National Center for Toxicological Research, US Food and Drug Administration, 3900 NCTR Road, Jefferson, AR 72079, USA.
Division of Food Processing Science & Technology, Center for Food Safety and Applied Nutrition, US Food and Drug Administration, 6502 S. Archer Rd., Bedford Park, IL 60501, USA.
Toxins (Basel). 2022 Aug 15;14(8):554. doi: 10.3390/toxins14080554.
Staphylococcal food poisoning (SFP) is a common food-borne illness often associated with contamination during food handling. The genes for Staphylococcal enterotoxin (SE) isoforms SEA and SEB are frequently detected in human nasal isolates and these toxins are commonly associated with SFP. Past studies described the resistance of preformed SE proteins to heat inactivation and their reactivation upon cooling in foods. Full thermodynamic analyses for these processes have not been reported, however. The thermal stabilities of SEA, SEB, and SEH and reversibility of unfolding in simple buffers were investigated at pH 4.5 and pH 6.8 using differential scanning calorimetry (DSC). SEA and SEB unfolding was irreversible at pH 6.8 and at least partially reversible at pH 4.5 while SEH unfolding was irreversible at pH 4.5 and reversible at pH 6.8. Additional studies showed maximum refolding for SEB at pH 3.5-4.0 and diminished refolding at pH 4.5 with increasing ionic strength. SE-stimulated secretion of interferon-gamma by human peripheral blood mononuclear cells was used to assess residual SE biological activity following heat treatments using conditions matching those used for DSC studies. The biological activities of SEB and SEH exhibited greater resistance to heat inactivation than that of SEA. The residual activities of heat-treated SEB and SEH were measurable but diminished further in the presence of reconstituted nonfat dry milk adjusted to pH 4.5 or pH 6.8. To different extents, the pH and ionic strengths typical for foods influenced the thermal stabilities of SEA, SEB, and SEH and their potentials to renature spontaneously after heat treatments.
葡萄球菌食物中毒（SFP）是一种常见的食源性疾病，通常与食品处理过程中的污染有关。人类鼻腔分离物中经常检测到葡萄球菌肠毒素（SE）同工型 SEA 和 SEB 的基因，这些毒素通常与 SFP 有关。过去的研究描述了预形成的 SE 蛋白对热失活的抗性及其在食品冷却时的重新激活。然而，这些过程的完整热力学分析尚未报道。使用差示扫描量热法（DSC）在 pH 4.5 和 pH 6.8 下研究了 SEA、SEB 和 SEH 的热稳定性以及在简单缓冲液中解折叠的可逆性。SEA 和 SEB 在 pH 6.8 时解折叠不可逆，在 pH 4.5 时至少部分可逆，而 SEH 在 pH 4.5 时解折叠不可逆，在 pH 6.8 时可逆。进一步的研究表明，SEB 的最大折叠在 pH 3.5-4.0 时达到，随着 pH 4.5 下离子强度的增加，折叠减少。使用与 DSC 研究中使用的条件匹配的热处理方法，通过 SE 刺激人外周血单核细胞分泌干扰素-γ来评估 SE 生物活性的残留。SEB 和 SEH 的生物学活性对热失活的抗性大于 SEA。经热处理的 SEB 和 SEH 的残留活性可测量，但在 pH 4.5 或 pH 6.8 下用重组非脂干乳调整后进一步降低。在不同程度上，食品中典型的 pH 值和离子强度影响了 SEA、SEB 和 SEH 的热稳定性及其在热处理后自发复性的潜力。
Zotero 插件
