Necrotizing fasciitis is a severe type of skin infection caused by group A beta-hemolytic streptococci (streptococcus pyogenes). Most scientists now agree that various bacterial species can result in necrotizing fasciitis, either alone or together. Sometimes, fungal species can also cause necrotizing fasciitis. It is a rapidly progressing infection that can destroy top skin layers, underlying muscles, and also subcutaneous tissues. Because of this rapid nature, necrotizing fasciitis is also called "flesh-eating" or "skin-eating" infection, and the causative organisms as "flesh-eating bacteria."

Even though this infection is rare, you can get infected even through a tiny cut. If failed to diagnose and treat promptly, it can be fatal. Around 600 and 700 cases of necrotizing fasciitis are reported in the United States every year, and 25 to 30 % of these cases result in death. The mortality rate of necrotizing fasciitis affecting the scrotum is 75 %, but infection in other regions of the body, legs, or arms, is around 25 to 30 %.

What Are the Types of Necrotizing Fasciitis?

Necrotizing fasciitis is divided into the three following types:

Type 1 - Infection caused by more than one type of bacteria or by rare bacterial species such as Vibrio vulnificus or fungus Candida. Commonly occurs after trauma or surgery.
Type 2 - Infection caused by streptococcus bacteria, rarely seen after minor cuts, abrasion, and insect bites.
Type 3 (gas gangrene) - Wounds that get infected with clostridium bacteria.

How Are Flesh-Eating Bacteria Transmitted?

Bacteria that cause necrotizing fasciitis can enter your body through:

Minor cuts.
Surgical incision.
Any other injury.
Burns.
Insect bites.
Abrasions.

Sometimes, the infection can start without any apparent cause. But once it starts spreading, it rapidly destroys skin, muscle, and fat underneath. Various types of bacteria cause necrotizing fasciitis, and the most common type is group A streptococcus. But, other bacteria that can cause necrotizing fasciitis are Aeromonas hydrophila, Escherichia coli, Clostridium, Klebsiella, and Staphylococcus aureus.

What Are the Symptoms of Necrotizing Fasciitis?

Symptoms of necrotizing fasciitis usually appear after 24 hours of the entry of bacteria into the body. If the bacteria entered the body through a surgical wound, the patient would develop the following symptoms:

Severe pain in the surgical site.
Swelling or inflammation.
Fever.
Nausea.

The other signs and symptoms include:

Severe pain after a minor injury, such as a cut, abrasion, or opening.
The area around the wound looks red and feels warm.
Other flu-like symptoms include nausea, fever, chills, dizziness, diarrhea, malaise, and body pain.
Dehydration results in intense thirst.

Signs and symptoms that can develop at the site of infection within three to four days include:

Purplish-blue skin rash with swelling.
Violet marks that become blisters and are filled with foul-smelling fluid.
Black scabs (necrotic scabs).
Crackling sensation under the skin due to gas formation.
Foul-smelling fluid drains from the wound.
Gangrene - the tissues die and become discolored, peel, and flaky.

If left untreated, necrotizing fasciitis can lead to a drastic drop in blood pressure, toxic shock, loss of consciousness, and death.

How Is Necrotizing Fasciitis Diagnosed?

Doctors often diagnose necrotizing fasciitis based on the symptoms. They might conduct various tests to confirm the diagnosis. This might include taking a tissue sample from the affected skin. The causative organism will be isolated from this sample. To look at gas formation in tissues and the extent of the infection, the doctor might suggest Doppler ultrasound, CT (computed tomography) scan, or MRI (magnetic resonance imaging). If needed, the doctor will also suggest:

White blood cell (WBC) counts, which gets elevated in necrotizing fasciitis.
BUN (blood urea nitrogen) and sodium, which are decreased in necrotizing fasciitis.

What Are the Complications of Necrotizing Fasciitis?

Necrotizing fasciitis can lead to:

Sepsis (abnormal body's response to chemicals in the blood due to infection).
Streptococcal toxic shock syndrome (a very serious illness caused by group A streptococcus, where the body goes into shock, resulting in low blood pressure and multiple organ failure).
Loss of limbs.
Severe scarring.
Death.

One out of three people affected with necrotizing fasciitis dies even with treatment.

How Is Necrotizing Fasciitis Treated?

The microorganisms isolated from the tissue sample need to be tested for antibiotic resistance because most bacteria that cause this infection are resistant to multiple drugs.

IV (Intravenous) Antibiotics - Once the doctor suspects necrotizing fasciitis, they usually do not wait for a confirmatory diagnosis. The patient is immediately admitted, and IV antibiotics are administered. Most doctors prefer multiple antibiotics to be started at the same time to protect the patient from methicillin-resistant staphylococcus aureus (MRSA) and infection with multiple bacteria.

Antibiotic Susceptibility Tests - These tests are done on microorganisms isolated from the patient. This will help choose the antibiotics that will be most effective against the infection.

Surgical Drainage and Debridement - A surgeon will drain the pus and fluid from the infection site, and if needed, all the necrotic tissue will be removed.

Vacuum Dressings - A controlled negative pressure is applied to the wound to stimulate granulation tissue formation and wound healing.

Hyperbaric Oxygen Therapy - Here, a specialized chamber is used to give oxygen to the patient under pressure. Oxygen can stop the growth of anaerobic bacteria and promote tissue healing. When done along with surgical treatment and antibiotics, this therapy has shown to reduce mortality by 10 % to 20 %.

Skin Grafting - In cases where there is extensive damage to the skin, normal tissue from some part of the body is grafted on to the damaged part.

Amputation - When there is extensive damage to the limbs, amputation might be needed to stop the spread of the infection.

Multiple organ failure (heart, kidney, liver) and sepsis need to be treated aggressively to improve prognosis. The patient might need IV fluids, breathing tubes, and drugs to support the heart.

Can Necrotizing Fasciitis Be Prevented?

As a person with necrotizing fasciitis cannot spread the infection to other individuals, preventive antibiotics are not given to close contacts. There are no vaccines available to prevent infection with group A streptococcus,and the only way to protect ourselves is by good wound care.

Make it a point to clean all minor cuts and wounds with soap and water.
Always cover an open wound with dry bandages after you properly clean it.
If the wound is too deep, consult a doctor immediately.
And if you have any open injury, avoid using hot tubs, swimming pools, and rivers or lakes.

For more information on necrotizing fasciitis, you can consult an online doctor.