Verotoxigenic Escherichia coli Laboratory

Credit: Rocky Mountain Laboratories, NIAID, NIH – NIAID (public domain).

Research Scientist
Alexander Gill, Ph.D.
Bureau of Microbial Hazards, Food Directorate, Health Canada

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Research activity

Escherichia coli are a species of bacteria that is commonly carried by humans and animals. The majority of E. coli do not cause human illness. E. coli strains that do cause illness are known as pathogens and there are several different types of E. coli pathogen. The most significant E. coli pathogen in Canada and North America are verotoxigenic E. coli (VTEC) as they are highly infectious and can cause life-threatening illness which is challenging to treat. VTEC produce the toxin, verotoxin. The terms Shiga toxin producing E. coli (STEC) and enterohemorrhagic E. coli (EHEC) are also used for these pathogens. VTEC infection occurs following ingestion of contaminated food or water. E. coli can be divided into groups call serotypes. The most common serotype of VTEC in North America is E. coli O157:H7, though VTEC of many other serotypes are also responsible for human illnesses.

Research at the VTEC laboratory aims to protect Canadians from VTEC by improving methods for the detection of VTEC and identifying methods for reducing exposure to VTEC. To improve the capability of regulatory and public health authorities to respond to VTEC, we are conducting research to identify markers with which to identify VTEC and to develop methods for the detection and isolation of VTEC from foods.

Due to the difficulty in treating VTEC illnesses, preventing the exposure of Canadians to these pathogens is crucial to reducing their impact. The VTEC Laboratory conducts research to evaluate the effectiveness of technologies to control VTEC and the potential for VTEC to survive in foods during production. The laboratory also collaborates with other federal and provincial food safety partners to investigate food-borne outbreaks of VTEC with the aim of understanding their causes so that similar events can be prevented in the future.

Consumer information on E. coli

Health Canada Regulations

Methods of Analysis

Canadian Food Inspection Agency

Public Health Agency of Canada

International Links

Current research projects

  1. Development of methods for the detection of VTEC in food
    • Escherichia coli are genetically diverse and so the detection of VTEC in samples remains challenging as the sole factor for the differentiation of VTEC from other E. coli is the potential to produce verotoxin (Shiga toxin). The VTEC laboratory conducts research to provide the Government of Canada laboratories with reliable and robust protocols for the detection of VTEC in food samples.
  2. DNA aptamer based detection of verotoxin
    • Isolation of VTEC from samples remains laborious, as individual colonies must be screened for production of verotoxin or the presence of its gene. To address this problem the application of aptamers (synthetic oligonucleotides with binding affinity) for verotoxin is being investigated for application to the detection of verotoxin expression by colonies growing on a solid substrate.
  3. Analysis of VTEC and other microbiota in naturally contaminated foods.
    • To support food safety investigations and to provide information to inform the development of guidance and policy, the VTEC laboratory accepts samples for analysis submitted by food safety partners. Specifically, the VTEC lab conducts analysis on the levels and diversity of bacterial pathogens and other microbiota in food samples, as well as physicochemical properties. The information generated can support understanding of the causes of contamination. It also supports the development of guidance concerning sampling plans, detection methodologies, inactivation strategies, storage conditions, and indicator organisms.
  4. VTEC survival in low moisture foods
    • Reports of VTEC isolation from flour and associated outbreaks indicates that low moisture foods are a potential source of consumer exposure to VTEC. The VTEC laboratory conducts research to determine the potential of VTEC to survive storage in low moisture foods, and to identify factors that effect that potential.
  5. Pathogen inactivation in foods with high pressure processing
    • High pressure processing (HPP) is a non-thermal treatment, which can be applied to foods to inactivate microorganisms by the application of hydrostatic pressure. VTEC Laboratory maintains laboratory scale HPP equipment and conducts research on the inactivation of VTEC and other microbial pathogens in food with this technology.


High Pressure Processing Facility

Recent publications

Google Scholar Profile

ORCiD Profile

Gill, A., Dussault, F., McMahon, T., Petronella, N., Wang, X., Cebelinski, E., Scheutz, F., Weedmark, K., Blais, B., and Carrillo, C. 2022. Characterisation of atypical Shiga toxin gene sequences and description of Stx2j, a new subtype. Journal of Clinical Microbiology. 60(3):e0222921. DOI: 10.1128/jcm.02229-21

Pitino, M.A., Unger, S., Gill, A., McGeer, A.J., Doyen, A., Pouliot, Y., Bazinet, R.P., Kothari, A., Mazzulli, T., Stone, D., and O'Connor, D.L. 2022. High pressure processing inactivates human cytomegalovirus and hepatitis A virus while preserving macronutrients and native lactoferrin in human milk. Innovative Food Science & Emerging Technologies. 75:102891. DOI: 10.1016/j.ifset.2021.102891

Gill, A., McMahon, T., Dussault, F., Jinneman, K., Lindsey, R., Martin, H., Stoneburg, D., Strockbine, N., Wetherington, J., and Feng, P. 2022. Delayed Lactose Utilization among Shiga toxin-producing Escherichia coli of serogroup O121. Food Microbiology. 102:103903. DOI: 10.1016/

McMahon, T., Bastian, J., Alshawa, I., and Gill, A. 2021 PCR primers for screening food for verotoxin-producing Escherichia coli, inclusive of three vt1 and seven vt2 subtypes. Journal of Food Protection. 84(2): s 296–302. DOI: 10.4315/JFP-20-233

Nasheri, N., Doctor, T., Chen, A., Harlow, J., and Gill, A. 2020. Evaluation of high-pressure processing in inactivation of the Hepatitis E Virus. Frontiers in Microbiology. 11:461. DOI: 10.3389/fmicb.2020.00461

Wang, Z., Fang, Y., Zhi, S., Simpson, D., Gill, A., McMullen, L.M., Neumann, N.F., and Gänzle, M.G. 2020. The locus of heat resistance confers resistance to chlorine and other oxidizing chemicals in Escherichia coli. Applied and Environmental Microbiology. 86(4):e02123-19. DOI: 10.1128/AEM.02123-19

Gill, A., McMahon, T., Dussault, F., and Petronella, N. 2020. Shiga toxin-producing Escherichia coli survives storage in wheat flour for two years. Food Microbiology. 87:103380. DOI: 10.1016/

Petronella, N., Kundra, P., Auclair, O., Hébert, K., Rao, M., Kingsley, K., De Bruyne, K. Banerjee, S., Gill, A., Pagotto, F., Tamber, S. and Ronholm, J. 2019. Changes detected in the genome sequences of Escherichia coli, Listeria monocytogenes, Vibrio parahaemolyticus, and Salmonella enterica after serial subculturing. Canadian Journal of Microbiology. DOI: 10.1139/cjm-2019-0235

Devleesschauwer, B., Pires, S.M., Young, I., Gill, A., Majowicz, S.E., and the study team. 2019. Associating sporadic, foodborne illness caused by Shiga toxin-producing Escherichia coli with specific foods: a systematic review and meta-analysis of case-control studies. Epidemiology and Infection. 147:e235. DOI: 10.1017/S0950268819001183

Pires, S.M., Majowicz, S., Gill, A., and Devleesschauwer, B. 2019. Global and regional source attribution of Shiga toxin-producing Escherichia coli infections using analysis of outbreak surveillance data. Epidemiology and Infection. 147:e236. DOI: 10.1017/S095026881900116X

Gill A., Carrillo, C., Hadley, M., Kenwell, R. and Chui, L. 2019. Bacteriological analysis of wheat flour associated with an outbreak of Shiga toxin-producing Escherichia coli O121. Food Microbiology. 82:474-481. DOI: 10.1016/

Gill, A.O., Tamber, S and Yang, X. 2019. Relative response of populations of Escherichia coli and Salmonella enterica to exposure to thermal, alkaline and acidic treatments. International Journal of Food Microbiology. 293:94-101. DOI: 10.1016/j.ijfoodmicro.2019.01.007

Mottawea, W., Duceppe, M-O., Dupras, A.A., Usongo, V., Jeukens, J., Freschi, L., Emond-Rheault, JG., Hamel, J., Kukavica-Ibrulj, I., Boyle, B., Gill, A., Burnett, E., Franz, E., Arya, G., Weadge, J.T., Gruenheid, S., Wiedmann, M., Huang, H., Daigle, F., Moineau, S., Bekal, S., Levesque, R.C., Goodridge, L., and Ogunremi, D. 2018. Salmonella enterica prophage sequence profiles reflect genome diversity and can be used for high discrimination subtyping. Frontiers in Microbiology. DOI: 10.3389/fmicb.2018.00836

Pollari, F., Christidis, T., Pintar, K.D.M., Nesbitt, A., Farber, J., Lavoie, M-C, Gill, A., Kirsch, P., Correa, J.A., and Johnson, R. 2017. Evidence for the benefits of food chain interventions on E. coli O157:H7/NM prevalence in retail ground beef and human disease incidence: a success story. Canadian Journal of Public Health. 108(1):e71-e78. DOI: 10.17269/cjph.108.5655

Gill, A.O. 2017. The importance of bacterial culture to food microbiology in the age of genomics. Frontiers Microbiology. DOI:10.3389/fmicb.2017.00777

Laboratory methods

Blais, B., Martinez, A., Gill, A., McIlwham, S., Mohajer, S., and Gauthier, M. 2014. Isolation and identification of priority verotoxigenic Escherichia coli (VTEC) in foods. MFLP-52, Health Canada Compendium of Analytical Methods, Volume 3


Canadian VTEC network


The federal Verotoxigenic Escherichia coli Network was established jointly by Health Canada, the Canadian Food Inspection Agency, the Public Health Agency of Canada and Agriculture Agri-Food Canada to support collaboration on Canada's food safety objectives regarding VTEC.


The VTEC Network provides a forum for scientists and regulators to share information and perspectives and to coordinate and collaborate on laboratory research.


The shared objectives of VTEC Network participants include:

Contact information

For further information and inquiries contact Dr. Alex Gill at

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