Table 1: Definitions of superficial, deep, and organ/space SSIs as defined by the National Healthcare Safety Network. The comments are specifically applied to elective colon surgery.

DefinitionComments specific for elective colon surgery

Superficial SSI: infection occurs within 30 days after any NHSN operative procedure, infection involves only skin or subcutaneous tissue of the incision, and the patient has at least one of the following.
(1) Purulent drainage, with or without laboratory confirmation, from the superficial incision.
(2) Organisms isolated from an aseptically-obtained culture of fluid or tissue from the superficial incision.
(3) Superficial incision is deliberately opened by a surgeon and is culture-positive or not cultured, and patient has at least one of the following signs or symptoms: pain or tenderness: localized swelling; redness; or heat. A culture negative finding does not meet this criterion.
(4) Diagnosis of superficial incisional SSI by the surgeon or attending physician, or other designee (nurse practitioner or physician’s assistant).
(1) There are two specific types of superficial incisional SSIs.
(i) Superficial Incisional Primary (SIP): a superficial incisional SSI that is identified in the primary incision in a patient that has had an operation with one or more incisions (e.g., primary laparotomy site in a colectomy).
(ii) Superficial Incisional Secondary (SIS): a superficial incisional SSI in a secondary incision (e.g., second incision site of a colostomy closure).
(2) Do not report stitch abscess (minimal inflammation and discharge confined to the points of suture penetration).
(3) Do not report a localized stab wound or drain site infection as an SSI.
(4) Do not report cellulitis by itself as an SSI.
(5) Incisional SSI that extends into the fascial and muscle layers is reported as a deep incisional SSI, not a superficial SS.

Deep SSI: infection occurs within 30 days after elective colon resection and involves deep soft tissues of the incision (e.g., fascial and muscle layers), and the patient has one of the following.
(i) Purulent drainage from the deep incision (i.e., pus)
(ii) A deep incision that spontaneously dehisces or is deliberately opened by a surgeon and is culture-positive or not cultured, and the patient has at least one of the following signs and symptoms: fever (>38°C); localized pain or tenderness. A culture-negative finding does not meet this criterion.
(iii) An abscess or other evidence of infection involving the deep incision that is found on direct examination, during invasive procedure, or by histopathologic examination or imaging test.
(iv) Diagnosis of a deep incisional SSI by a surgeon or attending physician or other designee (nurse practitioner or physician’s assistant).
(i) There are two types of deep incisional SSIs.
(a) Deep Incisional Primary (DIP): a deep incisional SSI that is identified in a primary incision where multiple incisions exist (e.g., midline laparotomy and colostomy closure site).
(b) Deep Incisional Secondary (DIS): a deep incisional SSI that is identified in the secondary incision where multiple incisions may exist (e.g., colostomy closure site).
(ii) Infections involving both superficial and deep sites should be classified as deep incisional SSIs.
(iii) The attending physician is interpreted to mean.
(a) Surgeon
(b) Infectious disease specialist
(c) Other physician on the case
(d) Emergency physician
(e) Physician’s designee

Organ/Space SSI: infection occurs within 30 days after elective colon resection and infection involves any part of the body, excluding the skin incision, fascia, or muscle layers, that is opened or manipulated during the operative procedure, and the patient has at least one of the following.
(i) Purulent drainage from a drain that is placed into the organ/space.
(ii) Organisms isolated from an aseptically-obtained culture of fluid or tissue in the organ space.
(iii) An abscess or other evidence of infection involving the organ/space that is found on direct examination, during invasive procedure, or by histopathologic examination or imaging test.
(iv) Diagnosis of an organ/space SSI by a surgeon or attending physician or other designee (nurse practitioner or physician assistant).
(i) Because an organ/space SSI involves any part of the body (excluding skin incision, fascia, or muscle layers) that is manipulated during the operative procedure, criterion for infection at these body sites must be met in addition to the organ/space SSI criteria.
(ii) If a patient has an infection in the organ/space being operated on and the surgical incision was closed primarily, subsequent continuation of this infection type during the remainder of the surveillance period is considered an organ/space SSI, if organ/space SSI and site-specific infection criteria are met.
(iii) Occasionally an organ/space infection drains through the incision and is considered a complication of the incision. Therefore, classify it as a deep incisional SSI. (e.g., subfascial abscess).