Department of Pathology, National Taiwan University Hospital Yunlin Branch, Yunlin, Taiwan.
School of Pharmacy, China Medical University, Taichung, Taiwan.
Acta Parasitol. 2024 Sep;69(3):1471-1479. doi: 10.1007/s11686-024-00871-6. Epub 2024 Aug 17.
The formalin-ethyl acetate (FEA) concentration method is commonly used in routine clinical practice to detect parasite eggs in feces. This procedure involves extraction of oil with the organic solvent ethyl acetate (EA), which reduces fecal sediment and provides a cleaner background for microscopic analysis. However, clinically, some sediment failed to float after EA treatment.
Hexane, commonly used in the food oil extraction from oilseeds did not float the feces. Gas chromatography-mass spectrometry (GC-MS) analysis showed that neither the amount of the oil nor the classes of the oil determined was differed whether hexane or EA was used to float the feces. Oil red, Bodipy and Calcofluor staining showed that the unabsorbed oil droplets in the fecal sediment were trapped within the leaf structure. HCl or acetic acid was added to see if the acid residue could dissolve the cellulose of the leaf to promote the bulk float.
Our result showed that the fecal bulk contained the loosened mesophyll cell wall. The addition of acid residues improved fecal bulk float. The proximity of cellulose fiber to EA, but not hexane, may enhance the efficacy of oil extraction from cellulose.
This is the first report that the interaction of cellulose with ethyl acetate in fecal solution has an effect on bulk float. This study improves the understanding of fecal bulk flotation and may assist in the visualization of parasite eggs in clinical practice with non-floating fecal samples in the FEA concentration method.
福尔马林-乙酸乙酯（FEA）浓度法常用于常规临床实践中检测粪便中的寄生虫卵。该方法通过用有机溶剂乙酸乙酯（EA）提取油脂，从而减少粪便沉淀物，并为显微镜分析提供更清洁的背景。然而，临床上有些沉淀物在用 EA 处理后仍未能漂浮。
己烷常用于从油籽中提取食用油，但不能使粪便漂浮。气相色谱-质谱（GC-MS）分析表明，无论使用己烷还是 EA 来使粪便漂浮，油的数量和油的种类都没有差异。油红、Bodipy 和 Calcofluor 染色表明，粪便沉淀物中未被吸收的油滴被困在叶结构内。添加盐酸或乙酸，观察酸残留是否能溶解叶纤维素以促进整体漂浮。
我们的结果表明，粪便的大块中含有疏松的叶肉细胞壁。酸残留的添加提高了粪便的整体漂浮效果。纤维素纤维与 EA 的接近程度，而不是己烷，可能增强了从纤维素中提取油脂的效果。
这是首次报道粪便溶液中的纤维素与乙酸乙酯之间的相互作用对整体漂浮有影响。本研究提高了对粪便整体漂浮的理解，并可能有助于在 FEA 浓度法中可视化临床实践中用非漂浮粪便样本检测寄生虫卵。
