Identification of infectious species after resection of soft-tissue sarcomas

Background: Pathogenic species in deep tissue infections after soft-tissue sarcoma (STS) resection is largely unstudied, particularly the role of anaerobic bacteria, risks factors for those pathogens, and the time course of infection presentation. Methods: Retrospective analysis of 64 patients requiring operative debridement for deep tissue infection after STS resection was undertaken to identify infectious species and study risk factors for anaerobic infections. Kaplan–Meier methods examined the time course of infection presentation. Results: STS subtypes were most commonly pleomorphic STS, myxofibrosarcoma, and undifferentiated STS. Staphylococcus aureus was the most common organism isolated (56%). Twenty (31%) infections were positive for ≥1 anaerobic organism. Twelve gram-positive and 10 gram-negative aerobic organisms were isolated. Most (90%) anaerobic-containing infections were polymicrobial, vs 52% of purely aerobic infections. No significant risk factors for anaerobic infections were identified. Median time from tumor resection until debridement was significantly greater for anaerobic infections (54.5 days) than for purely aerobic infections (29.5 days; P = 0.004), a difference so pronounced that using “presentation after 53 days” as a proxy for the presence of anaerobic pathogens had an accuracy of 81%. Conclusions: Because polymicrobial and anaerobic bacterial infections are common, we strongly support antibiotic use with anaerobic coverage at debridement, particularly for infections presenting later.