Quick Reference
Environment: ubiquitous
Microorganism: Gram + cocci
Spore former: NO
Motile: NO
Susceptibility: anyone; esp. those with weakened immune systems
Communicability: infectious
Exposure: scratch, open sores
Incubation: 24-48 hours
Primary Treatment: antibiotics, surgery
Prognosis: good with treatment
Quarantine recommended: YES
Use as a biological weapon: NO
Identification
First reported during the American Civil War when it was known as "hospital gangrene," group A streptococci, commonly referred to as "flesh eating bacteria", are responsible for an infection known as necrotizing fasciitis. Toxins destroy the skin and soft subcutaneous tissues. Though GAS are not the only bacteria responsible for causing necrotizing fasciitis, group A streptococci are one of the more common causes of infection.
GAS infections are commonly mild. It is only when rare strains of the bacteria enter the body through a wound or other site and begin to produce necrotizing toxins that the infection becomes deadly.
Laboratory indications:
-
Gram +
-
Anaerobic
Pathogenesis
Group A Streptococci normally infect the lining of the throat causing a severe irritation of the lining, strep throat. However, these bacteria occasionally enter deeper lying tissues and cause a deadly systemic infection. Scientists speculate that a coating on the exterior of these Streptococcal cells emit a chemical signal that convinces cells to mobilize. This effectively dissolves the barrier between the outer skin cells and the lining allowing the bacteria to enter the body. The chemical released by GAS mimics hyaluronic acid, a normal chemical released by cells when mobilization is necessary, such as during healing. The chemical binds to CD44 receptors on the surfaces of the cells and a gap opens between neighboring cells, allowing the bacteria to pass freely. The bacteria produce streptolysin S (SLS), a powerful toxin that possesses the ability to kill a wide variety of human cells.
Manifestations
A simple scratch acquired while walking in the woods or a shopping center can lead to this deadly infection. At first, the wound site may look like nothing more than an ordinary scratch or cut, but over the next 6-24 hours, the area will be become reddened and swollen and a fever will develop. Infection is often sudden and spreads rapidly, quickly becoming life-threatening.
As the infection spreads, serious illness and shock develop and tissue damage continues to advance. Hospitalization is necessary as surgery is required to stop the spreading infection. If the infection is allowed to continue unchecked, tissue degradation eventually leads to organ failure and death.
Treatment
Persons who have been diagnosed with a GAS infection should be prescribed antibiotics and isolated for 24 hours to decrease the likeliness of spreading the bacteria to others. Antibiotic treatment may include penicillin, aminoglycosides, cephalosporin, metronidazole, or clindamycin.
Additionally, patients with advanced or severe necrotizing fasciitis will require a hospital stay and surgery to halt the spread of infection. Patients may be placed in a hyperbaric chamber to speed recovery and healing.
Prevention
With mortality rates around 20%, necrotizing fasciitis is a very rare, but serious and deadly infection. Though anyone can develop necroting fasciitis, those with diabetes, cancer, and other chronic diseases are at greater risk. Even people who are in generally good health have succumbed to sudden infection and died as a result of a simple scratch.
Some factors that increase the risk of infection are:
- Weakened or compromised immune systems
- Surgical wounds
- Rashes
- Open sores or scratches
- Pre-existing or chronic health conditions, such as diabetes
It is important that people with diabetes take great care not to let sores, ulcers, and blisters fester since it creates a favorable environment for the development of necrotizing fasciitis.
Since infection can also be spread through direct human-to-human contact, hand washing is particularly important. It is equally important to keep all open sores clean and protected. Watch for signs of infection, such as swelling, redness, pain, and fluid at the wound site. Visit a doctor immediately if you suspect a GAS infection or if you have a severe sore throat accompanied by a high fever.
Necrotizing fasciitis
appearance of large,
black blisters typically
seen on infected
patients