Induction of Escherichia coli O157:H7 into the viable but non-culturable state by chloraminated water and river water, and subsequent resuscitation

Authors

  • Yanming Liu,

    1. Division of Analytical and Environmental Toxicology, Department of Laboratory Medicine and Pathology, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, Alberta, Canada.
    Search for more papers by this author
  • Chuan Wang,

    1. Division of Analytical and Environmental Toxicology, Department of Laboratory Medicine and Pathology, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, Alberta, Canada.
    Search for more papers by this author
  • Gregory Tyrrell,

    1. Division of Analytical and Environmental Toxicology, Department of Laboratory Medicine and Pathology, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, Alberta, Canada.
    Search for more papers by this author
  • Steve E. Hrudey,

    1. Division of Analytical and Environmental Toxicology, Department of Laboratory Medicine and Pathology, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, Alberta, Canada.
    Search for more papers by this author
  • Xing-Fang Li

    Corresponding authorSearch for more papers by this author

*E-mail: xingfang.li@ualberta.ca; Tel: (+1) 780 492 5094; Fax: (+1) 780 492 7800.

Summary

Induction of culturable Escherichia coli O157:H7 cells into a viable but non-culturable (VBNC) state by chloraminated tap water was carefully investigated; as many as 90% of initial cells entered into a VBNC state within 15 min, compared with 14% in river water within 14 weeks. To understand what specific stresses may induce E. coli O157:H7 into a VBNC state, chloraminated tap water, autoclaved river water, and media with known ingredients (PBS buffer and deionized water) at 4°C or 25°C were used to examine induction efficiency. Chloramination alone, or the combination of starvation with either low temperature or osmotic pressure, induced E. coli O157:H7 into a VBNC state, while starvation alone did not induce the bacteria into a VBNC state within 1.5 years. The mRNA of the rfbE and fliC genes was detected in the 10-month-old VBNC cells induced by river water, confirming the viability of E. coli O157:H7 VBNC cells. The VBNC cells induced by chloraminated water and the 10-month-old VBNC cells induced by river water were first resuscitated using autoinducers produced by E. coli O157:H7 itself in a serum-based medium; the VBNC cells of bovine isolates recovered more efficiently compared with those of clinical isolates. These results demonstrate a potential health risk of VBNC E. coli O157:H7 in environmental water and the utility of monitoring viable E. coli O157:H7 including VBNC cells based on the mRNA of the rfbE and fliC genes.

Ancillary