Yersinia - Plague, Food Poisoning and a Potential Cancer Treatment

This flea (Xenopsylla cheopis) has blood and a mass of Yersinia pestis cells in its midgut. The bacterial cells are passed to humans by flea bites and cause plague.
This flea (Xenopsylla cheopis) has blood and a mass of Yersinia pestis cells in its midgut. The bacterial cells are passed to humans by flea bites and cause plague. | Source

Yersinia Species - Harmful and Potentially Helpful Bacteria

Bacteria in the genus Yersinia have a terrible reputation. Yersinia pestis causes plague and was responsible for the frightening episode in history known as the Black Death. Yersinia enterocolitica causes a type of food poisoning known as yersiniosis and produces a wide variety of unpleasant symptoms. Yersinia ruckeri causes redmouth disease in fish. The infection produces subcutaneous bleeding in the mouth and other body parts and has a high fatality rate. This last bacterium may have a very important benefit for humans, however. It produces a toxin that might be able to fight cancer.

Yersinia is named after Alexandre Yersin, a physician and bacteriologist who discovered Pasteurella pestis in 1894. The bacterium was renamed Yersinia pestis in his honour.

This colourized picture seen through a scanning electron microscope shows Yersinia pestis (yellow) on the spines of the proventriculus, which is part of the digestive tract of a flea. The bacterium secretes a slime that connects its cells.
This colourized picture seen through a scanning electron microscope shows Yersinia pestis (yellow) on the spines of the proventriculus, which is part of the digestive tract of a flea. The bacterium secretes a slime that connects its cells. | Source

Characteristics of Yersinia Bacteria

The members of the genus Yersinia are rod-shaped bacteria that sometimes develop an oval or spherical shape. They are facultative anaerobes - that is, they can survive without oxygen in the environment as well as with oxygen. They change their biology when the environment lacks oxygen.

Yersinia bacteria are also versatile in other respects. For example, Y. enterocolitica often has flagella and is motile. Once it's entered the body or when it's in an environment at body temperature, however, it loses its flagella. (Y. pestis doesn't produce flagella and is nonmotile.) Y. enterocolitica can also survive at the low temperatures found in refrigerators as well as at body temperature.

Yersinia is gram negative. The gram stain is named after Hans Christian Gram, the bacteriologist who created the test in 1884. As a result of adding specific chemicals to the bacteria, gram positive bacteria appear purple and gram negative bacteria appear pink. The different results are due to the different amounts of peptidoglycan in the cell wall of the bacteria. Gram positive bacteria contain far more peptidoglycan than gram negative bacteria. Performing a gram stain is an important step in identifying a bacterium.

Yersinia is chemoorganotrophic. It gets its energy from the organic chemicals that it absorbs from its environment.

Yersinia pestis cells coloured by a fluorescent stain
Yersinia pestis cells coloured by a fluorescent stain | Source

Yersinia pestis - The Cause of Plague

The ultimate cause of plague is Yersinia pestis. The bacterium requires the help of rodents and fleas to cause an infection, however. The rodents act as a reservoir of bacteria. When a flea feeds on the blood of an infected rodent, it withdraws bacteria as well as blood. If the flea later bites a human to obtain blood, the bacteria travel into the person's body from the flea.

One reason for the transmission of bacteria from fleas to humans is the existence of so-called "blocked" fleas. The midgut of a flea is the site of food digestion and absorption. Bacteria obtained from a rodent multiply in the midgut, creating a dense mass. The bacterial mass blocks the proventriculus, a valve located at the top of the midgut. As a result, the hungry flea can no longer send a meal of blood into its midgut. In addition, every time it tries to swallow after biting a human, the blockage causes the flea to regurgitate bacteria from its midgut into the wound.

Bacteria on contaminated mouthparts of fleas also enter humans during a bite. This means that even fleas that aren't blocked or that are only partially blocked can infect humans with Yersinia.

The Secret Life of Fleas

Adaptations of Yersinia pestis for Infection

Y. pestis has some interesting features that help it to infect humans. Its cells secrete a slime while they are inside the flea's midgut. The slime connects the bacteria and forms a structure called a biofilm. The biofilm helps to block the flea's digestive tract, which leads to the regurgitation that sends the bacteria into a human.

Once Y. pestis has entered a human, it produces a variety of chemicals that stop the person's immune system from attacking it. This enables the bacterium to survive and to cause disease.

The rodent that supplied fleas in the Black Death is commonly believed to be the black rat, or Rattus rattus. It's also known as the house rat and the roof rat. Recently, there has been a suggestion that the rodent was actually the great or giant gerbil (Rhombomys opimus).

These are black rats (Rattus rattus) in a zoo. Black rats are believed to have played an important role in the Black Death.
These are black rats (Rattus rattus) in a zoo. Black rats are believed to have played an important role in the Black Death. | Source

Types of Plague

Yersinia pestis causes three types of plague - bubonic, septicemic and pneumonic. All three types can be deadly. Modern antibiotics are often an effective treatment, however. The treatment needs to be started early in the infection, especially in the case of pneumonic plague.

Bubonic Plague

Bubonic plague is the most common type of plague. In this form of the disease, bacteria enter the lymphatic system. Lymph nodes in the neck, armits or groin become swollen and painful. The swellings are known as buboes. The infected person also experiences symptoms that resemble those of the flu, such as fever, chills, a headache and weakness. This form of the disease isn't contagious under normal conditions. However, touching fluid that has leaked from buboes may transmit the disease.

Septicemic Plague

In septicemic plague, bacteria enter the blood. Bleeding occurs under the skin or in organs, which can lead to shock. The person may also experience abdominal pain, fever, chills and weakness. Septicemic plague may occur on its own or may accompany one of the other types of plague. Sometimes gangrene (tissue death) occurs in the fingers, toes and nose. These turn black as their cells die, giving the "Black Death" its name. Like bubonic plague, septicemic plague isn't contagious unless infected blood or tissue is touched.

Pneumonic Plague

In pneumonic plague, bacteria enter the lungs and cause pneumonia. This is the most serious form of the disease. The person experiences a cough, difficulty in breathing and chest pain. They may also cough up blood. Unlike the other two forms of plague, pneumonic plague is contagious. The bacterium is spread via airborne droplets released from the lungs.

Did the giant gerbil contribute to the Black Death?
Did the giant gerbil contribute to the Black Death? | Source

The Black Death

The Black Death was a widespread Yersinia pestis infection in Europe and Asia that had horrific results. Estimates of the percentage of Europeans that died from the infection range from one third to two thirds of the population. The largest outbreak occurred in the late 1340s and is the one that is generally referred to in descriptions of the Black Death, but smaller outbreaks occurred for centuries after. So many people died in the Black Death that it was hard to bury them fast enough. The situation must have been terrifying.

It's often reported that people who died of the Black Death had bubonic plague. If this was the case, the fact that the disease spread with such frightening rapidity over such a wide area is puzzling. Flea bites alone don't seem to be an adequate explanation. The bacterium can also be transmitted by direct contact with infected tissues, as might happen when handling the body of someone killed by the plague. Still, some researchers feeł that the disease must have been airborne to have spread so fast and that a large number of people must have had pneumonic plague.

The genomes of some strains of Yersinia pestis and Yersinia enterocolitica have been sequenced. This means that the order of DNA bases in their chromosome has been discovered. The bases form the genetic code of the bacterium. Now that the code has been discovered, researchers are trying to discover its meaning.

Plague of Justinian, the Black Death and Yersinia pestis

Yersinia pestis Today

Yersinia pestis still exists today. Although the potential for harm is still present and small outbreaks do occur, the infection is currently much less serious than in the past. This is partly because we have antibiotics to treat the disease. The fact that many cities have fewer rats than in the past may also be helpful. Researchers think there must be other reasons why plague is less common and the bacterium is less dangerous today, however.

Scientists have found Y. pestis DNA from the time of the Black Death and are comparing it with the DNA in the current version of the bacterium to see if it has changed in a significant way. So far, however, no significant differences have been found. Scientists are also looking at the human genome. It's possible that our genome has changed in a way that gives us more resistance to the bacterium. The research is important and is of more than academic interest. If the plague threatens to become a major problem again, we need to know how to deal with it.

Bubonic Plague in the Past, Present and Future

Yersiniosis and its Symptoms

Yersiniosis is a type of food poisoning or foodborne illness. It's caused by both Yersinia enterocolitica and Yersinia pseudotuberculosis. Infection by Y. enterocolitica is more common in North America, however.

The symptoms of yersiniosis depend on the patient's age. Children are generally affected more severely than adults. Common symptoms include abdominal pain, diarrhea and fever. The diarrhea may be bloody. In older children and adults, the pain may be located on the right side of the abdomen and there may be no diarrhea. As a result, the illness may be confused with appendicitis. Occasionally, an infected person may develop a skin rash or experience joint pain.

The symptoms of yersiniosis generally last for one to several weeks. The rash or joint problems may last for even longer. Although most symptoms disappear after a month, joint pain may last for as long as six months.

A doctor must be consulted to diagnose the problem and recommend treatment. Mild cases may not needed treatment, but this decision is up to the doctor. Antibiotics may be prescribed for more serious cases.

These are Yersinia enterocolitica cells that have been gram stained.
These are Yersinia enterocolitica cells that have been gram stained. | Source

Causes of Yersiniosis

Yersinioisis is generally caused by eating food contaminated by Y. enterocolitica. These foods include meat from pigs, cows and sheep that is either raw or inadequately cooked. Pork seems to be the most problematic meat. Raw chitterlings (pig intestines) are especially dangerous. The symptoms don't appear for four to seven days after eating the food, so it may be hard to link a food to the infection.

There are other causes of yersiniosis, included drinking unpasteurized milk and untreated water. Inadequate food hygiene can also result in transmission of the bacterium. The bacterium lives in the intestine of its host, so anything that is contaminated by intestinal contents or the stool of infected animals or humans may be dangerous. The infection is usually diagnosed by a stool test.

Raw and undercooked meat may contain pathogens and cause foodborne illness.
Raw and undercooked meat may contain pathogens and cause foodborne illness. | Source

Enteric Redmouth Disease in Fish

Enteric redmouth disease, or simply redmouth disease, is most common in fish belonging to the family Salmonidae, Fish in this family include salmon and trout. The disease is caused by a Yersinia ruckeri infection.

The bacterium causes subcutaneous bleeding in a fish's mouth and on its tongue, making them appear bright red. Subcutaneous bleeding or haemorrhages may also occur in the eyes, fins, and skin. In the late stage of the disease the abdomen may become swollen with fluid.

Redmouth disease affects fish that are used for food, especially those in fish farms, so it has economic importance. It can be treated with antibiotics. The mortality rate is high, however.

The brown trout is a member of the family Salmonidae. This family is affected by redmouth disease.
The brown trout is a member of the family Salmonidae. This family is affected by redmouth disease. | Source

Microfilaments are long, thin strands of protein that form part of the cell's cytoskeleton. The microfilaments are made of actin and are especially important in the process of cell division.

A Yersinia Toxin That May Fight Cancer

Yersinia ruckeri produces a toxin called Afp18. The toxin is an enzyme that deactivates a protein called RhoA. The protein is present in both fish and humans and has similar functions in each organism. One of its jobs is to control the production and breakdown of actin filaments in a cell. Actin filaments are required in the process of cell division. Cancer cells have a much higher rate of cell division than normal cells and have a high demand for actin. This has led scientists to suspect that AFP18 may be helpful in treating the disease.

Afp18 inactivates RhoA by attaching a sugar molecule called n-acetyglucosamine to the protein. The researchers say that this is an unusual reaction. When they injected the toxin into zebra fish embryos, which had rapidly dividing cells, actin filaments in the embryos broke down, the cells stopped dividing and the embryos failed to develop. It's possible that this destructive process may also happen to cancer cells when Afp18 is added to them. This remains to be seen, however. Some of the current cancer drugs work by interfering with cell division, although they don't target actin.

In principal, the use of the toxin for treating cancer by stopping cancer cell reproduction sounds great. There may be a problem with interfering with cell division, though. Some cells in the human body have a relatively high rate of cell division, so they may affected by the toxin as well. These cells are present in the lining of the intestine and in the red bone marrow. Still, the toxin could be very useful, especially if it affects only cancer cells.

Stained actin microfilaments from a mouse cell
Stained actin microfilaments from a mouse cell | Source

Yersinia in the Future

Yersinia has been interacting with humans for a very long time. It's an old enemy that still has the power to destroy. We are slowly starting to understand its complex and fascinating biology. It would be wonderful if the bacterium became a helper instead of a foe.

Further Reading

  • Plague, from the CDC (Centers for Disease Control and Prevention)
  • Yersiniosis, from the Vermont Department of Health
  • A bacterial toxin that may be useful for cancer treatment

© 2015 Linda Crampton

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50 comments

Buildreps profile image

Buildreps 16 months ago from Europe

Very impressive article. I must admit that I skimmed the text, but enough to pick up many interesting things that you won't find easily elsewhere. That shows that you're an expert in this area and wrote an authentic article.


AliciaC profile image

AliciaC 16 months ago from British Columbia, Canada Author

Thank you very much, Buildreps. I appreciate your visit and comment a great deal.


poetryman6969 profile image

poetryman6969 16 months ago

I hope that the promise of the anti cancer effects ring true.


AliciaC profile image

AliciaC 16 months ago from British Columbia, Canada Author

I hope so, too, poetryman. It would be wonderful if the toxin was helpful.


Jackie Lynnley profile image

Jackie Lynnley 16 months ago from The Beautiful South

This is a very interesting and fascinating writing. Whew; scary too! Lucky to have come so far and to use bad for good...well that is something else!

Great stuff! Needs to be shared. ^+


Peggy W profile image

Peggy W 16 months ago from Houston, Texas

I always learn something interesting from reading your hubs Alicia. This one was no exception. Hopefully our scientists and researchers will find a way to utilize this toxin in the fight against cancer where it will not impact the good cells of our bodies. That electron microscope image is amazing! Up votes and sharing.


jgshorebird profile image

jgshorebird 16 months ago from Earth

Great info. I'm eating more Trout! Just in case...


AliciaC profile image

AliciaC 16 months ago from British Columbia, Canada Author

Thanks for the kind comment, the share and the votes, Jackie! Yes, there is definitely a scary aspect to Yersinia. I hope it never becomes as serious a problem as it was in the past.


AliciaC profile image

AliciaC 16 months ago from British Columbia, Canada Author

Hi, Peggy. Thank you very much for the comment, votes and the share! Like you, I hope the toxin helps to fight cancer without hurting normal cells.


AliciaC profile image

AliciaC 16 months ago from British Columbia, Canada Author

Thanks for the visit and for commenting, jgshorebird. I hope you enjoy the extra trout!


whonunuwho profile image

whonunuwho 16 months ago from United States

This was enlightening and interesting my friend. Thank you for sharing. whonu


AliciaC profile image

AliciaC 16 months ago from British Columbia, Canada Author

Thank you, whonu. I appreciate your visit!


billybuc profile image

billybuc 16 months ago from Olympia, WA

Congratulations on your HOTD today. Well-deserved. Your articles are always informative and written in an interesting style.


midget38 profile image

midget38 16 months ago from Singapore

Wow. This is quite an insight. The parasites we seldom take notice of are so deadly!


AliciaC profile image

AliciaC 16 months ago from British Columbia, Canada Author

Thank you, Bill. I appreciate your comment and congratulations.


AliciaC profile image

AliciaC 16 months ago from British Columbia, Canada Author

Hi, Michelle. Yes, Yersinia can be deadly and very scary. I'm sorry that anybody has to suffer from its effects. Its biology is interesting, though. It does a lot for a microscopic organism!


Larry Rankin profile image

Larry Rankin 16 months ago from Oklahoma

It's always amazing what I learn about the world when I read your hubs.

Always a pleasure.


AliciaC profile image

AliciaC 16 months ago from British Columbia, Canada Author

Thank you, Larry! I always appreciate your visits.


MsDora profile image

MsDora 16 months ago from The Caribbean

Thanks for the information and the warnings. It seems that non-meat eaters are less inclined to suffer from the Y plagues, but there is still the water. Very helpful article!


AliciaC profile image

AliciaC 16 months ago from British Columbia, Canada Author

Thank you very much, Dora. As always, I appreciate your visit and comment.


tirelesstraveler profile image

tirelesstraveler 16 months ago from California

Very interesting. I am always grateful for people who desire to study science.


AliciaC profile image

AliciaC 16 months ago from British Columbia, Canada Author

Hi, tirelesstraveler. Yes, scientists have a lot to offer us, especially in the area of medicine. I'm grateful for their efforts, too.


Rachel L Alba profile image

Rachel L Alba 16 months ago from Every Day Cooking and Baking

The Bubonic Plague, The Black Death, always sounded so scary to me. I always try to be very careful when handling raw meat. Thanks for sharing. I voted up and interesting.

Blessings to you.


AliciaC profile image

AliciaC 16 months ago from British Columbia, Canada Author

Thank you very much for the comment and votes, Rachel. Blessings to you, too.


Faith Reaper profile image

Faith Reaper 16 months ago from southern USA

What extremes here from the plague to a cure of cancer! This one gave me the willies for lack of a better word just thinking about the bacteria and fleas and all else ... You always write in depth articles in a lot of areas not really known, at least to me.

Excellent hub as always

Up +++ and away


AliciaC profile image

AliciaC 16 months ago from British Columbia, Canada Author

Thank you very much, Faith. I appreciate your comment and votes, as I always do!


drbj profile image

drbj 16 months ago from south Florida

What a fascinating, educating hub, Alicia, as always. I anticipate learning more about yersinia and its possibilities as a cancer fighter.


AliciaC profile image

AliciaC 16 months ago from British Columbia, Canada Author

Thank you, drbj. I hope we hear good news about Yersinia and its effect on cancer very soon.


BlossomSB profile image

BlossomSB 16 months ago from Victoria, Australia

Thank you for such an interesting and informative article. You write so well and yet make it simple enough for the layman (or woman) to understand. Voted up.


AliciaC profile image

AliciaC 16 months ago from British Columbia, Canada Author

Thank you so much for the kind comment and the vote, Blossom. Your comment is especially meaningful for me because one of my goals is to make science information understandable.


thumbi7 profile image

thumbi7 16 months ago from India

Very informative. I remembered my classes on plague while reading this.

But I thought the incidence has come down.

Voted up and shared


AliciaC profile image

AliciaC 16 months ago from British Columbia, Canada Author

Thank you very much for the vote and the share, thumbi7. It is good that plague is much less common today, but it's a shame that it still occurs.


aviannovice profile image

aviannovice 16 months ago from Stillwater, OK

This is remarkable work, Linda. My concern now has to do with the fact that we no longer know where our food is coming from in the US, which makes me wonder of some of these catastrophic illnesses might come to light again.


AliciaC profile image

AliciaC 16 months ago from British Columbia, Canada Author

Thank you very much, Deb. The current state of the food supply system is worrying. In many cases, we seem to have given up nutrition in return for convenience.


bdegiulio profile image

bdegiulio 16 months ago from Massachusetts

Hi Linda. Very interesting and educational as always. It's amazing that something so deadly could in fact be helpful in the fight against cancer. Great job.


AliciaC profile image

AliciaC 16 months ago from British Columbia, Canada Author

Thank you very much, Bill. The possibility that Yersinia could help us is definitely an amazing thought!


Genna East profile image

Genna East 16 months ago from Massachusetts, USA

Fascinating and frightening info...so very well researched and presented, too! Congratulations on the richly deserved HOTD, Alicia. :-)


AliciaC profile image

AliciaC 16 months ago from British Columbia, Canada Author

Thank you very much for such a kind comment, Genna. I appreciate your visit very much! The hub isn't HOTD, though.


Mel Carriere profile image

Mel Carriere 16 months ago from San Diego California

Wouldn't it be wonderful if our old nemesis turned into our ally in the fight against cancer? I learned a ton reading this. Great hub!


AliciaC profile image

AliciaC 16 months ago from British Columbia, Canada Author

Yes, it would be be absolutely wonderful, Mel! Thanks for the visit. I appreciate your comment a great deal.


adevwriting profile image

adevwriting 16 months ago from United Countries of the World

Thanks for the insight into the diseases caused by Yersinia bacteria and the Black Death. Voted up.


AliciaC profile image

AliciaC 16 months ago from British Columbia, Canada Author

Thank you for the comment and the vote, adevwriting.


teaches12345 profile image

teaches12345 15 months ago

I always learn so much from your articles. This was very interesting and something new to me.


AliciaC profile image

AliciaC 15 months ago from British Columbia, Canada Author

Thank you very much, Dianna.


Nadine May profile image

Nadine May 15 months ago from Cape Town, Western Cape, South Africa

Thanks for this interesting and educational article. I'm glad to have stopped eating meat twenty years ago. I like the idea that our genome has changed in a way that gives us more resistance to many illnesses from the past but at the same time there are new diseases like aids, and what about Ebola? Or was that a red flag?


AliciaC profile image

AliciaC 15 months ago from British Columbia, Canada Author

Hi, Nadine. Yes, we may have resistance to some diseases, but there always seem to be new ones that we can't fight without help! Thank you for the visit and the comment.


RTalloni profile image

RTalloni 13 months ago from the short journey

Thanks for an interesting, though creepy for me, post worth reading and using as a reference. (Fleas creep me out almost as much as another bug that starts with an s and ends with an r.) We have so much to learn from the natural world and it is exciting to think what advances will provide in the form of disease treatments.


AliciaC profile image

AliciaC 13 months ago from British Columbia, Canada Author

Thanks for the visit and the comment, RTalloni. I agree - there is so much that we can learn from the natural world that may help us.


Peter Geekie profile image

Peter Geekie 8 weeks ago from Sittingbourne

Dear Alicia

Thank you for an interesting, well researched article, particularly the section on its relationship with cancer, I must look further into this.

kind regards Peter


AliciaC profile image

AliciaC 8 weeks ago from British Columbia, Canada Author

Thank you very much, Peter. I appreciate your comment.

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