1. PHT 381 Lab # 9

2. MIC : - It is the lowest concentration of the antimicrobial agent that inhibits the growth of the test organism but not necessarily kills it.

3. Methods for determination of MIC 1. Serial dilution method 2. Agar diffusion method 3. E- test

5. Agar Diffusion Method Material:  Culture of staph. aureus  Augmentin  Saline  Melted nutrient agar bottle  Sterile peri dish  4 sterile vials  2 sterile pipette 1ml  1 sterile pipette 5 ml

6. Procedure: 45°c S o.1 ml

7. AB 12 3 4 1 ml 1 ml saline

8. 4 Incubate the plate Uninverted at 37°c for 24h 3 2 1 4 3 2 1

9. Results: Measure the diameter of each inhibition zone * The diameter of the inhibition zones are directly proportional to the conc. of the antibiotic. Zone diameter Well diameter

10. Agar Diffusion Method Results: AB conc Log conc Zone diameter Well diameter X X² 100 50 25 12.5 X = Zone diameter – Well diameter 2 If Original Antibiotic Conc. = 200 µg/ml

11. Agar Diffusion Method x² Log conc Anti-log = MIC x x x x

12. Agar Diffusion Method Conc MIC *If use semi-log paper, then No need to calculate Log conc. x² x x x x

14. E-Test