This document discusses different antimicrobial susceptibility testing methods including disk diffusion, broth dilution, and E-test. It describes the principles, advantages, and disadvantages of disk diffusion testing which involves placing antibiotic disks on agar plated with a pathogen to measure zones of inhibition. Broth dilution is discussed as being performed in liquid media, unable to measure zones of inhibition, and more time consuming and prone to contamination. The document emphasizes the importance of rational antimicrobial use such as giving the proper dose, performing sensitivity testing, and completing antibiotic courses.

1. Antimicrobial Susceptibility Test
Dr. Md. Abdullah Yusuf
Assistant Professor, Department of Microbiology
National Institute of Neurosciences & Hospital
Dhaka, Bangladesh
Email: ayusuf75@yahoo.com

2. Learning Objectives
• Different Methods with Principles
• Advantages
• Disadvantages
• Application
• Rational Use of Antimicrobial Drugs

3. Different Methods with Principles
• Disk Diffusion method
• Broth dilution method
• E-test
• Automated

4. Disk Diffusion method
• Widely used method
• Performed in Muller-Hilton agar media
• Filter paper disk containing the antibiotics
• Measure the clear zone of inhibition

5. Advantages of DDM
• Disk diffusion method: The Kirby Bauer Technique
– Isolate pathogen in pure culture
– Spread onto solid agar
– Put discs easily containing antibiotic on agar
– Incubate plates
– Look for zones of inhibition
– Measure the Zone of inhibition

6. Chl Amp
Ery
Str
Tet
Disk Diffusion Test

7. Broth dilution method
• Performed in liquid media
• Can’t measure the zone of inhibition
• Mixes the bacteria with the liquid media
• Time consuming
• Cumbersome
• Chances of contamination is more

8. 8 4 02 1
Tetracycline (μg/ml)
MIC = 2 μg/ml
Determination of MIC

9. Application
• Antimicrobial sensitivity testing
• Research purposes

10. Rational Use of Antimicrobial drug
• Proper dose should be given
• Antibiotic given after sensitivity testing
• Avoid antibiotic in suspected viral infection
• Complete the antibiotic courses

11. Thank You