Antibiotic sensitivity testing of bacteria by microcolony inhibition and image analysis.

A rapid method for determining the sensitivity of Staphylococcus aureus to beta-lactams is described. The method involves the culture of microcolonies of the bacterium on the surface of antibiotic-containing agar medium on microscope slides. The areas of the microcolonies formed are measured by means of a microscope and image analyzer. The sensitivity of the bacterium can be estimated in 4 h by this technique and the results are comparable to those obtained by overnight incubation.