The Clinical and Laboratory Standards Institute (CLSI) has released updated versions of two veterinary microbiology documents. Methods for Broth Dilution Susceptibility Testing of Bacteria Isolated From Aquatic Animals; Approved Guideline—Second Edition (VET04-A2) provides the most up-to-date techniques for the determination of minimal inhibitory concentrations of aquatic bacteria by broth micro- and macrodilution, and criteria for data interpretation and quality control testing. Performance Standards for Antimicrobial Susceptibility Testing of Bacteria Isolated From Aquatic Animals; Second Informational Supplement (VET03/VET04-S2) provides updated tables for the CLSI antimicrobial susceptibility testing (AST) guidelines VET04-A2 and Methods for Antimicrobial Disk Susceptibility Testing of Bacteria Isolated From Aquatic Animals; Approved Guideline (VET03-A).

VET04-A2 includes a newly standardized method and associated quality control parameters for testing Group 3 gliding bacteria. It also contains the current best thinking of scientists in the field and their recommendations for conducting susceptibility tests on fastidious aquatic bacteria. Unlike the first edition of this standard, the tables are no longer included, but were moved to the document’s related supplement, VET03/VET04-S2.

“The One Health global approach to AST requires robust data on breakpoints so that antimicrobial resistance can be tracked and information shared between laboratories around the world. However, because of the numbers of pathogenic bacteria and the vast range of host species in aquaculture, generating the relevant pharmacokinetic and pharmacodynamic data for all hosts and their pathogens is a huge task,” noted Nicky Buller, PhD, Senior Microbiologist at the Animal Health Laboratories, Department of Agriculture and Food Western Australia, South Perth, Australia. “This document addresses many of these requirements and will enable diagnostic and research laboratories to provide information for disease treatment to practitioners that will lead to generation of data for tracking any developing antimicrobial resistance. This document is a valuable resource for diagnostic and research laboratories involved in testing bacterial pathogens from aquatic animals.”

Also released and available for purchase with VET04-A2 is VET03/VET04-S2—Performance Standards for Antimicrobial Susceptibility Testing of Bacteria Isolated From Aquatic Animals; Second Informational Supplement, which was updated with new tables for CLSI antimicrobial susceptibility testing guidelines VET03-A and VET04-A2.

VET03/VET04-S2 now has interpretive criteria (clinical breakpoints) and epidemiological cutoff values (wild-type cutoffs) for the aquatic bacterial pathogen Aeromonas salmonicida. This supplement is important for users of CLSI documents VET03-A and VET04-A2. The supplement is intended to be used primarily by fish disease diagnostic laboratories that typically conduct susceptibility tests less than once per week and need revised guidance for frequency of quality control.