Group B Streptococcus-Associated Necrotizing Soft Tissue Infection Following Minor Ankle Trauma: A Case Report.

Necrotizing soft tissue infections (NSTIs) are rapidly progressive, life- and limb-threatening emergencies requiring immediate surgical source control. Group B Streptococcus (GBS; Streptococcus agalactiae) is a rare cause of NSTIs in adults. We present a 44-year-old woman with poorly controlled diabetes who developed progressive right foot pain and swelling after minor ankle trauma. Examination showed spreading erythema, crepitus, dusky discoloration, malodor, and a deep plantar wound, accompanied by marked leukocytosis and diabetic ketoacidosis. Computed tomography demonstrated infection extending from the forefoot through the ankle into the anterior compartment of the leg, prompting emergent exploration that confirmed extensive NSTI. Two wound specimens obtained before antibiotics yielded heavy GBS growth, whereas deep intraoperative ankle and leg specimens collected after starting antibiotics grew heavy Streptococcus anginosus and moderate Prevotella species. Despite broad-spectrum antibiotics and debridement, transtibial amputation was required. This case highlights a rare GBS-associated polymicrobial NSTI and emphasizes early recognition of progressive soft-tissue findings despite an apparently minor musculoskeletal injury.