University of Lethbridge, Lethbridge, Alberta, Canada.
Agriculture and Agri-Food Canada, Lacombe, Alberta, Canada.
Appl Environ Microbiol. 2021 Nov 10;87(23):e0112621. doi: 10.1128/AEM.01126-21. Epub 2021 Sep 22.
Despite the importance of biofilm formation in the contamination of meat by pathogenic Escherichia coli at slaughter plants, drivers for biofilm remain unclear. To identify selection pressures for biofilm, we evaluated 745 isolates from cattle and 700 generic E. coli isolates from two beef slaughter plants for motility, the expression of curli and cellulose, and biofilm-forming potential. Cattle isolates were also screened for serogroup, , , , and . Generic E. coli isolates were compared by source (hide of carcass, hide-off carcass, and processing equipment) before and after the implementation of antimicrobial hurdles. The proportion of E. coli isolates capable of forming biofilms was lowest (7.1%; 0.05) for cattle isolates and highest (87.3%; 0.05) from equipment. Only one enterohemorrhagic E. coli (EHEC) isolate was an extremely strong biofilm former, in contrast to 73.4% of E. coli isolates from equipment. Isolates from equipment after sanitation had a greater biofilm-forming capacity (0.001) than those before sanitation. Most cattle isolates were motile and expressed curli, although these traits along with the expression of cellulose and the detection of were not necessary for biofilm formation. In contrast, isolates capable of forming biofilms on equipment were almost exclusively motile and able to express curli. The results of the present study indicate that cattle rarely carry EHEC capable of making strong biofilms in slaughter plants. However, if biofilm-forming EHEC contaminates equipment, current sanitation procedures may not eliminate the most robust biofilm-forming strains. Accordingly, new and effective antibiofilm hurdles for meat-processing equipment are required to reduce future instances of foodborne disease. As the majority of enterohemorrhagic E. coli (EHEC) isolates are not capable of forming biofilms, sources were undetermined for biofilm-forming EHEC isolated from "high-event periods" in beef slaughter plants. This study demonstrated that sanitation procedures used on beef-processing equipment may inadvertently lead to the survival of robust biofilm-forming strains of E. coli. Cattle only rarely carry EHEC capable of forming strong biofilms (1/745 isolates evaluated), but isolates with greater biofilm-forming capacity were more likely (0.001) to survive equipment sanitation. In contrast, chilling carcasses for 3 days at 0°C reduced (0.05) the proportion of biofilm-forming E. coli. Consequently, an additional antibiofilm hurdle for meat-processing equipment, perhaps involving cold exposure, is necessary to further reduce the risk of foodborne disease.
尽管生物膜形成在屠宰场肉品污染致病性大肠杆菌中非常重要，但生物膜形成的驱动因素仍不清楚。为了确定生物膜形成的选择压力，我们评估了来自两个牛肉屠宰场的 745 株牛源和 700 株普通大肠杆菌分离株的运动性、卷曲菌和纤维素的表达以及生物膜形成能力。还对牛源分离株进行了血清群、 、 、 、 筛查。在实施抗菌障碍之前和之后，比较了来自胴体皮、皮屑胴体和加工设备的普通大肠杆菌分离株的来源。能够形成生物膜的大肠杆菌分离株比例最低（7.1%；0.05）来自牛源分离株，最高（87.3%；0.05）来自设备。只有一株肠出血性大肠杆菌（EHEC）分离株是极强的生物膜形成者，而来自设备的 73.4%的大肠杆菌分离株则不是。经过卫生清洁后的设备分离株的生物膜形成能力（0.001）大于卫生清洁前的分离株。大多数牛源分离株是运动的，并且表达卷曲菌，尽管这些特性以及纤维素的表达和 检测不是生物膜形成所必需的。相比之下，能够在设备上形成生物膜的分离株几乎都是运动的，并且能够表达卷曲菌。本研究结果表明，在屠宰场，牛源很少携带能够形成强生物膜的 EHEC。然而，如果形成生物膜的 EHEC 污染了设备，目前的卫生清洁程序可能无法消除最具活力的生物膜形成菌株。因此，需要新的、有效的肉类加工设备抗菌障碍来减少未来食源性疾病的发生。由于大多数肠出血性大肠杆菌（EHEC）分离株不能形成生物膜，因此无法确定在牛肉屠宰场“高发期”分离出的形成生物膜的 EHEC 的来源。本研究表明，在牛肉加工设备上使用的卫生清洁程序可能会无意中导致具有更强生物膜形成能力的大肠杆菌菌株存活下来。牛源很少携带能够形成强生物膜的 EHEC（745 株评估分离株中的 1 株），但具有更高生物膜形成能力的分离株（0.001）更有可能在设备清洁后存活下来。相比之下，将胴体在 0°C 下冷却 3 天（0.05）降低了形成生物膜的 EHEC 的比例。因此，需要对肉类加工设备采取额外的抗菌障碍措施，也许涉及冷暴露，以进一步降低食源性疾病的风险。
