Dr. Charles "Pat" Davis, MD, PhD, is a board certified Emergency Medicine doctor who currently practices as a consultant and staff member for hospitals. He has a PhD in Microbiology (UT at Austin), and the MD (Univ. Texas Medical Branch, Galveston). He is a Clinical Professor (retired) in the Division of Emergency Medicine, UT Health Science Center at San Antonio, and has been the Chief of Emergency Medicine at UT Medical Branch and at UTHSCSA with over 250 publications.
Melissa Conrad Stöppler, MD, is a U.S. board-certified Anatomic Pathologist with subspecialty training in the fields of Experimental and Molecular Pathology. Dr. Stöppler's educational background includes a BA with Highest Distinction from the University of Virginia and an MD from the University of North Carolina. She completed residency training in Anatomic Pathology at Georgetown University followed by subspecialty fellowship training in molecular diagnostics and experimental pathology.
Do different types of necrotizing fasciitis exist?
Variations of necrotizing fasciitis are placed by some investigators into three general groups, roughly based on the genera of organisms causing the infection and some clinical findings that unfortunately vary from patient to patient. Type 1 is either caused by more than two bacterial genera (polymicrobial) or by the infrequently found single bacterial genus such as
Vibrio or fungal genera such as Candida. Type 2 is caused by Streptococcus spp, and
type 3 (or termed type 3 gas gangrene) is caused by
Clostridium spp. One example of clinical findings (gas in tissues) is more often found in
type 3, but can be found in types 1 and 2 also. Many investigators elect not to use this typing system and simply identify the organism(s) causing the necrotizing fasciitis.
What causes necrotizing fasciitis?
Most cases of necrotizing fasciitis are caused by bacteria; only rarely do other organisms such as fungi cause this disease. Group A
Streptococci and Staphylococci, either alone or with other bacteria, cause many cases of necrotizing fasciitis, although
Clostridium spp should be considered as a cause especially if gas is found in the infected tissue. Because of better microbial isolation techniques for anaerobic bacteria, bacterial genera such as
Bacteroides, Peptostreptococcus, and Clostridium are often cultured from the infected area. Frequently, culture of tissue involved by necrotizing fasciitis also yields a mixture of other
non-anaerobic bacterial genera such as
E. coli, Klebsiella, Pseudomonas, and others. Many investigators conclude that
non-anaerobic organisms damage tissue areas enough to cause local areas of hypoxia (reduced oxygen) where anaerobic organisms then can thrive and extend the infection further. This results in polymicrobial infection in which one type of bacteria aids the survival and growth of another type of bacteria (synergy). Infrequently,
Vibrio vulnificus causes the disease when a person, usually someone with liver function problems (for
example, alcoholics or immunosuppressed patients), eats contaminated seafood or a wound gets contaminated with seawater containing
Vibrio vulnificus.
In general, the bacteria that cause necrotizing fasciitis utilize similar methods to cause and advance the disease. Most produce toxins that inhibit the immune response, damage or kill tissue, produce tissue hypoxia, specifically dissolve connective tissue, or do all of the above. In polymicrobic infections, one bacterial genus may produce one toxic factor (for
example,
E. coli causing tissue hypoxia) while different types of coinfecting bacteria may produce other toxins that lyse
(disintegrate) damaged tissue cells or connective tissue.
MRSA (methicillin resistant Staphylococcus aureus) bacteria causes skin infections with the following signs and symptoms: cellulitis, abscesses, carbuncles, impetigo, styes, and boils. Normal skin tissue doesn't usually allow MRSA infection to develop. Individuals with depressed immune systems and people with cuts, abrasions, or chronic skin disease are more susceptible to MRSA infection.
Cellulitis is an acute spreading bacterial infection below the surface of the skin characterized by redness, warmth, inflammation, and pain. The most common cause of cellulitis is the bacteria Staph (Staphylococcus aureus).
Although a fever technically is any body temperature above the normal of 98.6 degrees F. (37 degrees C.), in practice a person is usually not considered to have a significant fever until the temperature is above 100.4 degrees F (38 degrees C.). Fever is part of the body's own disease-fighting arsenal: rising body temperatures apparently are capable of killing off many disease- producing organisms.
Sepsis (blood poisoning) is a potentially deadly infection with signs and symptoms that include elevated heart rate, low or high temperature, rapid breathing and/or a white blood cell count that is too high or too low and has more than 10% band cells. Most cases of sepsis are caused by bacterial infections, and some cases are caused by fungal infections. Treatment requires hospitalization, IV antibiotics, and therapy to treat any organ dysfunction.
Cuts, scrapes, and puncture wounds are common, and most people will experience one of these in their lifetime. Evaluating the injury, and thoroughly cleaning the injury is important. Some injuries should be evaluated by a doctor, and a tetanus shot may be necessary. Treatment will depend upon the severity of the injury.
Gangrene may result when blood flow to a tissue is lost or not adequate to keep the tissue alive. There are two types of gangrene: wet and dry. All cases of wet gangrene are infected by bacteria. Most cases of dry gangrene are not infected. If wet gangrene goes untreated, the patient may die of sepsis and die within hours or days. Dry gangrene usually doesn't cause the patient to die. Symptoms of dry gangrene include numbness, discoloration, and mummification of the affected tissue. Wet gangrene symptoms include swelling, pain, pus, bad smell, and black appearance of the affected tissue. Treatment depends upon the type of gangrene and how much tissue is compromised by the gangrene.
Group A streptococcal infections are caused by group A streptococcus, a bacteria that causes a variety of health problems, including strep throat, impetigo, cellulitis, erysipelas, and scarlet fever. There are more than 10 million group A strep infections each year.
Cellulite is caused by fat deposits that distort connective tissues under the skin, resulting in a dimpled appearance of the skin. Gender, skin thickness, heredity, and the amount and distribution of body fat all influence the presence and visibility of cellulite.
Bug bites and stings have been known to transmit insect-borne illnesses such as West Nile virus, Rocky Mountain spotted fever, and Lyme disease. Though most reactions to insect bites and stings are mild, some reactions may be life-threatening. Preventing bug bites and stings with insect repellant, wearing the proper protective attire, and not wearing heavily scented perfumes when in grassy, wooded, and brushy areas is key.
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