Different Types of Antibiotics

Antibiotics can be classified in different ways.

Broad-spectrum vs Narrow-spectrum

Narrow-spectrum antibiotics act against only limited types of bacteria.

List of narrow-spectrum antibiotics and their spectrum of activity:

  • Penicillin, Flucloxacillin, Dicloxacillin, Nafcillin sodium: Gram-positive bacteria.
  • Aztreonam: Gram-negative aerobic bacteria.
  • Linezolid: Gram-positive bacteria.
  • Polymyxin B: Gram-negative bacilli other than proteus.
  • Bacitracin: Gram-positive bacteria, especially staphylococci.
  • Vancomycin, Teicoplanin: Gram-positive bacteria, especially staphylococci.
  • Viomycin: Tubercle bacillus.
  • Isoniazid: Mycobacterium tuberculosis.
  • Streptomycin: Mycobacterium tuberculosis.
  • Streptogramins (Virginiamycin, Quinupristin/dalfopristin, Pristinamycin): gram-positive bacteria (mainly staphylococci, streptococci, and enterococci).
  • Fusidic acid: Staphylococcus aureus.
  • Fidaxomicin: Clostridium difficile.

Broad-spectrum antibiotics act against wide range of bacteria.

Commonly used broad-spectrum antibiotics:

  • Tetracyclines
  • Cephalosporins
  • Macrolides
  • Quinolones

Broad-spectrum antibiotics are particularly useful when the infecting bacteria is unknown. Their clear advantage is that there is less of a need to identify the infecting pathogen with real certainty before initiating the treatment.

On the other hand, a broad-spectrum antibiotics have a more profound effect on the normal flora and are more likely to lead to selection of resistant organisms.

Narrow-spectrum agents are preferred, where possible, as they are less likely to provoke the development of resistance and are less likely to be cause Clostridium difficile diarrhea.

Bacteriostatic vs Bactericidal

Bactericidal antibiotics kill the target bacteria. These drugs include penicillins, cephalosporins, carbapenems, aminoglycosides, fluoroquinolones, and nitroimidazoles.

Bacteriostatic antibiotics slow bacterial growth, allowing the immune system to fight the bacteria. These drugs include macrolides, tetracyclines, sulfonamides, clindamycin, and chloramphenicol.

Classification according to chemical structure

  • Penicillins
  • Cephalosporins
  • Macrolides and azalides
  • Fluoroquinolones (Quinolones)
  • Tetracyclines
  • Aminoglycosides
  • Sulphonamides
  • Glycopeptides
  • Oxazolidinones
  • Amphenicols
  • Lincosamides
  • Glycopeptide
  • Carbapenems
  • Nitroimidazoles


  • Natural penicillins
  • Aminopenicillins
  • Antistaphylococcals
    • Methicillin
    • Cloxacillin
    • Dicloxacillin
    • Nafcillin
    • Oxacillin
  • Antipseudomonals
    • Azlocillin
    • Carbenicillin
    • Mezlocillin
    • Piperacillin
    • Ticarcillin


  • First generation
    • Cephazolin (Ancef, Kefzol)
    • Cefadroxil (Duricef)
    • Cephalexin (Keflex)
  • Second generation
    • Cefaclor (Ceclor)
    • Cefuroxime (Ceftin)
    • Cefprozil (Cefzil)
    • Loracarbef (Lorabid)
  • Third generation
    • Cefotaxime (Claforan)
    • Cefixime (Suprax)
    • Cefpodoxime (Vantin)
    • Ceftazidime (Ceptaz)
    • Cefdinir (Omnicef)
  • Fourth generation
    • Cefepime (Maxipime)
    • Cefpirome (Cefrom)


  • Erythromycin
  • Clarithromycin (Biaxin)
  • Azithromycin (Zithromax)
  • Josamycin
  • Midecamycin
  • Roxithromycin
  • Dirithromycin (Dynabac)
  • Troleandomycin (Tao)

Fluoroquinolones (quinolones)

  • Ciprofloxacin (Cipro)
  • Gatifloxacin (Tequin)
  • Levofloxacin (Levaquin)
  • Lomefloxacin (Maxaquin)
  • Moxifloxacin (Avelox)
  • Norfloxacin (Noroxin)
  • Ofloxacin (Floxin)
  • Trovafloxacin (Trovan)



Author: OriginalDrugs Team
Last reviewed: May, 2013

Interesting Facts
  • There is not always a precise distinction between bacteriostatic and bactericidal antibiotics. High concentrations of some bacteriostatic agents are also bactericidal, whereas low concentrations of some bactericidal agents are bacteriostatic.