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Methods to assess the effect of meat processing on viability of Toxoplasma gondii: towards replacement of mouse bioassay by in vitro testing.
International Journal for Parasitology ( IF 3.7 ) Pub Date : 2020-04-28 , DOI: 10.1016/j.ijpara.2020.04.001
Marieke Opsteegh 1 , Cecile Dam-Deisz 1 , Paulo de Boer 2 , Stephane DeCraeye 3 , Andrea Faré 4 , Paul Hengeveld 1 , Ruud Luiten 4 , Gereon Schares 5 , Conny van Solt-Smits 6 , Bavo Verhaegen 3 , Theo Verkleij 7 , Joke van der Giessen 1 , Henk J Wisselink 6
Affiliation  

Consumption of meat containing viable tissue cysts is considered one of the main sources of human infection with Toxoplasma gondii. In contrast to fresh meat, raw meat products usually undergo processing, including salting and mixing with other additives such as sodium acetate and sodium lactate, which affects the viability of T. gondii. However, the experiments described in the literature are not always performed in line with the current processing methods applied in industry. It was our goal to study the effect of salting and additives according to the recipes used by industrial producers. Mouse or cat bioassay is the ‘gold standard’ to demonstrate the presence of viable T. gondii. However, it is costly, time consuming and for ethical reasons not preferred for large-scale studies. Therefore, we first aimed to develop an alternative for mouse bioassay that can be used to determine the effect of processing on the viability of T. gondii tissue cysts. The assays studied were (i) a cell culture method to determine the parasite’s ability to multiply, and (ii) a propidium monoazide (PMA) dye-based assay to selectively detect DNA from intact parasites. Processing experiments were performed with minced meat incubated for 20 h with low concentrations of NaCl, sodium lactate and sodium acetate. NaCl appeared to be the most effective ingredient with only one or two out of eight mice infected after inoculation with pepsin-digest of portions processed with 1.0, 1.2 and 1.6% NaCl. Results of preliminary experiments with the PMA-based method were inconsistent and did not sufficiently discriminate between live and dead parasites. In contrast, the cell culture method showed promising results, but further optimization is needed before it can replace or reduce the number of mouse bioassays needed. In future, standardised in vitro methods are necessary to allow more extensive testing of product-specific processing methods, thereby providing a better indication of the risk of T. gondii infection for consumers.



中文翻译:

评估肉加工对弓形虫生存能力影响的方法:通过体外测试替代小鼠生物测定。

食用含有活组织囊肿的肉被认为是人类感染弓形虫的主要来源之一。与新鲜肉类相反,生肉类产品通常经过加工,包括盐腌和与其他添加剂(如乙酸钠和乳酸钠)混合,这会影响弓形虫的生存能力。但是,文献中描述的实验并不总是与当前工业上应用的加工方法相一致的。我们的目标是根据工业生产商使用的配方研究盐分和添加剂的作用。小鼠或猫的生物测定是证明存在可行的弓形虫的“金标准”。但是,它昂贵,费时并且出于伦理原因而不是大规模研究的首选。因此,我们首先旨在开发一种小鼠生物测定的替代方法,该方法可用于确定加工过程对弓形虫生存能力的影响组织囊肿。所研究的测定法是(i)一种细胞培养方法,以确定寄生虫的繁殖能力,以及(ii)基于单叠氮化丙锭(PMA)染料的测定法,用于从完整的寄生虫中选择性检测DNA。将肉末与低浓度的NaCl,乳酸钠和乙酸钠孵育20小时进行加工实验。在用胃蛋白酶消化的1.0%,1.2%和1.6%NaCl处理的部分接种后,八只小鼠中只有一只或两只被感染,氯化钠似乎是最有效的成分。使用基于PMA的方法进行的初步实验的结果不一致,并且不能充分区分活寄生虫和死寄生虫。相比之下,细胞培养方法显示出可喜的结果,但是还需要进一步优化,才能替代或减少所需的小鼠生物检测数量。将来,必须使用标准化的体外方法,以便对特定于产品的加工方法进行更广泛的测试,从而更好地表明患病风险。消费者感染弓形虫

更新日期:2020-04-28
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