narrow spectrum antibiotic

Examples of narrow spectrum antibiotic in the following topics:

• Spectrum of Antimicrobial Activity

  • The range of bacteria that an antibiotic affects can be divided into narrow spectrum and broad spectrum.
  • Narrow spectrum antibiotics act against a limited group of bacteria, either gram positive or gram negative, for example sodium fusidate only acts against staphylococcal bacteria.
  • A broad spectrum antibiotic acts against both Gram-positive and Gram-negative bacteria, in contrast to a narrow spectrum antibiotic, which is effective against specific families of bacteria.
  • An example of a commonly used broad-spectrum antibiotic is ampicillin.
  • Broad spectrum antibiotics are also used for drug resistant bacteria that do not respond to other, more narrow spectrum antibiotics and in the case of superinfections, where there are multiple types of bacteria causing illness, thus warranting either a broad-spectrum antibiotic or combination antibiotic therapy.

• Antibiotics and Selective Toxicity

  • Antibiotics are able to selectively target specific types of bacteria without harming the infected host.
  • Antibiotics are commonly classified based on their mechanism of action, chemical structure, or spectrum of activity.
  • More specifically, narrow spectrum antibiotics target specific types of bacteria, such as Gram-negative or Gram-positive bacteria, whereas broad spectrum antibiotics affect a wide range of bacteria.
  • Useful antibiotics are often discovered using a screening process.
  • Most antibiotics identified in such a screen are already known and must therefore be disregarded.

• Antibiotic Classifications

  • Bactericidal antibiotics kill bacteria; bacteriostatic antibiotics slow their growth or reproduction.
  • Antibiotics can be divided into two classes based on their mechanism of action.
  • Bactericidal antibiotics kill bacteria; bacteriostatic antibiotics inhibit their growth or reproduction.
  • However, there is not always a precise distinction between them and bactericidal antibiotics.
  • "Narrow-spectrum" antibacterial antibiotics target specific types of bacteria, such as Gram-negative or Gram-positive bacteria, whereas broad-spectrum antibiotics affect a wide range of bacteria, usually both gram positive and gram negative cells.

• Kirby-Bauer Disk Susceptibility Test

  • Kirby-Bauer antibiotic testing (also called KB testing or disk diffusion antibiotic sensitivity testing) uses antibiotic-containing wafers or disks to test whether particular bacteria are susceptible to specific antibiotics.
  • A larger zone of inhibition around an antibiotic-containing disk indicates that the bacteria are more sensitive to the antibiotic in the disk.
  • Clinicians can use KB test results to choose appropriate antibiotics to combat a particular infection in a patient.
  • Administering antibiotics that specifically target the particular bacteria that are causing the infection can avoid using broad-spectrum antibiotics, which target many types of bacteria.
  • In Kirby–Bauer testing, discs containing antibiotics are placed on agar where bacteria are growing, and the antibiotics diffuse out into the agar.

• Primary and Secondary Metabolites

  • Primary and secondary metabolites are often used in industrial microbiology for the production of food, amino acids, and antibiotics.
  • Antibiotics such as erythromcyin and bacitracin are also considered to be secondary metabolites.
  • Erythromycin, derived from Saccharopolyspora erythraea, is a commonly used antibiotic with a wide antimicrobial spectrum.
  • Lastly, another example of an antibiotic which is classified as a secondary metabolite is bacitracin.
  • Bacitracin, derived from organisms classified under Bacillus subtilis, is an antibiotic commonly used a topical drug.

• Organ Toxicity

  • Use of some antibiotics, such as gentamicin, can cause a lose of hearing, or tinnitus ("ringing in the ears").
  • Ototoxicity is usually temporary with antibiotics, but permanent hearing damage, while rare, has been reported.
  • Broad-spectrum antibiotics in the family of fluoroquinolones can cause neurotoxicity by directly damaging neuronal receptors.
  • However, it should be noted that the side-effects due to broad-spectrum antibiotics are actually quite rare, with organ damage being even more rare.The potential side-effects of antibiotics or other antimicrobial drugs are offset by the benefits of combating the microbial infection.
  • This rash seen on a forearm is a typical reaction observed when an antibiotic causes phototoxicity.

• Visible Light

  • Visible light, as called the visible spectrum, is the portion of the electromagnetic spectrum that is visible to (can be detected by) the human eye.
  • Colors that can be produced by visible light of a narrow band of wavelengths (monochromaticlight) are called pure spectral colors.
  • Note that each color can come in many shades, since the spectrum is continuous.
  • The electromagnetic spectrum, showing the major categories of electromagnetic waves.
  • A small part of the electromagnetic spectrum that includes its visible components.

• Polyketide Antibiotics

  • Secondary metabolites are often restricted to a narrow set of species within a phylogenetic group.
  • Polyketide antibiotics, antifungals, cytostatics, anticholesteremic, antiparasitics, coccidiostats, animal growth promoters, and natural insecticides are in commercial use.
  • Examples of polyketides include: Macrolides; Pikromycin, the first isolated macrolide; the antibiotics erythromycin A; clarithromycin, and azithromycin; the immunosuppressant tacrolimus; Radicicol and Pochonin family (HSP90 inhibitor); Polyene antibiotics; Amphotericin; Tetracyclines and the tetracycline family of antibiotics.

• Damage to Proteins and Nucleic Acids

  • Depending on their application, bacteriostatic antibiotics, disinfectants, antiseptics, and preservatives can be distinguished.
  • Bacteriostatic antibiotics limit the growth of bacteria by interfering with bacterial protein production, DNA replication, or other aspects of bacterial cellular metabolism.
  • However, there is not always a precise distinction between them and bactericidal antibiotics.
  • Tetracycline is a broad-spectrum polyketide antibiotic produced by the Streptomyces genus of Actinobacteria, indicated for use against many bacterial infections.
  • It is also used to produce several semisynthetic derivatives, which together are known as the tetracycline antibiotics.

• Minimal Inhibitory Concentration (MIC)

  • In microbiology, minimum inhibitory concentration (MIC) is the lowest concentration of an antimicrobial (like an antifungal, antibiotic or bacteriostatic) drug that will inhibit the visible growth of a microorganism after overnight incubation.
  • The minimum inhibitory concentration of the antibiotic is between the concentrations of the last well in which no bacteria grew and the next lower dose, which allowed bacterial growth.
  • Clinicians use MIC scores to choose which antibiotics to administer to patients with specific infections and to identify an effective dose of antibiotic.
  • This is important because populations of bacteria exposed to an insufficient concentration of a particular drug or to a broad-spectrum antibiotic (one designed to inhibit many strains of bacteria) can evolve resistance to these drugs.
  • To identify the lowest concentration required for a given antibiotic to inhibit bacterial growth, an identical amount of bacteria is introduced into wells of liquid media containing progressively lower concentrations of the drug.