Abstract
As a common foodborne pathogen, Escherichia coli O157:H7 produces toxins causing serious diseases. However, traditional methods failed in detecting E. coli O157:H7 cells in the viable but non-culturable (VBNC) state, which poses a threat to food safety. This study aimed at investigating the formation, control, and detection of the VBNC state of E. coli O157:H7. Three factors including medium, salt, and acid concentrations were selected as a single variation. Orthogonal experiments were designed with three factors and four levels, and 16 experimental schemes were used. The formation of the VBNC state was examined by agar plate counting and LIVE/DEAD® BacLightTM bacterial viability kit with fluorescence microscopy. According to the effects of environmental conditions on the formation of the VBNC state of E. coli O157:H7, the inhibition on VBNC state formation was investigated. In addition, E. coli in the VBNC state in food samples (crystal cake) was detected by propidium monoazide–polymerase chain reaction (PMA-PCR) assays. Acetic acid concentration showed the most impact on VBNC formation of E. coli O157:H7, followed by medium and salt concentration. The addition of 1.0% acetic acid could directly kill E. coli O157:H7 and eliminate its VBNC formation. In crystal cake, 25, 50, or 100% medium with 1.0% acetic acid could inhibit VBNC state formation and kill E. coli O157:H7 within 3 days. The VBNC cell number was reduced by adding 1.0% acetic acid. PMA-PCR assay could be used to detect E. coli VBNC cells in crystal cake with detection limit at 104 CFU/ml. The understanding on the inducing and inhibitory conditions for the VBNC state of E. coli O157:H7 in a typical food system, as well as the development of an efficient VBNC cell detection method might aid in the control of VBNC E. coli O157:H7 cells in the food industry.
Highlights
Escherichia coli is one of the major bacterial contaminants associated with foodborne infections worldwide (Zhao et al, 2010b; Sayad et al, 2016; Bao et al, 2017a,b; Xie et al, 2017a; Liu et al, 2018a,b; Renuka et al, 2018; Xu et al, 2020)
In induction solutions 10 and 13, E. coli O157:H7 cells were able to survive for 33–48 days. These results suggest that the effect of acetic acid concentration on the survival of E. coli O157:H7 is stronger than that of salt concentration
When the acid concentration is 1% in induction solutions 4, 8, 12, and 16, E. coli O157:H7 cells died in 3 days regardless of the medium and salt concentrations
Summary
Escherichia coli is one of the major bacterial contaminants associated with foodborne infections worldwide (Zhao et al, 2010b; Sayad et al, 2016; Bao et al, 2017a,b; Xie et al, 2017a; Liu et al, 2018a,b; Renuka et al, 2018; Xu et al, 2020). E. coli has gradually developed into a health and safety issue of worldwide concern (Xu et al, 2007, 2008a,b, 2011b, 2016a,b; You et al, 2012; Lin et al, 2016; Miao et al, 2016, 2017a,b, 2018; Zhao et al, 2018a,b). E. coli O157:H7, capable of producing Shiga toxin or Shiga-like toxin, can cause hemorrhagic colitis and hemolytic uremic syndrome in human beings (Neil et al, 2012). E. coli O157:H7 is a typical foodborne pathogen, colonizing in food systems and drinking water (Ercumen et al, 2017; Bourely et al, 2018; Zeinhom et al, 2018)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
