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

Symptoms: 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.

Onset of symptoms: Illness onset is usually between 24 and 48 hours after ingestion.

Duration of symptoms: Symptoms may last over 1-2 days.

Infective Dose: 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

Websites:

Communicable Diseases - Australia

FDA 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.