| Yersinia enterocolitica | |
|---|---|
 | |
Scientific classification | |
| Domain: | Bacteria |
| Kingdom: | Pseudomonadati |
| Phylum: | Pseudomonadota |
| Class: | Gammaproteobacteria |
| Order: | Enterobacterales |
| Family: | Yersiniaceae |
| Genus: | Yersinia |
| Species: | Y. enterocolitica |
| Binomial name | |
| Yersinia enterocolitica (Schleifstein & Coleman 1939) | |
| Subspecies | |
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Yersinia enterocolitica is aGram-negative,rod-shapedbacterium, belonging to the familyYersiniaceae. It ismotile at temperatures of 22–29 °C (72–84°F), but it becomes nonmotile at normalhuman body temperature.[1][2]Y. enterocolitica infection causes the diseaseyersiniosis, which is ananimal-borne disease occurring in humans, as well as in a wide array of animals such as cattle, deer, pigs, and birds. Many of these animals recover from the disease and become carriers; these are potential sources of contagion despite showingno signs of disease.[3] The bacterium infects the host by sticking to its cells using trimeric autotransporteradhesins.
Y. enterocolitica is widespread in nature, occurring in reservoirs ranging from the intestinal tracts of numerous mammals, avian species, cold-blooded species, and even from terrestrial and aquatic niches. Most environmental isolates are avirulent; however, isolates recovered from porcine sources contain human pathogenic serogroups. In addition, dogs, sheep, wild rodents, and environmental water may also be a reservoir of pathogenicY. enterocoliticastrains. Human pathogenicstrains are usually confined to the intestinal tract and lead toenteritis/diarrhea.[4]
Within the genusYersinia, onlyY. pestis,Y. pseudotuberculosis, and certain strains ofY. enterocolitica are pathogenic for humans and certain animals. The other species are environmental in origin.[5]
Y.enterocolitica strains can be identified through the use of stool samples being grown on MacConkey plates and Yersinia Selective Agar. The MacConkey plates employ the fact thatY.enterocolitica is non-lactose fermenting, and therefore show up on the plates as 2mm translucent pale colonies. On Yersinia Selective Agar platesY.enterocolitica produces 1.5mm colonies with a dark pink center and translucent border.[6][5]
Y. enterocolitica is a heterogeneous group of strains, which are traditionally classified by biotyping into six biogroups on the basis of phenotypic characteristics, and byserotyping into more than 57 O serogroups, on the basis of their O (lipopolysaccharide or LPS) surface antigen. Five of the six biogroups (1B and 2–5) are regarded as pathogens. However, only a few of these serogroups have been associated with disease in either humans or animals. Strains that belong to serogroups O:3 (biogroup 4), O:5,27 (biogroups 2 and 3), O:8 (biogroup 1B), and O:9 (biogroup 2) are most frequently isolated worldwide from human samples. However, the most importantY. enterocolitica serogroup in many European countries is serogroup O:3 followed by O:9, whereas the serogroup O:8 is mainly detected in the United States.
There have been six identified pathways of transmission ofYersinia enterocolitica.[7]
The portal of entry is the gastrointestinal tract. The organism is acquired usually by insufficiently cooked pork or contaminated water, meat, or milk. In recent yearsY. enterocolitica has increasingly been causing smaller outbreaks via ready-to-eat (RTE) vegetables.[8] AcuteY. enterocolitica infections usually lead to mild, self-limitingenterocolitis or terminalileitis and adenitis in humans.Yersiniosis symptoms may include watery or bloodydiarrhea and fever, resemblingappendicitis, salmonellosis, or shigellosis. After oral uptake,Yersinia species replicate in the terminal ileum and invadePeyer's patches. From here, they can disseminate further tomesenteric lymph nodes causinglymphadenopathy. This condition can be confused with appendicitis, so is called pseudoappendicitis. In immunosuppressed individuals, they can disseminate from the gut to theliver andspleen and form abscesses. BecauseYersinia species aresiderophilic (iron-loving) bacteria, people withhereditary hemochromatosis (a disease resulting in high body iron levels) are more susceptible to infection withYersinia (and other siderophilic bacteria). In fact, the most common contaminant of stored blood isY. enterocolitica.[9]
Yersiniosis is usuallyself-limiting and does not require treatment. Forsepsis or severe focal infections, especially if associated withimmunosuppression, the recommended regimen includesdoxycycline in combination with anaminoglycoside. Other antibiotics active againstY. enterocolitica includetrimethoprim-sulfamethoxasole,fluoroquinolones,ceftriaxone, andchloramphenicol.Y. enterocolitica is usually resistant topenicillin G,ampicillin, andcefalotin due tobeta-lactamase production, but multidrug resistant strains have been reported in Europe.[8][10][11]
Y. enterocolitica infections are sometimes followed by chronicinflammatory diseases such asarthritis,[12]erythema nodosum, andreactive arthritis. This is most likely because of some immune-mediated mechanism.[13]
Y. enterocolitica seems to be associated with autoimmuneGraves–Basedowthyroiditis.[14]Although indirect evidence exists, direct causative evidence is limited.[15]Y. enterocolitica is probably not a major cause of this disease, but it may contribute to the development of thyroid autoimmunity arising for other reasons ingenetically susceptible individuals.[16]Y. enterocolitica infection has also been suggested to not be thecause of autoimmune thyroid disease, but rather anassociated condition, with both sharing a common inherited susceptibility.[17]More recently, the role ofY. enterocolitica has been disputed.[18]
