Department of Biological Sciences, Clemson University, Clemson University, Clemson, SC, USA.
J Appl Microbiol. 2012 May;112(5):927-35. doi: 10.1111/j.1365-2672.2012.05268.x. Epub 2012 Mar 29.
The purpose of this study was to determine the effect of moisture on thermal inactivation of Salmonella spp. in poultry litter under optimal composting conditions.
Thermal inactivation of Salmonella was studied in fresh poultry compost by simulating early phase of composting process. A mixture of three Salmonella serotypes grown in Tryptic soy broth with rifampin (TSB-R) was inoculated in fresh compost with 40 or 50% moisture at a final concentration of c. 7 log CFU g(-1). The inoculated compost was kept in an environmental chamber which was programmed to rise from room temperature to target composting temperatures in 2 days. In poultry compost with optimal moisture content (50%), Salmonella spp. survived for 96, 72 and 24 h at 50, 55 and 60°C, respectively, as compared with 264, 144 and 72 h at 50, 55 and 60°C, respectively, in compost with suboptimal moisture (40%). Pathogen decline was faster during the come-up time owing to higher ammonia volatilization.
Our results demonstrated that Salmonella spp. survived longer in fresh poultry compost with suboptimal moisture of 40% than in compost with optimal moisture of 50% during thermophilic composting. High nitrogen content of the poultry compost is an additional factor contributing to Salmonella inactivation through ammonia volatilization during thermal exposure.
This research validated the effectiveness of the current composting guidelines on Salmonella inactivation in fresh poultry compost. Both initial moisture level and ammonia volatilization are important factors affecting microbiological safety and quality of compost product.
本研究旨在确定在最佳堆肥条件下，水分对禽类粪便中沙门氏菌热失活的影响。
通过模拟堆肥过程的早期阶段，研究了新鲜禽类堆肥中沙门氏菌的热失活情况。在含有终浓度约为 7 log CFU g(-1) 的 rifampin（TSB-R）的 Tryptic soy 肉汤中生长的三种沙门氏菌血清型的混合物接种到新鲜堆肥中，初始水分含量分别为 40%或 50%。接种后的堆肥被放置在环境室中，该环境室编程为在 2 天内从室温升高到目标堆肥温度。在最佳水分含量（50%）的禽类堆肥中，沙门氏菌在 50°C、55°C 和 60°C 下分别存活 96、72 和 24 h，而在水分含量较低（40%）的堆肥中，沙门氏菌分别存活 264、144 和 72 h。由于氨挥发较高，在升温阶段，病原体的下降速度更快。
我们的结果表明，在热嗜温堆肥过程中，沙门氏菌在水分含量为 40%的新鲜禽类堆肥中比在水分含量为 50%的堆肥中存活时间更长。禽类堆肥中的高氮含量是通过热暴露期间氨挥发导致沙门氏菌失活的另一个因素。
本研究验证了当前堆肥指南在新鲜禽类堆肥中对沙门氏菌失活的有效性。初始水分水平和氨挥发是影响堆肥产品微生物安全性和质量的重要因素。
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