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For further information, see CMDT Part 33-31: Anaerobic Infections

Key Features

  • Prevotella melaninogenica and anaerobic spirochetes are commonly involved in periodontal infections

  • These organisms, fusobacteria, and peptostreptococci may cause

    • Chronic sinusitis

    • Peritonsillar abscess

    • Chronic otitis media

    • Mastoiditis

    • Venous thrombosis

  • Fusobacterium necrophorum has been recognized as a common cause of pharyngitis in adolescents and young adults

  • F necrophorum infection has been associated with septic internal jugular thrombophlebitis (Lemierre syndrome) and septic pulmonary embolization

Clinical Findings

  • Related to infected organ


  • Culture

  • CT scan


  • Tables 30–4 and 30–5

  • Penicillin alone is inadequate for infections caused by oral anaerobic organisms because of increasing penicillin resistance, usually due to β-lactamase production; therefore, the following can be used:

    • Ampicillin/sulbactam, 1.5–3 g intravenously every 6 hours (if parenteral therapy is required) or

    • Amoxicillin/clavulanic acid, 875 mg/125 mg orally twice daily or

    • Clindamycin, 600 mg intravenously every 8 hours or 300 mg orally every 6 hours

  • Antimicrobial treatment is continued for a few days after symptoms and signs have resolved

  • Indolent, established infections (eg, mastoiditis or osteomyelitis) may require prolonged courses of therapy (eg, 4–6 weeks or longer)

  • Hygiene, drainage, and surgical debridement are as important in treatment as antimicrobials

Table 30–4.Medication of choice for suspected or documented microbial pathogens (listed in alphabetical order, within classes).

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