15 Years of Surgical Wound Infection Surveillance at a Tertiary Care Center: Emerging Trends from an Analysis of 54,949 wounds

Michele Loor, University of Minnesota Medical Center; JJ Glover, University of Minnesota Medical Center; Catherine Statz, University of Minnesota Medical Center; Rachel Ott, University of Minnesota Medical Center; Jean Dominique Morancy, University of Minnesota Medical Center; Gregory Beilman, University of Minnesota

The first surgical site infection (SSI) surveillance systems emerged in the 1970s as an effort to improve outcomes through the analysis of SSI data. In this study, we examined 15 years of SSI data at a single tertiary care academic medical center, with a focus on trends and microbiologic characteristics.

An SSI surveillance program is able to capture SSI trends and microbial resistance.

We conducted a retrospective analysis of our prospectively-collected SSI surveillance data for general surgery patients from Jan 2000 through Dec 2014.  We compared three 5-year periods (2000-2004, 2005-2009, and 2010-2014) with respect to SSI rates and pathogens.

We analyzed 54,949 wounds: 13,312 for 2000-2004; 19,729 for 2005-2009; and 21,908 for 2010-2015.  Of these, 23,907 were class 1 and 28,111 were class 2.  Using the criteria of the National Healthcare Safety Network we identified 2,032 SSIs. Over our 15-yr study period, the overall SSI rate increased, primarily due to an increase in the number of class 2 SSI.  SSIs due to ESBL also increased over time; however, infections related to other pathogens did not change.

Figure 1.  SSIs by wound class. *P < 0.0002, 2-tailed Z test, vs. 2000-2004. 

Figure 2. Pathogens isolated from SSIs. *P = 0.002, Fisher exact test vs. 2000-2004.  ESBL = extended-spectrum beta-lactamase; MRSA = methicillin-resistant S aureus; VRE = vancomycin-resistant enterococci

SSI surveillance permits identification of SSI trends. Interestingly, class 2 and ESBL-related SSIs increased—perhaps reflecting an increasingly complex patient population and a corresponding increase in the complexity level for clean-contaminated cases. In addition, changes in infection control policies implemented during our 15-year study period may have contributed to our findings.  Correlating these SSI trends with causative factors will help us tailor future infection control protocols.