Editing Sepsis (section)

== Cause ==

[[File:Patient lying in bed in intensive care unit of hospital with apparatuses and hemodialysis machine.jpg|thumb|Patient of an [[intensive care unit]] of a German hospital (2015) with severe sepsis caused by a [[chain reaction]] of incidental negative events after a prior surgery of the [[abdomen]]. After an emergency surgery, he received [[antibiotics]], [[parenteral nutrition]] and [[pain killer]]s via automated injection employing [[infusion pump]]s (background right). [[Hemodialysis]] via the machine on the left became necessary due to [[kidney]] malfunction and [[multiple organ dysfunction syndrome]]. After three months in the hospital, the patient recovered within a month and has since then fully recovered (as of 2023).]]

Infections leading to sepsis are usually [[pathogenic bacteria|bacterial]] but may be [[mycosis|fungal]], [[Parasitic disease|parasitic]], or [[viral disease|viral]].<ref name= "Mandell2014"/> [[Gram-positive bacteria]] were the primary cause of sepsis before the introduction of antibiotics in the 1950s. After the introduction of antibiotics, [[gram-negative bacteria]] became the predominant cause of sepsis from the 1960s to the 1980s.<ref name="Polat"/> After the 1980s, gram-positive bacteria, most commonly [[staphylococci]], are thought to cause more than 50% of cases of sepsis.<ref name="Martin2012"/><ref name="BlochID"/> Other commonly implicated bacteria include ''[[Streptococcus pyogenes]]'', ''[[Escherichia coli]]'', ''[[Pseudomonas aeruginosa]]'', and ''[[Klebsiella]]'' species.<ref name="Ramachandran2014"/> [[Fungemia|Fungal sepsis]] accounts for approximately 5% of severe sepsis and septic shock cases; the most common cause of fungal sepsis is an infection by ''[[Candida (fungus)|Candida]]'' species of [[yeast]],<ref name="Delalove2014"/> a frequent [[hospital-acquired infection]]. The most common causes for parasitic sepsis are ''[[Plasmodium]]'' (which leads to [[malaria]]), ''[[Schistosoma]]'' and ''[[Echinococcus]]''.

The most common sites of infection resulting in severe sepsis are the lungs, the abdomen, and the urinary tract.<ref name= "Mandell2014"/> Typically, 50% of all sepsis cases start as an infection in the lungs. In one-third to one-half of cases, the source of infection is unclear.<ref name= "Mandell2014"/>