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, which belong to the Enterobacteriaceae family. As psychrophilic (= cold-loving) germs, they can be cultivated at temperatures between 4 °C and 42 °C. They are often found in the temperate climate zones.
14 species belong to the genus Yersinia. Enteropathogenic Yersinia (Y. enterocolitica and Y. pseudotuberculosis) as obligatory pathogenic pathogens are of importance for human medicine.
In 2019, typing of the 94 Y. enterocolitica isolates in the National Reference Centre for Yersiniosis revealed 90.4% bioserovar 4/O:3 and 9.6% bioserovar 2/O:9. In recent years, the disease incidence was highest in the age groups up to 14 years, while the incidence in the youngest age group up to 4 years has decreased significantly.
A purely symptomatic diagnosis based on the clinical picture alone is very difficult. Cultivation of bacteria from stool is the method of choice. This method is also used to determine sero- and biotypes. Blood, liquor, punctate, lymph node aspirate or peritoneal fluid can also be used. In untreated patients, bacteria can be excreted with the stool for weeks after clinical symptoms have ceased. Molecular biological methods such as PCR testing can also be used for pathogen detection.
Yersiniosis shows a wide range of symptoms.
Infants and toddlers usually experience a self-limiting acute gastroenteritis with vomiting, watery to bloody diarrhoea and fever. The disease can last up to one or two weeks.
Older children and adolescents usually experience acute mesenteric lymphadenitis (inflammatory swelling of abdominal lymph nodes) with abdominal pain. The clinical picture may resemble appendicitis (= inflammation of the appendix) ("pseudo-appendicitis").
In adults different clinical forms occur, such as flu-like symptoms with pharyngitis (= inflammation of the throat), myalgia (= muscle pain) and fever, or ileocolitis (= inflammation of the large and small intestine) with involvement of the mesenteric lymph nodes ("Pseudo-Crohn's disease").
Yersiniosis can 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 a gastro-enteritic clinical picture, Y. pseudotuberculosismore often lead to pseudo-appendicitis.