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Necrotizing Fasciitis from an essay by Katrina Tram Duong, edited by S.N. Carson M.D.

Necrotizing fasciitis, known commonly known as "flesh eating bacteria [infection]", occurs in a wide range of people 1. It occurs in the elderly, middle aged and younger patients. It occurs in athletes and debilitated individuals. It can occur in drug abusers with self inflicted wounds and healthy individuals with incidental injuries. It may occur in those with metabolic disorders such as diabetes and those with suppressed immune systems. It may occur in those with no underlying disorders and no known particular injury. It occurs under ordinary circumstances such as a seemingly harmless cut or scrape and in wounds resulting from major trauma such as an auto accident.

There is no single way of contracting necrotizing fasciitis. One patient reported that he caught it while he was at the beach and may have scraped his skin. There are some cases that have been reported after bug or dog bites. We have also seen confirmed drug users who got the infection but declared they didn't know how the bacteria could have entered their body. There have been numerous cases where injection of illicit drugs can produce infections that present with signs of a simple cutaneous abscess and yet unpredictably evolve into an extensive necrotizing soft tissue infection 1.

Fig1. This is a picture of a leg with full blown necrotizing fasciitis, just prior to surgery. Note the discoloration. The skin feels crepitant and the area is extremely tender. A larger picture with detail is available by clicking this thumbnail print.

Necrotizing fasciitis is a deep infection of the subcutaneous tissues that results in progressive destruction of fat and fascia. The progression is usually rapid and, as an example, this author has seen it spread throughout one leg in a little over one hour. Of course, this has an instant effect on the blood supply to these areas. Alternative names for necrotizing fasciitis are fasciitis-necrotizing; infection-necrotizing subcutaneous; subcutaneous infection-bacterial5. Untreated and unconstrained, it can destroy massive amounts of tissue and result in amputation and even death in a short period of time.

Fig. 2. Another leg as above presurgical for necrotizing fasciitis. When first seen two hours prior, the discoloration was only present at the ankle. A larger picture with detail is available by clicking this thumbnail print.

Necrotizing fasciitis is caused most commonly by Streptococcus pyogenes, group A streptococcus, which is the same bacteria that causes common strep throat 8. However, many findings suggest different types of bacteria cause necrotizing fasciitis Medical studies suggest that necrotizing fasciitis might be caused by a variety of aerobic, facultatively anaerobic bacteria and group B streptococcus2,4. Other findings suggest necrotizing fasciitis can also be cause by a mixture of bacteria2. The predominant aerobes include Staphylococcus aureus and Escherichia coli. The predominant anaerobes include Bacteroides fragilis, and Peptostreptococcus and Clostridium species4. Clostridium, of course, is the classic cause of "gas gangrene".

The invasions by group A streptococci cause the host to release cytokines, including interferon3. These substances, in combination with the bacterial toxin, can cause vascular thrombosis and ischemic gangrene of the overlying skin. This is one reason why the infection can advance rapidly and produce a lethal outcome for the patient.

Fig. 3. A sacral decubitus ulcer that tripled in size over a few hours and came to attention by extreme pain. This was a group A streptococci infection. This is a presurgical picture. A larger picture with detail is available by clicking this thumbnail print.

Most often the bacteria enters the body through an opening in the skin, very often a minor opening even as small as a paper cut, a staple puncture, or a pinprick. It can also enter through slightly disrupted skin, such as a bruise, blister, or abrasion 8. It my happen following a major trauma or surgery, and in a few cases there appears to be no identifiable point of entry. It is assumed that healthy individuals can fight off the disease, but it has taken its toll in seemingly healthy people. Those at greatest risk appear to be children with chicken pox, individuals with suppressed immune systems, and very young children and people over the age of 65 4.

Once the bacteria enter the body, they begin to grow and release toxins that kill tissues directly, interfere with the blood flow to the tissues and thus cause further delay in the immune response. The digested materials from the necrotic tissues allow the bacteria to thrive and spread rapidly. Visible expansion of the infection may occur in less than an hour 5.

Fig.4. Surgical fasciotomy incision with debridement of leg with necrotizing fasciitis. A larger picture with detail is available by clicking this thumbnail print. Over the next seven weeks this patient healed and returned to normal function.

Some of the early symptoms are pain in the general area of the injury, not necessarily at the site of injury but in the same region or limb of the body8. The pain is usually disproportionate to the injury, being much more severe than the injury appears 6. Flu like symptoms may occur, such as diarrhea, nausea, fever, confusion, dizziness, weakness, and general malaise. Intense thirst occurs as the body becomes dehydrated. All or most of these symptoms combined is a sign of advanced disease 5.

Within a short time (a few hours to a few days) some of the advanced symptoms appear. The area of body experiencing pain begins to swell, and the skin may become crepitant, and show a purplish or mottled rash 8. The limb may begin to have large, dark marks, that will become blisters filled with blackish fluid which causes the wound to appear necrotic with a bluish, white, or dark, mottled, flaky appearance. Later the body begins to go into toxic shock from the toxins the bacteria are given off. Blood pressure will drop severely and unconsciousness will occur as the bodies responses fail to fight off this infection.

Fig. 4. Fasciotomy and debridement involving knee area in a patient with necrotizing fasciitis. A larger picture with detail is available by clicking this thumbnail print.

In order to avert disaster and provide early treatment, the diagnosis is clinical, based on finding the above and having a high degree of clinical suspicion. Furthermore, diagnosis is based on identification of streptococci from clinical specimens, usually either blood cultures and/or aspiration of pus from tissue 7. Gram stain