Influence of subinhibitory concentrations of licochalcone A on the secretion of enterotoxins A and B by Staphylococcus aureus

Abstract

Enterotoxins produced by Staphylococcus aureus are the key pathogenicity factors that can cause a variety of illnesses in humans, including staphylococcal gastroenteritis and food poisoning. It has been proven that licochalcone A is a potentially effective antimicrobial agent against S. aureus. In this study, Western blot assays, tumour necrosis factor release assays, murine T-cell proliferation assays, and real-time reverse transcriptase-PCR were performed to evaluate the effect of subinhibitory concentrations of licochalcone A on the secretion of two major enterotoxins (SEA and SEB) by S. aureus. The results show that licochalcone A significantly decreased, in a dose-dependent manner, the secretion of SEA and SEB by both methicillin-sensitive S. aureus and methicillin-resistant S. aureus. These results may increase the desirability of using licochalcone A as a lead compound for the design of more potent antibacterial agents based on the chalcone template.

Recent advances in understanding the antibacterial properties of flavonoids

“…Decreased secretion of enterotoxins was also noted [129]. Real-time polymerase chain reaction (PCR) indicated that these effects were accompanied by a decrease in transcription of the agrA gene, suggesting that the observed results may actually be due to inhibition of virulence factor synthesis rather than virulence factor secretion [39,129]. In light of these PCR results, and the recent demonstration that epicatechin gallate binds predominantly to the cytoplasmic membrane [102], it seems plausible that the above flavonoids may interfere with AgrC (a cytoplasmic membrane-associated [108] quorum-sensing signal receptor found in S. aureus).…”

“…Decreased secretion of enterotoxins was also noted [129]. Real-time polymerase chain reaction (PCR) indicated that these effects were accompanied by a decrease in transcription of the agrA gene, suggesting that the observed results may actually be due to inhibition of virulence factor synthesis rather than virulence factor secretion [39,129].…”

Antimicrobial effect of lipoic acid against Cronobacter sakazakii

“…The growth curves were tested by the method described by Qiu et al (Qiu et al, 2010), with minor exceptions. Briefly, C. sakazakii strain ATCC 29544 was grown to an OD 600 value of 0.2 in TSB, whereupon 125 mL of the culture was transferred into each well on 96-well microtiter plates.…”

Effect of Subinhibitory Concentrations of Chlorogenic Acid on Reducing the Virulence Factor Production byStaphylococcus aureus

“…Because of their potent antimicrobial properties against a broad spectrum of microorganisms such as S. aureus, Salmonella, and Listeria monocytogenes, plant extracts, especially phytochemicals they contain, have gained great interest (Cowan, 1999;Carson et al, 2006). Many studies have been reported that natural extracts such as oil, licochalcone A, and eugenol have an antimicrobial function (Burt, 2004;Qiu et al, 2010aQiu et al, , 2010b.…”