sarA and cidA, rather than inhibiting icaA and agrA. These results indicate that different natural products inhibit the biofilm formation of S. aureus by regulating the expression of different genes
Summary
Staphylococcus aureus is an important foodborne pathogen, causing human food poisoning and infections worldwide [1]. It produces a wide variety of toxins, but enterotoxins (SEs) and hemolysins are known to be the main pathogenic factors of human food poisoning and infections, respectively [1,2]. 29 types of SEs have been reported, including the classical SEs (SEA to SEE) and the novel SEs (SEG to SEl27) [3,4]. Hemolysins can be divided into four types according to their genetic determinants: α, β, γ and δ. Among these hemolysins, α-hemolysin (Hla) is the main virulence factor of S. aureus for human infections [2]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
