Yersinia enterocolitica
John Krumme

Yersinia enterocolitica is a gram-negative, oxidase-negative (the bacterium does not contain cytochrome C oxidase), rod-shaped facultative anaerobe that ferments glucose.  The Yersinia genus contains some particularly nasty pathogens.  Some of the other organism in this genus are yersinia pestis (the causative agent of the black plaque), yersinia pseudotuberculosis (a rodent pathogen which causes lymphadenitis and septicemia), and yersinia ruckeri (causes redmouth disease in freshwater fish).  Yersinia enterocolitica like many in its genus is also a pathogen, and its target is the gastrointestinal tract.  This pathogen is commonly contracted through food products such as undercooked meat, unpasteurized milk, and water.

Yersinia enterocolitica is broken up into different classifications based on pathogenicity, ecological distribution, and geographic distribution.  The pathogenicity is mainly determined by the O antigen, which is a carbohydrate chain that is on the outer membrane lipopolysaccaride of this bacterium.  This O group determines to which of the five biogroups the different strands of yersinia enterocolitica will belong.  The groups are IA or IB, 2, 3, 4, and 5.  The interesting thing about yersinia enterocolitica is that not all of the strands are virulent.  These strands are in the biogroup IA mostly.  The strands in biogroups IB, 2, 3, 4, and 5 are mostly virulent strands.  Most cases occur from bacterium with O antigen three.

Another unusual trait of Yersinia enterocolitica is how it likes to grow.  It is psychotropic and can grow at temperatures below four degrees Celsius.  It can also readily withstand freezing temperatures.  This can be a problem because Yersinia enterocolitica can contaminate refrigerated food stocks, which most pathogenic bacteria can’t attack.  According to Roy M. Robins-Browne in Food Microbiology this bacterium also poses a problem for blood storage.  “The psychotropic nature of Yersinia enterocolitica also poses problems for the blood transfusion industry, mainly because of its ability to proliferate and release endotoxin in blood products stored at four degrees Celsius without manifestly altering their appearance” (218).  This means that these bacteria can replicate in stored blood, and if the blood is not checked properly, it could be introduced into transfusion patients.  Yersinia enterocolitica is also alkalotolerant.  It can grow in a pH range of 4 to 10 with an optimal growth pH of 7.6.  Yersinia enterocolitica is also a facultative anaerobe.  This means that it can grow in the presence of oxygen, but it cannot use the oxygen as a final electron acceptor in its electron transport chain because it lacks cytochrome c oxidase.  Therefore, other electron acceptors such as nitrate are used as the final electron acceptor in this bacterium.  This bacterium is very susceptible to heating, which is why food that is cooked properly and milk that is pasteurized usually does not contain Yersinia enterocolitica.

Even with Yersinia enterocolitica’s ability to colonize food animals, to proliferate at refrigeration temperatures, and to persist within an environment for long amounts of time, outbreaks are surprisingly uncommon.  In the cases that do occur, the strand with the O:3 antigen is mostly colonized.  In an outbreak in Atlanta in 1983, 15 infants and children were affected by this strand.  Other outbreaks include 138 school children in Canada in 1976 and in 1981 at a Diet Camp in New York State.  These outbreaks were traced back to poorly processed milk or contaminated milk products.

When this microbe enters the gastrointestinal tract causing Yersiniosis, a few common symptoms show up.  Symptoms of this infection include severe abdominal pain, diarrhea, nausea, vomiting, and fever.  The symptoms will generally appear within 24-30 hours, and can last up to 28 days in infants and as much as 14 days in adults.

The infection mainly occurs in the small intestine specifically the ileum.  To accomplish infection in humans, Yersinia enterocolitica utilizes three genes, which make the following proteins: invasion, ail, and YadA.  Invasion binds to an integral membrane protein on M-cells (microfold cells).   An attachment invasion locus (ail) is also involved in adhesion.  It is a membrane protein, which forms a protein complex with invasion.  Finally, YadA, an adhesion protein that protects Yersinia enterocolitica from phagocytosis and also helps break through the M-cells on the mucous membrane of the ileum, is utilized.  The bacterium will enter M-cells, and once through, will invade epithelial cells as well as macrophages. The macrophages will transport Yersinia enterocolitica to the liver and mesenteric lymph nodes.  Infection causes damage to the epithelial lining, which is the main cause for the abdominal pain symptom of infection.  The enterotoxin, Yst, is produced by Yersinia enterocolitica to promote fluid secretion from intestinal cells causing the infection symptom of diarrhea.

Treatment for a Yersinia enterocolitica infection is usually not necessary.  More than likely the body will fend off the bacterium on its own.  However, if treatment is necessary, penicillin type antibiotics are not effective due to the beta lactamases contained in this bacterium.  However, newer and more diverse antibiotics of the beta lactam type are quite effective.  This would include the antibiotics ceftriaxone, ceftazidime, and moxalactam.

This bacterium is a strange but potentially harmful bacterium.  It has some strange growing characteristics that make it surprisingly diverse in comparison to other gastrointestinal infecting bacteria.  To protect children from infection, food should always be prepared properly.  As long as society continues to exercise safe food practices, there is no immediate danger for a large-scale outbreak.  Though harmful, it can easily be contained.

Works Cited

Beuchat, Larry R. Food Microbiology : Fundamentals and Frontiers. Ed. Michael P. Doyle and Thomas J. Montville. Grand Rapids: Blackwell Limited, 2001.
Bhunia, Arun K. Foodborne Microbial Pathogens : Mechanisms and Pathogenesis. New York: Springer, 2007.
K Ruckdeschel, A Roggenkamp, V Lafont, P Mangeat, J Heesemann, B Rouot. Interaction of Yersinia enterocolitica with macrophages leads to macrophage cell death through apoptosis. Infection and Immunity, Volume 65, Number 11 (November 1997), pp. 4813-21, <>
Pepe, J. C., M. R. Wachtel, E. Wagar, and V. L. Miller. "Pathogenesis of defined invasion mutants of Yersinia enterocolitica in a BALB/c mouse model of infection." Infection and Immunity 63 (1995): 4557-563.

*Disclaimer - This report was written by a student participaring in a microbiology course at the Missouri University of Science and Technology. The accuracy of the contents of this report is not guaranteed and it is recommended that you seek additional sources of information to verify the contents.


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