Strategies are sought to reduce the carriage and dissemination of zoonotic pathogens and antimicrobial-resistant microbes within food-producing animals and their production environment. Thymol (an essential oil) is a potent bactericide in vitro but in vivo efficacy has been inconsistent, largely due to its lipophilicity and absorption, which limits its passage and subsequent availability in the distal gastrointestinal tract. Conjugation of thymol to glucose to form thymol-β-d-glucopyranoside can decrease its absorption, but in vivo passage of effective concentrations to the lower gut remains suboptimal. Considering that contemporary swine diets often contain 5% or more added fat (to increase caloric density and reduce dustiness), we hypothesized that there may be sufficient residual fat in the distal intestinal tract to sequester free or conjugated thymol, thereby limiting the availability and subsequent effectiveness of this biocide. In support of this hypothesis, the anti-Salmonella Typhimurium effects of 6 mM free or conjugated thymol, expressed as log₁₀-fold reductions of colony-forming units (CFU) ml⁻¹, were diminished 90 and 58%, respectively, following 24-h in vitro anaerobic fecal incubation (at 39°C) with 3% added vegetable oil compared to reductions achieved during culture without added oil (6.1 log₁₀ CFU ml⁻¹). The antagonistic effect of vegetable oil and the bactericidal effect of free and conjugated thymol against Escherichia coli K88 tested similarly were diminished 86 and 84%, respectively, compared to reductions achieved in cultures incubated without added vegetable oil (5.7 log₁₀ CFU ml⁻¹). Inclusion of taurine (8 mg/ml), bile acids (0.6 mg/ml), or emulsifiers such as polyoxyethylene-40 stearate (0.2%), Tween 20, or Tween 80 (each at 1%) in the in vitro incubations had little effect on vegetable oil-caused inhibition of free or conjugated thymol. Based on these results, it seems reasonable to suspect that undigested lipid in the distal gut may limit the effectiveness of free or conjugated thymol. Accordingly, additional research is warranted to learn how to overcome obstacles diminishing bactericidal activity of free and conjugated thymol in the lower gastrointestinal tract of food-producing animals.

寻求战略来减少人畜共患病病原体和抗微生物微生物在食用动物及其生产环境中的携带和传播。百里酚（一种精油）是一种有效的杀菌剂体外 但 体内疗效一直不一致，主要是由于其亲脂性和吸收性，这限制了其在远端胃肠道中的通过和随后的可用性。百里酚与葡萄糖结合形成百里酚-β-d-吡喃葡萄糖苷可降低其吸收，但 体内有效浓度传递到下肠道仍然是次优的。考虑到现代猪日粮通常含有 5% 或更多的添加脂肪（以增加热量密度和减少灰尘），我们假设远端肠道中可能有足够的残留脂肪来隔离游离或结合的百里酚，从而限制了可用性和后续这种杀菌剂的有效性。为支持这一假设，反沙门氏菌24 小时后，6 mM 游离或结合百里酚的鼠伤寒杆菌作用（表示为菌落形成单位 (CFU) ml ^{-1 的}log ₁₀倍减少）分别减少 90% 和 58%体外与不添加油的培养过程中实现的减少相比，添加 3% 植物油的厌氧粪便培养（在 39°C 下）（6.1 log ₁₀ CFU ml ^-1）。植物油的拮抗作用及游离和结合百里酚的杀菌作用大肠杆菌与在不添加植物油的情况下培养的培养物中实现的减少（5.7 log ₁₀ CFU ml ^-1）相比，类似地测试的 K88 分别减少了 86% 和 84% 。包含牛磺酸 (8 mg/ml)、胆汁酸 (0.6 mg/ml) 或乳化剂，例如聚氧乙烯-40 硬脂酸酯 (0.2%)、吐温 20 或吐温 80（各为 1%）体外孵育对植物油引起的游离或结合百里酚的抑制作用很小。基于这些结果，怀疑远端肠道中未消化的脂质可能会限制游离或结合百里酚的有效性似乎是合理的。因此，需要进一步研究以了解如何克服降低食品动物下胃肠道中游离和结合百里酚杀菌活性的障碍。