CLSI M51
Method for Antifungal Disk Diffusion Susceptibility Testing of Nondermatophyte Filamentous Fungi
This CLSI guideline provides a simple, rapid, and cost-effective alternative for antifungal susceptibility testing of nondermatophyte filamentous fungi (molds). It introduces a disk diffusion method for testing key antifungal agents, including amphotericin B, caspofungin, itraconazole, posaconazole, and voriconazole, making susceptibility testing more accessible to clinical microbiology laboratories.
M51 includes epidemiological cutoff values (ECVs) to help detect potential resistance mechanisms, even in the absence of clinical breakpoints. Compared to CLSI M38, qualitative results can often be determined in just 16 to 48 hours, streamlining fungal susceptibility testing.
Supplemental tables for M51 are published in CLSI document M51S.
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{{FormatPrice(nonMemberPrice)}} List PriceCLSI broth dilution reference methods are available for susceptibility testing of filamentous fungi (see CLSI document M38)(1) and yeasts (see CLSI documents M27(2) and M44(3)). There still remains, however, a need for an alternative simple, rapid, and cost-effective approach to determine the susceptibility of nondermatophyte filamentous fungi (moulds) to various classes of antifungal agents that would make antifungal susceptibility testing more readily available to clinical microbiology laboratories. The CLSI Subcommittee on Antifungal Susceptibility Testing developed a disk diffusion method for testing filamentous fungi to amphotericin B, caspofungin, itraconazole, posaconazole, and voriconazole.(4) Although clinical breakpoints have not been assigned, epidemiological cutoff values (ECVs) have been developed based on a comparison of zone diameters vs minimal inhibitory concentrations (MICs) or minimal effective concentrations (MECs) using the rate bounding method; control parameters for these agents have also been determined.(4) ECVs are not used as clinical breakpoints, but rather to detect those isolates that are likely to have acquired resistance mechanisms or reduced susceptibility to the tested agent as compared with the wild-type distribution. One significant advantage of this method is that qualitative results can usually be determined after only 16 to 48 hours incubation as opposed to 24 to 72 hours with CLSI document M38.(1) There are more antifungal agents and it is expected that this document will further encourage the development of disk diffusion testing for some of these agents.
With a need to make antifungal susceptibility testing more readily available to the clinical laboratory, this CLSI document provides an established method for disk diffusion testing of moulds, zone interpretive criteria, and recommended control ranges for amphotericin B, caspofungin, itraconazole, posaconazole, and voriconazole. The method described in this document is intended for testing moulds that cause invasive disease (Alternaria spp., Aspergillus spp., Bipolaris spp., Fusarium spp., Paecilomyces spp., Rhizopus oryzae [R. arrhizus] and other mucoraceous [zygomycetes] mould species, the Pseudallescheria boydii species complex, and Scedosporium prolificans).4 This method does not currently encompass the yeast or mould form of endemic dimorphic fungi or the dermatophytes. The method described herein must be followed exactly to obtain reproducible results. When new problems are recognized or improvements in these criteria are developed, changes will be incorporated into future editions of this guideline and also distributed in periodic informational supplements. This guideline is intended for use by, but not limited to, health care, academic, government, industry, or independent research organizations that perform antifungal susceptibility testing of filamentous fungi.
This document is available in electronic format only.
This archived document is no longer being reviewed through the CLSI Consensus Document Development Process. However, this document is technically valid and because of its value to the laboratory community, it is being retained in CLSI’s library.
The U.S. Food and Drug Administration (FDA) has evaluated and recognized this approved-level consensus standard for use in satisfying a regulatory requirement.
CLSI broth dilution reference methods are available for susceptibility testing of filamentous fungi (see CLSI document M38)(1) and yeasts (see CLSI documents M27(2) and M44(3)). There still remains, however, a need for an alternative simple, rapid, and cost-effective approach to determine the susceptibility of nondermatophyte filamentous fungi (moulds) to various classes of antifungal agents that would make antifungal susceptibility testing more readily available to clinical microbiology laboratories. The CLSI Subcommittee on Antifungal Susceptibility Testing developed a disk diffusion method for testing filamentous fungi to amphotericin B, caspofungin, itraconazole, posaconazole, and voriconazole.(4) Although clinical breakpoints have not been assigned, epidemiological cutoff values (ECVs) have been developed based on a comparison of zone diameters vs minimal inhibitory concentrations (MICs) or minimal effective concentrations (MECs) using the rate bounding method; control parameters for these agents have also been determined.(4) ECVs are not used as clinical breakpoints, but rather to detect those isolates that are likely to have acquired resistance mechanisms or reduced susceptibility to the tested agent as compared with the wild-type distribution. One significant advantage of this method is that qualitative results can usually be determined after only 16 to 48 hours incubation as opposed to 24 to 72 hours with CLSI document M38.(1) There are more antifungal agents and it is expected that this document will further encourage the development of disk diffusion testing for some of these agents.
With a need to make antifungal susceptibility testing more readily available to the clinical laboratory, this CLSI document provides an established method for disk diffusion testing of moulds, zone interpretive criteria, and recommended control ranges for amphotericin B, caspofungin, itraconazole, posaconazole, and voriconazole. The method described in this document is intended for testing moulds that cause invasive disease (Alternaria spp., Aspergillus spp., Bipolaris spp., Fusarium spp., Paecilomyces spp., Rhizopus oryzae [R. arrhizus] and other mucoraceous [zygomycetes] mould species, the Pseudallescheria boydii species complex, and Scedosporium prolificans).4 This method does not currently encompass the yeast or mould form of endemic dimorphic fungi or the dermatophytes. The method described herein must be followed exactly to obtain reproducible results. When new problems are recognized or improvements in these criteria are developed, changes will be incorporated into future editions of this guideline and also distributed in periodic informational supplements. This guideline is intended for use by, but not limited to, health care, academic, government, industry, or independent research organizations that perform antifungal susceptibility testing of filamentous fungi.
This document is available in electronic format only.
This archived document is no longer being reviewed through the CLSI Consensus Document Development Process. However, this document is technically valid and because of its value to the laboratory community, it is being retained in CLSI’s library.
The U.S. Food and Drug Administration (FDA) has evaluated and recognized this approved-level consensus standard for use in satisfying a regulatory requirement.