scope:

This standard describes the reference broth microdilution testing method for antifungal susceptibility testing of filamentous fungi (moulds) that cause invasive and/or cutaneous fungal infections.^1-10 This standard also covers testing conditions, including inoculum preparation and inoculum size, incubation time and temperature, media formulation, and end-point determination criteria.^1-9 QC reference ranges and limits and specific epidemiological cutoff values (ECVs) are summarized in the current editions of CLSI documents M61¹⁸ and M59,¹² respectively.^5,8-10,13-17

The intended audience includes medical laboratory personnel, clinicians, and microbiologists who routinely perform antifungal susceptibility testing and use antifungal susceptibility testing results to select suitable antifungal therapy, as well as those involved in emerging resistance surveillance. The reference method is also useful for establishing ECVs and developing and validating alternate commercial methods for determining antifungal susceptibility of filamentous fungi. Therefore, the standard is also of interest for both diagnostic and pharmaceutical companies and their regulatory counterparts.

This method has not been evaluated in studies of the yeast or mould forms of dimorphic fungi, such as Blastomyces dermatitidis, Coccidioides immitis/posadasii, Histoplasma capsulatum, or Talaromyces marneffei (Penicillium marneffei), and has been evaluated only for the mycelial form of Sporothrix schenckii species complex.¹ This method also has not been used in studies of dermatophytes with the echinocandins or nondermatophyte moulds with ciclopirox, griseofulvin, or terbinafine.

Antifungal susceptibility testing of other filamentous fungi that cause infections may also be tested by this method but have not been standardized and evaluated in collaborative studies. The appropriate testing parameters such as inoculum and incubation time for those fungi are unknown.

Commercially available susceptibility test systems are out of scope for this standard. It is recommended that users of these systems refer to the manufacturer's instructions as outlined in the package insert.