LUNG ABSCESS CAUSED BY SOLOBACTERIUM MOOREI IN A PATIENT WITH SEVERE COPD

Abstract

INTRODUCTION: Solobacterium moorei is a gram-positive anaerobic bacillus isolated from human feces. Samples taken from subjects with and without halitosis analyzed by bacterial culture and direct amplification of nucleic acids indicate Solobacterium moorei is associated with halitosis which produce volatile sulfur compounds which can be toxic to tissues. This bacteria is often associated with Fusobacterium nucleatum which has been indicated as a cause of pulmonary abscesses and upper airway infections (reference 1). Reports of infection with Solobacterium moorei are rare with two studies in the literature finding S. moorei in blood cultures in a septic patient with multiple myeloma. Another recent case reported S. moorei bacteremia in a patient with acute proctitis and cervical carcinoma. A third case implicates S. moorei as one of the pathogens in thrombophlebitis and septic pulmonary embolism emphasizing the thrombogenic potential of necrobacillosis organisms (reference 2). CASE PRESENTATION: A 47 year old female with a history of severe COPD presented with a 45 pound weight loss and malaise over six months. She was afebrile but experienced night sweats and back pain. Chest x-ray revealed a new cavitary lesion in the left upper lobe with elevated hilum and volume loss. CT of the chest showed a 5.7 by 6 cm large multiseptated thick-walled irregular cavitary lesion in the left upper lobe surrounded by parenchymal consolidation in the apical and posterior segments with air bronchograms seen within the consolidated portion as well as severe diffuse emphysema predominantly in the upper lungs consistent with her smoking history (figure 1). PET scan showed intense hypermetabolic activity in the left upper lobe corresponding to the lesion and the infiltrative aspect of the lesion (figure 2). A bronchoscopy with brush biopsy and bronchoalveolar lavage was performed. Anaerobic cultures from the lavage revealed gram positive rods which were isolated to be Solobacterium Moorei with the following MIC: Clindamycin 8 mug/ml, Ciprofloxin 0.75 mug/ml and Metronidazole 0.125 mug/ml. Left upper lobe biopsy was consistent with rare non-caseating granulomas. The patient received a 43 day course of metronidazole however her antibiotic regimen was changed to clindamycin for 54 days after she developed peripheral neuropathy in her lower extremities. The antibiotic course was finished after the symptoms subsided and follow-up CT showed a stable cavitary lesions. DISCUSSIONS: Solobacterium moorei may have clinically significant pathogenic potential as indicated by this case. It can be distinguished from Eubacterium, Lactobacillus, Propionibacterium and Bifidobacterium by metabolic end products of glucose fermentation. Most of the isolates are found in the oral cavity, periodontitis sites in patients with halitosis and most are associated with oro-dental diseases such as dental abscesses or odontogenic infections. Primary foci of necrobacillosis infection outside the head and neck are rare but we are reporting a primary source case in the lung. Portal of entry of the lung infection could not be established but periodontal disease constituted the most probable origin of the infection since S. moorei is essentially found among the oral flora. CONCLUSION(S): In the past, this organism has not been recognized as being clinically significant or pathological because of the specific growth requirements and lack of identification by formal testing. Often this organism if found is one of multiple species in an infection. However this case proves the pathological and significant clinical disease manifestations of this organism.