Levent G, Harvey R B, Ciftcioglu G, Beier R C, Genovese K J, He H L, Anderson R C, Nisbet D J
Food and Feed Safety Research Unit, Agricultural Research Service, U.S. Department of Agriculture, 2881 F&B Road, College Station, Texas 77845, USA; Department of Food Hygiene and Technology, Faculty of Veterinary Medicine, Istanbul University, 34320 Istanbul, Turkey.
Food and Feed Safety Research Unit, Agricultural Research Service, U.S. Department of Agriculture, 2881 F&B Road, College Station, Texas 77845, USA.
J Food Prot. 2016 Feb;79(2):299-303. doi: 10.4315/0362-028X.JFP-15-360.
Although thymol is bactericidal against many pathogens in vitro, its in vivo effectiveness against pathogens in the lower gastrointestinal tract is limited because of its rapid absorption in the proximal gut. Thymol-β-D-glucopyranoside (β-thymol), a conjugated form of thymol, can deliver thymol to the lower gastrointestinal tract and has shown antibacterial effects. In the present study, we examined the in vitro effects of β-thymol on Salmonella enterica serovar Typhimurium (ST) and Escherichia coli K88 (K88). We inoculated one-half strength Mueller-Hinton broth with 5.8 ± 0.09 log CFU/ml novobiocin- and naladixic acid-resistant (NN) ST (NVSL 95-1776) and 5.1 ± 0.09 log CFU ml(-1) NN-resistant K88, with or without porcine feces (0.1% [wt/vol]) (fecal incubations). The resultant bacterial suspensions were distributed under N2 to triplicate sets of tubes to achieve initial concentrations of 0, 3, 6, and 12 mM for ST treatments and 0, 3, 12, and 30 mM for K88 treatments. Samples were incubated at 39°C and then plated onto NN-containing brilliant green agar and NN-containing MacConkey agar; ST and K88 CFU concentrations were determined via 10-fold dilutions, and viable cell counts were performed at 0, 6, and 24 h. No differences in ST CFU counts were observed in β-thymol-treated tubes without the added porcine feces (i.e., pure culture) at 6 or 24 h. However, in tubes that contained fecal incubations, ST CFU counts were reduced (P < 0.05) from controls at 6 h in tubes treated with 6 and 12 mM β-thymol, whereas in tubes treated with 3, 6, and 12 mM β-thymol the CFU counts were reduced (P < 0.05) at 24 h. No differences were observed in K88 CFU counts in pure culture or in fecal incubations at 6 h, but K88 CFU counts were reduced (P < 0.05) in both pure and fecal incubations at 24 h. The results from this study demonstrate that β-thymol, in the presence of fecal suspensions, has anti-Salmonella and anti-E. coli effects, suggesting a role of β-glycoside-hydrolyzing microbes for the release of bactericidal thymol from β-thymol.
尽管百里酚在体外对许多病原体具有杀菌作用，但其在体内对下消化道病原体的有效性有限，因为它在近端肠道吸收迅速。百里酚-β-D-吡喃葡萄糖苷（β-百里酚）是百里酚的一种共轭形式，可将百里酚输送到下消化道，并已显示出抗菌作用。在本研究中，我们检测了β-百里酚对肠炎沙门氏菌鼠伤寒血清型（ST）和大肠杆菌K88（K88）的体外作用。我们用5.8±0.09 log CFU/ml的新生霉素和萘啶酸抗性（NN）ST（NVSL 95-1776）以及5.1±0.09 log CFU ml-1的NN抗性K88接种半强度的穆勒-欣顿肉汤，添加或不添加猪粪（0.1%[重量/体积]）（粪便培养）。将所得细菌悬液在N2下分配到一式三份的试管中，使ST处理的初始浓度为0、3、6和12 mM，K88处理的初始浓度为0、3、12和30 mM。样品在39°C下孵育，然后接种到含NN的亮绿琼脂和含NN的麦康凯琼脂上；通过10倍稀释测定ST和K88的CFU浓度，并在0、6和24小时进行活菌计数。在6或24小时时，在不添加猪粪的β-百里酚处理试管（即纯培养）中未观察到ST CFU计数的差异。然而，在含有粪便培养物的试管中，在用6和12 mM β-百里酚处理的试管中，6小时时ST CFU计数相对于对照降低（P<0.05），而在用3、6和12 mM β-百里酚处理的试管中，24小时时CFU计数降低（P<0.05）。在6小时时，纯培养或粪便培养中的K88 CFU计数均未观察到差异，但在24小时时，纯培养和粪便培养中的K88 CFU计数均降低（P<0.05）。本研究结果表明，在粪便悬液存在下，β-百里酚具有抗沙门氏菌和抗大肠杆菌的作用，提示β-糖苷水解微生物在从β-百里酚释放杀菌性百里酚中发挥作用。
