Table 1 Criteria for defining a surgical site infection (SSI), according to the CDC criteria (cf. https://www.cdc.gov/hicpac/SSI/table1-SSI.html)

Superficial incisional SSI ^†

Infection occurs within 30 days after the operation and infection involves only skin or subcutaneous tissue of the incision and at least one of the following:

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

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

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

 Diagnosis of superficial incisional SSI by the surgeon or attending physician

Do not report the following conditions as SSI

 Stitch abscess (minimal inflammation and discharge confined to the points of suture penetration)

 Infection of an episiotomy or newborn circumcision site

 Infected burn wound

 Incisional SSI that extends into the fascial and muscle layers (see deep incisional SSI)

Deep incisional SSI ^‡

Infection occurs within 30 days after the operation if no implant† is left in place or within 1 year if implant is in place and the infection appears to be related to the operation and infection involves deep soft tissues (e.g., fascial and muscle layers) of the incision and at least one of the following:

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

 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 °C), localized pain, or tenderness, unless site is culture-negative

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

 Diagnosis of a deep incisional SSI by a surgeon or attending physician

Organ/space SSI ^‡

Infection occurs within 30 days after the operation if no implant† is left in place or within 1 year if implant is in place and the infection appears to be related to the operation and infection involves any part of the anatomy (e.g., organs or spaces), other than the incision, which was opened or manipulated during an operation and at least one of the following:

 Purulent drainage from a drain that is placed through a stab wound‡ into the organ/space

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

 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

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