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Staphylococcus Epidermidis: Biofilms and Antibiotic Resistance

Linda Crampton is a writer and teacher with a first-class honors degree in biology. She often writes about the scientific basis of disease.

A colorized scanning electron micrograph of Staphylococcus epidermidis (green) and extracellular matrix (purple)

A colorized scanning electron micrograph of Staphylococcus epidermidis (green) and extracellular matrix (purple)

A Potentially Harmful Bacterium

Staphylococcus epidermidis is a normal component of our skin and mucous membrane flora and often causes no problems. It may even help us. Under certain conditions, however, it produces harmful and sometimes deadly infections. Researchers have recently discovered that some strains of the species are resistant to multiple antibiotics and are hard to treat. The bacterium has long been considered a nuisance in hospitals and care facilities because it contaminates patient specimens, but it may have entered a new and dangerous phase of its existence.

S. epidermidis is a strange bacterium with respect to its effects on our lives. Depending on the situation, the bacterium may be possibly helpful, apparently neutral, mildly harmful, or potentially deadly.

Staphylococcus epidermidis

Staphylococcus epidermidis is unicellular and is classified as a coccus, which means its body consists of a spherical cell. The cocci (the plural term) are arranged in grape-like clusters. The word “staphylo” is derived from an Ancient Greek word meaning “bunch of grapes”. The species name refers to the fact that the bacterium is often found on the outer layer of the skin, or the epidermis.

S. epidermidis survives with or without oxygen and is therefore said to be a facultative anaerobe. The species is non-motile, Gram-positive (appearing purple after a process called the Gram stain), and coagulase-negative (unable to make an enzyme called coagulase). The word "Gram" is capitalized when referring to the staining method and is often capitalized when referring to the bacteria. Hans Christian Gram (1853–1938) was a Danish biologist. He created the staining process.

S. epidermidis is found inside the body on mucous membranes as well as on our skin. The membranes line cavities and tubes that lead to the outside world. They’re found in the respiratory, digestive, and urinary tract, for example. Mucous membranes often secrete mucus, to a greater or lesser extent. Mucus is a protective and lubricating substance.

An enlarged view of two Staphylococcus epidermidis cells

An enlarged view of two Staphylococcus epidermidis cells

Possible Effects of the Bacterium

When it’s on the skin, the bacterium is thought to help us by hindering harmful bacteria. Even when it’s located on the mucous membranes inside our body, it's often harmless and may even be helpful. It’s an opportunistic pathogen, however. A pathogen is a microbe that causes disease. When conditions are suitable—which generally occurs when the host and the immune system are weakened in some way—the bacterium makes us ill. The infection may be serious. The bacterium is a special problem in hospitals and other care facilities.

Since Staphylococcus epidermidis can infect different areas in the body, symptoms of the infection vary. As with any other health problem, if someone experiences severe, recurring, or prolonged symptoms of ill health, a doctor should be consulted to obtain a diagnosis and treatment.

Staphylococcus epidermidis lives in the epidermis or the upper layer of the skin. The epidermis contains no blood vessels. If the bacterium reaches the blood vessels in the underlying dermis, it may spread to other parts of the body and cause disease.

Bacterial Biofilms

Nature of a Biofilm

Like some other bacteria, S. epidermidis has the ability to form biofilms in the body. This is one reason why it can be dangerous. In a biofilm, bacteria are surrounded by a slimy and sticky material that is attached to a surface. The film protects the bacterial cells and makes them very hard to attack with antibiotics. It also makes it hard for the body’s immune system to attack them. The film is technically known as an extracellular matrix and is produced by the bacteria that it contains. It consists of polysaccharides, proteins, and extracellular DNA, or deoxyribonucleic acid.

Examples of Biofilms

Dental plaque is a form of biofilm. It can be removed mechanically by brushing. Other biofilms in the body can be much harder to remove. They may form on hip replacements and on medical catheters and valves implanted in the body, for example. Some bacteria produce biofilms in wounds on the skin and in tissues within the body.

Activity of Biofilm Bacteria

The bacteria inside a biofilm are active, releasing chemicals into their immediate environment that enable them to communicate with one another and coordinate their activity. They are also able to feed on nutrients that enter the film. Narrow channels that allow nutrient chemicals to enter have been found in some biofilms. These channels may also release wastes and toxins made by the bacteria.

Some bacterial cells are released from the mature colony. These travel through the body and are said to be planktonic. If they aren't destroyed, they may eventually establish new colonies.

Biofilms can be found on surfaces outside the body as well as inside us, such as on food preparation surfaces that are inadequately cleaned, in pipes, and in bodies of water. They are sometimes a major problem.

How Antibiotic Resistance Develops

Even when it's not in a biofilm, Staphylococcus epidermidis is resistant to many antibiotics. Researchers have discovered that strains with a high tendency to form biofilms have a higher degree of antibiotic resistance than those with a low tendency.

The development of antibiotic resistance in bacteria is a natural process, as described below. Humans are speeding up the process by the overuse and misuse of the medications. Antibiotics are an essential treatment for some illnesses and should be used in these cases. It's important that the antibiotic is taken for the time prescribed, though, even if a person feels better when some of the medication is left.

The Nature of Genes

A gene is a segment of a DNA molecule that codes for a particular protein and controls a specific feature in the body. The code is "written" in a sequence of chemicals called nitrogenous bases. A bacterium (and a human) has many genes. Each gene exists in variant forms known as alleles.

Genetic Change

The genetic composition of a bacterium changes over time due to mutations and/or obtaining DNA from other bacteria. Mutations are genetic changes that are produced by mistakes made during DNA replication or by factors such as radiation or the influence of specific chemicals. DNA replication takes place before a bacterium divides to produce offspring. As a result of mutations and the arrival of new DNA, a bacterium may develop or pick up an allele that gives it resistance to a particular antibiotic.

Surviving an Antibiotic Attack

If a group of bacteria are exposed to the antibiotic, individuals that are sensitive to the medication's effects die. If any of the bacteria have the allele that gives them resistance to the antibiotic, they survive the treatment. The survivors reproduce (if they aren't destroyed by the immune system) and pass a copy of the beneficial allele to their offspring. The offspring then repeat the process. The allele gradually spreads through the bacterial population. Eventually, the majority of the population will be resistant to the effects of the antibiotic.

The white circles in the dishes above contain antibiotics. The bacteria in the dish on the left are sensitive to all of the antibiotics. The clear areas are spaces created by the death of the microbes. The bacteria in the dish on the right are resistant to some of the antibiotics and sensitive to the others.

Distribution and Resistance to Antibiotics

The recent research on antibiotic resistance in S. epidermidis was done by Australian scientists. Researchers from the University of Melbourne examined hundreds of Staphylococcus epidermidis specimens from seventy-eight hospitals around the world. They found multi-drug resistant forms of the bacterium in samples from ten countries. They also discovered three strains of the bacterium in Europe that “cannot be reliably tamed” by any antibiotic that is currently on the market.

Strains of a bacterial species have minor genetic differences from one another. These differences are not significant enough to cause the division of the bacterium into different species, but they may be significant with respect to their effect on humans.

At the moment, S. epidermidis primarily harms elderly patients, people who have an implanted urinary catheter, valve, or joint replacement, and people with a malfunctioning immune system. It's certainly not inevitable that people in these categories will become infected by the bacterium, that they will experience serious symptoms from the infection if it does develop, or that any unpleasant symptoms must be due to an S. epidermidis infection. If unexplained symptoms do appear, however, a doctor should be consulted.

Patients are generally seriously weakened by another factor before succumbing to the effects of S. epidermis at the moment. The fact that some people die from the infection is sad news. The situation may become even worse if antibiotic resistance in the species increases or if resistant strains spread.

It can be deadly, but it's usually in patients who already are very sick in hospital... it can be quite hard to eradicate and the infections can be severe.

— Ben Howden, University of Melbourne, via Medical Xpress

As might be expected, doctors and scientists are trying to minimize the possibility that a bacterial biofilm will form on a joint replacement such as an artificial hip.

An Unusual Genetic Change

The University of Melbourne researchers say that one surprising discovery related to S. epidermidis was that a small change in the DNA of some strains gives resistance or reduced susceptibility to two types of antibiotics commonly used to treat the infection. These antibiotics are not chemically similar to one another, so it’s strange that such a small change in the genetic material gives resistance to both types of medications.

The antibiotics that were explored with respect to the above observation were rifampin (also known as rifampicin), vancomycin, and teicoplanin. The last two antibiotics belong to a different chemical family from rifampin and are known as glycopeptide antibiotics. The researchers say that the strains of S. epidermidis that they investigated were resistant to rifampin and had reduced susceptibility to vancomycin and teicoplanin. Until quite recently, vancomycin has been thought of as a powerful and effective medication that works when other antibiotics don't. Unfortunately, multiple species of bacteria are becoming resistant to the drug.

Using Two Antibiotics at the Same Time

The existence of multiple drugs to attack bacteria is important. A patient with an S. epidermidis infection may be given two different types of antibiotics at the same time. The general idea behind giving two antibiotics at once is that if one fails to work or is only partially successful, the bacterium may still be killed by the other medication. If the bacterium is successfully killed, the patient is cured.

Another advantage of giving a patient two antibiotics is that the chance of antibiotic resistance developing in the bacterial population may be decreased. Even though the bacterium may be resistant to one of the two drugs, if it's destroyed by the other one, it can't reproduce or transfer DNA to other bacteria. The failure of the medications and the two-drug strategy could have serious effects.

Staphylocoocus epidermidis  on a titanium substrate

Staphylocoocus epidermidis on a titanium substrate

Fighting Staphylococcus epidermidis

The resistance of bacteria to substances designed to destroy them is a worrying development. We could be heading for a serious situation with regards to disease prevention and treatment.

Removing a medical device coated with a biofilm or surgically removing tissue covered by a film might cure a Staphylococcus epidermidis infection, but this may not be the case if bacteria have left the film and traveled to other areas of the body. Antibiotics may still be needed in order to kill the bacteria left in the body.

Researchers are searching for new substances to kill bacteria that cause disease. There are some signs of hope, but much more research is needed. Time is of the essence. We need effective drugs as soon as possible, not only to destroy S. epidermidis but also to kill other microbes that make us sick.

References

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.

© 2018 Linda Crampton

Comments

Linda Crampton (author) from British Columbia, Canada on March 30, 2020:

Thank you for the visit and the comment, Peggy.

Peggy Woods from Houston, Texas on March 30, 2020:

This was always a concern in hospitals when people tend to be more vulnerable for many reasons. Yes, people should always finish a prescribed dose of antibiotics! I learned something new from you today. I had no idea that dental plaque is a form of biofilm. Thanks for writing your informative posts!

Linda Crampton (author) from British Columbia, Canada on October 08, 2018:

Thank you very much, Dianna. I hope things go okay for your friend.

Dianna Mendez on October 08, 2018:

Thank you for the excellent material on this topic. I have a friend whose doctor advised surgery due to the formation of bacterial biofilm. Great information to have for those who have had surgery.

Linda Crampton (author) from British Columbia, Canada on September 28, 2018:

Thank you for the visit and the comment, Cynthia.

Cynthia Zirkwitz from Vancouver Island, Canada on September 28, 2018:

Linda,I appreciate the clarity and simplicity you bring to this subject. I don't think I want to get a hip replacement, though.

Linda Crampton (author) from British Columbia, Canada on September 10, 2018:

Thank you very much, Eman.

Eman Abdallah Kamel from Egypt on September 10, 2018:

An educational and useful article. Thanks, Linda.

Linda Crampton (author) from British Columbia, Canada on September 08, 2018:

Hi, Larry. It's certainly an interesting fact! I appreciate your visit.

Larry Rankin from Oklahoma on September 08, 2018:

Just weird that the stuff that is always present can also destroy us.

Very informative read.

Linda Crampton (author) from British Columbia, Canada on September 08, 2018:

I hope researchers find solutions for antibiotic resistance soon, too. I hope you have a great weekend as well, Heidi.

Heidi Thorne from Chicago Area on September 08, 2018:

Yikes! My hubby works in a hospital environment and these kinds of issues are always of concern for patients and for those that care for them. As I think you've addressed in other posts, the search is on for new ways to combat these types of organisms. I do hope they find some answers soon.

Thanks for all the great info, as always! Have a great weekend!

Linda Crampton (author) from British Columbia, Canada on September 08, 2018:

Hi, Mary. Thanks for the comment. There is certainly a lot to consider with respect to our health. The nature and effects of medications are vital topics to think about.

Mary Norton from Ontario, Canada on September 08, 2018:

Linda, the research in this area has made us understand many things we take for granted. I understood many things from your hub. We were in the hospital yesterday and it is amazing how much we have to look out for even in the medications we take and the helps we have to make us live a quality of life. More research has to be supported.

Linda Crampton (author) from British Columbia, Canada on September 08, 2018:

Thanks for the visit, Bill. Biology can certainly be complex, but I think it's also interesting and important. Humans and other life forms are amazing entities.

Linda Crampton (author) from British Columbia, Canada on September 08, 2018:

Hi, Manatita. Yes, there is hope. I sometimes hear about the discovery of a new chemical from nature that might be able to act as an antibiotic. The discoveries and testing are taking time, though.

Bill Holland from Olympia, WA on September 08, 2018:

Linda, your articles force us to think, darn it! lol There is no casual skimming of your articles, no understanding the message by just reading the first paragraph...this is complicated information which requires a commitment to read and comprehend. Thankfully you are good at "simplifying" it so we can comprehend.

Linda Crampton (author) from British Columbia, Canada on September 08, 2018:

That sounds like a dramatic movie, Flourish. Medical implants can be very useful. It's horrible when they are harmful as well.

Linda Crampton (author) from British Columbia, Canada on September 08, 2018:

Thanks, Pamela. The situation could be a problem for people with a variety of health conditions. I hope new ways of dealing with the microbe are discovered.

manatita44 from london on September 08, 2018:

Interesting, educational and frightening at the same time. You end with hope. Let's hope ...

FlourishAnyway from USA on September 08, 2018:

You've given me one MORE reason to be concerned about medical devices like hip replacements, various meshes and implants. I recently watched a documentary movie on Netflix called "The Bleeding Edge" that was so vivid and real in its warnings that it would make you really wary. Yikes!

Pamela Oglesby from Sunny Florida on September 08, 2018:

I imagine this is a real problem for those that are immunosuppressed, like those receiving cancer treatments or those with autoimmune diseases. It sounds extremely important to keep in the best health possible Excellent article.

Linda Crampton (author) from British Columbia, Canada on September 07, 2018:

Hi, RTalloni. I appreciate your visit. Yes, I think that overuse of antibiotics has played a major role in speeding up resistance. The medications are essential for some infections, but it's a great shame that they are sometimes prescribed when they aren't needed.

RTalloni on September 07, 2018:

Thanks for this understandable look this staph that can turn into an infection. It is interesting to read of the double antibiotic approach possibly reducing resistance.

As I understand it, doctors over prescribing antibiotics, especially writing prescriptions for some of the most powerful antibiotics to treat simpler infections has played a large part in antibiotic resistant infections. Do you think this is true?

Linda Crampton (author) from British Columbia, Canada on September 07, 2018:

Thank you very much, Jackie. I agree—it is important to stay as healthy as we can, especially as we grow older.

Jackie Lynnley from the beautiful south on September 07, 2018:

I would say this should encourage us to always keep our health in good shape and not let our resistance lower, especially as we age. Great information, easy to understand and serious enough to get our attention, Linda. Thank you.

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