scope:

This standard describes the CLSI antimicrobial susceptibility testing (AST) reference agar dilution method as well as the alternative broth microdilution method for Bacteroides spp. and Parabacteroides spp. organisms used to determine in vitro susceptibility to antimicrobial agents of bacteria that grow anaerobically. A method for β-lactamase testing on anaerobic bacteria is also described. This standard includes:

• Preparation of broth and agar dilution tests
• Testing conditions (including inoculum preparation and standardization, incubation time, and incubation temperature)
• Reporting minimal inhibitory concentration (MIC) results
• QC procedures
• Limitations of the dilution test methods
• A step-by-step guide to AST (see Appendix A)

To assist the medical laboratory, suggestions are provided for selecting antimicrobial agents for routine testing and reporting.

The disk diffusion method has not been standardized for use with anaerobic organisms and is not included. Methods for culturing and identifying anaerobic bacteria are not discussed. See CLSI document M5632 for information on methods for culturing and identifying anaerobic bacteria. Methods for AST of aerobic bacterial species are also not discussed. The AST methods provided in this standard can be used in laboratories around the world, including but not limited to:

• Medical laboratories
• Public health laboratories
• Research laboratories
• Food laboratories
• Environmental laboratories