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Necrotizing Fasciitis

Necrotizing fasciitis (NF) is a relatively uncommon but potentially fatal infection involving the subcutaneous tissue and fascia, a sheet of fibrous or tendinous tissue that lies deep to the skin or covers muscles and various body organs. It is commonly known as flesh-eating disease because the bacteria destroy everything in their path, digesting skin, fat, and even blood vessels. Deaths from NF can be sudden and sensational and often make headline news. The disease is not new. Hospital physicians had seen it in contaminated wounds since the Civil War. They knew it as "hospital gangrene," "putrid ulcer," "wasting flesh" and by other names.

Causative Agents

Necrotizing fasciitis has been subdivided into type I, or polymicrobial necrotizing fasciitis, and type II, or invasive group A streptococcal necrotizing fasciitis. Over the past decade the incidence of the disease due to group A streptococci has increased. The Centers for Disease Control and Prevention estimates 10,000 - 15,000 cases of invasive group A streptococcus annually, with 5-10% of those being necrotizing fasciitis 7. When necrotizing fasciitis is localized to the lower abdominal wall, perineum, or genitals, it is called Fournier gangrene.

Originally it was thought that the infection was caused by hemolytic streptococci. However, better culture techniques have demonstrated that organisms other than Streptococcus pyogenes are more common causative agents. When careful bacteriologic techniques are used, anaerobes, particularly Peptostreptococcus, Bacteroides, and Fusobacterium species, are found in 50 to 60 percent of cases. Aerobic organisms, especially Streptococcus pyogenes, Staphylococcus aureus, Proteus, Klebsiella, Pseudomonas, Citrobacter, members of the Enterobacteriaceae and Clostridia (C. perfringens and C. septicum) have also been isolated. Most infections are mixed aerobic-anaerobic infections, but a type of necrotizing fasciitis caused solely by Streptococcus pyogenes has been reported and is referred to by the lay press as "flesh eating bacteria." 3 The first two cases of necrotizing fasciitis caused by Clostridium tertium were reported in 2003 4,5. A case of necrotizing fasciitis caused by Ruminococcus productus, a Gram-positive, obligatory anaerobe was reported in 2008 12. Necrotizing fasciitis due to Vibrio vulnificus may result in overwhelming sepsis, leading to death in some patients. Significant risk factors for severe disease include preexisting liver disease 14. A trivial infection after a minor dog bite in an immunocompromised patient such as diabetes patient could result in a life-threatening infection 15.


Necrotizing fasciitis of the leg and foot


Necrotizing fasciitis
source: J Korean Med Sci. 2011

Risk Factors

The infection undermines adjacent tissue and leads to marked systemic toxicity. Thrombosis of subcutaneous blood vessels leads to necrosis of the overlying skin. Initial local pain is replaced by numbness or analgesia as the infection involves the cutaneous nerves. Most cases of fasciitis follow surgery or minor trauma. Although infectious complications from acupuncture are extremely rare, a case of severe necrotizing fasciitis (type 1) in an elderly nondiabetic male was reported in 2010 13. The highest incidence is seen in patients with small vessel diseases such as diabetes mellitus.

Signs and Treatment

Frequently, the patient has fever, excruciating pain, tachycardia, and low blood pressure. Later, systemic toxicity develops, and definitive evidence of necrotizing fasciitis appears. Early signs of the necrolytic process are redness of the skin, or red, shiny, swollen skin that progresses to bluish or purplish areas with fluid-filled blisters with a watery, thin, foul-smelling discharge, often termed "dish water pus." Swelling extends well beyond areas of redness 7,9

One of the three particularly feared types of group A streptococcal infections along with myositis and streptococcal toxic shock syndrome, necrotizing fasciitis has a high mortality (up to 40 percent). Early diagnosis and aggressive surgical treatment reduces risk. However, it is often difficult to diagnose NF, and sometimes patients are treated for simple cellulitis until they rapidly deteriorate. Broad-spectrum antibiotic therapy is mandatory, and early surgical exploration and debridement is critical to ensuring a good outcome 1. Surgical treatment may be too late at this stage because infection has extended to vital organs such as head, neck, chest, abdomen which are often impossible to debride 5.

Infections in Companion Animals

In dogs necrotizing fasciitis is similar to the disease caused by Streptococcus pyogenes in humans. Reports of rapidly progressive and fatal necrotizing fasciitis caused by Streptococcus canis,Staphylococcus pseudintermedius, and E. coli have been recorded. Though Streptococcus species is known to be carried on the skin and mucous membranes of healthy dogs, within the last few years veterinarians have been seeing necrotizing fasciitis in adult animals.

Necrotising fasciitis and necrotising myositis are rare but serious life threatening conditions reported mainly in human beings and dogs. However, cats can also have this disease. There have been reports of Fournier's gangrene with signs of lethargy, mucoid anal discharge, and fever, as well as rapidly progressing infections with Prevotella bivia, Acinetobacter baumannii, and Streptococcus canis in cats 16-19. Infections with Streptococcus canis seem to be particularly aggressive causing rapid progression from necrotizing fasciitis with skin ulceration to toxic shock-like syndrome, sepsis, and death in cats 20.

Staphylococcus pseudintermedius has been isolated from the nares of veterinary personnel and was the cause of a soft tissue infection in a human. While it is currently unclear whether S. pseudintermedius poses a zoonotic risk, it has been suggested that S. pseudintermedius is likely a zoonotic pathogen because of the genetic similarity between canine and human isolates and because zoonotic transmission of S. intermedius has been documented 10.

References
  1. Necrotizing fasciitis
  2. Levine EG, Manders SM. . Life-threatening necrotizing fasciitis
  3. Baron S, editor. Medical Microbiology. 4th edition
  4. Clostridium tertium in Necrotizing Fasciitis and Gangrene
  5. Streptococcal Toxic-Shock Syndrome: Spectrum of Disease, Pathogenesis, and New Concepts in Treatment
  6. Jeffrey C. Pommerville. Alcamo's Fundamentals of Microbiology
  7. Mark S. Granick, Richard L. Gamelli. Surgical Wound Healing And Management
  8. Steven L. Percival. Microbiology and Aging: Clinical Manifestations
  9. Noah Craft, Lowell A. Goldsmith, Lindy P. Fox. VisualDx: Essential Adult Dermatology
  10. J. Scott Weese, Roberta Poma, Fiona James, Gilbert Buenviaje, Robert Foster, and Durda Slavic. Staphylococcus pseudintermedius necrotizing fasciitis in a dog
  11. Worth AJ, Marshall N, Thompson KG.. Necrotising fasciitis associated with Escherichia coli in a dog
  12. Livaoglu M, Yilmaz G, Kerimoglu S, Aydin K, Karacal N. Necrotizing fasciitis with ruminococcus
  13. Macuha F Jr, Ahn A, Graham R. Necrotizing fasciitis associated with acupuncture: a case report
  14. Kenneth L. Muldrew, Russell R. Miller, Megan Kressin, Yi-Wei Tang, and Charles Stratton. Necrotizing Fasciitis from Vibrio vulnificus in a Patient with Undiagnosed Hepatitis and Cirrhosis
  15. A case of necrotizing fasciitis due to Streptococcus agalactiae, Arcanobacterium haemolyticum, and Finegoldia magna in a dog-bitten patient with diabetes
  16. Berube DE, Whelan MF, Tater KC, Bracker KE. Fournier's gangrene in a cat
  17. Sura R, Hinckley LS, Risatti GR, Smyth JA. Fatal necrotising fasciitis and myositis in a cat associated with Streptococcus canis
  18. Brachelente C, Wiener D, Malik Y, Huessy D. A case of necrotizing fasciitis with septic shock in a cat caused by Acinetobacter baumannii
  19. Pesavento PA, Bannasch MJ, Bachmann R, Byrne BA, Hurley KF. Fatal Streptococcus canis infections in intensively housed shelter cats
  20. Streptococcus

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