Susceptibility testing of anaerobic organisms is generally clinical indicated only when isolated from blood, CSF, joint, or other normally sterile body sites or when there has been a treatment failure. Clients will be consulted when susceptibilities are requested on organisms from sources other than those listed above, before actual testing is initiated.
The antibiotics tested are based on the organism's identification and if applicable, the beta lactamase result.
The following antibiotics are routinely tested on Bacteroides fragilis group, Clostridium sp. NOT perfringens, and beta-lactamase positive Anaerobic Gram Negative Bacillus (i.e. Prevotella, Porphyromonas, Fusobacterium, Bilophila): amoxicillin/clavulanic acid, cefoxitin, clindamycin, imipenem, metronidazole, piperacillin/tazobactam.
The following antibiotics are routinely tested on Clostridium perfringens, non-sporeforming Gram positive bacillus, and beta-lactamase negative Anaerobic Gram Negative Bacillus (i.e. Fusobacterium, Prevotella, Porphyromonas, Bilophila): clindamycin, metrondiazole, penicillin.
Susceptibility testing is not routinely performed on Anaerobic Gram positive cocci or Propionibacterium acnes even if recovered from sterile body sites. Consult Microbiology if susceptibility testing is needed on these isolates.