Bilateral Lower Extremity Necrotizing Fasciitis Caused by Extended-Spectrum Beta-Lactamase-Producing Escherichia coli in a Liver Transplant Recipient.

Necrotizing fasciitis (NF) is a rapidly progressive and life-threatening soft tissue infection that typically affects a single extremity, whereas bilateral or multifocal involvement is rare and associated with high mortality. Gram-negative organisms, including extended-spectrum beta-lactamase (ESBL)-producing Escherichia coli, are uncommon causes but are increasingly recognized in immunocompromised patients and are often associated with fulminant clinical courses. We report a rare case of bilateral lower extremity NF caused by ESBL-producing E. coli in a woman in her seventies with a history of liver transplantation under long-term immunosuppression. The patient initially presented with bilateral lower leg erythema and swelling without necrosis, leading to a preliminary diagnosis of cellulitis. Despite antimicrobial therapy, her condition deteriorated with the development of systemic inflammatory response, coagulopathy, and subsequent localized necrosis. Imaging revealed subcutaneous gas, and surgical exploration confirmed NF. Both blood and wound cultures grew ESBL-producing E. coli, prompting escalation to carbapenem therapy. Repeated surgical debridement was performed, resulting in eventual infection control and successful limb preservation. This case highlights several important clinical considerations. First, NF caused by ESBL-producing E. coli may present with subtle early cutaneous findings despite rapid systemic deterioration, particularly in immunocompromised hosts. Second, bilateral involvement, although rare, should be considered in patients with risk factors such as chronic lymphedema and bacteremia. Finally, early recognition, prompt surgical exploration, and aggressive debridement combined with appropriate antimicrobial therapy are critical for survival and limb preservation.