Module 12: Antibiotic Susceptibility Testing: Kirby-Bauer Disk Diffusion Method

As future nurses, understanding how antibiotics work and how we determine their effectiveness is essential to providing safe, evidence-based care. This module builds on your existing knowledge of antibiotics by introducing the Kirby-Bauer disk diffusion test, a standard lab method used to identify which antibiotics are most effective against specific bacterial infections. You’ll learn how to interpret lab results that classify bacteria as susceptible, intermediate, or resistant—information that directly impacts treatment decisions at the bedside. With antibiotic resistance on the rise, this knowledge is crucial for supporting proper medication use, improving patient outcomes, and contributing to responsible antibiotic stewardship in clinical practice.

Image: Adapted from “Disk Diffusion Method for Antibiotic Susceptibility Test” (Creative Biolabs, 2025).

Upon completion of this module, you will be able to:

1. Explain the principle and clinical relevance of the Kirby-Bauer disk diffusion method (Linked COs: 3).

2. Properly perform antibiotic susceptibility testing using standardized inoculation and disk placement techniques (Linked COs: 3).

3. Accurately measure zones of inhibition and interpret results using CLSI guidelines (Linked COs: 3).

4. Classify antibiotics by their mechanism of action and relate this to their effectiveness against specific bacteria (Linked COs: 2, 3).

To achieve these objectives: 

1. Read and understand the lab manual 
   
2. Read Chapter 8 in Microbiology for Nursing/Allied Health 
3. Complete the H5P questions in the lab manual

Module Pressbooks Resources and Activities