Consultant Laboratory for Yersinia

Yersinia enterocolitica and Yersinia pseudotuberculosis are enteropathogenic bacteria species which cause symptoms known as yersinioses. Yersinioses occur mostly sporadically after the intake of contaminated food (especially raw pork products such as minced pork meat) with outbreaks tending to be seldom. The most severely affected group is normally infants aged up to 3 years with whom Yersinia cause a self-limiting, acute gastroenteritis with fever, watery to bloody diarrhoea and vomiting. With school children and adolescents, a mesenteric lymphadenitis usually manifests itself with abdominal pain which can be taken for appendicitis. Symptoms such as acute rhinopharyngitis also occur in adults. If there is an underlying disease (e.g. diabetis mellitus, liver cirrhosis, immune suppression), extra-mesenteric diseases such as liver abscesses, endocarditis, pericarditis or pleuritis can occur. Long-term effects are known to be reactive arthritis, persistent ileitis (pseudo Crohn’s disease) and Erythema nodosum.

In Germany, yersinioses constitute the third most common bacterially caused gastrointestinal disease (approx. 2,700 reported cases in 2012). The vast majority of infections are caused by Y. enterocolitica, with the domestic pig being the biggest natural reservoir for the 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 could lie at approx. 106 colony-forming units. As yersiniae are capable of growing at refrigerator temperatures, the bacteria can also enrich under these conditions in contaminated foods. 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 rarely occurring extra-intestinal infections with Y. enterocolitica (e.g. sepsis) and infections with Y. pseudotuberculosis do not have to be registered up to now.

Main tasks of the consultant laboratory

The main tasks of the consultant laboratory include:

  • Detection and differentiation of the pathogens from foods and animal samples with the help of cultural (selective enrichment), biochemical (e.g. pyrazinamidase test), serological (agglutination test) and molecular (polymerase chain reaction, PCR) methods
  • Optimisation of the methods for the cultural detection of Yersinia in foods
  • Consultancy on questions of microbiological diagnostics (pathogen detection and serodiagnostics) and pathogen typing
  • Cultivation of  Yersinia and strain collection
  • Research on horizontal gene transfer and pathogen change in Yersinia


Enteropathogenic Yersinia can be detected and differentiated via a number of cultural, molecular and immunological methods. According to the method L00.00-90 of the official collection of examination methods in line with Art. 64 of the German Food and Feed Code (LFGB), which is identical with the standard DIN EN ISO 10273 (ISO, 2003), cultural detection is performed initially by enriching the bacteria in liquid media with a subsequent fractionated plating on solid selective media (e.g. CIN Agar). It has been proven, however, that other bacteria (in particular apathogenic Yersinia species) can also grow on these selective media, thus making the identification of pathogenic Yersinia more difficult. Yersinia detection can also be carried out with the help of PCR methods. Virulence genes localised on the virulence plasmid or in the chromosome of the bacteria are usually detected here to identify pathogenic strains. The results produced by PCR, however, do not give any information on the number of living pathogens as these are only detected indirectly via their nucleic acid sequences.

Yersinia isolates are usually differentiated by means of bio- and serotyping. In doing so, specific biochemical properties of the bacteria (e.g. the synthesis of certain enzymes) or their surface structures (O-antigen of the LPS) are tested. A fine differentiation of the bacteria can also be achieved through Multilocus Variable-Number Tandem-Repeat Analysis (MLVA) and Pulsed Field Gel Electrophoresis (PFGE).



Contact person:
Dr. Stefan Hertwig (Head of)




Contact person:
Dr. Eckhard Strauch