Surgical Site Infection

A surgical site infection (SSI) is an infection that occurs in the part of the body where surgery took place, developing within a defined window after the operation. SSIs are among the most common healthcare-associated infections and a leading category of postoperative complication, prolonging recovery and increasing morbidity.

Definition

A surgical site infection is an infection related to a surgical procedure that occurs at or near the surgical incision within a specified postoperative period, conventionally classified by depth as superficial incisional, deep incisional, or organ/space infection.

Scope

This topic covers the definition and standard classification of surgical site infections, the principal risk factors, the mechanisms by which they develop, and the evidence-based domains of prevention emphasized in major guidelines. It is a reference entry and does not prescribe antibiotic regimens or individualized care.

Key concepts

• Superficial incisional, deep incisional, and organ/space SSI
• Wound classification (clean, clean-contaminated, contaminated, dirty)
• Surgical antimicrobial prophylaxis
• Bacterial contamination and host defense balance
• Normothermia and glycemic control
• Skin antisepsis and aseptic technique

Mechanisms

SSIs develop when microbial contamination of the surgical site overwhelms local host defenses. Contaminating organisms are most often the patient's own skin, mucosal, or hollow-viscus flora introduced during the procedure. Whether contamination progresses to clinical infection depends on the inoculum and virulence of the organisms, the presence of devitalized tissue or foreign material, and the patient's immune and tissue-perfusion status. Prevention guidelines therefore target this balance through measures that reduce the microbial load (skin antisepsis, appropriately timed antimicrobial prophylaxis) and support host defenses (maintaining normothermia, perfusion, and glycemic control) (Berríos-Torres, 2017; Allegranzi, 2016).

Clinical relevance

Surgical site infection is a tracked indicator of surgical quality and infection control, and its prevention is a focus of national and international guidelines (Berríos-Torres, 2017; Anderson, 2014; Ban, 2017). This entry summarizes how SSIs are defined and the conceptual basis of prevention for reference; it is not a substitute for clinical protocols or individualized management.

Epidemiology

Surgical site infections are one of the most frequently reported healthcare-associated infections and a substantial source of postoperative morbidity and additional cost worldwide; their incidence varies with the wound class, operation type, and surveillance methods used (Berríos-Torres, 2017; Allegranzi, 2016).

Evidence & guidelines

Contemporary prevention rests on guidelines from the U.S. Centers for Disease Control and Prevention (Berríos-Torres, 2017), the World Health Organization (Allegranzi, 2016), the Society for Healthcare Epidemiology of America and partners (Anderson, 2014), and the American College of Surgeons with the Surgical Infection Society (Ban, 2017). These converge on bundled measures spanning skin antisepsis, prophylactic-antibiotic timing, normothermia, and glycemic control.

History

Antisepsis in surgery traces to the nineteenth-century work that introduced antiseptic wound management, but the systematic surveillance and standardized definition of surgical site infection are largely a development of late-twentieth-century infection control, later consolidated into the comprehensive prevention guidelines now in use (Berríos-Torres, 2017; Allegranzi, 2016).

Debates

How strong is the evidence for individual prevention bundle components?

Major guidelines grade their recommendations and acknowledge that some prevention measures rest on stronger evidence than others, so the relative contribution of individual bundle elements remains an area of ongoing evaluation.

Seminal works

• berrios-torres-2017
• allegranzi-2016

Frequently asked questions

How is a surgical site infection classified?

It is conventionally classified by depth as superficial incisional (skin and subcutaneous tissue), deep incisional (fascia and muscle), or organ/space (any anatomic structure opened or manipulated during the operation).

What are the main targets of SSI prevention?

Prevention focuses on reducing microbial contamination and supporting host defenses, through measures such as skin antisepsis, appropriately timed antimicrobial prophylaxis, and maintenance of normothermia and glycemic control (Berríos-Torres, 2017).