Mixta calida, not only an environmental bacterium, but a potential opportunistic threat: Case report of an osteitis with skin necrosis and mini review of the literature

Background: Mixta calida, previously known as Pantoea calida, is an environmental bacterium rarely associated with human pathologies. Rare case reports mention sepsis, meningitis and implantable defibrillator infection. Case presentation: A 67-year-old female with multiple comorbidities was referred to the emergency room for a comminuted fracture of both right tibial plateaus secondary to a fall and for which she benefited from an external fixator. After removal of the fixator, failure of osteosynthesis and placement of a new fixator, a skin necrosis appeared and a propeller distal anteromedial thigh perforator flap was performed. After 6 weeks, she presented a necrosis of the flap and an osteitis. The bone biopsy was positive with pure M. calida. The patient underwent an above-knee amputation, but 6 weeks later the wound was dehiscent and again positive with pure M. calida. Conclusions: Serious infections due to M. calida are uncommon but can occur in immunocompromised patients. This case illustrates the first reported osteitis and skin necrosis due to M. calida.