Listeria Research Laboratory

Research Scientist: Dr. Franco Pagotto

Research Associates: Karine Hébert, Kevin Tyler

Listeria monocytogenes

Research Activity

L. monocytogenes is an organism capable of growing at refrigeration temperatures (psychrotrophic organism) and is of concern in extended shelf life, refrigerated foods. The ability of the organism to grow over a wide temperature range and in the presence or absence of Oxygen (O2), enables it to multiply in many environments. Listeriosis is a generic term for a variety of syndromes caused by L. monocytogenes, which is a problem to the food industry in part due to the ubiquitous nature of the organism.

Our research program in the Listeria area focuses on three major areas that include and combine current and novel methodologies, molecular typing and ready-to-eat food safety. All of these areas are done in support of our policy, risk assessment and standard setting activities and it is being done in support of a Government of Canada policy on management of potential risks from emerging pathogens. Aspects of this work investigate the microbiological safety and control of fresh cut produce. Predictive modelling of the growth of L. monocytogenes (and possibly other foodborne pathogens) is done on fresh-cut fruits, vegetables, sprouts, and other ready-to-eat (or minimally processed) foods.

The Listeria research laboratory also has research projects that aim to address the phenomena of how foodborne pathogens are able to enter the farm-2-fork continuum and cause human illness. Often, as a result of a food process or simply from the journey from the environment to the human host, Listeria must be able to overcome many barriers and challenges. Our laboratory is interested in the actual mechanism(s) for understanding and tracking foodborne pathogens in the food chain continuum. We do this by developing projects that address questions such as how a pathogen is able to grow, adapt and survive in certain foods. Even the study of how certain pathogens are not a problem with foods can be useful in addressing global food safety. We also focus on how a food processing practice affects growth, survival and the "detectability" of a pathogen. Works focussing on these topics help us to answer the "how" and "why" certain pathogens are found in certain foods, and give useful information for the development of non-cultural or even more efficient and improved conventional methods for their detection and isolation.

Research Interests

  1. Ecology, virulence, detection and control of Listeria monocytogenes and other foodborne pathogens in ready-to-eat and minimally processed foods;
  2. Molecular genomics, proteomics and analyte-based diagnostic applications for foodborne pathogens.

Recent Publications

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.

MacLean, L.L., Pagotto, F., Farber, J.M., and Perry, M.B. 2009. The structure of the O-antigen in the endotoxin of the emerging food pathogen Cronobacter (Enterobacter) muytjensii strain 3270. Carbohydrate Research 344: 667-671.

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.

MacLean, L.L., Pagotto, F., Farber, J.M., and Perry, M.B. 2009. Structure of the antigenic repeating pentasaccharide unit of the LPS O-polysaccharide of Cronobacter sakazakii implicated in the Tennessee outbreak. Biochemistry and Cell Biology 87: 459-465.

Mattison, K., Brassard, J., Gagne, M.J., Ward, P., Houde, A., Lessard, L., Simard, C., Shukla, A., Pagotto, F., Jones, T.H., and Trottier, Y.-L. 2009. The feline calicivirus as a sample process control for the detection of food and waterborne RNA viruses. International Journal of Food Microbiology 132: 73-77.

Pagotto, F.J., and Farber, J.M. 2009. Cronobacter spp. (Enterobacter sakazakii): Advice, policy and research in Canada. International Journal of Food Microbiology 136: 238-245.

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.

MacLean, L.L., Vinogradov, E., Pagotto, F., Farber, J.M., and Perry, M.B. 2009. Characterization of the O-antigen in the lipopolysaccharide of Cronobacter (Enterobacter) malonaticus 3267. Biochemistry and Cell Biology 87: 927-932.

Miled-Bennour, R., Ells, T.C., Pagotto, F.J., Farber, J.M., Kérouanton, A., Meheut, T., Colin, P., Joosten, H., Leclercq, A., and Besse, N.G. 2010. Genotypic and phenotypic characterisation of a collection of Cronobacter (Enterobacter sakazakii) isolates. International Journal of Food Microbiology 139: 116-125.

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.

MacLean, L.L., Vinogradov, E., Pagotto, F., Farber, J.M., and Perry, M.B. 2010. The structure of the O-antigen of Cronobacter sakazakii isolate HPB2855 involved in a neonatal infection. Carbohydrate Research 345:1932-1937.

Book Chapters

F. Pagotto, N. Corneau, and J.M. Farber. 2006. Listeria monocytogenes. In H. Riemann and D.O. Cliver (editors.), 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.

Related Links

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 Campylobacter (CAMP) positive; and
  • L. monocytogenes is the only truly recognized human pathogen in the genus, although L. ivanovii and L. seeligeri have been isolated from ill patients.

a) 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; and
  • The disease Listeria causes is associated with a high case fatality rate.

b) 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; and
  • 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.

a) 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; and
  • Gastrointestinal symptoms such as nausea, vomiting and diarrhea may precede more serious forms of listeriosis or can be the only symptoms occurring.

b) Incubation Period

  • Invasive: 1-90 days with a mean of 30 days; and
  • Non-invasive: 11 hours to 7 days with a median of 18 hours.

c) 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; and
  • L. monocytogenes invades these cells and can spread internally from cell to cell, thus avoiding exposure to antibodies.

d) At-risk populations

  • Pregnant women and their fetuses, newborns, recipients of immuno¬suppressive 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; and
  • 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.

e) 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.

f) Diagnostic tests

  • A definitive test includes isolation of Listeria from the blood, Cerebrospinal fluid (CSF), placenta or aborted foetus, or other normally sterile site. Fecal cultures are not very sensitive.

g) Treatment

  • Listeriosis can be treated with antibiotics.
Report a problem or mistake on this page
Please select all that apply:

Thank you for your help!

You will not receive a reply. For enquiries, contact us.

Date modified: