Actinomycosis is rare, chronic, slowly progressive disease caused by gram-positive anaerobic organisms from the Actinomycosis family that normally colonizes the oral cavity. Actinomycotic osteomyelitis is even more rare and refractory disease because diagnosis by bacterial culture is not easy. In our case, 80-year-old man visited our clinic with a complaint of swelling and severe sinus tracts without teeth evolvement on anterior mandible. Computed tomography (CT) scan demonstrated erosive bone destruction on anterior mandible, clinically suspected actinomycotic osteomyelitis. The patient also had thoracic actinomycosis on Lt. lower lung. We could diagnosis actinomycosis by histopathologic examination. He treated by conservative surgery and long term antibiotics. After 2 year, no recurrence was seen in CT scan.

Osteomyelitis is an inflammatory condition of the bone caused by pathogenic bacteria. The causative pathogen is usually oral residing bacteria, but this is a report of patients with osteomyelitis infected with Enterobacteriaceae, which is not common. Enterobacteriaceae has been known to cause in-hospital infections for over last 30 years and is known to have multiple antibiotic resistances. Both cases in this study developed osteomyelitis after removal of the dentigerous cyst. Enterobacter aerogenes was cultured in one patient and Serratia marcescens in the other. After changing antibiotics through antibiotic susceptibility testing, clinical symptoms subsided and radiographic images confirmed that the callus formed and recovered at the same time.