Introduction to Lab Ex. 14: Antibiotic Sensitivity
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Introduction to Lab Ex. 14: Antibiotic Sensitivity Disc Diffusion Method. Introduction to Lab 10: Ex. Antibiotic Sensitivity Antibiotics are chemicals that are produced by other bacteria/fungi that have the ability to prevent other organisms (bacteria) from growing or killing them.

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Introduction to Lab Ex. 14: Antibiotic Sensitivity Disc Diffusion Method

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Introduction to lab ex 14 antibiotic sensitivity disc diffusion method

Introduction to Lab Ex. 14: Antibiotic Sensitivity

Disc Diffusion Method


Introduction to lab ex 14 antibiotic sensitivity disc diffusion method

Introduction to Lab 10: Ex. Antibiotic Sensitivity

Antibiotics are chemicals that are produced by other bacteria/fungi

that have the ability to prevent other organisms (bacteria)

from growing or killing them.

These have been used widely in controlling bacterial infections

in humans that cause diseases in humans.

There have been many antibiotics that have been developed.

These have been found to be effective in controlling various

infectious bacteria in humans and thus used extensively

in disease control (treatment of bacterial infections)


Introduction to lab ex 14 antibiotic sensitivity disc diffusion method

While there are many different kinds of antibiotics and still

many more kinds of bacteria, not all antibiotics are

effective in inhibiting all bacteria.

Hence, it is essential to determine whether an organism is

sensitive to the inhibitory action of the antibiotic or not.

Many procedures have been developed to determine

antibiotic sensitivity.

The most common method is the Disc diffusion method:

Filter paper discs are saturated with specific amounts of

certain antibiotics and placed on a growth of the particular

bacterial culture to be tested.

If growth is inhibited then sensitivity is seen

If growth is seen then the culture is resistant to the

antibiotic action and is not inhibited

(which will mean that it cannot be used to treat an infection

by the bacterium)


Introduction to lab ex 14 antibiotic sensitivity disc diffusion method

It has also been discovered that antibiotics inhibit bacteria

by stopping their growth (bacteriostatic) or

by killing them (bactericidal).

Antibiotics have been found to have different modes of action

to inhibit bacteria:destruction of cell wall

destruction of cell membrane

inhibition of protein synthesis

inhibition of DNA synthesis

inhibition of intermediary metabolism

Also, most antibiotics are effective only against bacteria

(which have a prokaryotic cell structure and processes different

from eukaryotic cells – resulting in antibiotics being effective

primarily against prokaryotic cells i.e. other bacteria)


Introduction to lab ex 14 antibiotic sensitivity disc diffusion method

The disc diffusion method

- E.coli representing the Gram negative organisms

- S.aureus representing the Gram positive bacteria

Antibiotics that are effective against a wide range of bacteria

(G+ and G-) are called broad spectrum

Those that have effect against a small specific group of bacteria

(either G+ or G-) are called narrow spectrum.


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