Principal of treatment of most anaerobically caused infections is drainage of an
abscess (when present), plus antibiotics. The choice of antibiotic(s) must include
coverage for both aerobes and B. fragilis.
Antibiotics Of all anaerobes, Bacteroides group are the most
resistant to antibiotics, while oral anaerobes are the most sensitive.
- B. fragilis group - uniformly resistant to penicillin
Susceptible to: Metronidazole (100%) Ampicillin + Sulbactam (96%), Ticarcillin/Clavulanic
acid (98%) Imipenem (98%), Cefoxitin (90%), Cefotetan (80%), Clindamycin (80-85%),
Ceftizoxime (80%), Chloramphenicol (100%), Piperacillin (80%).
Not susceptible to: Ampicillin, oxacillin, 1st generation cephalosporins, other 3rd
generation cephaloporins, quinolones, tetracycline, and sulfa based antibiotics.
- P. bivia, P. disiens
Similar to B. fragilis, but overall more susceptible - not penicillin.
- P. melanogenic, P. gingivola, P. oralis
May be susceptible to penicillin and most antibiotics listed above.
- Fusobacterium - penicillin sensitive, although occasional resistance has been