Table 1 SSI definition according to Mangram et al. [18]

Superficial SSI is an infection that involves only skin or subcutaneous tissue of the surgical incision. An infection occurs within 30 days after the index operation and the infection involves only skin or subcutaneous tissue of the incision and at least one of the following:

a. Purulent drainage, with or without laboratory confirmation, from the superficial incision

b. Organisms isolated from an aseptically obtained culture of fluid or tissue from the superficial incision

c. At least one of the following signs or symptoms of infection: pain or tenderness, localized swelling, redness, or heat and superficial incision that is deliberately opened by the surgeon, unless incision is culture negative

d. Diagnosis of superficial incisional SSI by the surgeon or attending physician

Deep incisional SSI is an infection which involves deep soft tissues. Deep soft tissues are typically any tissue beneath skin and immediate subcutaneous fat, for example, fascial and muscle layers. It is an infection that occurs at the surgical site within 30 days after the principal operative procedure and involves deep soft tissues and at least one of the following:

a. Purulent drainage from the deep incision but not from the organ/space component of the surgical site

b. A deep incision spontaneously dehisces or is deliberately opened by a surgeon when the patient has at least one of the following signs or symptoms: fever (> 38.0° C, localized pain, or tenderness, unless the site is culture-negative

c. An abscess or other evidence of infection involving the deep incision is found on direct examination, during reoperation, or by histopathologic or radiologic examination

d. Diagnosis of a deep incision SSI by a surgeon or attending physician

Organ/space SSI is an infection that involves any part of the anatomy (e.g., organs or spaces), other than the incision, which was opened or manipulated during an operation. It is an infection that occurs within 30 days after the principal operative procedure and involves any of the anatomy (e.g., organs or spaces), other than the incision, which was opened or manipulated during the operation and at least one of the following:

a. Purulent drainage from a drain that is placed through a stab wound into the organ/space. This does not apply to drains placed during the principal operative procedure, which are continually in place, with continual evidence of drainage/infection since the time of the principal operative procedure

b. Organisms isolated from an aseptically obtained culture of fluid or tissue in the organ/space

c. An abscess or other evidence of infection involving the organ/space that is found on direct examination, during reoperation, or by histopathologic or radiologic examination

d. Diagnosis of an organ/space SSI by a surgeon or attending physician