Yersinia enterocolitica is a nasty food poisoning organism which causes severe illness and is a major issue for refrigerated foods.
Yersinosis And It Symptoms
The organism causes severe intestinal cramps, acute enteritis and gastritis, and various other stomach related issues such as pseudoappendicitis and lymphadenitis. A real problem for any when unfortunate enough to be poisoned by it (Zadernowska et al., 2014). Medically it is called Yersinosis and children are most prone to infection and its severe disease symptoms especially pseudoappendicitis.
The faecal-oral route is the main method by which it is transmitted but contamination from soil, water, even meat is known (Shwimmer et al., 2007). It ranks third in the list of enteropathogens causing disease based on EFSA (European Food Safety Authority) (EFSA, 2013, 2014) data. It is implicated in major outbreaks of food poisoning in the USA particularly.
The Nature Of The Organism
Yersinia is a Gram-negative rod bacterium which belongs to the Enterobacteriaceae family. It is also a facultative anaerobic growing bacterium which is widespread in nature particularly in both wild and domesticated animals. Not all forms of Y. enterocolitica are pathogenic for humans however.
Like many bacteria which cause such intestinal complaints, it binds to the stomach lining especially the intestinal mucosa where it inflicts cellular damage and alters the morphology of the cells in the local vicinity. The result is extreme diarrhoea. The incubation period is about one to five days or though this can be longer and the bacteria can persist in out stools even longer – at least a month !
As a psychotroph, it dominates other bacteria especially under cold or refrigeration conditions. The optimum temperature for growth of Y. enterocolitica is 22–29 °C and can survive at even lower temperatures near the point of freezing. It is usually the case that the majority of pathogens cannot grow competitively at low temperatures but this one is particularly problematic.
Dairy products especially raw milk are most susceptible to contamination and subsequent growth of the micro-organism. Chocolate milk and reconstituted powdered milk seems to be a favourite source too ! Outbreaks have also involved various pork products especially raw pork, salami, turkey and that Chinese dish favourite chow mein, shellfish, unwashed vegetables, liquid egg and some salads. It is especially the case if such products are kept for some time and with the demands for longer shelf-life on such foods, an increasingly persistent issue.
One major issue is cross-contamination in this industry so all equipment, storage and management of a herd is paramount in keeping infection rates as low as possible (Yucel and Ulusoy, 2006). Cases are reported from anywhere with a strong dairy industry – Australia, the UK, Ireland, and the USA. It is often associated with incidents of diarrhoea in Germany, Sweden and Norway for example.
In the last decade there has been a reduction in the reporting of confirmed cases of yersinosis reported by laboratories in England and Wales but not in Scotland.
In 2011 there were just over 7,000 cases of yersinosis with some of the most severe reported in Finland and other Baltic states. One particularly bad case of yersinosis occurred in Norway which was linked to bagged salads. In 2012, it was behind another 12 outbreaks in Europe alone (EFSA, 2013, 2014; Zadernowska et al., 2014).
EFSA. (2013). The European Union summary report on trends and sources of zoonoses, zoonotic agents and food-borne outbreaks in 2011. The EFSA Journal, 11, pp. 4.
EFSA. (2014). The European Union summary report on trends and sources of zoonoses, zoonotic agents and food-borne outbreaks in 2012. The EFSA Journal, 12, pp. 2.
Shwimmer, A., Freed, M., Blum, S., Khatib, N.,Weissblit, L., Friedman, S., Elad, D. (2007) Mastitis caused by Yersinia pseudotuberculosis in Israeli dairy cattle and public health implications. Zoonoses Public Health 547.
Eley, A. (2012) Food Poisoning In: Hygiene For Management. Edt. R.A. Sprenger. Highfield Co.Uk Ltd. pp. 29-51
Yucel, N., Ulusoy, H. (2006). A Turkey survey of hygiene indicator bacteria and Yersinia enterocolitica in raw milk and cheese samples. Food Control, 17, pp. 383–388.
Zadernowska, A., Chajecka-Wierzchowska, W. & Laniewska-Trokenheim, L. (2014) Yersinia enterocolitica: a dangerious, but often ignored, foodborne pathogen. Food Rev. Int. 30 pp. 53-70