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Renin Angiotensin Mechanism.

Assessment of a New Antibiotic.

 

Introduction:

  • Antimicrobial Resistance (AMR) is a way through which microbes change their ways through which a particular antibiotic is acting on them making it ineffective.

  • The AMR is giving rise to tougher microbial strains, some of them are even resistant to all the antibiotics available today we call such stains as superbugs.

  • If new antibiotics are not introduced, the patients will die due to the previously treatable infections.

  • The antibiotics are assessed in many ways like their efficiency, side effects, health gains, spectrum etc.

  • Minimum Inhibitory Concentration is a one of criteria that establishes efficiency of an antibiotic.

  • Minimum Inhibitory Concentration is the minimum concentration at which an antibiotic inhibits the growth of microorganism but not necessarily kills it.

  • MIC the term is applicable to antibiotics, disinfectants, antiseptics and preservatives.

  • MIC of an antibiotic is tested either by one of the following ways,

    • Liquid Dilution Method.

    • Solid Dilution Method.

Liquid Dilution Method (Test Tube Method)

  • Twelve test tubes are taken and are labelled as per table 1.1.


Tube Number

Volume of Double Strength Medium (ml)

Volume of Test Chemical (ml)

Volume of Sterile Water (ml)

0 (Uninoculated)

5

0.0

5

0 (Control)

5

0.0

5

1

5

0.5

4.5

2

5

1.0

4.0

3

5

1.5

3.5

4

5

2.0

3.0

5

5

2.5

2.5

6

5

3.0

2.0

7

5

3.5

1.5

8

5

4.0

1.0

9

5

4.5

0.5

10

5

5.0

0.0


  • Double strength medium is added in all test tubes.

  • First test tube (Uninoculated) inoculum is not added and is used to check sterility of the medium used.

  • In all other remaining eleven test tubes 3-4 drops of inoculum is added to reach 105-106 cells/ ml concentration of the test microorganism.

  • In all test tubes except “Uninoculated” and “Control” chemical agent under test are added from 0.5 ml to 5.0 ml.

  • The final volume of 10 ml is adjusted using sterile water in all test tubes.

  • Contents of all test tubes are mixed well and incubated @ 37℃ for 2-3 days.

  • After incubation all tests tubes are examined for growth of microorganism and the minimum inhibitory concentration is calculated.

  • It is necessary to carry out a preliminary experiment to determine the range of MIC of the chemical agent under test.

Solid Dilution Method:

  • In this method the chemical agent under test is mixed in the molten agar and then is poured in the petri dish.

  • After solidification, the inoculum is spread on the surface of the agar medium.

  • All the plates are incubated @ 37℃ for 2-3 days.

  • After incubation all petri dishes are examined for growth of microorganism and the minimum inhibitory concentration is calculated.

Advantages:

  1. Several microorganisms can be studied once by using a multipoint inoculator.

  2. Contaminations can easily be detected as colony features are distinctive here rather than turbidity difference.
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