Streptococcus milleri group (SMG) is a common inhabitant of the mouth and gastrointestinal tract, and can be an aggressive pathogen causing abscess formation at various sites in the body. However, it has rarely been listed as a cause of head and neck infections. The present study was performed to evaluate the clinical significance of SMG by reviewing the microbiology and clinical records of patients with SMG in head and neck infections retrospectively. A retrospective review of all patients diagnosed as having SMG bacterial infections at Onomichi General Hospital, Hiroshima, between the years 2001 and 2002 was performed; 17 patients developed head and neck infections with SMG. Here, we describe the clinical features and management of SMG in head and neck infection. The patient population consisted of 12 males and 5 females with a median age of 62 years (age range, 8-78 years). The sites of infection were as follows: maxillary sinus (n=6), peritonsillar region (n=4), subcutaneous (n=3), submandibular space-retropharyngeal space (n=1), deep neck-mediastinum (n=1), parapharyngeal space (n=1), submandibular space (n=1), tonsil (n=1), parotid gland (n=1), and masseter muscle (n=1). Ten cases (59%) were of suppurative diseases. Six cases (35%) had mixed SMG with anaerobe infection. Three cases showed deteriorating clinical courses, and all three of these cases were culture-positive for SMG with anaerobes. In addition, one deteriorating case showed gas gangrene regardless of repeated surgical debridement and intravenous antibiotic therapy; hyperbaric oxygen therapy improved this patient’s condition.

Hirai, Kimura, Mori, , , , , , (2005). Head and neck infections caused by Streptococcus milleri group: an analysis of 17 cases. Auris, nasus, larynx, 2005 Mar;32(1):55-8. https://www.ncbi.nlm.nih.gov/pubmed/15882827