Antibiotics And It's Effects

Antibiotics And It's Effects

Lab Report: Micro Biology

Antibiotics and it’s effects
Objective: to determine the effects of four different antibiotics on E. coli (gram -) and B.             megaterium (gram +)
Materials: 2 sterile argar plates
        Swabs and paper towels
        Incubator
      Broth culture of both E. coli and B. megaterium
        Antibiotics   a) tetracycline
              b) ampicillin
              c) streptomycin
              d) chloramphenicol
Method: Kirby-Bauer Assay is antibiotic testing which uses antibiotic-impregnated disc         to test     whether particular bacteria are susceptible to specific antibiotics. A             known quantity of bacteria are placed on agar plates in the presence of thin disc         containing relevant antibiotics. If the bacteria are susceptible to a                 particular antibiotic, an area of clearing surrounds the disc where bacteria are not         capable of growing (called a zone of inhibition).

This along with the rate of antibiotic diffusion are used to estimate the bacteria's sensitivity to that particular antibiotic. This information can be used to choose appropriate antibiotics to combat a particular infection.

Procedure: 1. Dip swab in broth culture and swab agar pates with bacteria
      2. Dispense antibiotic disc onto paper towel and use tweezers to place disc onto           plate
      3. Place control paper in the center of the disc
      4. Incubate for 24 hours
            5. Measure diameter surrounding the bacteria and record data
Results: If the antibiotic works successfully, a clear ring will appear around the disc in 24/48 hours. The ring is called the zone of inhibition. It is measured in mm to see how wide it is. The larger this zone of inhibition, the more effective that antibiotic is against that particular type of bacteria, the smaller the zone the more antibiotic is needed.
measurements for bateria B. megaterium:

antibiotic Tetracycline: 1.5mm...