Antimicrobial Therapy for Infections Involving Commonly Encountered Anaerobic Gram-Negative Rods
| Category 1 (Nearly Always Active) | Category 2 (Usually Active) | Category 3 (Variable Resistance) | Category 4 (Resistance) |
|---|---|---|---|
| Carbapenems (imipenem, meropenem, doripenem) β-Lactam/β-lactamase inhibitor combinations (ampicillin/sulbactam, ticarcillin/clavulanic acid, piperacillin/tazobactam) Chloramphenicolb | High-dose anti-pseudomonal penicillins | Cephamycins (cefoxitin, cefotetan) Penicillins Cephalosporins | Aminoglycosides Monobactams Trimethoprim-sulfamethoxazole |
aUsually needs to be given in combination with aerobic bacterial coverage. For infections originating below the diaphragm, aerobic gram-negative coverage is essential. For infections from an oral source, aerobic gram-positive coverage is added. Metronidazole also is not active against Actinomyces, Propionibacterium, or other gram-positive non-spore-forming bacilli (e.g., Eubacterium, Bifidobacterium) and is unreliable against peptostreptococci.
bDespite excellent in vitro activity against all clinically important anaerobes, this drug is less desirable than other active drugs because of documented clinical failures.