| Gram-Negative Cocci |
| Moraxella catarrhalis | Cefuroxime, amoxicillin-clavulanic acid | Ceftriaxone, cefuroxime axetil, a fluoroquinolone,1 a macrolide,2 a tetracycline,3 TMP-SMZ4 |
| Neisseria gonorrhoeae (gonococcus) | Ceftriaxone + azithromycin or doxycycline | Cefixime + azithromycin or doxycycline5 |
| Neisseria meningitidis (meningococcus) | Penicillin6 | Ceftriaxone, ampicillin |
| Gram-Positive Cocci |
| Enterococcus faecalis | Ampicillin ± gentamicin7 Ampicillin ± ceftriaxone | Vancomycin ± gentamicin |
| Enterococcus faecium | Vancomycin ± gentamicin7 | Linezolid,8 quinupristin-dalfopristin,8 daptomycin,8 tigecycline,8 tedizolid,8 oritavancin8 |
| Staphylococcus, methicillin-susceptible | Cefazolin or Penicillinase-resistant penicillin10 | Vancomycin, a cephalosporin,9 clindamycin, amoxicillin-clavulanic acid, ampicillin-sulbactam |
| Staphylococcus, methicillin-resistant | Vancomycin | TMP-SMZ,4 doxycycline, minocycline, linezolid,8 tedizolid,8 daptomycin,8 televancin,8 dalbavancin,8 oritavancin,8 ceftaroline, delafloxacin |
| Streptococcus, hemolytic, groups A, B, C, G | Penicillin6 | Macrolide,2 a cephalosporin,9 vancomycin, clindamycin |
| Streptococcus pneumoniae11 (pneumococcus) | Penicillin6 | A cephalosporin,9 vancomycin, clindamycin, a tetracycline,3 respiratory fluoroquinolones1 |
| Viridans streptococci | Penicillin6 | Cephalosporin,9 vancomycin |
| Gram-Negative Rods |
| Acinetobacter | Imipenem, meropenem | Tigecycline, minocycline, doxycycline, aminoglycosides,12 colistin, cefiderocol |
| Bacteroides, gastrointestinal strains | Metronidazole | Ampicillin-sulbactam, piperacillin-tazobactam, ertapenem |
| Brucella | Doxycycline + rifampin3 | TMP-SMZ4 ± gentamicin; ciprofloxacin + rifampin |
| Burkholderia mallei (glanders) | Streptomycin + tetracycline3 | Chloramphenicol + streptomycin |
| Burkholderia pseudomallei (melioidosis) | Ceftazidime | Tetracycline,3 TMP-SMZ,4 amoxicillin-clavulanic acid, imipenem or meropenem |
| Campylobacter jejuni | Azithromycin | A fluoroquinolone1 |
| Enterobacter | Ertapenem, imipenem, meropenem, cefepime | Aminoglycoside, a fluoroquinolone,1 TMP-SMZ4 |
| Escherichia coli (uncomplicated outpatient urinary infection) | Nitrofurantoin, fosfomycin | Fluoroquinolones,1 TMP-SMZ,4 oral cephalosporin |
| Escherichia coli (sepsis)13 | Cefotaxime, ceftriaxone | Ertapenem,13 imipenem13 or meropenem,13 aminoglycosides,12 aztreonam, ticarcillin-clavulanate, piperacillin-tazobactam, ceftazidime-avibactam,13,15 ceftolozane-tazobactam,13,14 meropenem/vaborbactam,15 imipenem/cilastatin-relebactam13,14,15 |
| Haemophilus (respiratory infections, otitis) | Ampicillin-clavulanate | Doxycycline, azithromycin, ceftriaxone, cefuroxime, cefuroxime axetil, TMP-SMZ4 |
| Haemophilus (serious infection) | Ceftriaxone | Aztreonam |
| Helicobacter pylori | Proton pump inhibitor (PPI), clarithromycin, amoxicillin, and metronidazole | PPI, clarithromycin, and amoxicillin or metronidazole |
| Klebsiella13 | Ceftriaxone | TMP-SMZ,4 aminoglycoside,12 ertapenem,13 imipenem13 or meropenem,13 a fluoroquinolone,1 aztreonam, ticarcillin-clavulanate, piperacillin-tazobactam, ceftazidime-avibactam,13 ceftolozane-tazobactam,13,14 meropenem/vaborbactam,15 imipenem/cilastatin-relebactam13,14,15 |
| Legionella species (pneumonia) | Azithromycin, or fluoroquinolones1 ± rifampin | Doxycycline ± rifampin |
| Prevotella, oropharyngeal strains | Clindamycin | Metronidazole |
| Proteus mirabilis | Ampicillin | TMP-SMZ,4 a fluoroquinolone,1 a cephalosporin9 |
| Proteus vulgaris and other species (Morganella, Providencia) | Ceftriaxone | Ertapenem, imipenem or meropenem, TMP-SMZ,4 a fluoroquinolone1 |
| Pseudomonas aeruginosa | Piperacillin-tazobactam or ceftazidime or cefepime, or imipenem or meropenem or doripenem or aztreonam (any one of the previous agents) ± aminoglycoside12 | Ciprofloxacin (or levofloxacin) ± piperacillin-tazobactam; ciprofloxacin (or levofloxacin) ± ceftazidime; ciprofloxacin (or levofloxacin) ± cefepime; ... |