1 School of Food and Agriculture, The University of Maine , Orono, Maine.
Foodborne Pathog Dis. 2013 Nov;10(11):944-50. doi: 10.1089/fpd.2013.1504. Epub 2013 Aug 14.
The antimicrobial activity and model of action of polyphenolic compounds extracted from lowbush wild blueberries (LWB) were studied against Escherichia coli O157:H7. Polyphenols in LWB were extracted using 80% vol/vol methanol and designated as total blueberry phenolics (TBP). The fraction was further separated by a C-18 Sep-Pak cartridge into monomeric phenolics acids (MPA) and anthocyanins plus proanthocyanidins (A&P). The A&P fraction was further separated into anthocyanins and proanthocyanidins using a LH-20 Sephadex column. Each fraction was diluted in 0.85% wt/vol NaCl, inoculated with E. coli O157:H7 to achieve 8 log colony-forming units (CFU)/mL, and incubated at 25 °C for 1 h. The survival populations of E. coli O157:H7 in the phenolic fractions were determined by a viable cell counts method. The permeability of the cell membrane of E. coli O157:H7 was determined using LIVE/DEAD viability assay, and the damage was visualized by using transmission electron microscopy (TEM). Significant (p<0.05) reductions of 5 log CFU/mL of E. coli O157:H7 were observed for MPA at 0.4 g/L gallic acid equivalents (GAE), A&P at 0.9 g/L GAE, and anthocyanins at 0.65 g/L GAE. Reductions of 6-7 CFU/mL were observed for MPA at 0.8 g/L GAE, A&P at 1.8 g/L GAE, and anthocyanins at 1.3 g/L GAE compared to the control. The cell membrane of E. coli O157:H7 exhibited a significantly increased permeability when treated with proanthocyanidins (0.15 g/L GAE), A&P (0.45 g/L GAE), anthocyanins (0.65 g/L GAE), and TBP (0.14 g/L GAE). TEM confirmed the inactivation and increased membrane permeability of E. coli O157:H7. This study demonstrated the antimicrobial effect of polyphenols from LWB against E. coli O157:H7 and the probable mode of action.
从野生矮蔓越橘（LWB）中提取的多酚化合物的抗菌活性和作用模式对大肠杆菌 O157:H7 进行了研究。使用 80%vol/vol 甲醇从 LWB 中提取多酚，并将其命名为总蓝莓酚（TBP）。该馏分通过 C-18 Sep-Pak 小柱进一步分离为单体酚酸（MPA）和花色苷加原花青素（A&P）。A&P 馏分使用 LH-20 Sephadex 柱进一步分离为花色苷和原花青素。将每个馏分用 0.85%wt/vol NaCl 稀释，接种大肠杆菌 O157:H7 至 8 log 菌落形成单位（CFU）/mL，在 25°C 下孵育 1 h。通过活菌计数法确定酚类馏分中大肠杆菌 O157:H7 的存活菌数。使用 LIVE/DEAD 活力测定法测定大肠杆菌 O157:H7 细胞膜的通透性，并通过透射电子显微镜（TEM）观察损伤情况。在 0.4 g/L 没食子酸当量（GAE）的 MPA、0.9 g/L GAE 的 A&P 和 0.65 g/L GAE 的花色苷时，观察到大肠杆菌 O157:H7 的 5 log CFU/mL 显著减少（p<0.05）。在 0.8 g/L GAE 的 MPA、1.8 g/L GAE 的 A&P 和 1.3 g/L GAE 的花色苷时，与对照组相比，观察到 6-7 CFU/mL 的减少。当用原花青素（0.15 g/L GAE）、A&P（0.45 g/L GAE）、花色苷（0.65 g/L GAE）和 TBP（0.14 g/L GAE）处理时，大肠杆菌 O157:H7 的细胞膜通透性显著增加。TEM 证实了大肠杆菌 O157:H7 的失活和增加的膜通透性。本研究表明，野生矮蔓越橘中的多酚对大肠杆菌 O157:H7 具有抗菌作用，并证实了其可能的作用模式。
