This document discusses microbiological assays for testing antibiotics. It describes biological assays using microorganisms and the two main types of microbiological assays: agar diffusion assays and turbidimetric assays. The agar diffusion assay uses discs containing antibiotics placed on an agar plate seeded with bacteria, and measures zones of inhibition of bacterial growth. The turbidimetric assay measures inhibition of bacterial growth in liquid culture containing known concentrations of antibiotics.

1. Presentation on
Microbiological Assay Of Antibiotics
Roll: 06,Semester:7th

2. Contents
• Antibiotics
• Biological Assay
• Microbiological Assay
• Microbiological Assay Of Antibiotics
• Types of Microbiological Assay Of Antibiotics
• Agar Diffusion Assay

6. Biological assay
•A bioassay is an analytical method to
determine concentration or potency of a
substance by its effect on living cells or
tissues.
•Experimental animals include mice, rats,
rabbits, cats, dogs etc.

7. Microbiological Assay
•A type of biological assay is performed with
micro-organisms.
e.g, bacteria, yeasts and molds.

8. Microbiological Assay Of Antibiotics
•The microbiological assay of antibiotics is based
upon a comparison of the inhibition of growth of
micro-organisms by measured concentration of
the antibiotics to be examined with that produced
by known concentrations of a standard
preparation of the antibiotic having a known
activity.

9. Types of Microbiological Assay Of Antibiotics
A. The cylinder-plat(or cup-plate)
method.
B. The turbidimetric method.

10. A. The cylinder-plate(or cup-plate) method.
•The cylinder-plate method depends upon diffusion of the
antibiotic from a vertical cylinder through a solidified agar
layer in the petri dish or plate to and extend such that
growth of the added micro- organism is prevented entirely in
a zone around the cylinder containing a solution of
antibiotic.

12. Description

13. B. Turbidimetric or Tube Assay method
•This method depends upon the inhibition of growth
of a microbial culture in a uniform solution of the
antibiotic in a fluid medium that is favourable to its
rapid growth in the absence of the antibiotic.

14. Description

15. Agar diffusion assay
•The disk diffusion test, or agar diffusion test
is a test of the antibiotic sensitivity of
bacteria.
•It uses antibiotic discs to test the extent to
which bacteria are affected by those
antibiotics.

16. Agar diffusion assay