Mandibular osteomyelitis due to Raoultella species.

Introduction: Raoultella is a genus of aerobic Gram-negative bacilli belonging to the family Enterobacteriaceae that are commonly found in water, soil and aquatic environments. With improved bacterial identification techniques, Raoultella species (namely R. planticola and R. ornithinolytica) have been an increasingly reported cause of infections in humans.

Case presentation: An 85-year-old man presented to hospital with a several-week history of left jaw pain and trismus. His medical history was significant for left mandibular osteomyelitis treated 1 year previously with amoxicillin-clavulanate. On admission, a computed tomography scan demonstrated a 2.6×1.7×1.6 cm peripherally enhancing collection surrounding the left posterior mandibular body. Two aspirates of the abscess grew a bacterium belonging to the genus Raoultella, with discordant species identification (R. ornithinolytica versus R. planticola) using two different techniques. A potential source of infection included a left lower molar tooth which was extracted months preceding the original diagnosis of osteomyelitis.

Conclusion: This is the first case of mandibular osteomyelitis caused by Raoultella species reported in the literature. In contrast to other forms of osteomyelitis, the pathogenesis of mandibular osteomyelitis involves contiguous spread from an odontogenic focus. Risk factors for mandibular osteomyelitis include a history of fracture, irradiation, diabetes and steroid therapy. This report adds to the growing literature of infections caused by this genus of bacteria, and raises the possibility of this organism's role in odontogenic infections.