Listeriosis Reference Service for Canada

Co-Director/Research Scientist: Dr. Franco Pagotto, Bureau of Microbial Hazards, Health Canada

Co-Director/Research Scientist: Dr. Matt Gilmour, National Microbiology Laboratory, Public Health Agency of Canada

Research Technical Support: Karine Hébert, Kevin Tyler

Major goals of the Listeriosis Reference Service (LRS) include investigation of listeriosis cases and maintenance of a national collection of isolates. The LRS houses a comprehensive molecular epidemiological database of all isolates in Canada for use as a resource for outbreak investigations, research and other microbiological investigations. The pulsed-field gel electrophoresis (PFGE), ribotype and serological profiles (genotypic and phenotypic molecular fingerprints) are being established and stored for clinical, food, environmental, and possibly animal strains of L. monocytogenes. The LRS pursues research activities for investigation and implementation of other molecular methods for characterizing L. monocytogenes isolates. Other molecular-based methods, such as multiple loci variable number of tandem repeats analysis (MLVA) and DNA sequence-based typing schemes are being investigated on selected diversity sets.

The LRS participates in PulseNet Canada for real-time molecular surveillance for listeriosis, and utilizes PFGE typing for outbreak investigations. The molecular epidemiological data, timely coordination and exchange of information is aimed at helping to reduce the incidence of listeriosis in Canada.

Specific Information

1. Name of organism: Listeria monocytogenes

  • Gram positive, non-sporeforming, rod-shaped, demonstrating tumbling motility;
  • Catalase positive, hemolytic on horse or sheep blood agar, and are CAMP positive;
  • L. monocytogenes is the only truly recognized human pathogen in the genus, although L. ivanovii and L. seeligeri have been isolated from ill patients;
    1. Salient features of organism and/or disease
      • Listeria is a psychrotroph and can therefore grow at refrigeration temperatures;
      • Listeria is very widespread in the environment;
      • The organism appears to be slightly more heat tolerant than many vegetative microbes;
      • The disease Listeria causes is associated with a high case fatality rate.
    2. Source of organism
      • Listeriae can be found in soil, sewage, vegetation, stream water and silage;
      • Listeriae are also extremely prevalent in the animal population especially in cattle, sheep and chickens;
      • Human carriers exist in up to 5% of the general population, but much higher in certain groups such as slaughterhouse workers.

2. Disease Characteristics:

Name of Disease: Listeriosis is the disease caused by the organism. There are two forms, invasive and non-invasive. Invasive listeriosis has a case-fatality rate of approximately 20-30% with a hospitalization rate nearing 90%. Non-invasive listeriosis has been termed "febrile gastroenteritis". Listeria does not produce a lethal toxin.

  1. Symptoms (invasive listeriosis)
    • flu-like symptoms such as fever, headache, diarrhoea, vomiting, meningitis, septicaemia, spontaneous abortion in pregnant women.
    Symptoms (non-invasive listeriosis)
    • diarrhoea, fever, muscle pain, headache, and less frequently, abdominal cramps and vomiting;
    • Gastrointestinal symptoms such as nausea, vomiting and diarrhea may precede more serious forms of listeriosis or can be the only symptoms occurring.
  2. Incubation Period
    • Invasive: 1-90 days with a mean of 30 days,
    • Non-invasive: 11 hours to 7 days with a median of 18 hours.
  3. How listeriosis is caused
    • For invasive infections, organisms enter via the oral route and are believed to be taken up by specialized epithelial cells (M cells) in the small intestine and transported to the underlying lymphoid tissue, where they are taken up by macrophages,
    • L. monocytogenes invases these cells and can spread internally from cell to cell, thus avoiding exposure to antibodies.
  4. At-risk populations
    • Pregnant women and their fetuses, newborns, recipients of immunosuppressive or corticosteroid therapy, especially transplant recipients, cancer and AIDS patients, those with diseases such as hepatitis, diabetes and alcoholism and those undergoing long-term hemodialysis,
    • Most healthy individuals rarely develop clinical signs and thus will not become ill from foodborne listeriosis. Febrile gastroenteritis is usually self-limiting and resolves within one to three days
  5. Case-fatality rate
    • Listeria is more likely to cause death than other bacteria that cause food poisoning, i.e., 20-30% of foodborne listeriosis infections in high-risk individuals may be fatal.
  6. f) Diagnostic tests
    • A definitive test includes isolation of Listeria from the blood, cerebral spinal fluid (CSF), placenta or aborted foetus, or other normally sterile site. Fecal cultures are not very sensitive.
  7. Treatment
    • Listeriosis can be treated with antibiotics.

Current Activities

  1. To assist physicians and Provincial Departments of Health when foodborne listeriosis is suspected;
  2. To examine suspect foods and clinical specimens submitted for analysis;
  3. To rapidly alert responsible agencies when commercial foods are involved;
  4. To maintain reference cultures of Listeriae;
  5. To liaise with centres that have similar interests and responsibilities in Canada and abroad.

Academic Associations Collaborations

Adjunct professor
Department of Biochemistry, Microbiology and Immunology
University of Ottawa


Pagotto, F., Ng, L.-K., Clark, C. and Farber, J. 2006. Canadian Listeriosis Reference Service Foodborne Pathogens and Disease 3: 132-137.

Leclair, D., Pagotto, F., Farber, J.M, Cadieux, B. and Austin, J.W. 2006. Comparison of DNA fingerprinting methods for use in investigation of type E botulism outbreaks in the Canadian Arctic. Journal of Clinical Microbiology 44: 1635-1644.

J. Kirkwood, A. Ghetler, J. Sedman, D. Leclair, F. Pagotto, J.W. Austin and A. Ashraf. 2006. Differentiation of Group I and Group II strains of Clostridium botulinum by focal plane array fourier transform infrared spectroscopy. Journal of Food Protection 69: 2377-2383.

D'Aoust, J.-Y., Pagotto F., Akhtar, M., Bussey, J., Cooper, C., McDonald, C., Meymandy, M., and Tyler, K. 2007. Evaluation of the BAX gel and fluorometric systems for the detection of foodborne Salmonella. Journal of Food Protection 70:835-840.

Lyautey, E., Lapen, D.R., Wilkes, G., McCleary, K., Pagotto, F., Tyler, K., Hartmann, A., Piveteau, P., Rieul, A., Robertson, W.J., Medeiros, D.T., Edge, T.A., Gannon, V., and Topp, E. 2007. Distribution and characteristics of Listeria monocytogenes isolated from surface waters of the South Nation River Watershed. Applied and Environmental Microbiology 73:5401-5410.

Lyautey, E., Hartmann, A., Pagotto, F., Tyler, K., Lapen, D.R., Wilkes, G., Piveteau, P., Rieu, A., Robertson, W.J., Medeiros, D.T., Edge, T.A., Gannon, V., and Topp, E. 2007. Characteristics and frequency of detection of fecal Listeria monocytogenes shed by livestock, wildlife, and humans. Canadian Journal of Microbiology 53:1158-1167.

R.F. Lenati, D.L. O'Connor, K.C. Hébert, J.M. Farber, and F.J. Pagotto. 2008. Growth and survival of Enterobacter sakazakii in human breast milk with and without fortifiers as compared to powdered infant formula. International Journal of Food Microbiology 122: 171-179.

Greco, C., Mastronardi, C., Pagotto, F., Mack, D. and Ramirez-Arcos, S. 2008. Assessment of biofilm-forming ability of coagulase-negative staphylococci isolated from contaminated platelet preparations in Canada. Transfusion 48: 969-977.

Pagotto, F., Corneau, N., Mattison, K., and Bidawid, S. 2008. Development of a DNA microarray for the simultaneous detection and genotyping of noroviruses. Journal of Food Protection 71:1434-1441.

Blais, B.W., Martinez-Perez, A., Gauthier, M., Allain, R., Pagotto, F., and Tyler, K. 2008. Development of unique bacterial strains for use as positive controls in the food microbiology testing laboratory. Journal of Food Protection 71: 2301-2306.

G. Palcich, C. de Moraes Gillio, L.C. Aragon-Alegro, F.J.. Pagotto, J.M. Farber, M. Landgraf., and M.T. Destro. 2009. Enterobacter sakazakii in dried-infant formulas and milk kitchens of maternity wards in Sao Paulo, Brazil. Journal of Food Protection 72: 37-42.

Chiarini, E. Tyler, K., Farber, J.M., Pagotto, F., and Destro, M.T. 2009. Listeria monocytogenes in two different poultry facilities: manual and automatic evisceration. Poultry Science 88: 791-797.

Clark, C.G., Farber, J., Pagotto, F., Ciampa, N., Doré, K., Nadon, C., Bernard, K., Ng, L.-K., and the CPHLN. 2009. Surveillance for Listeria monocytogenes and listeriosis, 1995-2004. Epidemiology and Infection 138: 559-572.

Xue, J.Z., Pagotto, F., and Blais, B.W. 2010. Cloth-based hybridization array system for the identification of food-borne Listeria and confirmation of Listeria monocytogenes. Internet Journal of Food Safety 12: 87-94.

Book Chapters

F. Pagotto, N. Corneau, and J.M. Farber. 2006. Listeria monocytogenes. In H. Riemann and D.O. Cliver (eds.), Foodborne infections and intoxications, third edition. Academic Press, pp. 313-340.

F. Pagotto, N. Corneau, C. Scherf, P. Leopold, C. Clark, and J.M. Farber. 2005. Molecular typing and differentiation of foodborne bacterial pathogens. In P.M. Fratamico, A.K. Bhunia, and S.L. Smith (ed.), Foodborne Pathogens: Microbiology and Molecular Biology, Caister Academic Press, pp. 51-75.

J.M. Farber, F. Pagotto and C. Scherf. Incidence and behaviour of Listeria monocytogenes in meat products. Listeria, Listeriosis, and Food Safety, Third Edition, 2007. CRC Press, pp. 503-570.

F.J. Pagotto, R.F. Lenati and J.M. Farber. 2008. Enterobacter sakazakii. In M.P. Doyle and L.R. Beuchat (ed.), Food Microbiology: Fundamentals and Frontiers, 3rd edition, ASM Press, pp. 271-291.

J.M. Farber, F.J. Pagotto and J.-L. Cordier. 2008. Regulatory aspects. In J.M. Farber and S.J. Forsythe (ed.), Enterobacter sakazakii, ASM Press, pp. 235-253.

J.M. Farber, F.J. Pagotto and R. Lenati. 2008. Pathogenicity of Enterobacter sakazakii. In J.M. Farber and S.J. Forsythe (ed.), Enterobacter sakazakii, ASM Press, pp. 127-144.

F. Pagotto and A. Reid. 2009. Emerging methods for bacterial subtyping. In S. Brul, P. Fratamico, and T. McMeekin (ed.) Tracking pathogens in the food chain. Woodhead Publishing Ltd.

Internet links

Related Warnings, Advisories and Recalls

Additional resources

Official Methods

Pagotto, F., Daley, E., Farber, J., and Warburton, D. 2011. MFHPB-30: Isolation of Listeria monocytogenes from all food and environmental samples. Official methods for the microbiological analysis of foods. Compendium of Analytical Methods, volume 2, Health Protection Branch.

Pagotto, F., Corneau, N., Blais, B. and Phillippe L.M. 2011. MFLP-78: Identification of presumptive positive Listeria monocytogenes from foods and environmental samples by the polymerase chain reaction. Official methods for the microbiological analysis of foods. Compendium of Analytical Methods, volume 3 Health Protection Branch.

Warburton, D. Boville, A., Pagotto, F., Daley, E. and Chow, C. 2011. MFHPB-07: The detection of Listeria spp. in foods and environmental samples using Palcam broth. Official methods for the microbiological analysis of foods. Compendium of Analytical Methods, volume 2 Health Protection Branch.

Pagotto, F., Daley, E. Farber, J.M. 2011. MFLP-74: Enumeration of Listeria monocytogenes in foods. Official methods for the microbiological analysis of foods. Compendium of Analytical Methods, volume 3 Health Protection Branch.

Page details

Date modified: