The Effect of Erythromycin on the Bacterial Resistance of Escherichia Coli and Staphylococcus Epidermidis

The goal of this experiment was to determine whether or not bacteria such as Escherichia Coli and Staphylococcus Epidermidis could develop resistance to antibiotics such as Erythromycin over multiple generations.  Bacteria exposed to the antibiotics were used to generate new generations with the hopes that the exposed bacteria would develop some kind of resistance.  The bacteria growing closest to the zone of inhibition around each antibiotic disc on the test Petri dish was transferred to a new Petri dish where it would generate a new population of bacteria that was again exposed to an antibiotic.  After a 24 hour period, the average radius of each trial’s zone of inhibition was recorded and new trials were prepared using the previous trial’s bacteria.  The process was repeated for four generations of bacteria with each new generation being exposed to the same amount of Erythromycin.

In the case of the Staph bacteria, the results showed an entirely insignificant level of change in zone of inhibition size between the first and fourth trial days, meaning the resistance of the bacteria did not change in any significant way.  The E. coli bacteria results did change significantly, but not as anticipated.  Rather than gaining a significant resistance, the E. coli’s bacteria resistance was found to become significantly weaker to the antibiotic between the first and fourth trial days.

In the grand scheme of things, the relevance of this experiment lies in the world of medicine.  If bacteria are found to be gaining resistance to medication, the medication becomes obsolete.  If it were possible to monitor and control the change in resistance of bacteria, the obsolescence of medication would no longer be a problem scientists would have to face.

Research Done By:

Jacob Gross
Fraser High School

Trevor Torres
Sterling Heights High School High School