Selection of media for antimicrobial susceptibility testing of fish pathogenic bacteria

The available data concerning antimicrobial susceptibility testing of fish pathogens showed that there is no consensus to the basal medium currently being employed. Different media recommended for susceptibility testing of human pathogens (Mueller-Hinton Agar, Tryptone Soya Agar, Antibiotic Medium 3, Diagnostic Sensitivity Test Agar) have been used in addition to media (Brain Heart Infusion Agar, Heart Infusion Agar, Columbia Blood Agar) normally utilized for cultivating fastidious bacteria. When testing marine pathogens, sodium chloride or seawater has been included in the media. Media normally used for cultivation of pathogens with specific growth requirements like Flavobacterium species and Renibacterium salmoninarum have been used for susceptibility testing. The Mueller-Hinton Agar and different modifications of this medium was used most frequently in published studies on resistant pattern in fish pathogenic bacteria. The American guideline from The National Committee for Clinical Laboratory Standards (NCCLS) recommends Mueller-Hinton Agar for susceptibility testing of human pathogens and this validated medium appears to be adequate for the rapidly growing fish pathogens. Following the NCCLS guideline with susceptibility testing of fastidious organisms, the use of modified Mueller-Hinton Agar for testing of pathogens with specific growth requirements, like, e.g. Flavobacterium species and R. salmoninarum, has been initiated. For the testing of susceptibility of fish pathogenic bacteria, it is suggested that, if possible, a chemically defined well-known medium such as Mueller-Hinton Agar or modification of Mueller-Hinton Agar be used for further investigations. (C) 2001 Elsevier Science B.V. AH rights reserved.