Antibacterial activity detection and evaluation based on the detection of multiple concentric circles with the Hough transform

This paper presents a method for the detection and measurement of inhibition halos of antibacterial activity. It is a difficult problem because there is a wide range of non-homogeneous culture mediums, with a wide range of contrasts between background and halos and some halos have diffuse and irregular or discontinuous contours. In addition, the size, position and number of halos are variable and unforeseeable. The technique exploits the circularity of both the target bacteria and the surrounding halos and uses the Hough Transform to detect multiple concentric circles. In order to reduce time and memory space the circle detection with the HT is separated in two stages. Several HT center detection methods were tested. Prior to the halos detection the images are preprocessed to remove noise and locate the region of interest. Experimental results show the effectiveness of the proposed technique on different culture mediums.