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Y. enterocolitica , a small rod-shaped, Gram-negative bacterium, is often isolated from clinical specimens such as wounds, faeces, sputum and mesenteric lymph nodes. However, it is not part of the normal human flora. Y. pseudotuberculosis has been isolated from the diseased appendix of humans.
Both organisms have often been isolated from such animals as pigs, birds, beavers, cats, and dogs. Only Y. enterocolitica has been detected in environmental and food sources, such as ponds, lakes, meats, ice cream, and milk. Most isolates have been found not to be pathogenic.
The name of the disease is Yersiniosis.
There are 3 pathogenic species in the genus Yersinia , but only Y. enterocolitica and Y. pseudotuberculosis cause gastroenteritis. To date, very few food borne outbreaks caused by Y. pseudotuberculosis have been reported, human infections transmitted via contaminated water and foods have been reported in Japan.
Yersiniosis is frequently characterized by such symptoms as gastroenteritis with diarrhoea and/or vomiting; however, fever and abdominal pain are the hallmark symptoms. Yersinia infections mimic appendicitis and mesenteric lymphadenitis, but the bacteria may also cause infections of other sites such as wounds, joints and the urinary tract.
Infective dose is unknown.
Illness onset is usually between 24 and 48 hours after ingestion, which (with food or drink as vehicle) is the usual route of infection.
Diagnosis of yersiniosis begins with isolation of the organism from the human host's faeces, blood, or vomit, and sometimes at the time of appendectomy. Confirmation occurs with the isolation, as well as biochemical and serological identification, of Y. enterocolitica from both the human host and the ingested foodstuff. Diarrhoea is reported to occur in about 80% of cases; abdominal pain and fever are the most reliable symptoms.
Because of the difficulties in isolating yersiniae from faeces, several countries rely on serology. Acute and convalescent patient sera are titered against the suspect serotype of Yersinia spp .
Strains of Y. enterocolitica can be found in meats (pork, beef, lamb, etc.), oysters, fish, and raw milk. The exact cause of the food contamination is unknown. However, the prevalence of this organism in the soil and water and in animals such as beavers, pigs, and squirrels, offers ample opportunities for it to enter our food supply. Poor sanitation and improper sterilization techniques by food handlers, including improper storage, cannot be overlooked as contributing to contamination.
Yersinia is heat-sensitive and will be killed by thorough heating (over 70 °C). Raw or undercooked foods and cross-contamination, when cooked material comes into contact with raw produce or contaminated materials (cutting boards), are the main causes of infection. Proper cooking and hygienic food handling thus can prevent Yersinia infections to a large extend.
The most susceptible populations for the main disease and possible complications are the very young, the debilitated, the very old and persons undergoing immunosuppressive therapy.
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