Antibiotics research. Culture plate for testing the resistance of Staphylococcus aureus bacteria to six different antibiotics, viewed through a magnifying lens. A bacterial 'lawn' is prepared by coating an agar plate with a solution containing the bacterium. Disks of filter paper soaked in antibiotic are applied and the amount of bacterial growth is observed. The antibiotics are (clockwise from upper right): penicillin and erythromycin (to which the bacterium is resistant), fusidic acid, trimethoprim, chloramphenicol and gentamicin. The diameters of the clear areas around the latter four antibiotics can be measured to determine their effectiveness.