Influence of subinhibitory concentrations of plant essential oils on the production of enterotoxins A and B and α-toxin by Staphylococcus aureus

Abstract

The data presented show the ability of subinhibitory concentrations of plant essential oils to influence the production of enterotoxins A and B and AE-toxin by Staphylococcus aureus. Subinhibitory concentrations of the oils of bay, clove, cinnamon, nutmeg and thyme had no significant effect on the overall quantity of extracellular protein produced. Haemolysis due to AE-toxin was significantly reduced after culture with all five plant essential oils. This reduction was greatest with the oils of bay, cinnamon and clove. These three oils also significantly decreased the production of enterotoxin A; the oils of clove and cinnamon also significantly decreased the production of enterotoxin B. INTRODUCTIONStaphylococcus aureus is an important medical pathogen, with different strains being responsible for a number of disease states including toxic shock syndrome, scalded skin syndrome and foodborne illness (Le Loir et al., 2003). The ability to cause disease is, in part, dependent upon the production of a range of extracellular proteins, including catalase, fibrinolysin, superoxide dismutase, hyaluronidase, haemolysins (AE, â, ª and ä), epidermolytic toxins and enterotoxins. The enterotoxins are a group of serologically distinct proteins (A, B, C 1-3 , D, E and F) that are the causative agents of staphylococcal food poisoning. Although their exact mode of action has yet to be fully elucidated they are believed to stimulate an enteric-vagus nerve reflex triggering the vomiting centres of the brain (Sears & Kaper, 1996;Arbuthnott et al., 1990). The enterotoxins can also act as superantigens, stimulating T lymphocytes to release cytokines and T-cell proliferation (Balaban & Rasooly, 2000;Krakauer, 1999). Considerable research at present is also aimed at investigating the properties of newly identified enterotoxins, including enterotoxins K, L and U (Orwin et al., 2001(Orwin et al., , 2003Letertre et al., 2003).One of the most extensively studied of the extracellular proteins is AE-haemolysin (AE-toxin). This is secreted as a soluble protein of 33 kDa. Penetration of host cell membranes by AE-toxin results in the formation of a hexameric transmembrane pore that causes the leakage of ions and low molecular mass compounds. These pores also trigger secondary cellular reactions such as eicosanoid production, cytokine release and apoptosis.In both the food and pharmaceutical industries there is a continuing need to find new and improved antimicrobial agents, especially in view of the increasing incidence of antibiotic resistance. One of the areas which is subject to considerable interest is plant extracts and in particular their essential oils. The antimicrobial properties of plant essential oils against a wide range of micro-organisms are well established (Vardar-Unlu et al., 2003;Valero & Salmeron, 2003;Burt & Reinders, 2003;Smith-Palmer et al., 1998Friedman et al., 2002;Delaquis et al., 2002;Elgayyar et al., 2001;Hammer et al., 1999;Deans & Ritchie, 1987). However, in comparison to many other conventional antimicrobial agent...

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

“…Antivirulence agents may impose less pressure on a pathogen than antibiotics do, which could stimulate the emergence of resistance. It has been demonstrated that some plant compounds could influence virulence factor production when used at subinhibitory concentrations (22,32,33). Qiu et al (22) observed that subinhibitory concentrations of thymol decreased the production of ␣-hemolysin and staphylococcal enterotoxins A and B in S. aureus.…”

Eugenol Reduces the Expression of Virulence-Related Exoproteins in Staphylococcus aureus

“…Staphylococcal gastroenteritis and food poisoning do not result from the ingestion of S. aureus itself but rather from enterotoxins that are preformed within the food (22,35 (3). Therefore, apart from the inhibition of the growth of vegetative bacterial cells, food microbiologists are also interested in the inhibition of toxin expression (7).…”

“…S. aureus infections are difficult to control due to a combination of toxinmediated virulence, invasiveness, and antibiotic resistance. Therefore, there is a continuing need to discover new and improved antimicrobial agents to treat S. aureus illnesses, with potential benefits for both the food and pharmaceutical industries (35).…”

“…Staphylococcal enterotoxins (SEs) are a group of major serological heat-stable enterotoxins (SEA to SEE and SEG to SEJ) (3). These toxins cause staphylococcal gastroenteritis, food poisoning, toxic shock-like syndromes, and several allergic and autoimmune diseases (3,22,35). TSST-1 is the key causative toxin of toxic shock syndrome (TSS), which is an acute-onset and potentially lifethreatening staphylococcal syndrome (23).…”

Design, Synthesis and in Vitro Evaluation of Antibacterial and Antiadhesive Potentials of Some Substituted Imidazolones Derivatives of Cinnamaldehyde

“…1) an active ingredient of turmeric has been shown to be effective in inhibiting the formation of biofilms; making this compound a potential treatment for pathogens (Karaman et al, 2013). transCinnamaldehyde a constituent of cinnamon bark or found in cinnamon oil has also been shown to significantly decrease the production of two virulence factors, A and α-toxin in S aureus (Smith-Palmer et al, 2004). Low levels of trans-cinnamaldehyde have also been noted to inhibit the cell-density dependent on the regulation of gene expression in E. coli and biofilm synthesis in Vibrio spp.…”