Yersinia enterocolitica, Yersinia pseudotuberculosis
Enteric yersiniosis occurs worldwide and is the third most common bacterial zoonosis in the EU. Y. enterocolitica is prevalent in the environment and in the animal population, primarily in pigs, less frequently in dairy cows. Y. enterocolitica can also be found in wild animals. Y. pseudotuberculosis can be found primarily in the environment. Similar to Listeria, Y. enterocolitica can also multiply on contaminated food in the refrigerator.
Yersiniosis is usually caused faecal-orally by consumption of contaminated food and water, especially raw or medium-cooked pork and raw or inappropriately heated dairy products. The bacteria can also multiply at 4 °C (e.g. refrigerator). In major foodborne Y. pseudotuberculosis outbreaks in the EU, contaminated vegetables (bean sprouts, tofu), water and milk have been confirmed as vehicles of infection. Transmission can also occur through contaminated blood supplies. Direct transmission from infectious animals and humans is rare.
In children, the disease usually manifests itself with gastrointestinal symptoms, whereas adults may show signs of appendicitis (pseudo-appendicitis). The classic symptoms are diarrhea, fever, and severe abdominal pain (untreated for a duration of 1-3 weeks). The diarrhea may be watery but also bloody; after a few days, joint pain, joint inflammation and skin changes may also occur. In rare cases, the so-called Reiter syndrome (arthritis, urethritis, conjunctivitis) may develop.
In pigs, which are considered to be the main reservoir for Y. enterocolitica, bloody diarrhoea may occur in individual cases, and joint and lung inflammation can be found in young animals. In most cases, however, infections remain asymptomatic and unnoticed by the animal owner.
In 2022, 201 Yersinia spp. first isolates were submitted to the National Reference Center for Yersinia. Of these, 107 were pathogenic and 94 were apathogenic. Of the pathogenic isolates, 105 strains were identified as Y. enterocolitica. In two cases, infection with Y. pseudotuberculosis was detected. The incidence of Yersiniosis culturally confirmed by the reference center was 1.18 per 100,000 population in 2022. There were 131 cases reported to the Epidemiologic Reporting System (EMS) (as of 05/26/2023).
Yersinia are facultatively anaerobic (i.e. growing even in the absence of oxygen), pleomorphic, Gram-negative (stained red in the so-called Gram stain) rods that belong to the Enterobacteriaceae family. As psychrophilic (= cold-loving) germs, they can be grown at temperatures between 4°C and 42°C. They are commonly found in temperate climates.
The genus Yersinia includes 14 species, with enteropathogenic Yersinia(Y. enterocolitica and Y. pseudotuberculosis) being of human medical importance as obligate pathogens.
In 2022, typing of 105 Y. enterocolitica isolates at the National Reference Center for Yersiniosis revealed 88 isolates bioserovar 4/O:3 (84%) and 17 bioserovar 2/O:9 (16%). In recent years, the incidence of the disease shows the highest incidence in the age groups up to 14 years. In 2022, two cases have been imported, one each from Cuba and Spain. Both imported isolates were Y. enterocolitica serovar O:3, biovar 4.
A purely symptomatic diagnosis is very difficult on the basis of the clinical picture alone. The cultivation of germs from stool is the method of choice, also to determine serotypes and biotypes. Blood, cerebrospinal fluid, punctates, lymph node aspirate or peritoneal fluid can also be used. In untreated patients, the germs can still be excreted in the stool for weeks after the clinical symptoms have subsided. Molecular biological methods such as PCR tests are also available for pathogen detection.
The infections caused - so-called yersinioses - show a broad spectrum of symptoms.
In infants and young children, a self-limiting, acute gastroenteritis with vomiting, watery to bloody diarrhea and fever usually occurs. The illness may last one to two weeks.
In school-age children and adolescents, the infections usually present as acute mesenteric lymphadenitis (inflammatory swelling of abdominal lymph nodes) with abdominal pain. The clinical picture may resemble appendicitis ("pseudoappendicitis").
In adults, different clinical forms occur, such as flu-like infections with pharyngitis (= pharyngitis), myalgia (= muscle pain) and fever, or ileocolitis (= inflammation of the colon and parts of the small intestine) with involvement of the mesenteric lymph nodes ("pseudocrohn's").
Yersiniosis may be associated with concomitant or secondary symptoms: reactive arthritis, erythema nodosum (= acute inflammation of the subcutaneous fat tissue), arthralgia (= joint pain) or myalgia (= muscle pain). Y. enterocolitica is more likely to lead to gastroenteritis, Y. pseudotuberculosis more often to pseudoappendicitis.
Last updated: 31.08.2023