Antibiotics acting on bacterial cell wall | | |
A. Beta-lactams |
1. Penicillins | Naturally occurring (penicillin G, penicillin V) | Gram-positive cocci, excluding staphylococci and most enterococci. Gram-positive rods, including anaerobes. Spirochetes. |
Penicillinase-resistant antistaphylococcal (methicillin, oxacillin, nafcillin, dicloxacillin) | Methicillin-susceptible staphylococci (MSS). Gram-positive cocci, but not many enterococci. |
Aminopenicillins (ampicillin, amoxicillin) | All the above plus enterococci, Listeria monocytogenes, Hemophilus influenzae, Moraxella catarrhalis, and some enteric Gram-negative rods. |
Carboxy-penicillins and ureido- penicillins (ticarcillin, piperacillin) | All the above plus Enterobacter, Klebsiella, Pseudomonas, Acinetobacter species, and anaerobes. |
2. Cephalosporins | First generation (cefadroxil, cefazolin, cephalexine, cephradine) | Gram-positive cocci including MSS, excluding enterococci. Some strains of Escherichia coli, Klebsiella, Proteus mirabilis. Not active against indole-positive Proteus and Serratia. |
| Second generation (cefamandole, cefaclor, cefprozil, cefuroxime, cefotetan, cefoxitin, loracarbef) | Similar to first generation, plus Hemophilus influenzae, Enterobacter species, indole-positive Proteus and Serratia, Neisseriae. Cephamycins (cefotetan, cefoxitin) have good anaerobic activity against Bacteroides fragilis but poor against Gram-positive cocci and Enterobacter species. |
| Third generation (cefotaxime, ceftriaxone, ceftazidime, cefoperazone, cefixime) | Enhanced activity against Gram-negative rods. Ceftazidime has good, cefoperazone moderate, and the rest poor activity against Pseudomonas aeruginosa. Good against Gram-negative cocci. Variable activity against Gram-positive cocci, cefotaxime and ceftriaxone being excellent for pneumococci. Poor anaerobic activity. |
| Fourth generation (cefepime, cefpirome) | Good activity against Gram-positive cocci, with enhanced activitiy against Pseudomonas aeruginosa and other Gram-negative rods. |
3. Monobactams | (aztreonam) | Gram-negative rods including Pseudomonas aeruginosa and some strains of Acinetobacter baumannii. Poor against Gram-positive bacteria and anaerobes. |
4. Carbapenems | (meropenem, imipenem/ cilastatin, ertapenem) | Excellent activity against Gram-negative rods, including Enterobacter species, as well as multidrug-resistant Klebsiella pneumoniae, Pseudomonas aeruginosa, and Acinetobacter baumannii (not ertapenem). Good Gram-positive activity. No advantage over ampicillin for enterococci. Compared to imipenem, meropenem has better Gram-negative but worse Gram-positive activity. Ertapenem has narrower spectrum than the other two. |
B. Glycopeptides | (vancomycin, teicoplanin) | Excellent activity against Gram-positive cocci, including MRS, highly resistant pneumococci, and enterococci. |
Antibiotics acting on bacterial cell membrane |
C. Polypeptides |
1. Bacitracin | | Used only topically against Gram-positive bacteria. |
2. Polymyxins | (polymyxin B and polymyxin E also known as colistin) | Gram-negative microbes including multidrug-resistant Klebsiella pneumoniae, Pseudomonas aeruginosa, and Acinetobacter baumannii. Naturally inactive against Proteus. Poor Gram-positive activity. |
D. Lipopeptides | (daptomycin) | Similar activity to glycopeptides. Good against vancomycin-resistant enterococci. |
Antibiotics acting on bacterial protein synthesis |
E. Macrolides | (erythromycin, clarithromycin, azithromycin) | Good against Gram-positive cocci (excluding many staphylococci and most enterococci), Mycoplasma and Chlamydia species, Legionella pneumoniae, and nontuberculous mycobacteria. |
F. Tetracyclines | (tetracycline, minocycline, doxycycline) | Similar to macrolides plus rickettsiae, Brucella species and spirochetes. |
G. Glycylcyclines | (tigecycline) | Gram-positive cocci, including MRS, highly resistant pneumococci, and enterococci. Gram-negative bacteria, including multidrug-resistant Klebsiella pneumoniae and Acinetobacter baumanii, but not Pseudomonas aeruginosa. Good anaerobic activity |
H. Aminoglycosides | (streptomycin, gentamicin, tobramycin, amikacin, netilmicin, kanamycin) | Gram-negative bacteria including multidrug-resistant Klebsiella pneumoniae,Acinetobacter baumannii and Pseudomonas aeruginosa. Moderate activity against Gram-positive cocci. Poor anaerobic activity. |
I. Chloramphenicol | | Gram-positive and negative cocci including MRS and Neisseria meningitidis. Enterobacteriaceae. Not active against Pseudomonas aeruginosa and Enterobacter species. Good anaerobic activity. |
J. Lincosamides | (clindamycin) | Activity against Gram-positive cocci, including some MRS. Excellent anaerobic activity. |
K. Mupirocin | | Topical antistaphylococcal agent active against MRS. |
L. Oxazolidinones | (linezolid) | Similar activity to glycopeptides. Good against vancomycin-resistant enterococci (VRE). |
M. Streptogramins | (quinupristin/dalfopristin, pristinamycin) | Similar activity to glycopeptides. Good against vancomycin-resistant Enterococcus faecium but not Enterococcus faecalis. Good activity against Gram-positive anaerobes. |
N. Fusidic acid | | Gram-positive cocci, active against many MRS but not enterococci. Gram-negative cocci. Poor activity against Gram-negative rods except Moraxella and Legionella species. |
Antibiotics acting against cell metabolism |
O. Sulfonamides | (sulfomethoxazole, sulfacetamide, sulfasalazine, sulfadiazine) | Moderate antistaphylococcal activity, also against some MRS. Poor against streptococci and enterococci. Good Gram-negative activity, including Haemophilus influenza, Moraxella, enteric Gram-negative rods, Stenotrophomonas maltophilia and Acinetobacter species. Poor anaerobic activity. Good against nocardiosis, Pneumocystis jiroveci, toxoplasmosis. |
Antibiotics acting on DNA synthesis |
P. Quinolones | | |
1. First generation quinolones (nonfluorinated) | (nalidixic acid, cinoxacin,† enoxacin,† norfloxacin) | Gram-negative activity, mainly Enterobacteriaceae. |
2. Second generation, fluoroquinolones | (ofloxacin, ciprofloxacin, levofloxacin*) | Wide Gram-negative activity. Additional activity against intracellular microbes. Ciprofloxacin and (to a lesser degree) levofloxacin have good anti-pseudomonal activity. Moderate activity against Gram-positive cocci. |
3. Third generation, respiratory quinolones | (levofloxacin,* moxifloxacin, sparfloxacin,† gatifloxacin†) | Added good activity against streptococci, especially pneumococcus. |
4. Fourth generation | (clinafloxacin,§ trovafloxacin,† prulifloxacin) | Wide spectrum of activity with additional Gram-positive (including MRS, highly resistant pneumococci, and enterococci) and anaerobic activity to the previous categories. |
Q. Rifampin | | Specific Gram-positive and Gram-negative microbes (staphylococci including MRS, neisseriae, brucella). First line antimycobacterial. Always used combined with other antibiotics. |
R. Nitroimidazoles | (metronidazole, tinidazole) | Excellent antianaerobic activity. |
Various mechanisms of action |
S. Beta-lactamase inhibitors | (clavulanic acid, sulbactam, tazobactam) | Enhance the spectrum and activity of aminopenicillins and carboxypenicillins. Sulbactam used as monotherapy against highly-resistant Acinetobacter baumannii in ICUs. |