Yersinia

Yersinia enterocolitica is one of the three species within the Yersinia genus that are pathogenic to humans. Human yersiniosis is widely distributed and is generally a sporadic infection ¹ ; however, it is the third most common cause of bacterial gastroenteritis in developed countries, after Campylobacter and Salmonella. ^2,3 Infants and young children are more often affected than adults. ^4,5 This predominantly intracellular located bacterium causes acute or chronic gastrointestinal and systemic diseases that are associated with the consumption of contaminated food or water. The most frequent outbreaks of Y. enterocolitica originate from undercooked pork meat, but bacteria have also been found in many other animals, such as farm animals, domestic pets, and free-living and captive wild animals. Pigs and dogs are considered to be the primary reservoir of human pathogenic Y. enterocolitica strains in the world, and the isolation rate from tonsil samples is the highest. ^6–9 The correlation between strains isolated from pigs and those that produce clinical signs in humans has been sufficiently proven. ^9,10 The species contains an extrachromosomal 70 kb plasmid essential for the pathogenicity that encodes the Yersinia outer proteins and the protein microinjection apparatus, the type III secretion system (TTSS), which is used to translocate the effector proteins from the bacterial cytoplasm into the cytosol of eukaryotic cells. ¹¹