MICROBIOLOGY

• Anaerobic, Gram-negative bacteria
  
  • Slender rods with pointed ends [Fig] sometimes appear pleomorphic (coccoid, spheroid).
    • It may grow under anaerobic conditions on a number of media, such as 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 is part of dental plaque flora and is also a cause of invasive infection of the head/neck and elsewhere.
    • F. necrophorum: cause of pharyngotonsillitis, Lemierre syndrome (septic jugular vein thrombophlebitis) and peritonsillar abscess, especially in children and young adults
    • Other: F. mortiferum (occasional cause of bacteremia)
  • Fusobacterium spp. are sensitive to colistin and kanamycin, distinguishing them from Bacteroides and Porphyromonas.
• Produces significant LPS, which may account for virulence.
• Historically thought to be part of normal human flora; some, especially for F. nucleatum, believe it is more likely a pathogen if recovered.