Editing Necrotizing fasciitis (section)

===Bacteria===
Necrotizing fasciitis is divided into four classes by the type of bacteria causing the infection. This classification system was first described by Giuliano and his colleagues in 1977.<ref name=Paz2014/><ref name=Hak2014/>

'''Type I infection''': This is the most common type of infection, and accounts for 70 to 80% of cases. It is caused by a mixture of bacterial types, usually in abdominal or groin areas.<ref name="Paz2014" /> These bacterial species include:

* [[Gram-positive]] cocci (''[[Staphylococcus aureus]]'', ''[[Streptococcus pyogenes]]'', and [[Enterococci]])<ref name="CDC2016" />
* [[Gram-negative]] rods (''[[Escherichia coli]]'', ''[[Pseudomonas aeruginosa]], [[Klebsiella]] species,'' ''[[Bacteroides]]'' species, ''[[Prevotella]]'' species)<ref name="CDC2016" />
* ''[[Clostridium]]'' species (''[[Clostridium perfringens]]'', ''[[Clostridium septicum]]'', and ''[[Clostridium sordellii]]'')<ref name="Paz2014" />

In polymicrobial (mixed) infections, [[Streptococcus pyogenes|Group A Streptococcus]] (''S. pyogenes'') is the most commonly found bacterium, followed by ''[[Staphylococcus aureus|S. aureus]].''<ref name=":6" /> However, when the infection is caused solely by ''S. pyogenes'' and/or ''S. aureus'', it is classified as a Type II infection.

Gram-negative bacteria and anaerobes like ''Clostridia'' are more often implicated in [[Fournier gangrene]]. This is a subtype of Type I infections affecting the groin and perianal areas.<ref name=":6" /> ''Clostridia'' account for 10% of overall type I infections and typically cause a specific kind of necrotizing fasciitis known as [[gas gangrene]] or myonecrosis.

'''Type II infection''': This infection accounts for 20 to 30% of cases, mainly involving the extremities.<ref name=Paz2014/><ref name="SaraniStrong2009">{{cite journal |last1=Sarani |first1=Babak |last2=Strong |first2=Michelle |last3=Pascual |first3=Jose |last4=Schwab |first4=C. William |title=Necrotizing Fasciitis: Current Concepts and Review of the Literature |journal=Journal of the American College of Surgeons |volume=208 |issue=2 |pages=279–288 |year=2009 |pmid=19228540 |doi=10.1016/j.jamcollsurg.2008.10.032 }}</ref> This involves ''[[Streptococcus pyogenes]]'', alone or in combination with [[Staphylococcus|staphylococcal]] infections. [[Methicillin-resistant Staphylococcus aureus|Methicillin-resistant ''Staphylococcus aureus'']] (MRSA) is involved in up to a third of Type II infections.<ref name="Paz2014" /> Infection by either type of bacteria can progress rapidly and manifest as [[Toxic shock syndrome|shock]]. Type II infection more commonly affects young, healthy adults with a history of injury.<ref name=Hak2014/>

'''Type III infection''': ''[[Vibrio vulnificus]]'' is a bacterium found in [[Seawater|saltwater]]. It occasionally causes NF after entering the body through a break in the skin.<ref name=":7">{{Cite journal |last=Coerdt |first=Kathleen M |last2=Khachemoune |first2=Amor |date=2021-03-01 |title=Vibrio vulnificus: Review of Mild to Life-threatening Skin Infections |url=https://www.mdedge.com/dermatology/article/236136/infectious-diseases/vibrio-vulnificus-review-mild-life-threatening-skin |journal=Cutis |volume=107 |issue=2 |doi=10.12788/cutis.0183}}</ref> One in three patients with a ''V. vulnificus'' infection develop necrotizing fasciitis.<ref name=":7" /> Disease progression is similar to type II but sometimes with few visible skin changes.<ref name=Hak2014/>

'''Type IV infection''': This type of NF accounts for less than 1% of cases. It is mostly caused by the ''[[Candida albicans]]'' fungus. Risk factors include age and immunodeficiency.<ref name=Paz2014/><ref>{{Cite journal |last1=Buchanan |first1=Patrick J. |last2=Mast |first2=Bruce A. |last3=Lottenburg |first3=Lawrence |last4=Kim |first4=Tad |last5=Efron |first5=Philip A. |last6=Ang |first6=Darwin N. |date=June 2013 |title=Candida albicans Necrotizing Soft Tissue Infection |url=https://journals.lww.com/annalsplasticsurgery/abstract/2013/06000/candida_albicans_necrotizing_soft_tissue.32.aspx |journal=Annals of Plastic Surgery |volume=70 |issue=6 |pages=739–741 |doi=10.1097/SAP.0b013e31823fac60|pmid=23123606 |url-access=subscription }}</ref>