MICROBIOLOGY

• Anaerobic, Gram-negative bacteria
  
  • Slender rods with pointed ends [Fig] but sometimes appear pleomorphic (coccoid, spheroid).
    • May grow under anaerobic conditions on a number of media: e.g., CVE (crystal-violet erythromycin) agar, modified chopped meat medium added with 2% agar or Brucella blood agar.
  • Multiple species but usually two account for most human disease:
    • Fusobacterium nucleatum: part of dental plaque flora, also cause of invasive infection of head/neck and elsewhere.
    • F. necrophorum: cause of pharyngotonsillitis, Lemierre syndrome (septic jugular vein thrombophlebitis) and peritonsillar abscess, especially children and young adults
    • Other: F. mortiferum (occasional cause of bacteremia)
  • Fusobacterium spp. are sensitive to colistin and kanamycin, which distinguishes them from Bacteroides and Porphyromonas.
• Produces significant LPS which may account for virulence.
• Historically, thought to be part of normal human flora, now some believe to be more likely a pathogen if recovered, especially F. nucleatum.