Yersinia pseudotuberculosis

Yersinia pseudotuberculosis is a Gram-negative bacterium that causes Far East scarlet-like fever in humans, who occasionally get infected zoonotically, most often through the food-borne route. Animals are also infected by Y. pseudotuberculosis. The bacterium is urease positive. In animals, Y. pseudotuberculosis can cause tuberculosis-like symptoms, including localized tissue necrosis and granulomas in the spleen, liver, and lymph nodes. In humans, symptoms of Far East scarlet-like fever are similar to those of infection with Yersinia enterocolitica (fever and right-sided abdominal pain), except that the diarrheal component is often absent, which sometimes makes the resulting condition difficult to diagnose. Y. pseudotuberculosis infections can mimic appendicitis, especially in children and younger adults, and, in rare cases, the disease may cause skin complaints (erythema nodosum), joint stiffness and pain (reactive arthritis), or spread of bacteria to the blood (bacteremia). Far East scarlet-like fever usually becomes apparent five to 10 days after exposure and typically lasts one to three weeks without treatment. In complex cases or those involving immunocompromised patients, antibiotics may be necessary for resolution; ampicillin, aminoglycosides, tetracycline, chloramphenicol, or a cephalosporin may all be effective. The recently described syndrome 'Izumi-fever' has been linked to infection with Y. pseudotuberculosis. The symptoms of fever and abdominal pain mimicking appendicitis (actually from mesenteric lymphadenitis) associated with Y. pseudotuberculosis infection are not typical of the diarrhea and vomiting from classical food poisoning incidents. Although Y. pseudotuberculosis is usually only able to colonize hosts by peripheral routes and cause serious disease in immunocompromised individuals, if this bacterium gains access to the blood stream, it has an LD50 comparable to Y. pestis at only 10 CFU. Genetically, the pathogen causing plague, Y. pestis, is very similar to Y. pseudotuberculosis. The plague appears to have evolved from Y. pseudotuberculosis about 1500 to 20,000 years ago. A 2015 paper in Cell argued for an older divergence. To facilitate attachment, invasion, and colonization of its host, this bacterium possesses many virulence factors. Superantigens, bacterial adhesions, and the actions of Yops (which are bacterial proteins once thought to be 'Yersinia outer membrane proteins') that are encoded on the ' for Yersinia virulence' – commonly known as the pYV – cause host pathogenesis and allow the bacteria to live parasitically.