Acinetobacter—imipenem, meropenem (alternatives: tigecycline, ertapenem, minocycline, doxycycline, aminoglycosides, colistin)
Bacteroides, gastrointestinal strains—metronidazole (alternatives: ticarcillin-clavulanate, ampicillin-sulbactam, piperacillin-tazobactam, carbapenem)
Enterobacter—ertapenem, imipenem, meropenem, cefepime (alternatives: aminoglycoside, a fluoroquinolone, TMP-SMZ)
Escherichia coli—cefotaxime, ceftriaxone (alternatives: imipenem or meropenem, aminoglycosides, a fluoroquinolone, aztreonam, ticarcillin-clavulanate, ampicillin-sulbactam, piperacillin-tazobactam)
Haemophilus—cefotaxime, ceftriaxone (alternative: aztreonam)
Klebsiella—cephalosporin (alternatives: TMP-SMZ, aminoglycoside, imipenem or meropenem, a fluoroquinolone, aztreonam, ticarcillin-clavulanate, ampicillin-sulbactam, piperacillin-tazobactam)
Prevotella, oropharyngeal strains—clindamycin (alternative: metronidazole)
Proteus mirabilis—ampicillin (alternatives: An aminoglycoside, TMP-SMZ, a fluoroquinolone, a cephalosporin)
Proteus vulgaris and other species (Morganella, Providencia)—cefotaxime, ceftriaxone (alternatives: aminoglycoside, imipenem, TMP-SMZ, a fluoroquinolone)
Pseudomonas aeruginosa—piperacillin-tazobactam or ceftazidime or cefepime, or imipenem or meropenem or doripenem ± aminoglycoside (alternatives: ciprofloxacin (or levofloxacin) ± piperacillin-tazobactam; ciprofloxacin (or levofloxacin) ± ceftazidime; ciprofloxacin (or levofloxacin) ± cefepime; piperacillin-tazobactam + tobramycin; ceftazidime + tobramycin; cefepime + tobramycin; meropenem (imipenem, doripenem) + tobramycin)
Salmonella (bacteremia)—ceftriaxone (alternative: a fluoroquinolone)
Serratia—carbapenem (alternatives: TMP-SMZ, aminoglycosides, a fluoroquinolone, cefotaxime, ceftriaxone)