Inhibitory effects of grape seed extract on growth, quorum sensing, and virulence factors of CDC “top-six” non-O157 Shiga toxin producing E. coli

Abstract

Non-O157 Shiga toxin producing Escherichia coli (STECs) have become a growing concern to the food industry. Grape seed extract (GSE), a byproduct of wine industry, is abundant in polyphenols that are known to be beneficial to health. The objective of this study was to evaluate the effect of GSE on the growth, quorum sensing, and virulence factors of Centers for Disease Control and Prevention (CDC) "top-six" non-O157 STECs. Minimal inhibitory concentration (MIC) of GSE was 2mg/ml against E. coli O26:H11, and 4mg/ml against the other non-O157 STECs tested. Minimal bactericidal concentration (MBC) was the same as MIC for all six non-O157 STECs tested. At 5×10(5)CFU/ml inoculation level, 4mg/ml GSE effectively inhibited the growth of all tested strains, while 0.25-2mg/ml GSE delayed bacterial growth. At a higher inoculation level (1×10(7)CFU/ml), GSE had less efficacy against the growth of the selected six non-O157 STECs. Its impact on bacterial virulence was then assessed at this inoculation level. Autoinducer-2 (AI-2) is a universal signal molecule mediating quorum sensing (QS). GSE at concentration as low as 0.5mg/ml dramatically reduced AI-2 production of all non-O157 STECs tested, with the inhibitory effect proportional to GSE levels. Consistent with diminished QS, GSE at concentration of 0.125mg/ml caused marked reduction of swimming motility of all motile non-O157 STECs tested. In agreement, GSE treatment reduced the production of flagella protein FliC and its regulator FliA in E. coli O103:H2 and E. coli O111:H2. Furthermore, 4mg/ml GSE inhibited the production of Shiga toxin, a major virulence factor, in E. coli O103:H2 and E. coli O111:H2. In summary, GSE inhibits the growth of "top-six" non-O157 STECs at the population level relevant to food contamination. At higher initial population, GSE suppresses QS with concomitant decrease in motility, flagella protein expression and Shiga toxin production. Thus, GSE has the potential to be used in food industry to control non-O157 STEC.

Plant Phenolics and Phenolic-Enriched Extracts as Antimicrobial Agents against Food-Contaminating Microorganisms

“…Furthermore, naringenin, quercetin, sinensetin and apigenin were effective quorum sensing antagonists and biofilm suppressors in E. coli O157:H7 strain [120]. For non-O157 Shiga toxin producing E. coli strains, Sheng et al [121] found that the grape seed extract inhibited well the quorum sensing system.…”

Antimicrobialin vitroactivities of condensed tannin extracts on avian pathogenicEscherichia coli

“…Moreover, E. coli use their flagella to move, hence, if one of these flagella has a problem, the bacterium will stop swimming then fall (Mears et al ). On the other hand, during swimming activity, the bacterial cells move relatively independently, but swarming activity requires that bacteria work together which involves bacteria sensing the extracellular signals produced by other bacteria (Sheng et al ). Furthermore, these findings supported by the suggestion mentioned by O’May et al () about the relationship between motility and biofilm.…”

“…The growth curve of APEC was determined according to Sheng et al (). Overnight APEC cultures were diluted in LB medium to give 1 × 10 7 CFU per ml, and 200 µ l of this mixture which was added to 96‐well microtitre plates that supplemented with a range of CT concentrations.…”

Treatment Strategies for Infections With Shiga Toxin-Producing Escherichia coli

“…An inhibition of cytotoxicity of Stx of E. coli O:157:H7 was found for white carob tree (Prosopsis alba) and Ziziphus mistol extracts (Pellarin et al, 2013) and for Ellagitannin from the Aleppo oak (Quercus infectoria) (Voravuthikunchai et al, 2012). Moreover, bacterial products such as lactic acid, linoleic acid, (Pittman et al, 2012), green tea extracts (Isogai et al, 1998(Isogai et al, , 2001, fruit juices (Nogueira et al, 2003), and other plant products (Takemasa et al, 2009;Lacombe et al, 2010;Lee and Stein, 2011;Sheng et al, 2016;Sewlikar and D'Souza, 2017;Patel et al, 2018) have been shown to have a beneficial effect on STEC-infected cells and animals alone or in combination of other agents, e.g., antibiotics.…”