University of Alberta, Department of Laboratory Medicine and Pathology, Edmonton, Alberta, Canada.
University of Alberta, Department of Laboratory Medicine and Pathology, Edmonton, Alberta, Canada; Provincial Laboratory for Public Health, Alberta Precision Laboratories, Edmonton, Alberta, Canada.
Food Microbiol. 2020 Jun;88:103400. doi: 10.1016/j.fm.2019.103400. Epub 2019 Dec 11.
The purpose of this study was to identify Escherichia coli isolates obtained from patients experiencing acute gastroenteritis that possess the locus of heat resistance (LHR) and characterize their heat resistance upon exposure to temperatures of 60 °C and 71 °C. From a collection of 613 clinical E. coli strains, 3 heat resistant E. coli isolates were identified. Two of the 3 isolates were stx positive; no isolates possessed stx as determined by qPCR. D-values of heat resistant isolates all exceeded 10.20 min with one isolate's D-values ranging from 20.46 to 72.47 min. The presence of 4% additional NaCl significantly increased D-values of 2 clinical isolates. Cell reductions of heat resistant isolates in ground beef patties grilled to 60 °C and 71 °C remained above 2.8 and 4.9 log CFU/mL, respectively, compared to reductions of 6.1 log CFU/mL and greater in heat sensitive E. coli. Constitutive expression of novel Clp protease ClpK, encoded on open reading frame 3 of the LHR, was identified in all heat resistant isolates by SDS-PAGE and peptide mass fingerprinting. This data is the first to report heat resistant E. coli possessing the LHR involved in clinical infection, highlighting the potential threat of heat resistant enteric pathogens on food safety.
本研究的目的是鉴定从患有急性肠胃炎的患者中获得的具有耐热性基因座（LHR）的大肠杆菌分离株，并在 60°C 和 71°C 下对其耐热性进行表征。从 613 株临床大肠杆菌菌株中，鉴定出 3 株耐热大肠杆菌分离株。这 3 株分离株中有 2 株 stx 阳性；通过 qPCR 确定没有分离株携带 stx。耐热分离株的 D 值均超过 10.20 分钟，其中一株分离株的 D 值范围为 20.46 至 72.47 分钟。4%额外 NaCl 的存在显著增加了 2 株临床分离株的 D 值。与热敏大肠杆菌相比，在 60°C 和 71°C 烤制的碎牛肉饼中，耐热分离株的细胞减少量分别保持在 2.8 log CFU/mL 以上和 4.9 log CFU/mL 以上，而热敏大肠杆菌的细胞减少量大于 6.1 log CFU/mL。通过 SDS-PAGE 和肽质量指纹图谱鉴定，所有耐热分离株均在 LHR 的开放阅读框 3 上编码的新型 Clp 蛋白酶 ClpK 存在组成型表达。该数据首次报道了具有耐热性基因座的耐热性大肠杆菌参与临床感染，突出了耐热性肠道病原体对食品安全的潜在威胁。
