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Which antibiotic is most effective?

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Hypothesis: There will be a zone of inhibition around the antibiotic on the agar plate due to the antibiotic inhibiting the growth of microorganisms (such as bacteria). In this case it can be seen that the antibiotic A is far more successful in killing the bacteria than B. This is evident as the diameter of the inhibition zone of A, shown by the arrow, is far larger than that of the inhibition zone of B.1 Increasing the concentration of a bactericidal antibiotic such as penicillin should increase the number of bacterial colonies it kills. Apparatus: * Agar plate seeded with known Bacteria * Sterile Pasteur pipette * Bunsen burner * Beaker of disinfectant, 1% Virkon or equivalent * Bench spray of disinfectant, 1% Virkon or equivalent * Bactericidal soap * Paper towels * Marker pen * Forceps * Mast ring or antibiotic impregnated paper discs * Adhesive tape * Incubator set at 30 �C Method: 1. ...read more.


Controlled Variable: * Temperature of the incubator-It is fundamental that the temperature of the incubator is controlled as this can affect the rate of bacterial growth. For any given bacterium there are maximum and minimum temperatures beyond which growth will not occur. Penicillin (one of the antibiotics to be used in the pilot study) is a time dependent bactericidal antibiotic that interferes with bacterial growth-hence the rate of bacterial growth is influential to the final result. Therefore to ensure that the rate of growth is uniform in all samples; the agar plates will be incubated in an oven at a constant temperature of 35�C. * Volume of Bacteria used-The volume of bacteria pipetted into a Petri dish will remain consistent regardless of the culture technique it is introduced to. Risk Precaution Contamination of agar plates It is possible to culture pathogenic bacteria if contamination occurs, in which case this is potentially hazardous as the agar is a nutrient rich medium which would nourish pathogenic bacteria. ...read more.


There appeared to be no anomalous results for this experiment. Evaluation I believe that my experiment was fairly accurate and reliable; as I didn't have any outliers this can increase the chance that there was no or very little human error. I used the apparatus and measuring equipment carefully and accurately to reduce the chances of systematic error and increasing the accuracy of my results and as I took 2 sets of data for each concentration and both were the same/similar results this proves that my results were quite reliable. After performing the experiment I feel there is still room for improvement. In the event of a future investigation, I would; * Make more replicates of both the spread and pour plating technique, as well as other culturing techniques (e.g. streak plating) to produce a clear picture of the overall results. * Alternate the chemical class and concentration of the antibiotic to determine whether the effect of culture technique is universal for various antibiotics. * Perform an antibiotic sensitivity test using more antibiotics (5+) of varied chemical class and produce samples using different culturing techniques ?? ?? ?? ?? Which antibiotic is most effective? ...read more.

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