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Klebsiella pneumoniae Facts, Possible Effects, and Discoveries

Linda Crampton has an honors degree in biology and many years of teaching experience. She finds the study of microorganisms fascinating.

Multidrug-resistant Klebsiella pneumoniae (colorized scanning electron micrograph)

Multidrug-resistant Klebsiella pneumoniae (colorized scanning electron micrograph)

A Bacterium With Many Potential Effects

Klebsiella pneumoniae is a rod-shaped bacterium that is found in the human body and in the environment. Its effects in humans range from harmless to dangerous, depending on the strain of the bacterium, its location in the body, the ability of the immune system to control or destroy it, and the effect of medical treatment. The most serious effects usually occur in people weakened by pre-existing conditions who are spending time in hospitals or healthcare facilities.

The microbe is capable of living in multiple places in the body. It’s commonly stated that K. pneumoniae living in the digestive tract is harmless and that healthy people are unlikely to be affected by the bacterium. This seems to be generally true. Scientists have recently discovered that while the bacterium is in the digestive tract, it may cause problems in some people and in specific circumstances. Further research is required, but the information obtained so far is fascinating and could be very significant.

White blood cells are a major part of the immune system and play an important role in fighting Klebsiella.

White blood cells are a major part of the immune system and play an important role in fighting Klebsiella.

Features of Klebsiella pneumoniae Cells

The photo of K. pneumoniae cells shown at the start of this article is real, but the colours aren't. Colour was added to make the different parts of the photo easier to see. The cells are interacting with a type of white blood cell known as a neutrophil. The photo was taken with the aid of a scanning electron microscope, which produces a highly magnified image in shades of grey. It's wonderful to see such a detailed view of organisms in scanning electron micrographs, as the photos made with the microscope are called.

Like other bacteria, K. pneumoniae is unicellular. Its cell is a short and bulky rod that occurs singly, in a pair (as in the photo above), in a chain, or occasionally in a group. The cell is non-motile. Its contents are covered by an inner cell membrane, a cell wall made of peptidoglycan, and an outer cell membrane. These coverings are in turn surrounded by a capsule. Encapsulated bacteria are often harder to attack than ones without a capsule. Klebsiella cells are gram negative, which means they are stained pink by a particular lab procedure. Gram-positive cells are stained purple by the procedure.

Potential Problems Caused by the Bacterium

K. pneumoniae can sometimes be a special problem in healthcare settings. The bacterium can cause a variety of disorders, including:

  • pneumonia
  • urinary tract infections
  • blood infections
  • infected skin wounds and surgical sites
  • meningitis (infection of the meninges, or the membranes around the brain)

There are many other causes of these problems. Anyone experiencing symptoms suggesting their presence should visit a doctor for a diagnosis and treatment.

Infection by the Microbes

According to the CDC (Centers for Disease Control and Prevention), the bacteria must enter specific areas to cause infections. For example, to cause pneumonia they must enter the lungs and to cause an infected skin wound they must enter the injured site.

The personnel of most health institutions are well aware of the possibility of bacterial transmission and are careful to prevent this from happening. Since the bacteria are microscopic and can't be seen by the unaided eye, however, they are sometimes transferred accidentally on contaminated hands or equipment. Anyone with questions about potential contamination in a particular situation should consult a medical professional.

Since Klebsiella bacteria are mainly transferred by direct contact, washing the hands is important in both health institutions and home situations. It's important to wash the hands:

  • after using a toilet or after helping someone to do this
  • before and after touching a wound or applying an item such as bandage
  • after touching the nose or mouth or materials expelled from them
  • after touching items in hospitals or other places that may have bacteria on their surface
  • before eating food
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The CDC recommends that even healthy people take these precautions both outside their homes and inside them. It's a good idea to avoid casually touching the face at any time in order to reduce the chance of sending bacteria into the body.

Washing the hands after an activity that may transfer harmful bacteria is very important.

Washing the hands after an activity that may transfer harmful bacteria is very important.

The Importance of Strain

Like many bacteria, K. pneumoniae exists in the form of different strains. The strain affects the bacterium's ability to cause disease and the ability of medications to destroy it. Members of a strain have slightly different features from members of other strains in the species. The differences aren't large enough to create a new species, but they may be very significant with respect to a bacterium's effect on our body. Multiple bacteria have strains that are harmless, cause only minor problems, or are even beneficial as well as ones that are dangerous.

The effects of K. pneumoniae depend on its strain, its location, the body's reaction to its presence, and probably other factors. Understanding the details is important because of the microbe's ability to cause serious health problems. It's also important because of another situation. At least one strain is becoming resistant to the effects of a group of antibiotics known as carbapenems. This is of great concern because carbapenems are considered to be the drugs of last resort for some infections. The development of antibiotic resistance in bacteria is a serious problem today.

The large intestine contains the greatest concentration of gut bacteria.

The large intestine contains the greatest concentration of gut bacteria.

The Intestinal or Gut Microbiome

The strains of K. pneumoniae that live in the digestive tract are often assumed to be harmless, at least in that location. They may frequently be so. Recent research has suggested that this may not true for everyone. The digestive tract is also known as the gastrointestinal or GI tract and the gut.

It may seem strange that bacteria can survive in our digestive tract. In fact, we have a large population of microbes living in our gut, especially in the large intestine. The community is often referred to as the intestinal or gut microbiome. It's an important community because some species make substances or perform activities that are helpful for us. Research shows that there are at least sometimes harmful species in the gut as well, but they often seem to be kept under control by beneficial or apparently neutral species.

Alcohol Production by a Bacterium

A very interesting report has shown a possible link between K. pneumoniae in the gut, alcohol production inside the human body, and a potentially serious liver problem. The problem was discovered in a Chinese man who became so drunk after eating a meal rich in carbohydrate or sugar that he sometimes lost consciousness. He had experienced this problem for around ten years before his condition was studied by researchers.

As might be expected, some people at first suspected that the man was a secret drinker. Research showed that this wasn't the case, however. The man was placed in an intensive care unit of a hospital and observed carefully. The doctors discovered that after he ate a meal that contained a lot of sugar, his blood alcohol level rose dramatically and sometimes reached 400 milligrams per deciliter. In more familiar terms, this is the level of alcohol found in 15 shots of 40% whisky.

The researchers analyzed the man's feces at different times and looked for bacterial DNA in the stool. They made a significant discovery. When the man was most intoxicated, Klebsiella pneumoniae formed 18.8% of the bacteria in his stool. This was 900 times greater than the normal level of the bacterium in the feces. The bacteria apparently absorbed components of the man's food and then produced alcohol.

The researched analyzed the Klebsiella bacteria that were present during the man's periods of intoxication. By giving the bacteria sugar, they found that the microbes could be divided into strains that produced a high amount of alcohol, a moderate amount, or a low amount.

Nonalcoholic fatty liver disease, or NAFLD, is a condition in which fat builds up in the liver. Some people who have the disease eventually experience cirrhosis of the liver or liver cancer. Cirrhosis involves the replacement of liver tissue with nonfunctional scar tissue. This can be serious because the liver is a vital organ with many functions. NASH, or nonalcoholic steatohepatitis, is the most serious form of NAFLD. It involves inflammation and cell damage.

Although certain health problems have been linked to the development of NAFLD, the cause of the condition is unknown. Some researchers have previously suggested that gut bacteria are a cause, but the idea hasn't been widely accepted.

The patient mentioned above had NASH. Despite the "nonalcoholic" in the condition's name, his condition may have been caused by alcohol produced by his gut bacteria. When he took antibiotics to kill the Klebsiella and also altered his diet, he no longer became drunk and his liver condition was "alleviated". Evidence described below suggests that his problem was due to the bacteria in his gut and only indirectly to his diet.

Carbapenem-resistant Klebsiella pneumoniae and a neutrophil

Carbapenem-resistant Klebsiella pneumoniae and a neutrophil

In an attempt to confirm the information described above, the researchers performed four additional experiments.

1. The scientists examined the feces of 43 patients with NAFLD and 48 without the disease. 61% of the people with the liver disease had high or medium alcohol-producing strains of K. pneumoniae in their feces while only 6% of the people without the disease did.

2. The researchers divided mice into three groups and fed them a high alcohol strain of K. pneumoniae, alcohol, or a mixture of yeast and sugar. At the end of four weeks, the first two groups had liver damage while the third group did not.

3. In another experiment, the researchers put K. pneumoniae from the man described above into mice that had no bacteria in their gut. These mice developed liver damage.

4. Phages are viruses that attack bacterial cells but are unable to attack human ones. A group of mice were pre-treated with phages that were able to destroy the Klebsiella in their gut. When the mice were then given the high alcohol strain of the microbe, no liver damage occurred. This results of this experiment suggest that phages might be useful as a treatment for some cases of NASH.

During their experiments, the researchers discovered that simply having a high alcohol strain of the bacterium in their gut was not enough for the mice to exhibit symptoms of inebriation. If they were fed glucose while they contained the bacterium, however, their blood alcohol level rose and they became drunk. Results in mice don't necessarily apply to humans, but they are sometimes very significant for us.

Understanding how Klebsiella pneumoniae affects our digestive tract and our liver is very important.

Understanding how Klebsiella pneumoniae affects our digestive tract and our liver is very important.

Further Research Is Important

Most of us don't need to worry about Klebsiella pneumoniae in the gut or anywhere else in our body. Unfortunately, this isn't the case for everyone. Since K. pneumoniae is known to cause serious health problems in certain situations, studying its abilities and finding ways to destroy it are very important.

The possible ability of the bacterium living in the digestive tract to cause problems when conditions are suitable is intriguing. I think it's a topic that should be further investigated. The results of the research performed so far are very interesting. If the idea that K. pneumoniae in the gut is never harmful is wrong, we need to know this and find ways to deal with the situation.

Exploring the effects of the microbe is complex due to genetic variability in the bacterium and variation in people's ability to deal with it. The situation is worth exploring, though. The exploration may help to improve some people’s health.


  • Klebsiella pneumoniae in healthcare settings from the CDC
  • K. pneumoniae and disease information from WebMD
  • The intestinal microbiome and health from the US National Library of Medicine
  • A possible link between a microbe, alcohol production in the body, and liver disease from Science (the website of the American Association for the Advancement of Science, or AAAS)

This content is accurate and true to the best of the author’s knowledge and does not substitute for diagnosis, prognosis, treatment, prescription, and/or dietary advice from a licensed health professional. Drugs, supplements, and natural remedies may have dangerous side effects. If pregnant or nursing, consult with a qualified provider on an individual basis. Seek immediate help if you are experiencing a medical emergency.

© 2019 Linda Crampton


Linda Crampton (author) from British Columbia, Canada on February 14, 2020:

Thank you very much, Peggy. Exploring bacteria and their actions is an interesting topic.

Peggy Woods from Houston, Texas on February 14, 2020:

This is fascinating information and hopefully, more research is being done with regard to this. The fact that Klebsiella pneumoniae bacteria negatively affect some people, while not affecting others, is important to know. What I thought was most interesting in this article was the fact that it could produce alcohol and affect the liver in some people. Keep writing these articles, Linda. You are good at doing so!

Linda Crampton (author) from British Columbia, Canada on December 30, 2019:

There are a lot of interesting things to think about in biology at the moment! It's a fascinating subject.

Mel Carriere from Snowbound and down in Northern Colorado on December 30, 2019:

Are we at the point now where we are going to start developing viruses to do the work of outmoded antibiotics? This seems to have scary implications, because of the the ability of viruses to mutate so rapidly. Fascinating work, I was particularly captivated by the story of the man who got drunk on his own bacteria.

Linda Crampton (author) from British Columbia, Canada on September 29, 2019:

I appreciate your kindness, Cynthia. I think that the study of our body's microbiome is fascinating.

Cynthia Zirkwitz from Vancouver Island, Canada on September 29, 2019:

Wow, Linda, another excellent science hub. If I had had you as a teacher back in my high school years I do believe that I would have understood biology much better-- or at least would have been more interested in what was being taught. The video about the microbiome was also clearly presented. Good work!

Linda Crampton (author) from British Columbia, Canada on September 27, 2019:

Hi, Flourish. Yes, there must have been many

problems for the man. I'm glad the real cause of his condition was eventually discovered.

FlourishAnyway from USA on September 27, 2019:

The story about the man suspected to be a closet drinker is so sad. Just imagine the social, financial, legal, and other impacts from having this.

Linda Crampton (author) from British Columbia, Canada on September 26, 2019:

I agree, Liz. The drug resistance problem is very worrying. Thanks for the visit.

Liz Westwood from UK on September 26, 2019:

This is a detailed and interesting article. I find it quite frightening to see how drug resistant some strains are becoming.

Linda Crampton (author) from British Columbia, Canada on September 25, 2019:

Thanks, Haleema. I appreciate your visit.

Rêveuse Consciente from Pakistan on September 25, 2019:

This hub is really helpful. Thanks for sharing this!

Linda Crampton (author) from British Columbia, Canada on September 25, 2019:

Thank you very much, Hari.

Hari Prasad S from Bangalore on September 25, 2019:

Very useful and comprehensive hub this is Linda. Thanks. :-)

Linda Crampton (author) from British Columbia, Canada on September 25, 2019:

Thank you, Shaloo. I appreciate your visit and your kind comment.

Shaloo Walia from India on September 25, 2019:

A very detailed and well researched hub. Your hubs are always full of so much new and interesting information. Thanks for sharing!

Linda Crampton (author) from British Columbia, Canada on September 25, 2019:

Thank you very much for the comment, Heidi. It is amazing to think of the microscopic organisms and particles around and within us. The living world is fascinating.

Heidi Thorne from Chicago Area on September 25, 2019:

One of the most fascinating things is that we are swimming in a pool of almost unlimited bacteria and viral strains. It's amazing we've survived. This is certainly an example of how nature keeps this all in balance (at least most of the time).

Thanks for sharing your wealth of health and science knowledge with us!

Linda Crampton (author) from British Columbia, Canada on September 25, 2019:

Thanks for the comment, Penny. I was familiar with the bacterium before I started writing this article, but what really sparked my interest was the recent report about its effects. I'm going to follow the news about K. pneumoniae closely.

Penny Leigh Sebring from Fort Collins on September 25, 2019:

Very interesting. This is a bacterium I was previously unfamiliar with!

Linda Crampton (author) from British Columbia, Canada on September 25, 2019:

Thanks for the comment and for sharing your recollection, Bill. Remembering loved ones can sometimes be a moving event.

Linda Crampton (author) from British Columbia, Canada on September 25, 2019:

Hi, Pamela. I appreciate your comment. The report about the link between the bacteria and alcohol production in the body is a recent one. I think it's fascinating research.

Bill Holland from Olympia, WA on September 25, 2019:

Once more a fascinating look inside our vessels. My mother would have read this and then convinced herself she was feeling sick. lol Funny what we think of from time to time...that just jumped into my head. My mother was always convinced she was sick. :)

Pamela Oglesby from Sunny Florida on September 25, 2019:

This is such an interesting article. I have seen people that have his bacteria when I was working as a RN. I sure never heard of the diet (without drinking alcohol) making you drunk. Then, the consequences of serious liver disease is also very concerning. You obviously did a lot of research and wrote an excellent article, Linda.

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