[论文解读] Survival of Salmonella spp. in Composting using Vial and Direct Inoculums Technique

Sunar, N. M., Douglas I. Stewart+2 more|arXiv (Cornell University)|Apr 21, 2014

Composting and Vermicomposting Techniques参考文献 17被引用 5

一句话总结

本研究比较了直接接种与试管接种两种方法在实验室规模堆肥过程中评估沙门氏菌属存活率的差异。结果表明，在55–60°C条件下，直接接种组在8天内即实现完全灭活，符合英国PAS 100标准；而试管接种组在20天后仍保持较高病原体水平，凸显了病原体与堆肥物料直接接触在病原体灭活过程中的关键作用。

ABSTRACT

The survival of Salmonella spp. as pathogen indicator in composting was studied. The inoculums technique was used to gives the known amounts of Salmonella spp. involved in composting. The inoculums of Salmonella spp. solution was added directly into the compost material. The direct inoculum was compared with inoculums in vial technique. The Salmonella spp. solution placed into a vial and inserted into the middle of compost material before starting the composting process. The conventional method that is used for the enumeration of Salmonella spp. is serial dilution followed by standard membrane filtration as recommended in the compost quality standard method PAS 100 and the British Standard (BS EN ISO 6579:2002). This study was designed to investigate the relationship of temperature and contact material that may also involve in pathogen activation specifically to Salmonella spp. The exposure to an average temperature during composting of about 55-60°C was kept for at least 3 days as it was reported sufficiently kills the vast majority of enteric pathogen (Deportes et al., 1995). The amount of Salmonella spp. and temperature for both samples was set as indicator to determine the survival of Salmonella spp. in direct and non-direct inoculums. This study gives the figures of die-off rate for Salmonella spp. during composting. The differentiation between direct contact (Sample A) and non-contact of Salmonella spp. with compost material (Sample B) during composting was also revealed. The results from laboratory scale of composting study has been showed that after 8 days (which included at least at 66°C) the numbers of Salmonella spp. in Sample A were below the limits in UK compost standard (known as PAS 100)(BSI, 2005) which required the compost to be free of Salmonella spp. Meanwhile, Sample B still gives high amount of Salmonella spp. in even after composting for 20 days.

研究动机与目标

• 评估接种方法对沙门氏菌属在堆肥过程中存活率的影响。
• 评估温度及病原体与堆肥物料之间的物理接触对病原体灭活的影响。
• 比较直接接种与试管接种技术在病原体持续存活方面的差异。
• 确定符合PAS 100标准的堆肥条件是否能在不同接种方案下有效灭活沙门氏菌属。

提出的方法

• 沙门氏菌属被直接接种至堆肥物料中（样品A），或通过插入堆肥中的试管引入（样品B）。
• 堆肥过程在受控的实验室条件下进行，温度持续监测。
• 病原体计数采用系列稀释法与标准膜过滤法，符合PAS 100及BS EN ISO 6579:2002标准。
• 温度曲线维持在55–60°C至少三天，符合既定的病原体灭活阈值。
• 在20天内定期取样，评估灭活速率。
• 灭活速率基于沙门氏菌计数随时间的log10减少量计算。

实验结果

研究问题

• RQ1 在堆肥过程中，沙门氏菌属直接接种至堆肥与试管接种相比，其病原体存活率有何差异？
• RQ2 在嗜热条件下，沙门氏菌与堆肥物料之间的物理接触在多大程度上影响灭活速率？
• RQ3 在55–60°C下持续堆肥至少三天，是否能实现两种接种方法中沙门氏菌属的完全灭活？
• RQ4 为何试管接种组在20天后仍保持较高沙门氏菌水平，而直接接种组则显著降低？
• RQ5 这些发现对标准堆肥质量检测及病原体指示物可靠性有何启示？

主要发现

• 在55–60°C下堆肥8天后，直接接种组（样品A）的沙门氏菌属水平降至英国PAS 100标准要求的检测限以下。
• 相比之下，试管接种组（样品B）在堆肥20天后仍表现出较高的沙门氏菌属水平。
• 沙门氏菌与堆肥物料的直接接触显著加快了灭活速度，而试管法中病原体被隔离，灭活效果较差。
• 本研究证实，当发生直接接触时，持续维持55–60°C至少三天的温度条件可有效灭活沙门氏菌属。
• 试管法可能因与堆肥基质的相互作用有限，导致对病原体灭活效果的低估，从而可能高估病原体存活率。
• 这些结果表明，接种方法对病原体灭活结果具有决定性影响，必须在堆肥质量检测方案中予以充分考虑。