Binding of Neisseria meningitidis Pili to Berry Polyphenolic Fractions

Abstract

Blocking bacterial adhesion to host surfaces provides novel potential to control infections. The present study was directed to binding and inhibitory activity of different fresh berries and berry and fruit juices against Neisseria meningitidis . Berries and juices were fractionated according to their molecular size into three fractions. A microtiter well assay for binding of N. meningitidis pili to berry and juice fractions was constructed. In addition, adhesion inhibition to human epithelial cells (HEC-1B) was tested. The active fractions were then subfractionated by employing solid-phase extraction. Subfractions were characterized by RP-HPLC-DAD, and the pili binding was evaluated by using microtiter well binding assay. Binding and inhibitory activity were detected to bilberry, cranberry, lingonberry, and crowberry fractions, which contained anthocyanins or a mixture of proanthocyanidins and flavonols. Thus, the findings identify several previously unknown binding and inhibitory activities and may suggest Vaccinium berries and crowberry as promising sources against meningococcal adherence.

Inhibition of adhesion of Neisseria meningitidis to human epithelial cells by berry juice polyphenolic fractions

“…Inhibition of the bacterial attachment to human cells may offer a way to avoid infections (Ofek et al ., 2003). In the present study it was shown that bilberry, cranberry, crowberry and lingonberry juice polyphenolic fractions containing anthocyanins and proanthocyanidins (Toivanen et al ., 2009) act as antiadhesives. These fractions inhibited the attachment of N. meningitidis to epithelial cells in vitro .…”

“…Significant antiadhesion activity was achieved with relatively low concentrations, 1 µg/mL of cranberry and lingonberry, and 5 µg/mL of bilberry and crowberry juice polyphenolic fractions. Although the methodologies used in the experiments differ, effective concentrations of the inhibition were on the same level as the concentrations in our previous microtiter well assay studies, where the isolated pili bound significantly to 0.39–12.5 µg/mL of these fractions (Toivanen et al ., 2009). None of the studied berry juice polyphenolic fractions gave total inhibition for the attachment of meningococci and the highest inhibition was achieved up to 75% with the cranberry juice polyphenolic fraction at a concentration of 5 µg/mL.…”

“…The eluted subfractions were analysed using RP‐HPLC‐DAD. Subfractions (here polyphenolic fractions), which were eluted with water and contained anthocyanins and proanthocyanidins (Toivanen et al ., 2009) were used in the inhibition experiments of the cell culture studies.…”

“…In previous studies it was shown that N. meningitidis pili , Streptococcus pneumoniae bacterial cells and Streptococcus agalactiae bacteria bind to berry molecular size fractions especially from Vaccinium species and they inhibit hemagglutination caused by Streptococcus suis (Toivanen et al ., 2009, 2010). The results (Toivanen et al ., 2009) showed that berry juice molecular size fractions of 10–100 kDa inhibited the binding of isolated N. meningitidis pili to membrane‐bound epithelial cells in a dot assay. Additionally, meningococcal pili bound to bilberry, cranberry, crowberry and lingonberry juice polyphenolic fractions containing anthocyanins and proanthocyanidins.…”

Targeting the bacteria–host interface

“…Proanthocyanidins inhibit the adhesion and co-aggregation of UPEC, Helicobacter pylori and the oral pathogen Porphyromonas gingivalis , among others 42 - 44 . Their mechanism of action seems to be binding to flagella and pili, thus inhibiting bacterial surface attachment, swarming motility and aggregation into biofilms 42 , 45 , 46 . Clinical studies evaluating the effects of consumption of both cranberry juice and cranberry extracts on the incidence of UTIs had mixed outcomes, with some reporting no significant benefit and others reporting significant decreases in the rate of infection upon consumption 47 - 50 .…”