Yersinia is a genus of gram-negative, rod-shaped bacteria from the Enterobacteriacae family that cause yersiniosis. These pathogens are the third most common cause of bacterial intestinal diseases in Germany after salmonella and campylobacter. Of 18 known species, Yersinia (Y.) enterocolitica and Y. pseudotuberculosis cause disease in humans. One special case is Yersinia pestis, which triggered the major plague pandemics in the 6th, 13th through 15th and 19th centuries, yet today only occurs in isolated cases in the US. In Europe, the Y. enterocolitica strains of the so-called bioserovar 4/O:3 are the most frequent cause of yersiniosis (more than 90 per cent), the bioserovar 1B/O:8 has so far been geographically limited to North America, and in Europe is associated with travel. The species Y. pseudotuberculosis generally occurs only in 0.5 to 1 percent of cases worldwide. Both Y. enterocolitica and Y. pseudotuberculosis are zoonoses (diseases that can be transmitted from animals to humans and vice versa), where the main reservoir is found in animal species such as pigs and cattle, but also goats or dogs. This is why, in case of major outbreaks, human and veterinary medicine must work jointly to examine infections and find the origin of contamination as soon as possible.
In most cases, yersinia is transmitted through consumption of undercooked or contaminated pork. However, water, milk and vegetables that have come into contact with animal excrement can be carriers of yersinia bacteria as well. This route of infection poses a major health risk, especially for small children. A transmission from human to human, or animal to human, is almost impossible.
After an incubation period of three to seven days, initial symptoms including enterocolitis, a combined inflammation of the small intestine and the large intestine, can occur. In small children, yersiniosis caused by Y. enterocolitica results in one to three weeks of gastrointestinal disorder with fever, abdominal pain and bloody diarrhoea. In adolescents and adults, infection also manifests itself as fever and swelling of the lymph nodes, appendicitis-like pain on the right side of the abdomen, inflammation of the throat or other flu-like symptoms. Men, as well as children under the age of five, are more likely to be affected than other demographic groups.
The basic hygiene requirements must be maintained. An isolation of the patient is only necessary if gastroenteric symptoms occur. Yersinia spp. must be reported in Germany.
Yersinia often survive the processing, transport and storage of beef and pork. Refrigerating meat is not sufficient to contain spreading of the bacteria and the associated risk of infection, as they can multiply even at low temperatures of four degrees Celsius. An exact survival time is not known.
The required spectrum of activity against yersinia is: bactericidal.