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| Effect of environmental stresses on the survival and cytotoxicity of Shiga toxin-producing Escherichia coli |
| Brian Byongkwon Yoo*,***, Yanhong Liu**, Vijay Juneja*, Lihan Huang*, Cheng-An Hwang* |
| *Residue Chemistry and Predictive Microbiology Research Unit and **Molecular Characterization of Foodborne Pathogens Research Unit, Eastern Regional Research Center, Agricultural Research Service, United States Department of Agriculture, Wyndmoor, Pennsylvania, USA |
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Abstract The objective of this study was to determine the effect of environmental stresses on the cytotoxicity of Shiga toxin-producing Escherichia coli (STEC). STEC O157:H7 and six non-O157 STEC strains (O26:H11, O103:H1, O104:H4, O111:NM, O121:NM, and O145:NM) were subjected to osmotic (aw 0.95–0.98), acid (pH 4–7), and chlorine (1–5 ppm) stresses. After stress treatments, bacterial populations, expression of virulence-associated genes, and Vero-cytotoxicity were determined. Among the strains, O145:NM survived at aw0.97 longer than other serotypes, while O111:NM was significantly more sensitive to osmotic stress. At pH 4, O103:H1 was more resistant to the stress, while O26:H11 and O111:NM had significantly less growth. For 2 ppm chlorine stress, O26:H11, O103:H1, and O145:NM had higher populations (>3log) than other strains. Stressed strains showed a significant increase in relative gene expression levels of stx1, stx2, and eae in O103:H1, O104:H4, and O145:NM than non-stressed control. Additionally, significantly higher Vero-cytotoxicity, as indicated by lactate dehydrogenase assay, of stressed O26:H11, O103:H1, O104:H4, and O145:NM was observed. The results suggest that the growth and cytotoxicity of selected pathogenic E. coli may be enhanced after being exposed to environmental stresses.
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Received: 04 January 2017
Published: 06 July 2017
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Corresponding Authors:
Cheng-An Hwang, Residue Chemistry and Predictive Microbiology Research Unit, Eastern Regional Research Center, Agricultural Research Service, United States Department of Agriculture, 600 East Mermaid Lane,Wyndmoor, PA 19038, USA.
E-mail: andy.hwang@ars.usda.gov
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环境胁迫对产志贺毒素大肠杆菌存活率和细胞毒性的影响
本文的目的是研究环境胁迫作用对产志贺毒素大肠杆菌（STEC）细胞毒性的影响。STEC O157：H7和六个非O157 STEC菌株（O26：H11，O103：H1，O104：H4，O111：NM，O121：NM和O145：NM）在不同渗透压（aw 0.95-0.98），酸（pH 4-7）和氯含量（1-5ppm）下的应激力。环境胁迫处理后，对菌群总数、细胞毒素相关基因的表达和细胞毒性进行了检测分析。在这些菌株中，O145：NM在aw 0.97的存活时间比其他类型大肠杆菌长，而O111：NM对渗透性更敏感。在pH 4时，O103：H1对抗压力更强，而O26：H11和O111：NM增殖速度显著降低。对于2 ppm氯应激，O26：H11，O103：H1和O145：NM比其他菌株具有较高的菌群数（> 3log）。胁迫后的菌株（O103：H1，O104：H4和O145：NM）的基因（stx1，stx2和eae）表达水平显着高于非胁迫对照组。另外，通过乳酸脱氢酶测定所表明的，环境胁迫后的菌株O26：H11，O103：H1，O104：H4和O145：NM的细胞毒性显著提高。结果表明，特定的致病性大肠杆菌在环境胁迫之后其生长和细胞毒性可能被增强。
关键词：
致病性大肠杆菌,
胁迫,
生长,
基因,
细胞毒性
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