Surveillance and outbreak report Open Access
Like 0


In May 2016, two separate clusters of febrile gastroenteritis caused by were detected by the local health authority in Piedmont, in northern Italy. We carried out epidemiological, microbiological and traceback investigations to identify the source. The people affected were students and staff members from two different schools in two different villages located in the Province of Turin; five of them were hospitalised. The epidemiological investigation identified a cooked beef ham served at the school canteens as the source of the food-borne outbreak. was isolated from the food, the stools of the hospitalised pupils and the environment of the factory producing the cooked beef ham. All isolates except one were serotype 1/2a, shared an indistinguishable PFGE pattern and were 100% identical by whole genome sequencing (WGS). By combining a classical epidemiological approach with both molecular subtyping and WGS techniques, we were able to identify and confirm a gastroenteritis outbreak associated with consumption of sliced cold beef ham.


Article metrics loading...

Loading full text...

Full text loading...



  1. Jordan K, Leong D, Ordònez Alvarez A. Listeria monocytogenes in the food processing Environment. SpringerBriefs in food, health and nutrition. Springer; 2015. p. 3-4.
  2. Ryser ET, Marth EH, editors. Listeria, listeriosis and food safety. 3rd ed. New York: CRC Press; 2007.
  3. Scallan E, Hoekstra RM, Angulo FJ, Tauxe RV, Widdowson MA, Roy SL, et al. Foodborne illness acquired in the United States--major pathogens. Emerg Infect Dis. 2011;17(1):7-15.  https://doi.org/10.3201/eid1701.P11101 
  4. Goulet V, Hebert M, Hedberg C, Laurent E, Vaillant V, De Valk H, et al. Incidence of listeriosis and related mortality among groups at risk of acquiring listeriosis. Clin Infect Dis. 2012;54(5):652-60.  https://doi.org/10.1093/cid/cir902 
  5. Sauders BD, D’Amico DJ. Listeria monocytogenes cross-contamination of cheese: risk throughout the food supply chain. Epidemiol Infect. 2016;144(13):2693-7.  https://doi.org/10.1017/S0950268816001503 
  6. Goulet V, Lepoutre A, Rocourt J, Courtieu A-L, Dehaumont P, Veit P. (Listeriosis epidemic in France. Final assessment and results of the epidemiological survey). Epidemie de listeriose en France. Bilan final et resultats de l’enquete epidemiologique. Bull Epidemiol Hebdomadaire.1993;4:13-4.
  7. StataCorp. Stata/SE version 14.1. College Station: StataCorp LP; 2016. Available from: www.stata.com
  8. Centers for Disease Control and Prevention (CDC). Standard operating procedure for PulseNet PFGE of Listeria monocytogenes. Atlanta: CDC; 2013. Available from: https://www.cdc.gov/pulsenet/pdf/listeria-pfge-protocol-508c.pdf
  9. Afgan E, Baker D, van den Beek M, Blankenberg D, Bouvier D, Čech M, et al. The Galaxy platform for accessible, reproducible and collaborative biomedical analyses: 2016 update. Nucleic Acids Res. 2016;44(W1):W3-10.  https://doi.org/10.1093/nar/gkw343 
  10. Larsen MV, Cosentino S, Rasmussen S, Friis C, Hasman H, Marvig RL, et al. Multilocus sequence typing of total-genome-sequenced bacteria. J Clin Microbiol. 2012;50(4):1355-61.  https://doi.org/10.1128/JCM.06094-11 
  11. Kaas RS, Leekitcharoenphon P, Aarestrup FM, Lund O. Solving the problem of comparing whole bacterial genomes across different sequencing platforms. PLoS One. 2014;9(8):e104984.  https://doi.org/10.1371/journal.pone.0104984 
  12. Leekitcharoenphon P, Kaas RS, Thomsen MCF, Friis C, Rasmussen S, Aarestrup FM. snpTree--a web-server to identify and construct SNP trees from whole genome sequence data. BMC Genomics. 2012;13(Suppl 7):S6.  https://doi.org/10.1186/1471-2164-13-S7-S6 
  13. Goulet V, King LA, Vaillant V, de Valk H. What is the incubation period for listeriosis? BMC Infect Dis. 2013;13(1):11.  https://doi.org/10.1186/1471-2334-13-11 
  14. Norton DM, McCamey MA, Gall KL, Scarlett JM, Boor KJ, Wiedmann M. Molecular studies on the ecology of Listeria monocytogenes in the smoked fish processing industry. Appl Environ Microbiol. 2001;67(1):198-205.  https://doi.org/10.1128/AEM.67.1.198-205.2001 
  15. Nesbakken T, Kapperud G, Caugant DA. Pathways of Listeria monocytogenes contamination in the meat processing industry. Int J Food Microbiol. 1996;31(1-3):161-71.  https://doi.org/10.1016/0168-1605(96)00978-6 
  16. Rørvik LM, Caugant DA, Yndestad M. Contamination pattern of Listeria monocytogenes and other Listeria spp. in a salmon slaughterhouse and smoked salmon processing plant. Int J Food Microbiol. 1995;25(1):19-27.  https://doi.org/10.1016/0168-1605(94)00080-P 
  17. Senczek D, Stephan R, Untermann F. Pulsed-field gel electrophoresis (PFGE) typing of Listeria strains isolated from a meat processing plant over a 2-year period. Int J Food Microbiol. 2000;62(1-2):155-9.  https://doi.org/10.1016/S0168-1605(00)00395-0 
  18. Althaus D, Lehner A, Brisse S, Maury M, Tasara T, Stephan R. Characterization of Listeria monocytogenes strains isolated during 2011-2013 from human infections in Switzerland. Foodborne Pathog Dis. 2014;11(10):753-8.  https://doi.org/10.1089/fpd.2014.1747 
  19. Stephan R, Althaus D, Kiefer S, Lehner A, Hatz C, Schmutz C, et al. Foodborne transmission of Listeria monocytogenes via ready-to-eat salad: A nationwide outbreak in Switzerland, 2013-2014. Food Control. 2015;57:14-7.  https://doi.org/10.1016/j.foodcont.2015.03.034 
  20. Swaminathan B, Gerner-Smidt P. The epidemiology of human listeriosis. Microbes Infect. 2007;9(10):1236-43.  https://doi.org/10.1016/j.micinf.2007.05.011 
  21. Pichler J, Much P, Kasper S, Fretz R, Auer B, Kathan J, et al. An outbreak of febrile gastroenteritis associated with jellied pork contaminated with Listeria monocytogenes. Wien Klin Wochenschr. 2009;121(3-4):149-56.  https://doi.org/10.1007/s00508-009-1137-3 

Data & Media loading...

Submit comment
Comment moderation successfully completed
This is a required field
Please enter a valid email address
Approval was a Success
Invalid data
An Error Occurred
Approval was partially successful, following selected items could not be processed due to error