Surgical Site Infection Prevention Quiz

Preventing Surgical Site Infections: Basic Principles and Pathogenesis

• Surgical site infections (SSIs) have been a consistent complication of surgical care throughout history.
• The introduction of antiseptics and antibiotics have helped to prevent SSIs, but they still account for 22% of all hospital-acquired infections and are responsible for extended hospital stays and excess costs.
• SSIs occur due to a complex interaction between microbial contamination, host response, and the local environment.
• Essentially every surgical site is contaminated with bacteria by the end of the procedure.
• The source of the pathogen for SSIs may be the air of the operating room, surgical instruments, or breaches in the surgeons' gloves.
• Contamination commonly arises from the endogenous microflora of the patient's skin, and operations that violate areas of normal colonization increase the risk of infection.
• The probability of infection is determined by the interaction of four clinical variables: inoculum of bacteria, virulence of bacteria, adjuvants in the microenvironment, and efficiency of host defenses.
• The risk for SSI is related to the number of microorganisms contaminating the wound, and a quantitative threshold can be identified for each microbe.
• The largest inoculum of bacteria into the surgical site occurs when the operation invades a body structure that is ordinarily heavily colonized with bacteria.
• The human rectosigmoid colon may have bacterial density of 1012 bacteria per gram of content, meaning any procedure that enters the colon lumen will result in major microbial contamination of the surgical site.
• Experienced surgeons know that the complexity of the multiple interactions of microbe and host will result in infections in even the most skilled of surgical hands.
• Acceptable methods for the prevention of infection include proper hand hygiene, surgical attire, and use of prophylactic antibiotics, among others.

Risk Factors for Surgical Site Infections

• The virulence of the bacterial contaminant is a variable that contributes to the risk for surgical site infections (SSIs).
• Coagulase-positive staphylococci, group A streptococci, and Clostridium perfringens require only a small inoculum to cause severe infections at the surgical site.
• Escherichia coli has endotoxin as a component of the cell structure, which can cause severe local and systemic inflammatory effects.
• Bacteria release exotoxins that can directly damage tissue or inhibit host defenses.
• Microbial synergism is a possibility where one microbe can cause severe infections when part of a polymicrobial infection.
• The microenvironment of the surgical wound can predispose to infection.
• Hemoglobin at the surgical site in the form of a hematoma stimulates microbial proliferation.
• Foreign bodies such as surgical sutures or implanted surgical devices provide a surface for microbial proliferation.
• The presence of necrotic tissue is thought to provide a sanctuary for contaminants to avoid phagocytic actions of the host.
• Surgical wounds with large dead space result in the accumulation of serum and other inflammatory fluids that pose an obstacle for the phagocytosis of contaminants by leukocytes.
• Different patients may have different rates of SSI because of the efficiency of their host defense.
• Many patient-related factors have been evaluated to determine those patients who might have risks likely to cause postoperative infectious complications.
• The traditional wound classification system of categorizing procedures into risk groups based on the degree of microbial contamination has been used for over 40 years to stratify patients by risk for SSI, but it has the shortcoming that it uses only the inoculum of bacterial contamination expected during a procedure as the principal variable for predicting infection.