Outcomes of Beta-Hemolytic Streptococcal Necrotizing Skin and Soft Tissue Infections and the Impact of Clindamycin Resistance

Background: Beta-hemolytic streptococci are frequently implicated in necrotizing soft tissue infections (NSTI). Clindamycin administration may improve outcomes in patients with serious streptococcal infections. However, clindamycin resistance is growing worldwide, and resistance patterns in NSTI and their impact on outcomes are unknown. Methods: Between 2015 and 2018, NSTI patients at a quaternary referral center were followed for death, limb loss, and streptococcal toxic shock syndrome (STSS). Surgical wound cultures and resistance data were obtained within 48 hours of admission as part of routine care. Risk ratios for the association between these outcomes and the presence of beta-hemolytic streptococci, or presence of clindamycin-resistant beta-hemolytic streptococci were calculated using log-binomial regression, controlling for age, transfer status, and injection drug use-related etiology. Results: Of 445 NSTI identified, 85% had surgical wound cultures within 48 hours of admission. 31% grew beta-hemolytic streptococci, and clindamycin resistance was observed in 32% of patients. The presence of beta-hemolytic streptococci was associated with greater risk of amputation (RR 1.80 [95% CI 1.07-3.01]), as was the presence of clindamycin- resistance among beta-hemolytic streptococci infections (RR 1.86 [95% CI 1.10-3.16]). Discussion: Beta-hemolytic streptococci are highly prevalent in NSTI, and in our population clindamycin resistance was more common than previously described. Greater risk of limb loss amongst patients with beta-hemolytic streptococci—particularly clindamycin-resistant strains—may portend a more locally aggressive disease process or may represent pre-existing patient characteristics that predispose to both infection and limb loss. Regardless, these findings may inform antibiotic selection and surgical management to maximize the potential for limb salvage.