Necrotizing Soft Tissue Infections: Wound Microbiology and Outcomes at a Regional Quaternary Referral Center
Juan Vazquez; Karina Charipova; Melissa McLawhorn; Lauren Moffatt; Jack Sava; Jeffrey Shupp
Background:The incidence of Necrotizing Soft Tissue Infections (NSTI) remains consistently low; however, morbidity and mortality rates remain high. Clinical diagnosis remains nuanced, and suspicion of NSTI often results in transfer to regional referral centers. Etiologic microorganisms can be grouped into Type I (Polymicrobial), Type II (Group A β-hemolytic Streptococci +/- Staphylococci), or Type III (monomicrobial, Clostridium spp. or Gram negative). A retrospective review was conducted to examine the outcomes of NSTI patients based on wound microbiology.
Hypothesis:Patients with Type II NSTI will have increased morbidity and mortality compared to patients with Type I NSTI.
Methods:An 8-year retrospective chart review was performed, including all patients evaluated by the acute care surgery or burn surgery service with NSTI, confirmed by operative report and positive wound cultures. Demographic data was collected, as well as culture and laboratory results. Mortality was the main outcome measure. Non-parametric continuous data were analyzed using a Mann-Whitney U test. Categorical data were analyzed by Fisher’s exact test.
Results:Sixty-nine patients met inclusion criteria. Most (58%) were female, with a median age of 55. 72.5% were African American. Forty-two cases were classified as Type I, 25 as Type II, and 2 cases as Type III. One patient had cultures positive for Vibrio vulnificus and two patients had 6 different bacteria isolated from their wounds. The overall mortality rate was 7.25, with a median length of stay of 16 days (IQR = 8.8-30) Type II patients had a significantly higher mortality (4) compared to Type I (1, p = 0.0368). Immature granulocyte percentage and PTT were higher in Type II (p = 0.03; < 0.0001) compared to Type I. Lactate (p = 0.101) level and white cell count (p = 0.845) were not significantly different between types.
Conclusions:Patients in the Type II group had a significant increase in mortality. Overall mortality rates were lower than reported elsewhere. This may represent selection bias, or improvements in aggressive surgical care. Bacterial subtype may be an important driver of outcomes in this important disease, and should be the topic of further study.