Viable but non-culturable state and toxin gene expression of enterohemorrhagic Escherichia coli O157 under cryopreservation

Junyan Liu; Rong Zhou; Lin Li; Brian M Peters; Bing Li; Chii-Wann Lin; Tsung-Liang Chuang; Dingqiang Chen; Xihong Zhao; Zhiyong Xiong; Zhenbo Xu; Mark E Shirtliff

doi:10.1016/j.resmic.2016.11.002

Viable but non-culturable state and toxin gene expression of enterohemorrhagic Escherichia coli O157 under cryopreservation

Res Microbiol. 2017 Apr;168(3):188-193. doi: 10.1016/j.resmic.2016.11.002. Epub 2016 Nov 21.

Authors

Junyan Liu¹, Rong Zhou², Lin Li², Brian M Peters³, Bing Li², Chii-Wann Lin⁴, Tsung-Liang Chuang⁴, Dingqiang Chen⁵, Xihong Zhao⁶, Zhiyong Xiong², Zhenbo Xu⁷, Mark E Shirtliff⁸

Affiliations

¹ College of Food Science and Engineering, South China University of Technology, Guangzhou 510640, PR China; Department of Clinical Pharmacy, College of Pharmacy, University of Tennessee Health Sciences Center, Memphis, TN 38163, USA.
² College of Food Science and Engineering, South China University of Technology, Guangzhou 510640, PR China.
³ Department of Clinical Pharmacy, College of Pharmacy, University of Tennessee Health Sciences Center, Memphis, TN 38163, USA.
⁴ Institute of Biomedical Engineering, National Taiwan University, Taipei 10617, Taiwan.
⁵ Department of Laboratory Medicine, First Affiliated Hospital of Guangzhou Medical University, Guangzhou 510120, PR China.
⁶ Key Laboratory for Green Chemical Process of Ministry of Education, Hubei Key Laboratory of Novel Reactor and Green Chemical Technology, School of Chemical Engineering and Pharmacy, Wuhan Institute of Technology, Wuhan 430073, PR China. Electronic address: xhzhao2006@gmail.com.
⁷ College of Food Science and Engineering, South China University of Technology, Guangzhou 510640, PR China; Department of Microbial Pathogenesis, School of Dentistry, University of Maryland, Baltimore, MD 21201, USA. Electronic address: zhenbo.xu@hotmail.com.
⁸ Department of Microbial Pathogenesis, School of Dentistry, University of Maryland, Baltimore, MD 21201, USA.

PMID: 27884785
DOI: 10.1016/j.resmic.2016.11.002

Abstract

As major food-borne pathogens worldwide, Escherichia coli are capable of toxin production directly causing severe human disease. However, routine methods are incapable of detecting viable but non-culturable (VBNC) bacteria in food products and raw materials, leading to false-negative identification. In this study, VBNC E. coli O157 strains were acquired after cryopreservation at -20 °C, with and without freeze-thawing; morphology was observed to be of shorter rod-shape, and toxin expression remained at relatively high levels. PMA-PCR assay for VBNC detection was also validated. Therefore, these results suggest that VBNC E. coli O157 strains may represent a strong threat to public health and food safety.

Keywords: Cryopreservation; E. coli O157; PMA-PCR; Toxin expression; VBNC state.

MeSH terms

Bacterial Toxins / genetics*
Cryopreservation*
Escherichia coli O157 / cytology
Escherichia coli O157 / genetics*
Escherichia coli O157 / isolation & purification
Escherichia coli O157 / physiology*
Food Safety
Humans
Microbial Viability*
Microscopy, Electron, Scanning
Polymerase Chain Reaction

Substances

Bacterial Toxins