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Antibiotic Susceptibility test
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Antibiotic Susceptibility Test
College of Pharmacy
Department of Pharmacognosy
Practical Medical Microbiology
Second stage- Lab 6
Assist. Lecturer: Shokhan Osman
Question?
???
Why it is important to
doing AST Test in Lab?
Reasons
- To know the sensitivity and the resistant rates of
a specific microorganism to several antibiotics.
- It help us to choose an effective antibiotics to stop the growth of Microorganism that infecting individuals.
- To decrease Antibiotic resistant bacteria by reducing Antibiotic misuse by the physicians patients.
- To determine Antibiotic sensitive and resistant strains of bacteria and other microorganism in Kurdistan Region.
Headlines
- Introduction
- Antibiotic Susceptibility
- Methods
- Preparation of Bacterial inoculum
- Kirby-bauer Method (Disc diffusion Test) & procedure.
- Measurement of the inhibition zones diameter.
Headlines
Learning Outcomes
Learning Outcomes
At the end of this Lab you will learn:
- Different methods for determining the sensitivity of bacteria to antibiotics.
- Procedure of Kirby-Bauer method.
- Measurement of the sensitivity of bacteria to drug depend on the standard Antibiotic table.
Antibiotic Sensitivity Test
Introduction
- is a laboratory method for determining the susceptibility of Microorganisms to the antibiotics.
- AST is carried out to determine which antibiotic will be most successful in
treating bacterial infection invivo.
Methods
AST methods
1. Kirby-Bauer Method (Disc diffusion method).
2. Dilution method.
3. Epsilometer test or simply E-Test.
Pictures
1. Kirby-bauer method
- Bacterial inoculum: McFarland standards are used as a reference to adjust the turbidity of bacterial suspensions so that the number of bacteria will be within a given range (1.5* 10*8 CFU/mL).
- emulsify 2-3 colonies in sterile saline matching the turbidity that standard.
Kirby-Bauer Method
Materials
1. Muller Hinton Agar.
2. Bacterial culture.
3. Antibiotic Disks.
4. Turbidity Standard (0.5 Mcfarland)
5. Swabs.
6. Flame.
7. Gloves.
8. Forceps
9. Ruler
Kirby-bauer method
1. Kirby-bauer Procedure
Procedure
1. Muller Hinton agar is used for AST test.
2. Take 24-48 hours old broth (Liquid) culture of bacteria to be tested.
3. Place a sterile cotton swab in the bacterial suspension.
4. Streak the swab in three directions over the surface of the Mueller-Hinton agar to obtain uniform growth.
5. Allow the plates to dry for five minutes.
6. Using sterile forceps to transfer Antibiotic disks with a fixed concentration on the
surface agar plates at equal distance.
7. Incubate the plates at 37C for
24 hours then measure the
diameter of inhibition zones.
2
1
4
5
3
Practical
work
7
5
6
4
Procedure
Video
Measurment of inhibition zones
in diameter
Measurment of results
Questions...?
References
Students activity
- Group A (AST test for Staphylococcus aureus)
- Group B (AST test for Streptococcus sp.)
- Group C (AST test for E. coli)
Students
Activity
Learning material
Learning Materials
HMU-MOODLE;
Shokhan Mahmud