Necrotizing Fasciitis Caused by ESBL-Producing Raoultella ornithinolytica in an Immunocompromised Patient with VEXAS Syndrome

VEXAS (vacuoles, E1 enzyme, X-linked, autoinflammatory somatic) syndrome has a poor prognosis, with infections being a major cause of death. Raoultella ornithinolytica is an environmental bacterium found predominantly in soil and water. Although R. ornithinolytica can cause various infections, necrotizing fasciitis due to this bacterium has not been reported. We describe the case of an 84-year-old Japanese male with VEXAS syndrome who developed septic shock and necrotizing fasciitis while he was under immunosuppressive therapy. The pathogen was initially misidentified as R. planticola by mass spectrometry but later confirmed by whole-genome sequencing as extended spectrum β-lactamase (ESBL) produced by R. ornithinolytica. Although a life-saving leg amputation was required, the patient recovered with appropriate antibiotic therapy. R. ornithinolytica is thus able to cause severe skin infections in immunocompromised individuals.