Editing Necrotizing fasciitis (section)

==Causes==

===Risk factors===
Vulnerable populations are typically older with medical comorbidities such as diabetes mellitus, obesity, and immunodeficiency.<ref name="Paz2014" />  Other documented risk factors include:

* Any trauma or lacerations
* Injection drug use
* Recent surgery
* Injury of mucous membranes, including hemorrhoids, rectal fissures
* Peripheral artery disease
* Cancer
* Alcohol use disorder
* Pregnancy or recent childbirth<ref name=":5" />

For reasons that are unclear, it can also infect healthy individuals with no previous medical history or injury.<ref name=":5" /><ref>{{cite journal |vauthors= Pricop M, Urechescu H, Sîrbu A, Urtilă E |title= Fasceita necrozantă cervico-toracică: caz clinic și recenzie a literaturii de specialitate |trans-title= Necrotizing cervical fasciitis: clinical case and review of literature |language= ro |journal= Revista de Chirurgie Oro-Maxilo-Facială și Implantologie |issn= 2069-3850 |volume= 2 |issue= 1 |pages= 1–6 |date= Mar 2011 |url= http://www.revistaomf.ro/(1)Colectia-pe-ani/(15)Anul-2011/(16)Numarul-1-2011/(17)Fasceita-necrozanta-cervico-toracica-caz-clinic-si-recenzie-a-literaturii-de-specialitate |url-status= dead |archive-url= https://web.archive.org/web/20160322050522/http://www.revistaomf.ro/(1)Colectia-pe-ani/(15)Anul-2011/(16)Numarul-1-2011/(17)Fasceita-necrozanta-cervico-toracica-caz-clinic-si-recenzie-a-literaturii-de-specialitate |archive-date= 2016-03-22 |access-date= 2016-04-07 }}</ref>

[[Non-steroidal anti-inflammatory drug|NSAIDs]] may increase the rates of necrotizing infections by impairing the body's immune response. NSAIDs inhibit the production of [[Prostaglandin E2|prostaglandins]] responsible for fever, inflammation, and pain. In theory, it also prevents [[Leukocyte extravasation|white blood cells from migrating to infected areas]], thus increasing the risk of soft-tissue infections.<ref name="Hak2014" /><ref name=":5" />

Skin infections such as abscesses and ulcers can also complicate NF. A small percentage of people can also get NF when bacteria from [[streptococcal pharyngitis]] spreads through the blood.<ref name=":6">{{Cite journal |last=Olsen |first=Randall J. |last2=Musser |first2=James M. |date=2010-01-01 |title=Molecular Pathogenesis of Necrotizing Fasciitis |url=https://www.annualreviews.org/doi/10.1146/annurev-pathol-121808-102135 |journal=Annual Review of Pathology: Mechanisms of Disease |language=en |volume=5 |issue=1 |pages=1–31 |doi=10.1146/annurev-pathol-121808-102135 |issn=1553-4006|url-access=subscription }}</ref> For infection of the perineum and genitals ([[Fournier gangrene]]), [[urinary tract infection]], [[Kidney stone disease|renal stones]], and [[Bartholin gland]] abscess may also be implicated.<ref name="Hak2014" />

=== Prevention ===
Good wound care and handwashing reduces the risk of developing necrotizing fasciitis.<ref name="CDC2016" /> It is unclear if people with a weakened immune system would benefit from taking antibiotics after being exposed to a necrotizing infection.  Generally, such a regimen entails 250 mg penicillin four times daily for 10 days.<ref name=":5" />

===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>