Screening of Condensed Tannins from Canadian Prairie Forages for Anti–Escherichia coli O157:H7 with an Emphasis on Purple Prairie Clover (Dalea purpurea Vent)

Abstract

Tannins from forages grown (n = 10) on the Canadian prairie, as well as from Quebracho, Rhus semialata, and brown seaweed (Ascophyllum nodosum), were screened for anti-Escherichia coli O157:H7 activity against E. coli O157:H7 strain 3081 at a concentration of 400 μg/ml for each tannin type, except for brown seaweed, which was at 50 μg/ml. Growth of the bacteria was assessed by measuring the optical density at 600 nm over 24 h. Tannin from seaweed at a concentration of 50 μg/ml inhibited growth of strain 3081. Among the terrestrial forages, only condensed tannins (CT) from purple prairie clover (Dalea purpurea Vent; PPC) increased (P < 0.05) the lag time and reduced (P < 0.05) the growth rate of E. coli O157:H7. The anti-E. coli O157:H7 activity of PPC CT was further assessed by culturing E. coli strain ATCC 25922 and eight strains of E. coli O157:H7 with PPC CT at 0, 25, 50, 100, or 200 μg/ml. Selected strains were enumerated after 0, 6, and 24 h of incubation, and fatty acid composition was determined after 24 h of incubation. E. coli strain 25922 was cultured with 0, 50, or 200 μg of CT per ml and harvested during the exponential growth phase for examination by transmission electron microscopy. Increasing CT concentration linearly increased (P < 0.001) the lag times of seven strains and linearly reduced (P < 0.001) the growth rates of eight E. coli O157:H7 strains. Proportions of unsaturated fatty acids in the total fatty acids were decreased (P < 0.01) by CT at 50 μg/ml. Transmission electron microscopy showed that CT disrupted the outer membrane structure. Anti-E. coli O157:H7 activity of PPC CT at levels of up to 200 μg/ml was bacteriostatic rather than bactericidal, and the mechanism of anti-E. coli activity may involve alteration in the fatty acid composition and disruption of the outer membrane of the cell.

Condensed Tannins in Sainfoin: Composition, Concentration, and Effects on Nutritive and Feeding Value of Sainfoin Forage

“…McMahon et al (1999) reported that feeding 10 to 20% sainfoin (fresh and hay) along with alfalfa reduced frothy bloat by 45 to 93% in a 3‐yr study. In another 3‐yr study to compare incidence of bloat, ruminal fermentation, and feed intake of steers grazing alfalfa and mixed alfalfa–sainfoin pastures showed that inclusion of 35% sainfoin in mixed alfalfa–sainfoin pastures reduced but did not eliminate bloat (Wang et al, 2006). In a 3‐yr grazing study, Sottie et al (2014) observed that bloat incidence increased from 5 to 43 and from 1 to 48 when the percentage of sainfoin was reduced from 29 to 7% and from 28 to 5% in sainfoin–alfalfa mixture, respectively.…”

“…Some of the observed advantages of feeding sainfoin to ruminants compared with other comparable legume forages such as alfalfa include improved organic matter (OM) and protein digestion, increased intestinal amino acids absorption and N retention, more efficient utilization of energy and protein, and enhanced growth. Probably the most significant feed‐related characteristic of sainfoin is its non‐bloating nature (Sottie et al, 2014; Wang et al, 2006). Sainfoin has also been reported to reduce parasites such as nematodes in the ruminant digestive tract (Hoste et al, 2012).…”

“…Progress in characterizing sainfoin polyphenolics has been made during the last two decades, providing insight into why these compounds alter digestion and intestinal ecology in a manner that differs from other fodder legumes. New sainfoin populations that are suitable for survival in high‐performance grazing alfalfa pasture have been developed, and strategy to utilize sainfoin CT to prevent alfalfa pasture bloat by incorporating sainfoin into alfalfa pasture has been demonstrated to be effective (Acharya et al, 2013; Sottie et al, 2014; Wang et al, 2006). This review attempts to capture the latest research in characterizing the impact of polyphenolics on the feeding and nutritive value of sainfoin with an emphasis on CT. On the basis of the HCl‐butanol assay, as described by Terrill et al (1992), CT in plant material can be described by three fractions: extractable, protein‐bound, and fiber‐bound CT.…”

Effects of purple prairie clover (Dalea purpurea Vent.) on feed intake, nutrient digestibility and faecal shedding of Escherichia coli O157:H7 in lambs

“…Purple prairie clover has been shown to possess high CT concentrations (up to 94 g/kg DM) throughout the year (Berard et al, 2011;Jin et al, 2012;Li et al, 2014). In vitro studies showed that among tannins isolated from forages common to western Canada, only PPC CT possessed strong anti-E. coli O157:H7 and anti-generic E. coli activity (Wang et al, 2013a), a toxicity that was linked to disruption of the bacterial cell membrane (Liu et al, 2013). Therefore, PPC offers promise as a forage for dietary mitigation of E. coli O157:H7.…”

Antibacterial activity of ethanolic extracts from Zingiber zerumbet rhizome against Salmonella spp.

“…The inhibitory action of tannins on microbes occurs in cell membranes, through cell aggregation and disruption of membranes and cell function, in general tannins cause protein deposition, but tannin's anti-microbial activity is specific, according to the chemical composition and structure of tannins. Condensed tannins isolated from several plants have been shown to have strong activity against Gram-negative bacteria, including Salmonella, Shigella, Staphylococcus, Pseudomonas and Helicobacter pylori (Liu et al 2013;Wang et al 2013). Tannins are known to have anti-inflammatory, astringent, and antiseptic activities, they inhibit the enzyme systems of microorganisms, tannic acid inhibits phosphatidylcholine liposomes which damage microorganism membranes, is also able to bind iron that is needed by microorganisms, resulting in malfunctioning of aerobic microorganisms (Linarti et al 2011).…”