Subinhibitory Concentrations of Perilla Oil Affect the Expression of Secreted Virulence Factor Genes in Staphylococcus aureus

Abstract

BackgroundThe pathogenicity of staphylococcus aureus is dependent largely upon its ability to secrete a number of virulence factors, therefore, anti-virulence strategy to combat S. aureus-mediated infections is now gaining great interest. It is widely recognized that some plant essential oils could affect the production of staphylococcal exotoxins when used at subinhibitory concentrations. Perilla [Perilla frutescens (L.) Britton], a natural medicine found in eastern Asia, is primarily used as both a medicinal and culinary herb. Its essential oil (perilla oil) has been previously demonstrated to be active against S. aureus. However, there are no data on the influence of perilla oil on the production of S. aureus exotoxins.Methodology/Principal FindingsA broth microdilution method was used to determine the minimum inhibitory concentrations (MICs) of perilla oil against S. aureus strains. Hemolysis, tumour necrosis factor (TNF) release, Western blot, and real-time RT-PCR assays were performed to evaluate the effects of subinhibitory concentrations of perilla oil on exotoxins production in S. aureus. The data presented here show that perilla oil dose-dependently decreased the production of α-toxin, enterotoxins A and B (the major staphylococcal enterotoxins), and toxic shock syndrome toxin 1 (TSST-1) in both methicillin-sensitive S. aureus (MSSA) and methicillin-resistant S. aureus (MRSA).Conclusions/SignificanceThe production of α-toxin, SEA, SEB, and TSST-1 in S. aureus was decreased by perilla oil. These data suggest that perilla oil may be useful for the treatment of S. aureus infections when used in combination with β-lactam antibiotics, which can increase exotoxins production by S. aureus at subinhibitory concentrations. Furthermore, perilla oil could be rationally applied in food systems as a novel food preservative both to inhibit the growth of S. aureus and to repress the production of exotoxins, particularly staphylococcal enterotoxins.

Effects of Subinhibitory Concentrations of Menthol on Adaptation, Morphological, and Gene Expression Changes in Enterohemorrhagic Escherichia coli

“…A determination of the amount of Shiga toxin and/or other major virulence factors produced by the adapted bacteria might serve to validate this hypothesis. Our results are in agreement with those of recent work showing that exposure of S. aureus (23,(34)(35)(36), Shigella strains (19), Listeria monocytogenes (42), Klebsiella pneumoniae (9), E. coli, Vibrio harveyi (29), and uropathogenic E. coli (16) to SI concentrations of EOs or their constituents reduces the expression of virulence factors. As interest rises in the targeting of bacterial virulence factors as an alternative strategy to develop new types of anti-infective agents, both our work and the reports cited above suggest that EOs, as well as the molecules forming them, might be good candidates to explore.…”

Antimicrobial and Virulence-Modulating Effects of Clove Essential Oil on the Foodborne Pathogen Campylobacter jejuni

“…This type of response seems to be essential for the C. jejuni cell for survival, downregulating its virulence-associated gene pool. Our results are in accordance with the reports on perilla oil, affecting exotoxin production in S. aureus (62), and oregano, affecting Shiga toxin production in enterohemorrhagic Escherichia coli (63).…”

Punicalagin Inhibits Salmonella Virulence Factors and Has Anti-Quorum-Sensing Potential

“…With the advent of antibiotic resistance of Salmonella, especially Salmonella enterica serovar Typhimurium definitive type 104, there is an increasing demand for the development of new therapeutics to prevent and treat infections caused by these resistant strains (5). Plant materials have received a great deal of interest for development as an alternative method to control pathogenic microorganisms.…”