Do all antibiotics kill bacteria equally well? When you take medicine for an infection, the specific antibiotic matters. Some are far more effective than others against the same germ. You swab the hands of ten people and grow the bacteria on blood agar plates. After identifying coagulase-negative staphylococcus through gram staining and catalase testing, you spread it on Mueller Hinton plates. Discs soaked in different antibiotics are placed on each plate. After overnight incubation, you measure the death zone around each disc with a caliper. Compare the death zone sizes to discover which antibiotic destroys this common skin bacterium most effectively.