Necrotizing fasciitis is a bacterial infection that causes the necrosis of the fatty subcutaneous skin layer and the fascia. Type I necrotizing fasciitis is the polymicrobial variant of the disease; more than one bacterial species is causing tissue necrosis. Type II necrotizing fasciitis is caused solely by hemolytic group A streptococcus, staphylococci species, or methicillin-resistant staphylococci aureus.

What is type I necrotizing fasciitis?

Definition:

Type I necrotizing fasciitis is the polymicrobial subtype of the disease. 

Incidence: 

Type I necrotizing fasciitis is more common than type II.

Organisms involved: 

A concoction of aerobic and anaerobic bacterial species is involved in type I necrotizing fasciitis. These include gram-positive organisms like Staphylococcus aureus, streptococcus pyogenes, gram-negative aerobes like Escherichia coli and Pseudomonas species; and anaerobic organisms, such as Clostridium species.

Risk factors:

Immunocompromised individuals are likely to be affected by type I necrotizing fasciitis. Examples of these include diabetics and those with renal or hepatic failure.

Location:

Type I necrotizing fasciitis affects the perineum or the trunk.

Gas formation: 

Type I necrotizing fasciitis has gas buildup within the tissue. It may have a foul odor.

What is type II necrotizing fasciitis?

Definition: 

Type II necrotizing fasciitis is the monomicrobial variant of the disease.

Incidence:

Type II necrotizing fasciitis is less common than type I.

Organisms involved:

Type II necrotizing fasciitis is caused by a single bacterial species. It is either hemolytic group A streptococcus or staphylococci species such as methicillin-resistant staphylococci aureus.

Risk factors: 

It often affects young and healthy individuals but can involve any age group. It often occurs as a superinfection over skin conditions such as Varicella. There is an increased risk of developing type II necrotizing fasciitis with pregnancy, affecting the postpartum surgical sites.

Location: 

Type II necrotizing fasciitis mainly involves the limbs.

Gas formation: 

Gas formation in tissues is not seen in type II necrotizing fasciitis.

Difference between type I and type II necrotizing fasciitis

Definition: 

Type I necrotizing fasciitis is the polymicrobial subtype of the disease. Type II necrotizing fasciitis is the monomicrobial variant of the disease.

Incidence: 

Type I necrotizing fasciitis is more common than type II.

Organisms involved: 

Both aerobic and anaerobic bacterial species are involved in type I necrotizing fasciitis. These include gram-positive organisms like Staphylococcus aureus, streptococcus pyogenes, gram-negative aerobes like Escherichia coli and Pseudomonas species; and anaerobic organisms, such as Clostridium species. Type II necrotizing fasciitis is caused by a single bacterial species. It is either hemolytic group A streptococcus or staphylococci species such as methicillin-resistant staphylococci aureus.

Risk factors:

Immunocompromised individuals are likely to be affected by type I necrotizing fasciitis. Examples of these include diabetics and those with renal or hepatic failure. Type II necrotizing fasciitis often affects young and healthy individuals but can involve any age group. It often occurs as a superinfection over skin conditions such as Varicella. There is an increased risk of developing type II necrotizing fasciitis with pregnancy, affecting the postpartum surgical sites.

Location:

Type I necrotizing fasciitis mainly affects the perineum or the trunk whereas type II necrotizing fasciitis mainly involves the limbs.

Gas formation: 

Type I necrotizing fasciitis has gas buildup within the tissue, unlike type II necrotizing fasciitis which does not. 

Table of differences between type I and type II necrotizing fasciitis

FAQs

What is type II necrotizing fasciitis? 

Type II necrotizing fasciitis is the monomicrobial variant of the disease. It is caused by hemolytic group A streptococcus, staphylococci species, or methicillin-resistant staphylococci aureus. 

What is necrotizing fasciitis type 1? 

Type I necrotizing fasciitis is the polymicrobial variant of the disease. 

What is the classification of necrotizing fasciitis? 

There are three classes of necrotizing fasciitis: type I, II, and III. 

How can you tell the difference between necrotizing fasciitis? 

Biopsy and blood work are important to diagnose the type of necrotizing fasciitis.

What three types of bacteria can cause necrotizing fasciitis? 

Necrotizing fasciitis can be caused by gram-positive organisms like Staphylococcus aureus, streptococcus pyogenes, gram-negative aerobes like Escherichia coli and Pseudomonas species, and anaerobic organisms, such as Clostridium species.

What is the drug of choice for necrotizing fasciitis? 

Drugs such as piperacillin-tazobactam, vancomycin, carbapenem, cefotaxime, metronidazole or clindamycin are used to treat necrotizing fasciitis. 

Can Covid cause necrotizing fasciitis? 

Covid increases the risk of getting necrotizing fasciitis. 

What organs does necrotizing fasciitis affect? 

Skin and fascia. 

How fast does necrotizing fasciitis spread? 

It may spread as fast as an inch per hour.

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