Yersinia enterocolitica
Yersinia enterocolitica has been recognized as an important cause of foodborne disease since the late 1980s. It is found in the general environment as well as the gut of various animals, and is associated more with the temperate regions of the world.
Many foods have been implicated as a vehicle or source of infection. While Y. enterocolitica has been isolated from a wide range of domestic and wild animals and birds as well as from environmental sources, pigs are directly or indirectly the main primary source of the pathogenic serotypes that cause infections in man.
Contaminated food or water is regarded as the main source of human infections and there is a close association with consumption of raw or undercooked pork.
Water vegetables and fresh herbs have been linked to sporadic cases.
Yersinia enterocolitica is a cold tolerant organism and will survive frozen for extended periods and grow at refrigeration temperatures. Growth is slowed below 5ºC. It is not heat resistant and is destroyed by pasteurization 72ºC for 18 seconds.
The organism will most likely come into the kitchen environment on pork and pork products. The following measures are important in controlling this organism in the kitchen environment:
- All pork should be adequately cooked prior to consumption.
- Raw pork should be covered and refrigerated below cooked foods. Any drip should be promptly cleaned up.
- Prevent cross-contamination from raw to cooked foods.
- Ensure that cleaning equipment like sponges and dishcloths are disinfected.
- Wipe up meat juices with disposable paper towels.
- Wash hands thoroughly frequently and particularly after handling raw meats.
Description
Y. enterocolitica are Gram-negative rods or coccibacilli, that is often isolated from clinical specimens such as wounds, faeces, sputum and mesenteric lymph nodes. They have been isolated from animals such as pigs, birds, cats, and dogs, and has been in environmental and food sources, such as ponds, lakes, meats, ice cream, and milk. Most isolates have been found not to be pathogenic. They can survive and grow at temperatures down to 0°C and up to 60°C.
Nature of acute disease
The disease caused by Y. enterocolitica is often referred to as yersiniosis. The cells adhere and colonies the lining of the intestinal tract. In some cases they can spread to the liver, spleen and bloodstream. It is believe that they produce a toxin that is responsible for the illness.
Characteristics of Illness
Y. enterocolitica can cause gastroenteritis mainly in young children, with the most common symptoms being fever, abdominal pain and diarrhoea. In older children the bacteria can cause mesenteric adenitis (pseudoappendicitis). Arthritis and erythemia nosodium have been known to occur in adults.
Illness onset is usually between 24 and 48 hours after ingestion.
Symptoms may last over 1-2 days.
Unknown
Diagnosis of human illness
Yersiniosis can be diagnosed by isolating the organism from the faeces, blood or vomit, and sometimes at the time of appendectomy. Confirmation relies on isolation and biochemical and serological identification of Y. enterocolitica from both the human host and the ingested foodstuff.
Complications
The major complication is the unnecessary performance of appendectomies. Other complications can include bacteraemia (entrance of organisms into the blood stream), in which case the possibility of a disseminating disease may occur. Long term complaints can include persistent joint problems, ankylosing spondylitis, rheumatoid arthritis, insulin-dependent diabetes, nephritis, long standing thyroid disease and neurological disease.
Susceptible individuals
Complications can occur in the very young, the debilitated, the very old and persons undergoing immunosuppressive therapy.
Associated foods
Pathogenic strains of Y. enterocolitica have been isolated from a wide range of food products including pigs and pork, goats, raw milk, cream, meat and meat products, oysters, vegetables, fish and poultry. They have also been isolated from environment sources such as lakes, streams, well water and soil.
Food analysis
Y. enterocolitica can be isolated and presumptively identified using standard cultural techniques in 36 to 48 hours. Confirmation that a strain is pathogenic would require further testing consisting of biochemical and serological tests. See Hocking et al (1997) for more details.
Outbreaks
Y. enterocolitica can cause both sporadic infections and disease outbreaks. In most sporadic infections the cause of the infection is often difficult to investigate, although it is thought that pork products are the likely source. In the USA in 1981 to 1982 gastroenteritis caused by Y. enterocolitica occurred. The food implicated was tofu. Investigations into the manufacturer found that non-chlorinated water was being used. In the USA in 1982 an outbreak associated with the consumption of pasteurised milk occurred. The milk containers used for the milk were found to be the source of contamination.
Further Information
US Food and Drug Administration Bad Bug Book
Literature
- Hocking, A.D. et al. (1997). Foodborne Microorganisms of Public Health Significance. 5th ed. North Sydney. AIFST NSW Branch Food Microbiology Group.
- Doyle, M.P. (1989). Foodborne Bacterial Pathogens. Marcel Dekker; New York.