Page 164 - MNU-PM502- Pharmaeutical Microbiology Theoritical Book

Pharm D- Clinical Pharmacy Program Third Level Pharmaceutical Microbiology& Antimicrobials (PM 502)

What Does the Laboratory Need to Know about Antimicrobial Susceptibility
Testing (AST)?

• Which organisms to test?

• What methods to use?

• What antibiotics to test?

• How to report results?

Methods of Antimicrobial Susceptibility Testing

• Classical methods

• Diffusion: Disc diffusion, Well diffusion
• Dilution: Broth dilution, Agar Dilution

• Diffusion & Dilution: E-Test method
• Advanced automated methods
• Molecular technique

Preparing for Testing

1- Inoculum preparation:

Certain bacterial count should be used for each test.

- Number of test organisms can be determined using different methods:

• Direct count (Microscopic examination)

• The optical density (OD) at 600 nm (Spectrophotometry)

• Plate count: making dilution first
• Turbidity standard (McFarland) routinely performed.

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