Agent | Comments |
Nearly always active | |
Metronidazole | Limited activity (increased resistance) against microaerophilic streptococci (eg, S. milleri), Cutibacterium (formerly Propionibacterium), and Actinomyces species; bactericidal against most gram-negative anaerobic strains |
Carbapenems | Resist hydrolysis by most Bacteroides beta-lactamases, although it can occur occasionally[1,2] |
Beta-lactam plus beta-lactamase inhibitors | The addition of a beta-lactamase inhibitor to a beta-lactam dramatically increases activity against anaerobes that produce a beta-lactamase |
Variable activity | |
Clindamycin | B. fragilis group: 20 to 60% of strains resistant; some Clostridia including C. perfringens are resistant |
Cephamycins (Cefoxitin/Cefotetan) | B. fragilis group: 6 to 44% of strains resistant[2,3] |
Penicillin | Inactive against some or most penicillinase-producing anaerobes, including most of the B. fragilis group and many strains of Prevotella melaninogenica, P. intermedia, P. bivia, P. disiens, and some Clostridia, including C. perfringens |
Other cephalosporins | Overall, less activity in vitro than penicillin G against most anaerobes and not recommended for therapy of anaerobic infections |
Tetracycline | Inactive against many anaerobes and most strains of B. fragilis; doxycycline and minocycline are somewhat more active than tetracycline |
Vancomycin | Active against gram-positive anaerobes; inactive against gram-negative anaerobes except when given orally where vancomycin greatly diminishes the colon microbiota including B. fragilis[4] |
Linezolid | Active against gram-positive anaerobes only |
Daptomycin | Active against gram-positive anaerobes only |
Macrolides | Inactive against many Fusobacterium spp and some B. fragilis spp |
Fluoroquinolones | Not recommended for therapy of anaerobic infections due to increased resistance in Bacteroides spp, including B. fragilis sensu stricto |
Tigecycline | Active against some anaerobes, including strains of B. fragilis that are resistant to beta-lactams, clindamycin, and quinolones[2] |
Poor activity | |
Aminoglycosides | |
Trimethoprim-sulfamethoxazole | |
Monobactams (aztreonam) |
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