Antibiotic Mechanisms and Spectrum of Activity

Mechanism of Action: Inhibit protein synthesis by binding to 30s ribosomal subunit

Spectrum of Activity: Gram-positive and gram-negative bacteria

Not viable for anaerobes

Typical: Gentamycin, Tobramycin, Amikacin, Streptomycin, Kanamycin

Aminoglycosides

Mechanism of Action: Inhibits RNA synthesis by binding DNA-dependent RNA polymerase

Spectrum of Activity: Gram-positive bacteria; Certain gram-negative bacteria (Neisseria meningitidis)

Typical: Rifampin

Ansamycins

Mechanism of Action: Inhibit cell wall synthesis by binding enzymes involved in peptidoglycan production (Penicillin-binding proteins aka PBPs)

Spectrum of Activity: both gram-positive and gram-negative bacteria. Spectrum varies depending on the individual antibiotic

Typical: Penicillin; Ampicillin; Cephalosporins (Cefazolin); Carbapenems (Meropenem); Aztreonam

Beta-Lactams

Mechanism of Action: Inhibits protein synthesis by binding the 50s ribosomal subunit

Spectrum of Activity: Gram-positive and gram-negative bacteria

Chloramphenicol

Mechanism of Action: Interferes with the folic acid pathway by a sulfamide, usually sulfamethoxazole, binding dihydropteroate synthase and trimethoprim binding dihydrofolate reductase

Spectrum of Activity: Gram-positive and many gram-negative bacteria

Typical: Trimethoprim/sulfamethoxazole

Folate pathway inhibitors

Mechanism of Action: Inhibits DNA synthesis by binding DNA gyrase and topoisomerase IV

Spectrum of Activity: Gram-positive and gram-negative bacteria; Spectrum may vary with individual antibiotic

Typical: Ciprofloxacin; Levofloxacin

Fluoroquinolones

Mechanism of Action: Inhibit cell wall synthesis by binding to the end of PG interfering with crosslinking

Spectrum of Activity: Gram-positive bacteria; Including methicillin resistant Staphylococcus aureus (MRSA)

Typical: Vancomycin

Glycopeptides

Mechanism of Action: Inhibits protein synthesis by binding to the 30s ribosomal subunit

Spectrum of Activity: wide spectrum of gram-positive and gram-negative species; Including those resistant to tetracycline

Typical: Tigecycline

Glycylglycines

Mechanism of Action: Inhibits protein synthesis by binding to the 50s ribosomal subunit

Spectrum of Activity: Gram-positive cocci, including certain macrolide-resistant strains; Some fastidious gram-negative bacteria

Typical: Telithromycin

Ketolides

Mechanism of Action: Inhibits protein synthesis by binding to the 50s ribosomal subunit

Spectrum of Activity: Most aerobic and anaerobic gram-positive bacteria; Atypical bacteria; Clindamycin is primarily for anaerobes

Typical (M): Erythromycin; Azithromycin

Typical (L): Clindamycin

Macrolide-Lincosamide Group

Mechanism of Action: Binding and disruption of cell membrane

Spectrum of Activity: Gram-positive bacteria; Including resistant strains to beta-lactams and glycopeptides

Typical: Daptomycin

Lipopeptides

Mechanism of Action: Uncertain; Probable bacterial enzyme targets and DNA damage

Spectrum of Activity: Gram-positive and gram-negative bacteria; Treatment for UTI only

Typical: Nitrofurantoin

Nitrofurans

Mechanism of Action: Inhibits protein synthesis by binding to the 50s ribosomal subunit

Spectrum of Activity: Wide variety of gram-positive bacteria; Including those resistnat to other antimicrobials

Typical: Linezolid

Oxazolidinones

Mechanism of Action: Disruption of the cell membrane

Spectrum of Activity: Gram-negative bacteria

Typical: Polymyxin B; Colistin

Polymyxins

Mechanism of Action: Inhibits protein synthesis by binding to two sites on the 50s ribosomal subunit

Spectrum of Activity: Primarily gram-positive bacteria

Typical: Quinupristin/dalfopristin

Streptogramins

Mechanism of Action: Inhibits protein synthesis by binding to the 30s ribosomal subunit

Spectrum of Activity: Gram-positive bacteria; Several intracellular bacterial pathogens (Chlamydia trachomatis)

Typical: Doxycycline, minocycline, tetracycline

Tetracyclines

Chloramphenicol; Erythromycin and other macrolides; Clindamycin; Sulfonamides; Trimethoprim; Tetracyclines; Tigecycline; Tigecycline; Linezolid; Quinupristin/dalfopristin

Typical Bacteriostatic Agents

Aminoglycosides, Beta-lactams; vancomycin; dalbavanicin, oritavancin, telavancin; Daptomycin; Fosfomycin; Quinolones (ciprofloxacin, levofloxacin; Rifampin; Metronidazole

Typical Bactericidal Agents