Department of Food Science and Technology, The Ohio State University, Columbus, OH, United States.
Botany and Microbiology Department, Faculty of Science, Benha University, Benha, Egypt.
Front Cell Infect Microbiol. 2022 Jun 14;12:903979. doi: 10.3389/fcimb.2022.903979. eCollection 2022.
Contribution of food vehicles to pathogenicity of disease-causing microorganisms is an important but overlooked research field. The current study was initiated to reveal the relationship between virulence of serovar Enteritidis and egg yolk as a hosting medium. Mice were orally challenged with Enteritidis cultured in egg yolk or tryptic soy broth (TSB). Additionally, mice were challenged with Enteritidis cultured in TSB, followed by administration of sterile egg yolk, to discern the difference between pre-growth of the pathogen and its mere presence in egg yolk during infection. The pathogen's Lethal dose 50 (LD) was the lowest when grown in yolk (2.8×10 CFU), compared to 1.1×10 CFU in TSB, and 4.6×10 CFU in TSB followed by administration of sterile yolk. Additionally, mice that orally received Enteritidis grown in egg yolk expressed a high death rate. These findings were supported by transcriptional analysis results. Expression of promoters of virulence-related genes ( and ) in genetically modified Enteritidis reporter strains was significantly higher ( < 0.05) when the bacterium was grown in the yolk, compared to that grown in TSB. Sequencing of RNA (RNA-seq) revealed 204 differentially transcribed genes in Enteritidis grown in yolk . TSB. Yolk-grown Enteritidis exhibited upregulated virulence pathways, including type III secretion systems, epithelial cell invasion, and infection processes; these observations were confirmed by RT-qPCR results. The transcriptomic analysis suggested that upregulation of virulence machinery of Enteritidis grown in egg yolk was related to increased iron uptake, biotin utilization, flagellar biosynthesis, and export of virulence proteins encoded on pathogenicity island 1, 2, 4, and 5. These biological responses may have acted in concert to increase the virulence of infection in mice. In conclusion, growth in egg yolk enhanced Enteritidis virulence, indicating the significance of this food vehicle to the risk assessment of salmonellosis.
食物载体对致病菌致病性的贡献是一个重要但被忽视的研究领域。本研究旨在揭示肠炎沙门氏菌血清型毒力与卵黄作为宿主介质之间的关系。通过口服感染卵黄或胰蛋白酶大豆肉汤（TSB）培养的肠炎沙门氏菌，以及在 TSB 中培养肠炎沙门氏菌后给予无菌卵黄来挑战小鼠，以区分病原体的预生长和感染期间卵黄中的单纯存在之间的差异。与在 TSB 中生长的病原体（1.1×10 CFU）相比，在卵黄中生长的病原体的半数致死剂量（LD）最低（2.8×10 CFU），在 TSB 中生长后给予无菌卵黄的病原体 LD 为 4.6×10 CFU。此外，口服接受在卵黄中生长的肠炎沙门氏菌的小鼠死亡率很高。这些发现得到了转录分析结果的支持。与在 TSB 中生长的细菌相比，在遗传修饰的肠炎沙门氏菌报告株中，与毒力相关基因（ 和 ）启动子的表达显著更高（<0.05）。在卵黄中生长的肠炎沙门氏菌 RNA（RNA-seq）的测序显示 204 个差异转录基因。与在 TSB 中生长的细菌相比，在卵黄中生长的肠炎沙门氏菌表现出上调的毒力途径，包括 III 型分泌系统、上皮细胞侵袭和感染过程；这些观察结果通过 RT-qPCR 结果得到证实。转录组分析表明，卵黄中生长的肠炎沙门氏菌毒力机制的上调与铁摄取、生物素利用、鞭毛生物合成和编码在致病性岛 1、2、4 和 5 上的毒力蛋白的外排有关。这些生物学反应可能协同作用，增加肠炎沙门氏菌感染小鼠的毒力。总之，卵黄中的生长增强了肠炎沙门氏菌的毒力，表明这种食物载体对肠炎沙门氏菌病风险评估的重要性。
