Description

Susceptibility testing is indicated for any organism that contributes to an infectious process warranting antimicrobialchemotherapy if its susceptibility cannot reliably be predicted from existing antibiograms. Antimicrobial resistance patterns formany anaerobic bacteria have changed significantly over the last several years, resulting in a lack of predictability for manyspecies. Susceptibility testing of anaerobes is recommended for surveillance purposes and for specific clinical situations.

Two end-point-determining susceptibility testing methods for anaerobic bacteria are described in Clinical and LaboratoryStandards Institute document M11-A8 – Methods for Antimicrobial Susceptibility Testing of Anaerobic Bacteria; ApprovedStandard – Eighth Edition. The agar dilution method (Wadsworth) remains the reference standard, and is well suited forsurveillance testing and research. It is also the standard to which other methods are compared. Broth microdilution is well suitedfor the clinical laboratory, but is currently limited to testing of Bacteroides fragilis group organisms and selected antimicrobialagents. QC criteria for each procedure are also described.

The tables in CLSI document M100,1 when used in conjunction with this standard, represent the most current information fordrug selection, interpretation, QC, and antibiogram reports using the procedures standardized in M11. Users should replace tablespublished in earlier standards with these new tables. (Changes in the tables since the previous edition appear in boldface type).When new problems are recognized, or improvements in these criteria are made, changes will be incorporated into future editionsof this standard and also distributed as informational supplements.