MEASUREMENT OF INHIBITION ZONE DIAMETER IN DISK SUSCEPTIBILITY TESTS BY COMPUTERIZED IMAGE-ANALYSIS

This paper presents an application of computerized image analysis in m icrobiology. This application permits the automatic detection and diam eter measurement of inhibition zones in disk susceptibility tests. Eac h inhibition zone boundary was extracted according to an edge detectio n method based on the Student's t-test and a priori knowledge (geometr y, densitometry). Evaluation of the method was performed by comparing the results from an image analyser and a trained observer. For this pu rpose, we used kappa statistics and obtained a close agreement (a kapp a coefficient equal to 0.84) on a set of about 600 inhibition zones. T he results encourage us to develop the method further to include the d etection of antagonism and synergism.