Aquaculture Department, Southeast Asian Fisheries Development Center
Abstract
Disk diffusion method is based on the principle that antibiotic-impregnated disk, placed on agar previously inoculated with the test bacterium, pick-up moisture and the antibiotic diffuse radially outward through the agar medium producing an antibiotic concentration gradient. The concentration of the antibiotic at the edge of the disk is high and gradually diminishes as the distance from the disk increases to a point where it is no longer inhibitory for the organism, which then grows freely. A clear zone or ring is formed around an antibiotic disk after incubation if the agent inhibits bacterial growth.The Government of Japan Trust Fund through SEAFDEC Aquaculture Department provided financial support for the research project and publication of this manual. We would like to express our sincere thanks to Dr. Yasuo Inui and Dr. Kazuya Nagasawa, the former and current Fish Disease Experts and Leaders of the Regional Fish Disease Project, for their encouragement and critical suggestions; and the staff of the Fish Health Section, SEAFDEC Aquaculture Department, for their kind cooperation, especially to Dr. Celia R. Lavilla-Pitogo for carefully reading the manuscript and Dr. Edgar C. Amar for serving as the over-all coordinator in the preparation of drafts. Thanks also to Dr. Hisatsugu Wakabayashi, Emeritus Professor of Fish Pathology Laboratory at the University of Tokyo, for reviewing the manuscript
