Yersinia is a genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...

 of bacteria
Bacteria are a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria have a wide range of shapes, ranging from spheres to rods and spirals...

 in the family Enterobacteriaceae
The Enterobacteriaceae is a large family of bacteria that includes many of the more familiar pathogens, such as Salmonella, Escherichia coli, Yersinia pestis, Klebsiella and Shigella. This family is the only representative in the order Enterobacteriales of the class Gammaproteobacteria in the...

. Yersinia are Gram-negative
Gram-negative bacteria are bacteria that do not retain crystal violet dye in the Gram staining protocol. In a Gram stain test, a counterstain is added after the crystal violet, coloring all Gram-negative bacteria with a red or pink color...

 rod shaped bacteria
Bacteria are a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria have a wide range of shapes, ranging from spheres to rods and spirals...

, a few micrometers long and fractions of a micrometer in diameter, and are facultative anaerobes. Some members of Yersinia are pathogenic in humans; in particular, Y. pestis
Yersinia pestis
Yersinia pestis is a Gram-negative rod-shaped bacterium. It is a facultative anaerobe that can infect humans and other animals....

is the causative agent of the plague. Rodent
Rodentia is an order of mammals also known as rodents, characterised by two continuously growing incisors in the upper and lower jaws which must be kept short by gnawing....

s are the natural reservoirs of Yersinia; less frequently other mammals serve as the host
Host (biology)
In biology, a host is an organism that harbors a parasite, or a mutual or commensal symbiont, typically providing nourishment and shelter. In botany, a host plant is one that supplies food resources and substrate for certain insects or other fauna...

. Infection may occur either through blood (in the case of Y. pestis
Yersinia pestis
Yersinia pestis is a Gram-negative rod-shaped bacterium. It is a facultative anaerobe that can infect humans and other animals....

) or in an alimentary fashion, occasionally via consumption of food products (especially vegetables, milk-derived products and meat) contaminated with infected urine
Urine is a typically sterile liquid by-product of the body that is secreted by the kidneys through a process called urination and excreted through the urethra. Cellular metabolism generates numerous by-products, many rich in nitrogen, that require elimination from the bloodstream...

 or feces
Feces, faeces, or fæces is a waste product from an animal's digestive tract expelled through the anus or cloaca during defecation.-Etymology:...


Speculations exist as to whether or not certain Yersinia can also be spread via protozoonotic mechanisms, since Yersinia are known to be facultative intracellular parasites; studies and discussions of the possibility of amoeba
Amoeba is a genus of Protozoa.History=The amoeba was first discovered by August Johann Rösel von Rosenhof in 1757. Early naturalists referred to Amoeba as the Proteus animalcule after the Greek god Proteus, who could change his shape...

-vectored (through the cyst form of the protozoan) Yersinia propagation and proliferation are now in progress.

Microbial physiology

An interesting feature peculiar to some of the Yersinia bacteria is the ability to not only survive but actively proliferate at temperatures as low as 1-4 degrees Celsius
Celsius is a scale and unit of measurement for temperature. It is named after the Swedish astronomer Anders Celsius , who developed a similar temperature scale two years before his death...

 (e.g., on cut salads and other food products in a refrigerator). Yersinia bacteria are relatively quickly inactivated by oxidizing agent
Oxidizing agent
An oxidizing agent can be defined as a substance that removes electrons from another reactant in a redox chemical reaction...

s such as hydrogen peroxide
Hydrogen peroxide
Hydrogen peroxide is the simplest peroxide and an oxidizer. Hydrogen peroxide is a clear liquid, slightly more viscous than water. In dilute solution, it appears colorless. With its oxidizing properties, hydrogen peroxide is often used as a bleach or cleaning agent...

 and potassium permanganate
Potassium permanganate
Potassium permanganate is an inorganic chemical compound with the formula KMnO4. It is a salt consisting of K+ and MnO4− ions. Formerly known as permanganate of potash or Condy's crystals, it is a strong oxidizing agent. It dissolves in water to give intensely purple solutions, the...



Y. pestis is the causative agent of plague. The disease caused by Y. enterocolitica
Yersinia enterocolitica
Yersinia enterocolitica is a species of gram-negative coccobacillus-shaped bacterium, belonging to the family Enterobacteriaceae. Yersinia enterocolitica infection causes the disease yersiniosis, which is a zoonotic disease occurring in humans as well as a wide array of animals such as cattle,...

is called Yersiniosis
Yersiniosis is an infectious disease caused by a bacterium of the genus Yersinia. In the United States, most yersiniosis infections among humans are caused by Y. enterocolitica. Yersiniosis is mentioned as a specific zoonotic disease to prevent outbreaks in European Council Directive...


Y. pseudotuberculosis
Yersinia pseudotuberculosis
Yersinia pseudotuberculosis is a Gram-negative bacterium that causes Pseudotuberculosis disease in animals; humans occasionally get infected zoonotically, most often through the food-borne route.-Pathogenesis:In animals, Y...

sometimes but rarely causes disease.

Yersinia may be associated with Crohn's disease
Crohn's disease
Crohn's disease, also known as regional enteritis, is a type of inflammatory bowel disease that may affect any part of the gastrointestinal tract from mouth to anus, causing a wide variety of symptoms...

, an inflammatory autoimmune condition of the gut. Iranian sufferers of Crohn's disease were more likely to have had earlier exposure to refrigerators at home, consistent with Yersinia's unusual ability to thrive at low temperatures.

Yersinia is implicated as one of the causes of reactive arthritis
Reactive arthritis
Reactive arthritis , is classified as an autoimmune condition that develops in response to an infection in another part of the body. Coming into contact with bacteria and developing an infection can trigger the disease. Reiter's syndrome has symptoms similar to various other conditions collectively...


Also associated with pseudoappendicitis, which is an incorrect diagnoses of appendicitis due to a similar presentation.


Yersinia pestis, the first described species, was identified in 1894 by A.E.J. Yersin, a Swiss bacteriologist, and Kitasato Shibasaburō
Kitasato Shibasaburō
Baron was a Japanese physician and bacteriologist. He is remembered as the co-discoverer of the infectious agent of bubonic plague in Hong Kong in 1894, almost simultaneously with Alexandre Yersin.-Biography:...

, a Japanese bacteriologist. It was formerly described as Pasteurella
Pasteurella is a genus of Gram-negative, facultatively anaerobic bacteria. Pasteurella species are non-motile and pleomorphic. Most species are catalase-positive and oxidase-positive....

(known trivially
Common name
A common name of a taxon or organism is a name in general use within a community; it is often contrasted with the scientific name for the same organism...

as the plague-bacillus) by Lehmann and Neumann in 1896. In 1944, van Loghem reclassified the species P. pestis and P. rondentium into a new genus Yersinia. Following the introduction of the Bacteriological code, it was accepted as valid in 1980


The best treatment is a combination from streptomycin and tetracycline in case of failure of monotherapy by streptomycin or tetracycline.

External links

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