Bacteria: The Cause of Infectious Skin Diseases - The Great Courses Daily News

By Barry C. Fox, M.D., University of Wisconsin

Bacteria is also responsible for causing harmful skin infections such as, flesh-eating bacteria or necrotizing fasciitis in humans. It's said that flesh-eating bacteria are responsible for 10 percent of deaths in the United States. What are the causes and symptoms of such life-threatening bacterial skin infections?

The medical designation for flesh-eating bacteria is necrotizing fasciitis. (Image: Nephron/Public domain)

The Lymphatic System

Anatomically, within the dermis layer of the skin are channels of the body that help return extra fluids to the heart. This is known as the lymphatic system. Think of the lymphatic system as a giant spider web all over your body, which slowly helps move any fluid that's outside the arteries and veins back to the heart. 

This fluid is clear and yellow in color and resembles the fluid from the inside of a simple blister in its character. Well, aside from channeling the fluid, the lymph system also aids the immune system in transporting necessary cells to help fight infection.

The lymph system channels into lymph nodes, which is why lymph nodes are enlarged when there's any type of infection. When the lymphatic system is involved with infection, often with an abscess nearby, there's a visible red streaking of the skin, known as lymphangitis.

This is a transcript from the video series An Introduction to Infectious Diseases. Watch it now Wondrium.

Types of Bacterial Skin Infections

Another skin infection is known as cellulitis. When this occurs, the infection is larger than 5 cm and extends above and below the presumptive portal of entry. It usually is hot, thickened, painful, and very red and can spread to the bloodstream and the lymph nodes. Obviously, Staph aureus and streptococcal germs are the most common culprits in cellulitis. 

Lymphangitis reveals that the lymphatic system is dealing with an infection. (Image: TisforThan/Shutterstock)

Another example is erysipelas of the face, which is caused by streptococcal germs. All cellulitis and lymphangitis will require either oral or intravenous antibiotics, or both, depending upon the healthcare provider's assessment of the severity of the infection. 

Puncture wounds of the hands and feet, as well as animal bites, are also forms of cellulitis and lymphangitis. However, under these circumstances, it's the bacteria from the object that causes the puncture, such as the bacteria in the dog's or cat's mouth, that is the infection culprit, rather than the skin bacteria itself.

Flesh-Eating Bacteria: Causes, Symptoms, and Treatments

The worst type of skin infection involves all skin layers, leading to destruction and essentially the death of the skin tissue and muscle. This has many names, and the common layman's term is flesh-eating bacteria, but the medical name is necrotizing fasciitis. Although this can be caused by Staph aureus or Strep, there are other bacteria that alone, or in combination, can lead to this condition.

The management of necrotizing fasciitis is challenging. Virtually all patients have a body-wide sepsis response, which requires control of the infection, antibiotics, and intensive care support. Necrotizing fasciitis is considered a medical emergency, and surgery is always required. Multiple surgeries, and even amputation, may be necessary not only to control the infecting bacteria but to remove tissue that is no longer alive.

Learn more about the history of antibiotic development.

MRSA: Antibiotic-Resistant Bacteria

Methicillin-Resistant Staph aureus, abbreviated MRSA, has been singled out by the Centers for Disease Control, or CDC, as one of the most important resistant bacteria of the present day. The original strains of MRSA date back nearly 40 years to the hospital setting. Staph bacteria acquired a large extrachromosomal genetic element known as a plasmid, making it resistant to all antibiotics, with the exception of the antibiotic vancomycin.

Current concerns about MRSA focus on a slightly different variety of MRSA, called community-based MRSA. This organism appeared in the late 1990s and generally has continued to increase in prevalence in the community. It has a smaller resistance plasmid, so there are more antibiotics that can be used for treatment when compared to the hospital strain of MRSA.

Features of Antibiotic-Resistant Bacteria

MRSA is not necessarily any stronger or more virulent than Staph aureus, but since it is resistant to many common antibiotics, it's more difficult to treat and may be more likely to require intravenous therapy. It may also be more prone to cause abscess formation. Anyone can acquire the germ since it's spread from skin-to-skin contact or contact with infected surfaces.

The most common presentations of community-based MRSA are skin infections, typically boils. But simply having the germ on your skin does not automatically mean you will have problems with infections. An infection may never occur, and the germ may be replaced by normal bacteria of the skin over time.

Learn more about the diseases caused by bacteria.

Troubles of Infectious Skin Diseases While Traveling

One example of skin infections is caused by bot fly attacks. The larva of the fly infests the skin and lives in the subcutaneous layer, creating a painful pustule. Over time the larva continues growing, as does the pain. The adult bot fly resembles a bumblebee, so if traveling to Central or South America, be on the lookout.

The bite of a sandfly causes skin infections. (Image: YewLoon Lam/Shutterstock)

Another skin infection to watch out for is leishmaniasis. If traveling in one of 90 countries where the vector sandfly resides, beware of a small fly that is about 1/3 of the size of a mosquito.

Tourists in Costa Rica, for example, have presented with small bites that increase in size and become ulcerous. This infection is caused by Leishmania protozoa that are transmitted by the sandfly.

One more infection to watch out while traveling is called cutaneous larva migrans. This skin infection is due to a dog or cat intestinal hookworm, and it can be contracted by walking on contaminated lakes and ocean beaches. The first sign might be the intense itching of the site. Next, one would see a raised red rash with a snakelike progression, which is the worm's burrowing path.

Therefore, it is very important to remain cautious while traveling and seek immediate medical attention if the situation becomes difficult to control.

Common Questions about Bacterial Skin Infections

Q: What is lymphangitis?

Lymphangitis occurs when the lymphatic system becomes infected. Lymphangitis is caused by a bacterial infection but is not as dangerous as a flesh-eating bacteria infection.

Q: What is the culprit for flesh-eating infection?

Flesh-eating bacterial infections are usually caused by Staph aureus or Streptococcal, but other bacteria alone or in combination can cause this skin infection as well. It should be noted this infection is very hard to manage.

Q: What is the treatment for flesh-eating bacterial infection?

The most definitive treatment for eradicating flesh-eating bacterial infection is surgery. In some cases, amputation is required to remove dead tissues and to prevent the infection from progressing.

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