A Simple Experiment that Reveals Overgrowth of Fungi as a ?Side-Effect? of Antibiotic Use
Tested Studies in Laboratory Teaching, 2019, Volume 40
Kathleen A. Nolan, Victoria Ruiz, Allen J. Burdowski, Kristen Casares, & Onika Brown
Abstract
Students in the Biological Evolution course at St. Francis College noticed that the Luria–Bertani (LB) agar plates with and without ampicillin (amp) had become contaminated with mold after they were made and stored for two weeks in the refrigerator. We were supposed to use these plates for an antibiotic-selection experiment for E.coli but switched to an examination of the “contamination” instead. The LB plates plus ampicillin had more mold than the control LB plates, which puzzled us, until we read that this “overgrowth” was a side effect of the antibiotic. Ten white and 87 reddish brown colonies were found on the LB control plates, whereas 29 white and 112 reddish brown colonies were found on the LB + ampicillin plates. (p < 0.01 with a Chi-squared analysis.) The white colony size in mm average was slightly larger in LB control plates versus LB + amp plates (18 and 12 respectively), but the reddish brown colony size average was approximately 7 mm in both. This experiment represents a simulation of what can occur in the body as a result of antibiotic use.
