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Consultant Laboratory for Yersinia

Yersinia (Y.) enterocolitica and Y. pseudotuberculosis are enteropathogenic species of bacteria that cause a form of gastro-enteritis known as yersinioses. Yersinioses generally occur sporadically following the consumption of contaminated food (in particular undercooked or raw pork products such as ground pork); outbreaks tend to be rare.

In general most severely affected are small children up to the age of 3, in whom the bacteria cause self-limiting but acute gastrointestinal inflammation accompanied by fever, watery to bloody diarrhoea and vomiting. In school children and adolescents, the predominant symptom is painful inflammation in the abdominal region (mesenteric lymphadenitis) which can be mistaken for appendicitis. In adults, further symptoms can resemble those of flu-like infections. If there is an underlying disease (e.g. diabetes mellitus, liver cirrhosis, immune suppression), liver abscesses, endocarditis, pericarditis, pleuritis or pleurisy may occur. Known long-term effects are inflammation of the joints (reactive arthritis), persistent inflammation of the small intestine (pseudo Crohn’s disease) and acute inflammation of the subcutaneous fatty tissue (erythema nodosum).

Yersinioses are the third most common cause of bacterial gastrointestinal disease in Germany (approx. 2,400 reported cases in 2018). The overwhelming majority of these infections are caused by y. enterocolitica, and domestic pigs are the biggest natural reservoir for these bacteria. y. pseudotuberculosis, on the other hand, occurs more frequently in wild animals (rodents, birds, wild boar). The minimal infective dose for an enteritic Yersinia infection is not exactly known but data suggests it could be between 10⁴ and 10⁸ colony-forming units. As Yersinia are capable of growing at refrigerator temperatures, the bacteria can also accumulate in contaminated foods under these conditions. While pork meat products are often contaminated with Y. enterocolitica and lead to infections, there are reports of infection with Y. pseudotuberculosis via the consumption of raw vegetables (carrots, lettuce), but it is not known how these foods were contaminated. Intestinal infections of humans with Y. enterocolitica are notifiable in Germany, whereas infections with Y. pseudotuberculosis only have to be reported if a locally increased prevalence of infections over a short period of time indicates the presence of a serious threat to the general public.

Work of the Consultant Laboratory focuses on the following topics:

• Detection and differentiation of  these pathogens from foods and animal samples with the help of culture-based (selective enrichment), biochemical (colour strip tests), serological (agglutination test) and molecular (polymerase chain reaction, PCR) methods
• Optimisation of methods for culture detection of yersinia in foods
• Advice on questions relating to microbiological diagnostics (pathogen detection and sero-diagnostics) and pathogen typing
• Cultivation of yersinia and culture collection
• Research into horizontal gene transfer and naturally occurring genetic variations - pathogenevolution in yersinia spp.
• Organisation of interlaboratory external quality assurance exercises (ring trials)

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