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首页> 外文期刊>Applied Microbiology >Locus of Heat Resistance (LHR) in Meat-Borne Escherichia coli: Screening and Genetic Characterization
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Locus of Heat Resistance (LHR) in Meat-Borne Escherichia coli: Screening and Genetic Characterization

机译：耐热性（LHR）的岩石座（LHR）在肉类大肠杆菌中：筛选和遗传表征

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Microbial resistance to processing treatments poses a food safety concern, as treatment tolerant pathogens can emerge. Occasional foodborne outbreaks caused by pathogenic Escherichia coli have led to human and economic losses. Therefore, this study screened for the extreme heat resistance (XHR) phenotype as well as one known genetic marker, the locus of heat resistance (LHR), in 4,123 E. coli isolates from diverse meat animals at different processing stages. The prevalences of XHR and LHR among the meat-borne E. coli were found to be 10.3% and 11.4%, respectively, with 19% agreement between the two. Finished meat products showed the highest LHR prevalence (24.3%) compared to other processing stages (0 to 0.6%). None of the LHR~(+) E. coli in this study would be considered pathogens based on screening for virulence genes. Four high-quality genomes were generated by whole-genome sequencing of representative LHR~(+) isolates. Nine horizontally acquired LHRs were identified and characterized, four plasmid-borne and five chromosomal. Nine newly identified LHRs belong to ClpK1 LHR or ClpK2 LHR variants sharing 61 to 68% nucleotide sequence identity, while one LHR appears to be a hybrid. Our observations suggest positive correlation between the number of LHR regions present in isolates and the extent of heat resistance. The isolate exhibiting the highest degree of heat resistance possessed four LHRs belonging to three different variant groups. Maintenance of as many as four LHRs in a single genome emphasizes the benefits of the LHR in bacterial physiology and stress response.IMPORTANCE Currently, a “multiple-hurdle” approach based on a combination of different antimicrobial interventions, including heat, is being utilized during meat processing to control the burden of spoilage and pathogenic bacteria. Our recent study (M. Guragain, G. E. Smith, D. A. King, and J. M. Bosilevac, J Food Prot 83:1438–1443, 2020, https://doi.org/10.4315/JFP-20-103) suggests that U.S. beef cattle harbor Escherichia coli that possess the locus of heat resistance (LHR). LHR seemingly contributes to the global stress tolerance in bacteria and hence poses a food safety concern. Therefore, it is important to understand the distribution of the LHRs among meat-borne bacteria identified at different stages of different meat processing systems. Complete genome sequencing and comparative analysis of selected heat-resistant bacteria provide a clearer understanding of stress and heat resistance mechanisms. Further, sequencing data may offer a platform to gain further insights into the genetic background that provides optimal bacterial tolerance against heat and other processing treatments.
机译：微生物抗加工治疗造成食品安全问题，因为耐受性病原体可以出现。偶尔是由致病大肠杆菌引起的食源性爆发导致人类和经济损失。因此，该研究筛查了极端耐热性（XHR）表型以及一种已知的遗传标记，耐热性（LHR）的轨迹，在不同加工阶段的不同肉类动物中的4,123大肠杆菌分离物中。肉类大肠杆菌中XHR和LHR的普及分别为10.3％和11.4％，两者之间的协议19％。成品肉类产品显示出最高的LHR流行率（24.3％）与其他加工阶段相比（0至0.6％）。本研究中没有LHR〜（+）大肠杆菌将被认为是基于毒力基因的筛选的病原体。通过代表性LHR〜（+）分离株的全基因组测序产生了四种高质量基因组。鉴定了九个水平获得的LHRS，其特征是，四种质粒和五种染色体。九个新发现的LHRS属于CLPK1 LHR或CLPK2 LHR变体，共用61至68％的核苷酸序列标识，而一个LHR似乎是混合动力。我们的观察结果表明分离物中存在的LHR区域数量与耐热程度之间的正相关。表现出最高程度的耐热性的分离物具有属于三种不同的变体组的四个LHR。在单个基因组中维持多达四个LHRS强调LHR在细菌生理学和应激反应中的益处。目前，正在利用基于不同抗微生物干预（包括热量的组合）的“多跨障碍”方法正在利用肉类加工，以控制腐败和致病细菌的负担。我们最近的研究（M. Guragain，Ge Smith，Da King和JM Bosilevac，J Food Plot 83：1438-1443,2020，HTTPS://Do.org/103）表明美国牛肉牛港口大肠杆菌，具有耐热性（LHR）的轨迹。 LHR看似有助于细菌的全球压力耐受性，因此提出了食品安全问题。因此，重要的是要理解不同肉类加工系统的不同阶段鉴定的肉类细菌中LHR的分布。完全基因组测序和对选定的耐热细菌的比较分析提供了更清楚地了解应力和耐热机制。此外，测序数据可以提供一个平台，以进一步深入了解遗传背景，该遗传背景提供了针对热和其他加工处理的最佳细菌容差。

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