Obligate anaerobes

Microbiology

• Colonizes skin and mucosal surfaces
• Difficult to grow

Organisms

• Gram-negative
  • Bacilli
    • Bacteroides fragilis group:
      • Bacteroides: Bacteroides fragilis, Bacteroides thetaiotaomicron, Bacteroides distasonis, Bacteroides ovatus, Bacteroides uniformis
      • Parabacteroides: Parabacteroides gordonii, Parabacteroides goldsteinii, Parabacteroides distasonis, Parabacteroides merdae
      • Phocaeicola: Phocaeicola vulgatus, Phocaeicola dorei
    • Other Bacteroides spp.: Bacteroides gracilis, Bacteroides ureolyticus
    • Prevotella
      • Pigmented: P. melaninogenica, P. intermedia, P. denticola, P. loescheii, P. corporis, P. nigrescens
      • Non-pigmented: P. oris, P. buccae, P. oralis group (P. oralis, P. buccalis, P. veroralis), P. bivia, P. disiens
    • Porphyromonas: P. asaccharolytica, P. gingivalis, P. endodontalis
    • Fusobacterium: F. nucleatum, F. necrophorum, F. gonidiaformans, F. naviforme, F. mortiferum, F. verium
    • Bilophila: Bilophila wadsworthia
    • Sutterella
  • Cocci
    • Veillonella
• Gram-positive
  • Cocci
    • Peptostreptococcus spp.: P. magnus, P. asaccharolyticus, P. prevotii, P. intermedius, P. anaerobius, P. micros
  • Bacilli (spore-forming)
    • Clostridium: C. perfringens, C. ramosum, C. septicum, C. novyi, C. histolytica, C. sporogenes, C. bifermentans, C. butyricum, C. innocuum, C. sordellii, C. botulinum, C. tetani
    • Clostridioides difficile
  • Bacilli (non-spore-forming)
    • Propionibacterium: P. acnes, P. propionicum, P. granulosum
    • Eubacterium tentum
    • Bifidobacterium: B. eriksonii, B. dentium
    • Actinomyces: A. israelii, A. naestundii, A. viscosus, A. odontolyticus, A. meyerii

Management

• Ampicillin or penicillin (for Gram-positive anaerobes)
• β-lactam/β-lactamase inhibitor combinations,
• Cephamycins (e.g. cefoxitin)
• carbapenems
• clindamycin (though increasing resistance)
• metronidazole
• moxifloxacin
• tetracycline

Further Reading

• Brook I. Spectrum and treatment of anaerobic infections. J Infect Chemother (2015). doi: 10.1016/j.jiac.2015.10.010