Light-scattering methods for antibiotic sensitivity tests.

The total intensity of light scattered in the angular range 30 degrees-130 degrees by a suspension of bacteria can be used as the basis of a method of antibiotic sensitivity testing. A procedure is given in which the bacteria are incubated in the presence of antibiotic, as a test, and in its absence, as a control, for 60 minutes. An incubation time of 90 minutes gives slightly more reliable results. With this increased incubation time it is necessary to measure the intensity of scattered light only at a single fixed angle or, at most, a few angles. Measuring the angular dependence of the scattered intensity does not allow the incubation period to be reduced.