Jensen Annette Nygaard, Hansen Sussie Hjort, Baggesen Dorte Lau
Division of Microbiology and Production, National Food Institute, Technical University of Denmark, Kongens Lyngby, Denmark.
Front Microbiol. 2020 Jul 23;11:1613. doi: 10.3389/fmicb.2020.01613. eCollection 2020.
Findings of viable spp., which are important foodborne pathogens, are seemingly not reported in mealworms () for feed and food. Still, the bacterial load of mealworms is naturally high and includes members of the Enterobacteriaceae family to which belong. This indicates that may be able to thrive in mealworms if introduced into the production. Therefore, this study aimed to assess the quantitative level of serovar Typhimurium (ST) in mealworms over a 14-day course after exposure to substrate contaminated with ST levels from 1.7 to 7.4 log CFU/g at start (i.e., day 0). The level of ST found in larvae was below the quantitative detection level (1 or 2 log CFU/g) on day 1 in larvae exposed to contamination levels of 1.7, 3.4, and 3.6 log CFU/g opposed to contamination levels of 5.4, 5.6, and 7.4 log CFU/g, respectively. The maximum level of ST detected in individual 1-g larvae samples was 5.8 log CFU/g, but the level varied among the triplicate samples from each sampling, and the highest average value was 5.3 ± 0.3. Beyond day 7, only larvae exposed to the contamination level of 7.4 log CFU/g were >1.0 log CFU/g in the triplicate samples. However, qualitative testing (10 g) showed the presence of ST in larvae until the end of the experiment on day 14 except for the lowest contamination level of 1.7 log CFU/g. Parallel testing of surface disinfected larvae indicated that some larvae may be ST-positive due to residing on the surface only. Still, any detection of is of concern from a food safety perspective. In substrate with contamination levels below 3.6 log CFU/g, the level of ST was below the quantitative detection limit within a few days. Still, ST was detected until the end of experiment on day 14 except for the lowest contamination level of 1.7 log CFU/g. This study indicates the importance of avoiding introduction of into the production, e.g., via contaminated substrate in order to avoid positive larvae as they remained positive for at least 14 days (except at the lowest contamination level).
对于用作饲料和食品的黄粉虫，重要的食源性病原体——活菌的检测结果似乎未见报道。然而，黄粉虫的细菌载量天然就很高，其中包括属于肠杆菌科的成员。这表明，如果将[病原体名称未给出]引入生产中，它可能能够在黄粉虫体内繁衍。因此，本研究旨在评估在初始（即第0天）暴露于受鼠伤寒沙门氏菌血清型鼠伤寒（ST）污染水平为1.7至7.4 log CFU/g的基质后，14天内黄粉虫体内ST的定量水平。在暴露于1.7、3.4和3.6 log CFU/g污染水平的幼虫中，第1天幼虫体内ST的水平低于定量检测水平（1或2 log CFU/g），而分别对应于5.4、5.6和7.4 log CFU/g的污染水平。在单个1克幼虫样本中检测到的ST最高水平为5.8 log CFU/g，但每次采样的三份重复样本中的水平各不相同，最高平均值为5.3±0.3。在第7天之后，只有暴露于7.4 log CFU/g污染水平的幼虫在三份重复样本中的含量>1.0 log CFU/g。然而，定性检测（10克）显示，除了最低污染水平1.7 log CFU/g外，直到实验第14天结束，幼虫中都存在ST。对表面消毒的幼虫进行的平行检测表明，一些幼虫可能仅因ST存在于表面而呈阳性。不过，从食品安全角度来看，任何ST的检测都令人担忧。在污染水平低于3.6 log CFU/g的基质中，几天内ST的水平就低于定量检测限。然而，除了最低污染水平1.7 log CFU/g外，直到实验第14天结束都能检测到ST。本研究表明避免将[病原体名称未给出]引入生产的重要性，例如通过受污染的基质，以避免幼虫呈阳性，因为它们至少14天内都呈阳性（最低污染水平除外）。
