Methods for Standardization of Antibiotics

• Standardization of antibiotics using microbiological assays involves determining the potency and efficacy of the antibiotics based on their ability to inhibit the growth of specific microorganisms.
• Here are the main methods used for microbiological assays in the standardization of antibiotics:

1. Agar Diffusion Assay (Kirby-Bauer Method)

• Principle:

  • Based on the diffusion of antibiotics through an agar medium, inhibiting the growth of a bacterial lawn.

• Procedure:

  • Preparation: Inoculate an agar plate with a standardized bacterial suspension.
  • Application: Place antibiotic samples on paper discs or in wells on the agar surface.
  • Incubation: Incubate the plates to allow bacterial growth and diffusion of the antibiotic.
  • Measurement: Measure the diameter of the inhibition zones around the discs or wells.
  • Comparison: Compare the inhibition zones to those produced by standard antibiotic concentrations to determine potency.

• Applications:

  • Commonly used for antibiotic potency testing and sensitivity testing.

2. Tube Dilution Assay of Standardization of Antibiotics

• Principle:

  • Determines the minimum inhibitory concentration (MIC) by diluting the antibiotic in a liquid growth medium.

• Procedure:

  • Preparation: Prepare a series of test tubes with decreasing concentrations of the antibiotic.
  • Inoculation: Add a standardized bacterial suspension to each tube.
  • Incubation: Incubate the tubes to allow bacterial growth.
  • Measurement: Measure bacterial growth, typically by optical density (OD) at a specific wavelength or by visual inspection.
  • Comparison: Compare the MIC to the MIC of a standard reference antibiotic to determine potency.

• Applications:

  • Used to determine the effective concentration of antibiotics and compare the potency of different batches.

3. Turbidimetric Assay of Standardization of Antibiotics

• Principle:

  • Measures the turbidity (cloudiness) of a culture medium as an indicator of microbial growth.

• Procedure:

  • Preparation: Inoculate a liquid medium with bacteria and add the antibiotic samples.
  • Incubation: Incubate the mixture to allow microbial growth.
  • Measurement: Measure the turbidity using a spectrophotometer at a specific wavelength.
  • Comparison: Compare the growth inhibition caused by the test antibiotic to that of standard antibiotic solutions to determine potency.

• Applications:

  • Suitable for antibiotics that have a known effect on the growth rate of specific microorganisms.Top of Form

Thank you for reading from Firsthope's notes, don't forget to check YouTube videos!