One of the most commonly prescribed drugs are antibiotics. However, different bacteria have different susceptibilities to antibiotics. The easiest method for determining susceptibility is a technique called a Kirby-Bauer method. Small disks of paper with different concentrations and different types of antibiotic are placed on a lawn of bacteria on an agar plate. The antibiotic then diffuses through the agar.
Susceptibility is determined by measuring the zone of inhibition surrounding each disk.
Basically, the bigger the zone, the more susceptible the microbe is to that specific antibiotic. In addition, any resistant bacteria will appear as colonies within the zone of inhibition. This experiment will use standardized antibiotic disks as well as some of the household cleaners used by you and your classmates. Using a sterile swab, streak across the kitchen counter sample from the How Clean is Your Kitchen experiment. Open one labeled petri plate and inoculate the entire surface by painting it with the swab.