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Spud's Down to Earth Advice on...YERSINIA ENTEROCOLITICA |
Y. enterocolitica food poisoning (yersiniosis) is most commonly associated with pork products and can involve several symptoms, which vary according to the host and the particular strain of Y. enterocolitica involved. The most common symptom is a gastroenteritis. Other symptoms, not connected with the gastrointestinal tract, may also arise (e.g. septicaemia) which may not necessarily be preceded by gastroenteritis. Although the symptoms can be quite severe, fatalities are rare.
The microorganism is one of the few foodborne pathogens that can grow at refrigeration temperatures i.e. is psychrotrophic.
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Incubation Period, Symptoms & Duration
 Incubation Period
3-7 days
Symptoms
The most common symptoms are gastrointestinal ones i.e.
- abdominal pain
- diarrhoea
- mild fever
- vomiting (as a secondary symptom)
Sometimes (and particularly in adolescents) the abdominal pain may be confined to the lower right hand side of the body and can lead to a mistaken diagnosis of appendicitis.
Complications may include rashes/skin lesions (particularly in women), conjunctivitis, meningitis, and reactive arthritis (2-3% of cases). In the elderly, generalised septicaemia and abscesses in the liver and spleen are more common.
Duration
1 - 3 weeks, although untreated cases can excrete for 2-3 months.
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Source & Spread
Sources/Associated Foods
Y. enterocolitica can be found in a range of environmental sources, including soil, fresh water and the intestinal tract of many animals. Surveys have found the organism (albeit mostly non-pathogenic strains) in foods such as:
- meats (particularly pork)
- milk and dairy products
- poultry
- fish and shellfish
- fruits and vegetables
Those Y. enterocolitica strains most commonly involved in human infection (O3, O5.27, O8 and O9) are carried by pigs. Pigs are therefore thought to be the principal source of human infection, either directly (through raw/cured/undercooked pork) or indirectly through the contamination of other foods by faeces/waste products.
Spread
- Contaminated food
- Contaminated water
- Spread from person to person (via the faecal-oral route)
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Control
- The principal control measure must be the elimination of the microorganism from foods (especially pork and milk), a step that will be achieved by thorough cooking/thermal processing.
- Although refrigeration cannot guarantee the prevention of growth of Y. enterocolitica, it should be used throughout the supply chain as an additional food safety 'hurdle'.
- Prevention of cross contamination of processed, ready-to-eat foods with pork and porcine wastes, as well as human/animal faecal contamination.
- High standards of personal hygiene
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Exclusion/Return to Work Parameters
Cases in risk groups 1- 4 not to return until 48 hours after first normal stool.
[Group 1 - food handlers; Group 2 - health care workers; Group 3 - children under 5 in nurseries etc.; Group 4 - older children and adults who may find it difficult to implement good standards of personal hygiene]
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Additional Information
- Y. enterocolitica is a Gram -ve, non-sporeforming, motile, small, rod-shaped, facultatively anaerobic bacteria.
- In England and Wales between 1981 and 2003 there was an average of 235 cases of yersiniosis per year, with a maximum of 571 in 1989 (HPA website figures, January 2005).
- The incidence of yersiniosis is highest in the very young, the elderly and immuno-suppressed. Illness occurs most commonly in children under seven years old.
- Yersinia spp. have the ability to grow at low temperatures and are well adapted to survive in the environment. Yersiniosis is consequently more common in cooler climates, where it also displays a different seasonal variation from most other foodborne illnesses with a peak of reported cases occurring during the autumn and winter.
- National surveillance indicates that yersiniosis varies geographically. Although it is prevalent in Belgium (where raw pork is eaten commonly) and is the third most common foodborne bacterial infection in Sweden, in England and Wales the number of cases have ranged from 571 in 1989 to only 24 in 2000. Most cases are sporadic.
- The infectious dose is unknown.
Growth Factors
- Minimum Aw: >0.98
- pH range: Min. 4.5 - 9 (tolerant of high pH)
- Optimum pH: 7.0 - 8.0
- Temperature range: 0oC - 41oC i.e. psychrotrophic (able to grow at chill temperatures). It is easily killed by heating.
- Optimum temperature: 25 - 29oC
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