scope:

This guideline provides veterinary and aquatic animal disease diagnostic laboratories with standardized antimicrobial broth dilution susceptibility testing methods for Groups 1 and 3 bacteria isolated from aquatic animals (see VET03/VET04-S21 Table 1), including criteria for QC testing with two QC strains. It also provides recommended testing conditions for other fastidious aquatic animal bacterial pathogens. In order to avoid confusion, the organisms in each "Group" and their corresponding numbers have not changed since the last edition.

The corresponding VET03/VET04-S21 supplemental tables outline antimicrobial agents used in global aquaculture, methods for preparing stock solutions and dilutions of antimicrobial agents, and a list of bacteria pathogenic to fish.

Also included are the first consensus-approved clinical breakpoints and epidemiological cutoff values (ECVs) for an aquatic pathogen, Aeromonas salmonicida. The clinical breakpoints were established using antimicrobial susceptibility testing data, very limited pharmacokinetic (PK) data, and clinical efficacy data. The PK and efficacy data used were from studies employing normal dose regimens (ie, approved and/or routinely used in developed countries) administered in medicated feed (see VET03/VET04-S21 Table 12), whereas the ECVs were established using solely antimicrobial susceptibility data of a geographically diverse population of A. salmonicida isolates (see VET03/VET04-S21 Table 13). As more susceptibility data are generated using standard methods and PK data and clinical efficacy reports become available, this document and CLSI document VET033 will be revised to incorporate those data.