title: Inhibitory effects of broccoli extract on Escherichia coli O157:H7 quorum sensing and in vivo virulence.
abstract: Broccoli extract (BE) has numerous beneficial effects on human health including anticancer activity. Quorum sensing (QS), mediated by self-produced autoinducer (AI) molecules, is a key process for the production of virulence determinants in pathogenic bacteria. BE suppressed AI-2 synthesis and AI-2-mediated bacterial motility in a dose-dependent manner in Escherichia coli O157:H7. In addition, expression of the ler gene that regulates AI-3 QS system was also diminished in response to treatment with BE. Furthermore, in an in vivo efficacy test using Caenorhabditis elegans as a host organism, C. elegans fed on E. coli O157:H7 in the presence of BE survived longer than those fed solely on the pathogenic bacteria. Quantitative real-time PCR analysis indicated that quercetin was the most active among the tested broccoli-derived compounds in downregulating virulence gene expression, while treatment with myricetin significantly suppressed the expression of the eae gene involved in type III secretion system. These data suggest that BE and its flavonoid constituents can inhibit expression of QS-associated genes, thereby downregulating the virulence attributes of E. coli O157:H7 both in vitro and in vivo. This study clearly elucidates BE's QS-inhibitory activity and suggests that BE has the potential to be developed as an anti-infective agent.
authors: Department of Microbiology, College of Medicine, Yonsei University, Seoul, Korea.
authors: Kang-Mu
authors: KM
authors: Lee
authors: Jeesun
authors: J
authors: Lim
authors: Sunyoung
authors: S
authors: Nam
authors: Mi Young
authors: MY
authors: Yoon
authors: Yong-Kuk
authors: YK
authors: Kwon
authors: Byeong Yeal
authors: BY
authors: Jung
authors: Yongjin
authors: Y
authors: Park
authors: Sungsu
authors: S
authors: Park
authors: Sang Sun
authors: SS
authors: Yoon