BIOD 171:BIOD 171 Lab 5 Notebook: 100% Verified: Latest Updated 2026

Objective: To determine the threshold of antibiotic sensitivity across bacterial strains using the Kirby-Bauer method (AKA Standardized Disc Susceptibility Test). Procedure: 1. Streak bacteria A across an LB agar plate for continued growth using a sterile L-spreader. 2. Evenly place the paper antibiotic disc on the plate 3. Invert plate and incubate at 37 degrees C overnight 4. Measure Zones of inhibition (diameter) Areas of clearing surrounding antibiotic disc after overnight incubation. Measure in millimeters 5. Compare results with sensitivity chart Notes: Wet Lab  Supplies: o Non selective Mueller-Hinton plate,o L spreader to spread the bacteria o sterile forcepts o antibiotic disc - 8 different antibiotics  Write experiment number and today’s date  Coat the entire surface area of plate with the bacteria to have a nice uniform growth AKA lawn  Then you can test the plate to see if it will be resistant or susceptible to influence of the antibiotic. Meaning it would kill the bacteria  Using a pipette, adjust the volume by twisting the numbers, we are going to use 150 microliters of the culture  Add dropwise steps around the plate for equal distribution  Use a sterile wrap L spreader (has a flat surface and curved surface), using the surface without a line on it.  Keep the lid as close to the place as possible to avoid contamination and very gently guide the L spread around and move the culture around to evenly disperse it.  You may feel resistance, which is normal. This means that the culture is being absorbed into the agar.